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Compensation-based nonactive power definition
... Time-domain based approaches are mostly originated from the Fryze power theory [10]- [11], instantaneous p-q theory [12]- [13,14], and synchronous d-q frame theory [15]. In [16] and [17] an extension of Fryze power theory, and instantaneous power theory is utilized for the compensation of non-periodic current. The time-domain based techniques have the advantage of being simple and instantaneous under some specific conditions. ...
... The fast compensator window length is a short fraction of the generated voltage frequency period which results in higher compensation speed compared to other nonperiodic compensation techniques, which use windows equal or larger than the fundamental frequency period of the generated voltage. For example, in [16], a window length equal to ten times the period of the fundamental frequency of the voltage is chosen. The reactive compensator window length is largest window computationally available to assure lower reactive current fluctuation. ...
... The non-periodic part of the current has theoretically infinity large period [4,16,28]. Therefore, a longer compensation window results in a greater degree of compensation and higher power quality. However, such a calculation window is not applicable since it implies infinite energy storage on the DC-link of the active filter. ...
This paper presents a new technique for the compensation of non-periodic load current. The method provides control references for three co-located devices, each corresponding to one moving calculation window and one decomposed part of the compensated current. They are slow compensator with high power rating, large calculation window, and low switching frequency; fast compensator with lower power rating, shorter calculation window, and higher switching frequency; and the reactive compensator which is an ordinary static VAR compensator (SVC). A fuzzy based adaptive window is proposed for the slow compensator to find the optimum window for different load characteristics. The technique is evaluated using real-world data and controller hardware-in-the-loop (HIL) implementation.
... where i La (t), T Cnp >>T will be calculated by (6) with T Cnp = (5-10)T in the following analysis. T/2, i is the load current in any phase, i a is the calculated active current, i np , i anp being currents in the same phase with superscript "a" denoting the non-periodic current calculated using (13). The subharmonic component of the frequency 10 Hz and the set of the most important twelve harmonic components (h=2-13, the amplitude law I h =1/h p.u.) are present in the current i. ...
... We see that the estimated current i anp follows its actual waveform i np well, but some residual harmonic components in the current i anp remain. In general, we can say that the choices T C = T/2, T C = T provide us with similar results in the estimation of the non-periodic current component i anp by using (13). Nevertheless, for the currents i with high content of harmonics we could give a preference to the option T C = T where all harmonics are eliminated, which is not the case of Fig. 2. ...
... The remaining three non-active current components in (12) can be determined as follows (16) By summing these three components we obtain (17) which is in agreement with (12). So, all the load current components can be determined by calculating i La , i L1 , i + L1 , and i Lnp (6), (11), (11) for I + L1 , (13). However, it should be emphasized that the calculation of i Lnp by using (13) is only an approximation whose accuracy depends on the character of the nonperiodic current disturbances and a respective choice of the averaging interval T Cnp >>T. ...
... If the system voltage itself is used as the reference voltage v p (t), i s (t) will be proportional to and have the same shape as v s (t) as shown in Fig. 4.2. The blue waveforms are the system voltages (phase 1, 2, and 3 respectively, which are scaled by a factor of 5 for clearness) and the red waveforms are the source currents after compensation, which have the same shape as the system voltages [14]. ...
... The controller may be mostly on-board, personal computer (PC)-based, a processor linked to a PC, etc. depending on constraints and factors such as desired microturbine packaging, desired versatility, type of available features, and the sophistication/maturity of the system design [14]. ...
... SiC-based power devices possess the features of high voltage, high power, high frequency, and high-temperature operation in a smaller package. An SiC-based power converter would have the benefits of reduced losses, higher efficiency, a reduction of up to 2/3 in the heat-sink size, smaller passive components, and less susceptibility to extreme ambient heat [14]. ...
... An instantaneous nonactive (i.e., reactive) power theory [16] is adopted in this paper for the real-time calculation and control of DE voltage regulation. In the theory, definitions of instantaneous active current, instantaneous reactive current, average active power, average reactive power, apparent active power, and apparent reactive power are defined. ...
... Only the definitions that are related to the calculation and control in this paper are presented in this section. The full description of the theory is presented in [16]. In all the following equations, the lower case t indicates time. ...
... As pointed out in [16], the above generalized definition from (1) to (9) extends the traditional definition of instantaneous nonactive power from threephase, balanced, and sinusoidal systems to other cases. This unique feature makes it easy to be applied in modern distribution systems in which there are challenges like single-phase, non-sinusoidal, unbalanced, and non-periodic waveforms. ...
Distributed energy (DE) resources are power sources located near load centers and equipped with power electronics converters to interface with the grid, therefore it is feasible for DE to provide reactive power (along with active power) locally for dynamic voltage regulation. In this paper, a synchronous condenser and a DE source with an inverter interface are implemented in parallel in a distribution system to regulate the local voltage. Developed voltage control schemes for the inverter and the synchronous condenser are presented. Experimental results show that both the inverter and the synchronous condenser can regulate the local voltage instantaneously although the dynamic response of the inverter is much faster than the synchronous condenser. In a system with multiple DEs performing local voltage regulation, the interaction of multiple DE at different locations under different load levels may have an impact to the control parameter setting for each individual DE control system. Future research is needed to find out the interaction of DEs to identify the optimal control parameter settings with the consideration of many factors such as system configuration, load variation, and so on.
... In previous studies, the control algorithms for current and voltage compensators were often based on the assumption that the load currents and source voltages were periodic. The generalized nonactive power theory was applied compensation of the periodic and nonperiodic load current with a parallel active filter (AF) [19,20] and static synchronous compensator (STATCOM) [21]. The theory does not specify the characteristics of voltage v (t) or current i (t); they can theoretically be any wave shape. ...
... The instantaneous nonactive power theory was first presented by Fryze [25] for periodic (but nonsinusoidal) waveforms in the time domain. The generalized nonactive power theory [19] implemented on the USPAF system is based on Fryze's idea of nonactive power and an extension of the theory proposed in [26] for periodic and nonperiodic waveforms in the time domain. In this paper, all vectors are denoted by lowercase bold letters. ...
... given in [19]. The apparent power S(t), apparent active power P p (t), and apparent nonactive power Q(t) were also defined based on the RMS values of the voltage and currents. ...
This paper presents a 3-phase, 4-wire unified series-parallel active filter (USPAF) system for periodic and nonperiodic disturbance compensation using a generalized nonactive power theory. The USPAF system consists of a series active filter (AF), parallel AF, and split DC-link capacitors with the midpoint of the DC-link connected to the neutral wire. The generalized nonactive power theory is applicable to singlephase or multiphase, sinusoidal or nonsinusoidal, periodic or nonperiodic, and balanced or unbalanced electrical systems. The theory was implemented previously in a parallel AF. In this study, the USPAF system is proposed to compensate for the nonsinusoidal and nonperiodic currents and voltages. Distorted source voltages, source voltage sag, and unbalanced nonlinear load current compensation were simultaneously tested in the experiments. Subharmonic and stochastic nonperiodic current and voltage compensation were simulated in MATLAB/Simulink. Simulation and experimental results verified the validity of the generalized nonactive power theory for the compensation of periodic (nonsinusoidal) and nonperiodic current and voltage disturbances with the USPAF system.
... If the system voltage itself is used as the reference voltage v p (t), i s (t) will be proportional to and have the same shape as v s (t) as shown in Fig. 4.2. The blue waveforms are the system voltages (phase 1, 2, and 3 respectively, which are scaled by a factor of 5 for clearness) and the red waveforms are the source currents after compensation, which have the same shape as the system voltages [14]. ...
... The controller may be mostly on-board, personal computer (PC)-based, a processor linked to a PC, etc. depending on constraints and factors such as desired microturbine packaging, desired versatility, type of available features, and the sophistication/maturity of the system design [14]. ...
... SiC-based power devices possess the features of high voltage, high power, high frequency, and high-temperature operation in a smaller package. An SiC-based power converter would have the benefits of reduced losses, higher efficiency, a reduction of up to 2/3 in the heat-sink size, smaller passive components, and less susceptibility to extreme ambient heat [14]. ...
Distributed energy resources (DER) are quickly making their way to industry primarily as backup generation. They are effective at starting and then producing full-load power within a few seconds. The distribution system is aging and transmission system development has not kept up with the growth in load and generation. The nation's transmission system is stressed with heavy power flows over long distances, and many areas are experiencing problems in providing the power quality needed to satisfy customers. Thus, a new market for DER is beginning to emerge. DER can alleviate the burden on the distribution system by providing ancillary services while providing a cost adjustment for the DER owner. This report describes 10 types of ancillary services that distributed generation (DG) can provide to the distribution system. Of these 10 services the feasibility, control strategy, effectiveness, and cost benefits are all analyzed as in the context of a future utility-power market. In this market, services will be provided at a local level that will benefit the customer, the distribution utility, and the transmission company.
... In previous studies, the control algorithms for current and voltage compensators were often based on the assumption that the load currents and source voltages were periodic. The generalized nonactive power theory was applied compensation of the periodic and nonperiodic load current with a parallel active filter (AF) [19,20] and static synchronous compensator (STATCOM) [21]. The theory does not specify the characteristics of voltage v (t) or current i (t); they can theoretically be any wave shape. ...
... The instantaneous nonactive power theory was first presented by Fryze [25] for periodic (but nonsinusoidal) waveforms in the time domain. The generalized nonactive power theory [19] implemented on the USPAF system is based on Fryze's idea of nonactive power and an extension of the theory proposed in [26] for periodic and nonperiodic waveforms in the time domain. In this paper, all vectors are denoted by lowercase bold letters. ...
... Average active power P a (t) and average nonactive power P n (t), defined by averaging the instantaneous powers over time interval [ The RMS values of the system voltage, active current i a (t), nonactive current i n (t) and current i (t) were given in [19]. The apparent power S(t), apparent active power P p (t), and apparent nonactive power Q(t) were also defined based on the RMS values of the voltage and currents. ...
This paper presents a 3-phase, 4-wire unified series-parallel active filter (USPAF) system for periodic and nonperiodic disturbance compensation using a generalized nonactive power theory. The USPAF system consists of a series active filter (AF), parallel AF, and split DC-link capacitors with the midpoint of the DC-link connected to the neutral wire. The generalized nonactive power theory is applicable to single-phase or multiphase, sinusoidal or nonsinusoidal, periodic or nonperiodic, and balanced or unbalanced electrical systems. The theory was implemented previously in a parallel AF. In this study, the USPAF system is proposed to compensate for the nonsinusoidal and nonperiodic currents and voltages. Distorted source voltages, source voltage sag, and unbalanced nonlinear load current compensation were simultaneously tested in the experiments. Subharmonic and stochastic nonperiodic current and voltage compensation were simulated in MATLAB/Simulink. Simulation and experimental results verified the validity of the generalized nonactive power theory for the compensation of periodic (nonsinusoidal) and nonperiodic current and voltage disturbances with the USPAF system.
... One means of correcting these power quality problems is to provide nonactive power compensation. However, there are still no standard definitions of instantaneous nonactive power and instantaneous nonactive current [1][2][3][4]. A parallel active filter is an effective way to eliminate or mitigate the harmonics and unbalance in current [5][6]. ...
... The instantaneous power theory presented in [4] is used for the active filter presented in this paper because the definitions of instantaneous power and instantaneous nonactive power are suitable for real-time nonactive power compensation purpose. This instantaneous power theory will be elaborated in Section III. ...
... An instantaneous nonactive power theory [4] is adopted to calculate the instantaneous variables based on the measurements (v t , i l , i c , and v dc ), and to implement control, depending on the compensation objectives and control schemes. In a three-phase system with a voltage vector v(t) and a current vector i(t) (vectors for voltage and current will be denoted in bold), ( ...
A three-phase insulated gate bipolar transistor (IGBT)-based parallel active filter is used for current and/or voltage unbalance compensation. An instantaneous power theory is adopted for real-time calculation and control. Three control schemes, current control, voltage control, and integrated control are proposed to compensate the unbalance of current, voltage, or both. The compensation results of the different control schemes in unbalance cases (load unbalance or voltage source unbalance) are compared and analyzed. The simulation and experimental results show that the control schemes can compensate the unbalance in load current or in the voltage source. Different compensation objectives can be achieved, i.e., balanced and unity power factor source current, balanced and regulated voltage, or both, by choosing appropriate control schemes.
... Time-domain based approaches are mostly originated from the Fryze power theory [32]- [44], instantaneous p-q theory [45,46,34] , and synchronous d-q frame theory [47]. In [48] and [49] an extension of Fryze power theory, and instantaneous power theory is utilized for the compensation of non-periodic current. The time-domain based techniques have the advantage of being simple and instantaneous under some specific conditions. ...
... In [48], Fryze theory is proposed for the compensation of non-periodic load current. ...
In this dissertation, a new technique is proposed for the compensation of nonperiodic load current. The method provides control references for three co-located devices, each corresponding to one moving calculation window and one decomposed part of the compensated current. They are slow compensator with high power rating, large calculation window, and low switching frequency; fast compensator with lower power rating, shorter calculation window, and higher switching frequency; and the reactive compensator which is an ordinary static VAR compensator (SVC). To improve the flexibility of the technique, a fuzzy based adaptive window is proposed for the slow compensator to find the optimum window for different load characteristics. Moreover, three power quality criteria are proposed specifically for the non-periodic current compensation, namely, time-frequency distortion index, modulation index, and high frequency distortion index. The method is verified using both simulation and real-time implementation. First, the proposed method is verified in simulation using real-world data acquired from a local steel mill. Second, it is validated using a real-time controller-in-the-loop implementation. The proposed compensation approach demonstrates high flexibility and effectiveness in increasing power quality under various non-periodic load conditions. Finally, some practical aspects of the implementation of a three-part compensator including cost analysis are presented.
... In this study, a microcontroller-based control system is presented for a 3-phase, 12-pulse laboratory-size prototype of a STATCOM with the structure of a voltage source converter (VSC). The nonactive power theory presented in [8] was used to perform real-time reactive power compensation with a multipulse STATCOM. The control system has been implemented with low-cost 16-bit microcontrollers. ...
... The reactive current component required for the STATCOM's current control unit was computed using the nonactive power theory and a microcontroller-based control system. A detailed description of the nonactive power theory can be found elsewhere [8,10,11]. The microcontroller-based control system of the STATCOM is described in detail in Section 3. ...
... D'après [4], [5], [6] et [7], la théorie de la puissance réactive instantanée (en anglais "Instantaneous Reactive Power Theory") avec un filtre actif est appliqué pour résoudre le problème du déséquilibre dans un réseau quatre fils (trois phases + neutre) avec des charges non-linéaires. Cependant, dans notre étude, les harmoniques sont ignorés dans notre réseau électrique, les charges donc supposées linéaires. ...
... A partir de l'équation (6), nous pouvons déterminer la relation entre les rapports cycliques pour contrôler les interrupteurs : ...
... Akım ve gerilim dalga formundaki bozulmalar, Ģebekeden çekilen güç üzerinde aktif olmayan güç bileĢenlerinin oluĢturur. Bu yüzden güç üzerinde yapılan çalıĢmaların önemli bir bölümü aktif olmayan güçlerin yeniden tanımlanması, ölçümü, kompanzasyonu ve bu harmoniklerin bastırılması üzerine yoğunlaĢmıĢtır [3][4][5][6][7][8][9]. ...
... Çok fazlı sistemlerde aktif olmayan güç, hem ilgili kaynak yük arasında hem de fazlar arasında dolaĢan bir gücü temsil eder. Kaynak yük arasında dolaĢan güç sadece ortalama ve etkin değerler üzerine formülize edilirken, fazlar arası güç anlık temel üzerine dayandırılabilir [5][6][7]. ...
Günümüzde bilgisayar destekli eğitimin önemi, onun kullanışlılığı ve esnekliğinin sağladığı avantajlardan dolayı her geçen gün daha da artmaktadır. Bilgisayar ortamında uygulamalı dersler için deneysel çalışmalara ait bir aracın geliştirilmesi; bir yandan öğrencinin kolay bir şekilde dersi anlamasına olanak sağlarken, diğer taraftan laboratuar ortamında deney esnasında karşılaşılacak problemleri en aza indirger. Bu çalışmada, sinüsoidal olmayan gerilimin farklı R-L-C yük kombinasyonuna uygulanması sonucunda oluşan akım, gerilim, güç dalga şekillerini ve onların harmoniklerini incelemeye olanak sağlayan eğitsel amaçlı bir araç geliştirilmiştir. Bu araca ait ara yüz programı C# programlama dilinde yazılmıştır. Geliştirilen araçta kullanıcı gerilim, onun harmonikleri ve yük kombinasyonuna ait bileşenlerini tanımlayabilmekte olup, bu şartlarda oluşturduğu devredeki tüm gerilim, akım ve güç bileşenlerine ait analizleri veri ve grafiksel olarak inceleyebilmektedir. Bu veri ve grafikler bilgisayar ortamına kaydedilebilmekte ve ara yüz üzerinden çıktı alınabilmektedir. Bu hali ile araç kullanıcıya deneysel çalışmalarla ilgili raporlama imkânı da sağlamaktadır.
... al. [22] propõem a análise em regime não-senoidal e com sinais não periódicos, por meio da utilização da definição de Fryze, variando o período de integração no cálculo da potência ativa da carga e dos valores eficazes de tensão. ...
... ( Relacionando com a equação (1.75), tem-se: 22 22 XV hI hm n SDDD =++. ...
... As an extension of Fryze's idea of current components, Peng and Tolbert introduced the active (i p ) and non-active (i q ) currents for compensation reasons [5]- [7]: ...
... It was pointed out that the averaging interval T c can be zero, one fundamental cycle, one-half cycle, or multiple cycles, depending on the compensation purpose [5]- [7]. We must note that the active currents given by expression (22), have the same shapes and phases as the voltages (Fig. 2). ...
The paper is focused on the presentation of the different theories of powers and current decomposition methods in the compensating current calculation for three-phase three-wire shunt active filtering systems. The decomposition methods are grouped into two categories, depending on the type of coordinate system used in the processing measurements involved in calculations. The former is based on the phase coordinates system and includes: the theory of Fryze, the theory of Fryze-Buchholz-Depenbrock, the so-called generalized theories of instantaneous reactive and non-active powers, the Currents' Physical Components Theory (CPC) and the Conservative Power Theory (CPT). The latter refers to the orthogonal reference frame-based approaches such as the p-q theory and id-iq method. The applicability of each theoretical approach in the control of a shunt active power filter was analyzed. A summary highlighting the applicability under non-sinusoidal voltage and the main performance of each method is performed. Next, our platform for testing the control strategies of shunt power filters, based on DSP DS1103 system, is presented. An implementation on a dSpace 1103 DSP system of the theories presented above and some experimental results are given in the second part of the paper.
... In this study, a microcontroller-based control system is presented for a 3-phase, 12-pulse laboratory-size prototype of a STATCOM with the structure of a voltage source converter (VSC). The nonactive power theory presented in [8] was used to perform real-time reactive power compensation with a multipulse STATCOM. The control system has been implemented with low-cost 16-bit microcontrollers. ...
... The reactive current component required for the STATCOM's current control unit was computed using the nonactive power theory and a microcontroller-based control system. A detailed description of the nonactive power theory can be found elsewhere [8,10,11]. The microcontroller-based control system of the STATCOM is described in detail in Section 3. ...
In power transmission and distribution systems, the design of a compensator that adjusts the power factor without causing additional power losses requires the determination of the reactive current components that are going to be supplied into the system. In this study, the determination of the active and reactive current components is achieved via the use of the nonactive power theory and a microcontroller-based control system. The control system has been implemented with low-cost 16-bit microcontrollers. This system was used to control a 3-phase, 12-pulse laboratory-size prototype of a static synchronous compensator (STATCOM) with the structure of a voltage source converter (VSC). Verification of the STATCOM and its control circuit were examined via experiments and simulation studies conducted on a single-machine infinite-bus (SMIB) power transmission system. The simulation models for the power and control systems were built by employing the PSCAD / EMTDC program’s C programming interface and the graphics-based models in its model library. The experimental results are compared with the results obtained from the PSCAD / EMTDC simulation program.
... These currents interact with the impedance of the power distribution system and disturb voltage waveforms at Point of Common Coupling (PCC) that can affect other loads. These waveforms are considered as non-periodic, although mathematically the currents may still have a periodic waveform, but in any event, the period of the currents is not equal to the period of the line voltage [1]. ...
... The generalized non-active power theory [1] is based on Fryze's theory of non-active power/current. The instantaneous power p(t) and the average power P(t) is defined as the average value of the instantaneous power p(t) over the averaging interval [t-T c , t], that is ...
In this study, generalized non-active power theory based control strategy is proposed for a 3-phase 4- wire Combined Series-Parallel Active Filter (CSPAF) syste m using a Three-Dimensional (3D) Space Vector Pulse Width Modulation (SVPWM). The CSPAF system consists of a Series Active Filter (SAF) and a Parallel Active Filter (PAF) com bination connected a common Direct Current (DC) link for simultaneous compensating the source voltage and the load curren t. The generalized non-active power theory was applied in previous studies for the PAF control, in this study the theo ry is used for the CSPAF system control under non-sinusoidal and non- periodic current and voltage conditions. The closed loop control algorithm for the proposed CSPAF system has been described to direct control of filtering performance by measu ring source currents and load voltages for the PAF and the SAF, respectively. The proposed control strategy has been verified by simulating the CSPAF system in Matlab/Simulink environment.
... The main question of power decomposition and definition is how to choose power components p jp and p jq among infinite number of power components which fulfill equations (7), (8) and (9). One possible way of power decomposition is obtained when the active power components yield not only the same average power P but the same instantaneous power p and the oscillating non-active components yield zero instantaneous power [2], [7]- [9], [12], [13], i.e. such case is obtained when the time averaging interval is not equal to period T but tends to zero [10], [11]. This means that two different approaches related to the power transfer for a given source voltages can be observed: unchanged average power transfer or unchanged instantaneous power transfer. ...
... In case of unbalanced voltages, the minimal currents for a three-phase four wire system defined in [13] are obtained as a special case of (13) when M=4, and the minimal currents for a three-phase three-wire system defined in [13] are obtained as a special case of (13) when M=3. In case of balanced voltages, Fryze's active currents defined in [3], [7], [11] and zero neutral current are obtained as a special case of (13) when M=4, and only Fryze's active currents are obtained as a special case of (13) when M=3. The previous minimization procedure is also valid for single phase systems, for M=2 expression (13) yields Fryze's active currents in two wires of a single phase system [1] (two mutually equal currents of the oposite signs are obtained). ...
Based on the condition for the minimum rms value of line currents, a method for improving the power factor in poly-phase power systems under asymmetrical and non-sinusoidal conditions is presented. The paper offers a new formulation of active currents for poly-phase systems which is valid regardless of whether the voltages and currents are balanced or unbalanced and it permits any point of the system to be chosen for the voltage reference. Observing the constraints related to the reactive compensators, the line current minimization procedure is used for determination of optimal compensating capacitances for poly-phase systems. The definitions of power factors before and after the compensation are introduced. Experimental results are obtained to confirm the validity and applicability of the proposed compensation procedure.
... A new instantaneous nonactive power theory was presented in [8]. In the theory, definitions of instantaneous active current, instantaneous nonactive current, average active power, average nonactive power, apparent active power, and apparent nonactive power are defined. ...
... The averaging interval T c can be chosen from zero to infinity depending on the compensation objectives, and for different T c , the resulting active current and nonactive current will have different characteristics as shown inTable I. The choice of T c was discussed in detail in [8]. The instantaneous active current i a (t) and instantaneous nonactive current i n (t), are defined by, respectively, 2 ...
The nonactive-power-related ancillary services provided by distributed energy (DE) resources are categorized by voltage regulation, reactive power compensation, power factor correction, voltage and/or current unbalance compensation, and harmonics compensation. An instantaneous nonactive power theory is adopted to control the DE system to provide these ancillary services. Three control schemes, including nonactive current compensation, power factor correction, and voltage regulation, are developed which can perform one or more of the ancillary services. The control schemes are implemented in a DE system in simulation and experiments. The simulation and the experimental results show that DE is feasible for providing nonactive-power-related ancillary services.
... The generalized instantaneous nonactive power theory [11] is an extension of the theory in [9]. For a voltage vector v(t) and a current vector i(t) (vectors for voltage and current will be denoted in bold), ...
... The generalized instantaneous nonactive power theory [11] is an extension of the theory in [9]. ( ) [ ( ), ( ),..., ( ) ...
This paper presents a generalized nonactive power theory, in which the instantaneous currents (active and nonactive) and instantaneous powers (active and nonactive) are defined. This theory is implemented in a parallel nonactive power compensation system. The theory is valid if the system is three-phase or single-phase, sinusoidal or non-sinusoidal, periodic or non-periodic, balanced or unbalanced. Four cases, three-phase balanced RL load, three-phase unbalanced RL load, diode rectifier load, and single-phase RL load are tested in the experiments. Subharmonic load compensation and non-periodic load compensation are simulated in Matlab. The simulation and experimental results not only verify the validity of the theory, but also show that this theory can perform instantaneous nonactive power compensation with fast dynamic response
... For the -sinusoidal case, research on power definitions [3]- [14] has been carried out with very different objectives as mathematical meaning, physical meaning, power factor improvement, distortionless conditions, etc. Several recent papers have dealt with the definition and compensation of nonactive power [15]- [17], but the old contributions of Budeanu in frequency domain [3] and Fryze [4] in time domain remain 1549-8328/$25.00 © 2008 IEEE essential. The large number of papers published motivated by these two classic theories suggest that the work has not been finished. ...
... The multivectorial apparent power , can be given not only as in (9), but also in the form (14) where (15) (16) (17) In sinusoidal case, (8) can be expressed by (18) where and are now the Steinmetz classic phasors. The complex apparent power is defined by (19) where (20) and (21) are active and reactive powers, respectively. ...
In this paper, a generalization of the concept of electrical power for periodic current and voltage waveforms based on a new generalized complex geometric algebra (GCGA) is proposed. This powerful tool permits, in n -sinusoidal/nonlinear situations, representing and calculating the voltage, current, and apparent power in a single-port electrical network in terms of multivectors . The new expressions result in a novel representation of the apparent power, similar to the Steinmetz's phasor model, based on complex numbers, but limited to the purely sinusoidal case. The multivectorial approach presented is based on the frequency-domain decomposition of the apparent power into three components: the real part and the imaginary part of the complex-scalar associated to active and reactive power respectively, and distortion power, associated to the complex-bivector. A geometrical interpretation of the multivectorial components of apparent power is discussed. Numerical examples illustrate the clear advantages of the suggested approach.
... An APF can be improved without changing its design by adding more power-quality features such as compensating for voltage imbalance, dips, surges, flickers and dampening circuit resonances [10,11]. Even though the foregoing considerations raise the cost of harmonic mitigation, the additional energy requirements of the APF's inverter can be carried. ...
This work presents a way to handle the DC component of input signals for PLL and notch filter applications, which are utilized for filtering and synchronization. The input signal of a DC component may be due to some sort of malfunction, or it may be the result of the structure and restrictions of the measurement/conversion procedures. This part makes the system's loop oscillate at low frequencies and no filter can fully filter them out because that would significantly harm the system's dynamic response. The proposal involves augmenting the PLL structure with a new loop. It is basic architecturally and in contrast to a currently presented method and it does not detract from the algorithm's high-frequency filtering level. This Orthogonal Signal Generators (OSG) control algorithm is used for active power filter to maintain unity power factor, neutral current compensation using star/three single transformer & current harmonics mitigation. The MATLAB/Simulink results are demonstrated for the above stated Power Quality (PQ) problems.
... Novel reference current identification methods that perform effectively under a nonideal source have been proposed in the literature [62,[66][67][68]. A shunt active power filter, in general, cannot be used to correct unbalanced supply voltages resulting from upstream causes, to do so, a series active power filter which includes a series transformer at the point of common coupling (PCC) would be suitable [18,34]. ...
... The control strategy for a shunt active power filter (Fig.2) A three phase voltage inverter with current regulation is then used to inject the compensating current into the power line. There are some different methods for implementing the detection of harmonic currents [3], these methods were studied in symmetrical conditions in the literature. The aim of this paper is to qualitatively determine the differences between three of those methods under different conditions of mains voltage. ...
... The currents given in (28) can be considered as the unbalanced component of the currents ...
The main objective of this paper is to compare the applicability and performance of a switching compensa-tor when it is controlled by algorithms derived from the pq–Theory and from the Current’s Physical Components Power Theory (CPC-Theory) considering a micro-grid application. Compensation characteristics derived from each one of these set of power definitions are highlighted, and simulation results of test cases are shown. Special attention is put on the oscillating instantaneous real power, as it may produce torque oscillations or frequency variations in weak systems (micro-grids) generators. The oscillating instantaneous real power, as defined in the pq-Theory, gives the amount of energy oscillating between the source and the load, and its compensation using a switching compensator must have an energy storage element to exchange it with the load. The energy storage element can be easily calculated with the pq-Theory.
... Consequently, the oscillating nonactive components will yield zero instantaneous power. In other words, such cases of power decomposition are obtained when the time averaging interval is not equal to period but tends to zero [10], [11]. This means that two different approaches related to the power transfer for a given source voltage can be observed: unchanged average power transfer or unchanged instantaneous power transfer. ...
Based on the condition for the minimum rms value of line currents, a method for improving the power factor in power systems under asymmetrical and nonsinusoidal conditions is presented. This paper offers straightforward and convenient formulations of active currents for the three-phase four-wire, three-phase three-wire, and single-phase systems. Owing to the transformation matrix introduced in this paper, the formulation of active currents is valid regardless of whether the voltages and currents are balanced or unbalanced and it permits any point of the system to be chosen for the voltage reference. Observing the constraints related to the reactive compensators, the line current minimization procedure is used for the determination of optimal compensating capacitances for the three-phase four-wire, three-phase three-wire, and single-phase systems. The optimal reactive compensators based on up to six capacitors are proposed. The definitions of power factors before and after compensation are introduced. The influence analysis of nonactive power compensation on harmonic distortion of line currents has been also performed. Experimental results are obtained to confirm the validity and applicability of the proposed compensation procedure.
... The unused capacity of the PV inverter can then be put to use to produce opportunely reactive power. Then, the reactive power support and voltage regulation potential of PV PEIs could greatly benefit power system stability [1][2][3][4]. By utilizing the remaining capacity or slightly increasing the capacity of the inverter, PV systems can provide significant voltage/var support. ...
Over the last decade, various reasons have determined a continuous increase of grid-connected photovoltaic systems due to need of supplying the world rise demand for electric power. This gave rise to problems concerning the stability and safety of the utility grid as well as power quality issues. It has drastically changed the way in which the grid-connected photovoltaic systems should interact with the grid. In this context the purpose of this paper it is proposed a control methodology using the active and reactive power control strategy proposed by the authors in a previous paper in order to provide ancillary services to the grid to safeguard the reliability, the stability and the power quality of the electrical system. The simulations has been carry-out using Matlab/Simulink environment, demonstrating that the proposed control methodology is able to provide grid ancillary services according to a grid interconnection standard.
The increasingly extensive use of non-linear loads, mostly including static power converters, in large industry, commercial, and domestic applications, as well as the spread of renewable energy sources in distribution-generated units, make the use of the most efficient power quality improvement systems a current concern. The use of active power filters proved to be the most advanced solution with the best compensation performance for harmonics, reactive power, and load unbalance. Thus, issues related to improving the power quality through active power filters are very topical and addressed by many researchers. This paper presents a topical review on the shunt active power filters in three-phase, three-wire systems. The power circuit and configurations of shunt active filtering systems are considered, including the multilevel topologies and use of advanced power semiconductor devices with lower switching losses and higher switching frequencies. Several compensation strategies, reference current generation methods, current control techniques, and DC-voltage control are pointed out and discussed. The direct power control method is also discussed. New advanced control methods that have better performance than conventional ones and gained attention in the recent literature are highlighted. The current state of renewable energy sources integration with shunt active power filters is analyzed. Concerns regarding the optimum placement and sizing of the active power filters in a given power network to reduce the investment costs are also presented. Trends and future developments are discussed at the end of this paper. For a rigorous substantiation, more than 250 publications on this topic, most of them very recent, constitute the basis of bibliographic references and can assist readers who are interested to explore the subject in greater detail.
The paper is focused on presentation of a unified analytic method suitable for exact examinations of linear dynamical systems operating under composite periodic non-sinusoidal waveforms with excitations exhibiting possibly discontinuities. The main feature of this newly introduced approach lies in full release from the Gibbs effect that is immanently connected with applications of the Fourier series even in all cases whith the Fourier coefficients expressed as time functions. It has been demonstrated that the presented method makes possible the exact determination of the system's energy being equal to the surface of a loop on the energy phase plane with coordinates (q(t), u(t)) or equivalently (ψ(t), i(t)). Applying the BPR-N theorem it is possible to estimate the system energy without determining the instantaneous response of the system. This leads to choice of the form of an optimal excitation in the sense of energetic criterion. Energetic characteristics of periodic nonsinusoidal waveforms are established as an alternative to the up-to-now used mean value and root mean square value, respectively. The theoretical considerations are illustrated by results of suitable computer simulations of systems taken from the practice.
In the three-phase circuit at sinusoidal mode a constant and variable components of the vectorial instantaneous power (IP) define two new integrated powers: the power imbalance vector and the non-pulsed power vector. Together with the standard scalar powers of sinusoidal mode (the standard complex power and the complex pulsation power), these two vectorial powers determine power equation of unbalanced mode and pulsing mode. It is shown that under asymmetrical voltage the vectorial MM is zero only if the standard reactive power and the power imbalance equal to zero. The power factor is equal to unity. References 10, tables 2, figure 1.
Reactive power is the key controller in voltage regulation system. Distributed Energy Resources (DER) can be the solution to mitigate the voltage regulation problem with right control technique. DER can generate or consume reactive power with proper power electronics interface. It has also capacity to provide ancillary services. The new decentralize Adaptive technique has been implemented in this paper. Simulation results of adaptive method for different load condition satisfies the fast dynamic speed requirement without any oscillation and overshoot. In this paper the new methods for voltage regulation has been discussed which are Model Reference Adaptive System (MRAS), Direct and Indirect Self Tuning Regulator. These methods can solve the complex issue of voltage regulation in power system.
Traditional sinusoidal power theory is not feasible for non-sinusoidal condition. The existing non-sinusoidal instantaneous power theories have no clear physical meanings. To solve this problem, this paper presents a definition of instantaneous active and reactive power based on the parameter identification. The simplified equivalent model in time domain is built. Using the least squares approximation method, the approach of definition and measurement of instantaneous power is given. This definition has a distinct physical meaning. It is feasible for arbitrary non-sinusoidal voltage and current, especially for non-periodical waveforms. The theory is evaluated for linear, varying and non-linear loads in the presence of harmonics, showing the rationality and feasibility.
This paper is focused on the practical evaluation of two generalized theories of powers in phase coordinate system, namely generalized instantaneous reactive power and generalized instantaneous non-active power, by their implementation in the real time control of a three-phase three-wire shunt active power line conditioner through a dSPACE-based platform. Based on each theory concepts, specific blocks for reference current generation to achieve the global compensation were conceived first. Then, experimental tests were conducted to prove the ability of the active filtering system to compensate a nonlinear distorted and unbalanced load under nonideal voltage conditions. The good dynamics behaviour of the compensating system is illustrated too.
This paper is oriented towards implementation of the main theories of powers in the compensating current generation stage of a three-phase three-wire shunt active power system. The system control is achieved through a dSPACE 1103 platform which is programmed under the Matlab/Simulink environment. Four calculation blocks included in a specifically designed Simulink library are successively implemented in the experimental setup. The first two approaches, namely those based on the Fryze-Buchholz-Depenbrock theory and the generalized instantaneous reactive power theory, make use of phase quantities without any transformation of the coordinate system and provide the basis for calculating the compensating current when total compensation is desired. The others are based on the p-q theory concepts and require the direct and reverse transformation to/from the two-phases stationary reference frame. They are used for total compensation and partial compensation of the current harmonic distortion. The experimental results, in terms of active filtering performances, validate the control strategies implementation and provide arguments in choosing the most appropriate method.
Traditional sinusoidal power theory is not feasible for non-sinusoidal condition. The existing non-sinusoidal power theories have no clear physical meanings. To solve this problem, this paper presents a time-varying power theory based on the instantaneous sinusoidal expression of DFT (Discrete Fourier Transform). For arbitrary voltage and current signals, use the DFT to get their sinusoidal expression, and calculate the time-varying active power and the time-varying reactive power. This definition is feasible for any periodical and non-periodical signals. It has a distinct physical meanings, especially the time-varying reactive power can show the scale and direction of load's electromagnetic energy oscillation. It can embrace the sinusoidal power, Budeanu power and Fryze'active power. Finally, the rationality and feasibility of this time-varying power is demonstrated by theoretical analysis and work examples.
This paper is focused on the implementation of the different theories of powers and current decomposition methods in the compensating current calculation for three-phase three-wire shunt active filtering systems. They are grouped into two categories, depending on the type of coordinate system used in the processing measurements involved in calculations. The former is based on the phase coordinates system and includes the theories of Fryze, Fryze-Buchholz-Depenbrock as well as the so-called generalized theories of instantaneous reactive and non-active powers. The latter refers to the orthogonal reference frame-based approaches such as the p-q theory and id-iq method. The applicability of each theoretical approach in the control of a shunt active power filter was analyzed through a lot of simulations on a Matlab-Simulink platform purposely developed by authors. Both the operation of the active filtering system under sinusoidal and nonsinusoidal voltage conditions are taken into consideration. It is shown that all formulations based on the powers flow can lead to unity power factor after compensation when the supply voltage is not distorted. Finally, conclusions are drawn by analyzing the capability of each method to meet different compensation objectives in any conditions of the supply voltage and taking into consideration the complexity of the calculations required in implementation.
Grid-connected photovoltaic (PV) systems with power electronic interfaces can provide both real and reactive power to meet power system needs with appropriate control algorithms. This paper presents the control algorithm design for a three-phase single-stage grid-connected PV inverter to achieve either maximum power point tracking (MPPT) or a certain amount of real power injection, as well as the voltage/var control. The switching between MPPT control mode and a certain amount of real power control mode is automatic and seamless. Without the DC-to-DC booster stage, PV DC voltage stability is an important issue in the control design especially when the PV inverter is operating at maximum power point (MPP) with voltage/var control. The PV DC voltage collapse phenomenon and its reason are discussed. The method based on dynamic correction of the PV inverter output is proposed to ensure PV DC voltage stability. Simulation results of the single-stage PV system during system disturbances and fast solar irradiation changes confirm that the proposed control algorithm for single-stage PV inverters can provide appropriate real and reactive power services and ensure PV DC voltage stability during dynamic system operation and atmospheric conditions.
This paper proposes a plug-and-play control method to coordinate multiple distributed energy resources (DER or DE) to regulate voltages in future distribution systems with a high DE penetration. Theoretical analysis shows that there exists a corresponding formulation of the dynamic control parameters with multiple DEs to give the desired responses. Therefore, the proposed control method has a solid theoretical basis. The method is based on dynamically and adaptively adjusting DE control parameters to ensure that actual voltage responses follow the desired outputs. Also, it is based on local and the other DEs' voltages without the need of the full system data and extensive studies to tune the control parameters. Hence, the method is autonomous and adaptive for variable operational situations, and has the plug-and-play feature with a high tolerance to unavailable or inaccurate system data. Thus, it is suitable for broad utility application. Simulation results from various conditions, such as asynchronous start of multiple DEs, disappearance of the original disturbance in the middle of the control process, and operation in looped distribution systems, confirm the performance, validity, and flexibility of the proposed control method. The possible impact of communication latency on the performance of the proposed method is also discussed.
This paper investigates Peng's control strategy in harmonics compensation with the aim to reduce the size of DC link capacitor. A simple design is proposed to achieve the goal, i.e. implementing a DC voltage regulator to estimate the power loss of the converter and feedback that losses into the original Peng's control strategy. A three-phase, four-wire system which couple to some nonlinear loads is simulated for this study. Simulation results are presented to validate the effectiveness of the proposed design.
This paper presents the analysis and design of a 3-phase 4-leg (3P4L) unified series–parallel active filter (USPAF) with ultracapacitor energy storage (UCES) for improving the power quality in three-phase four-wire (3P4W) distribution system. The series and parallel active filter (AF) of 3P4L USPAF system are realized by four-leg voltage source inverters (VSIs) to a common dc-link capacitor. Due to its high power density, the UCES is well-suited to supply high power for short period of time. The objective of this paper is to enhance the unbalanced voltage sag mitigating capability of the 3P4L USPAF system by adding UCES, directly connected in the dc-link. This is achieved by injecting energy from the UCES to maintain the dc-link voltage constant. Thus, the proposed system is capable of mitigating unbalanced voltage sag with zero-sequence component in the source voltage and compensating harmonic, reactive power and unbalanced current of the load in 3P4W distribution systems. The proposed scheme is validated by an experimental prototype with a 1.93 F UCES bank and using dSPACE DS1103 real-time control platform in the laboratory. The experimental results show that the combined system offer improved performance to maintain the load voltage constant at its rated value during unbalanced voltage sag in the supply voltage.
This article analyzes the inefficiencies present in four wire electrical systems where linear unbalanced loads are connected. The new reference currents are proposed for the selective compensation of the inefficiencies using a three-legs shunt active power converter. The positive-, negative- and zero-sequence components of voltages and currents in load terminals determine the compensating currents that cancel the inefficient power flows. A new method for the control of the voltage unbalances in the split DC bus is proposed. Simulation and experimental results demonstrate how the proposed compensating currents improve efficiency in systems with voltage asymmetries and current unbalances.
The concept of differential protection based on current quantities has been discussed in many paper and researches. For certificating and inverting of currents and voltages through converter systems, there is no conventional current differential relay, which can compare current quantities, because they are different in form and frequencies. An overview over a new concept of differential protection for converters based on instantaneous power quantities will be discussed in this paper. To drive the power quantities a mathematical background of the space vectors will be introduced. A simple DC- Link is preceded in this paper and a power analysis description and simulation is derived using Matlab®/ SimulinkTM concerning a certain construction scheme of Power Differential Relay System. Finally a complete analysis of three phase fault in DC-Link Rectifier is discussed to ensure the ability of Power Differential Protection System to detect the fault in main and selectivity protection sections. Keywords—Space Vectors, Power Differential Relay (PDR), Short Circuit Power, Diode Recovery Energy, Detected Power Differential Signal (DPDS), Power Space Vector (PSV), Power Space Vector Protection Area (PSVPA).
This paper presents a new method of non-active power compensation in power systems under non-sinusoidal conditions. The basic idea of the compensation procedure stems from the condition for the minimum rms value of line currents. The application of optimization procedure, observing the above criterion, results in the required compensator. Three different compensators are derived: total non-active power compensator, compensator without energy storage, and reactive compensator. The paper introduces the factors which define the amount of active power in total power before and after the non-active power compensation. The compensation procedure is valid for single-phase and polyphase systems. Simulation results confirm the validity and applicability of the compensation procedure for a diversity of load currents.
This paper presents detailed analysis to compare and evaluate the performances of four control strategies for extracting the reference currents of shunt active power filter under distorted and unbalanced source and load conditions. The four controllers are based on instantaneous reactive power (p-q), d-q coordinate formulation (d-q), unity power factor (UPF), and perfect harmonic cancellation (PHC) . Detailed analysis and simulation results (performed with SimulinkMatlab) are used to highlight the advantages and limitations of each control approach.
This paper presents a new calculation method to obtain the reference currents for a selective shunt active power compensator (APC) with the capability of distinguishing between selective and global operating modes. This selective compensation operation is done through an identification of the current terms related to the physical phenomena that exist in electrical systems following a new equivalent conductance concept. Through this identification, this paper proposes the adequate set of reference currents that, used by a shunt APC (SAPC), achieve the selective cancellation of a desired nonefficient phenomenon. Furthermore, by combining the different current terms, it is possible to derive the sets of reference currents that allow the cancellation of a desired combination of nonefficient phenomena. By using these reference currents, a selective compensation feature is added to the SAPC control. An SAPC based on a three-phase three-leg inverter with a split dc bus has been implemented. The neutral wire of the electrical installation is connected to the midpoint of the dc bus, so the selective SAPC is able to work in four-wire electrical systems. The experimental results obtained demonstrate that the proposed selective compensation properly works in three-phase electrical systems with load-current unbalances, voltage asymmetries, and harmonic components. The electric quality is improved with the use of the proposed selective control based on this new equivalent conductance approach.
Many definitions have been formulated to characterize, detect, and
measure active and nonactive current and power for nonsinusoidal and
nonperiodic waveforms in electric systems. This paper presents
definitions and compensation of nonactive current from the compensation
standpoint and provides guidance on how to determine compensation
objectives and select detection parameters. The proposed definition is
valid to both single and multi-phase power systems. Clear and easy
guidance to determine objectives and design parameters of compensation
systems is provided
This paper presents a general control method that fully utilizes the inherent capability of AC-fed PWM converters to compensate for reactive and harmonic currents absorbed by other loads. For this purpose, suitable definitions of instantaneous active and reactive current and power terms are introduced. Simulated results demonstrate the capabilities of the proposed compensation method, which can also be implemented in existing systems, as only modifications of the control section are needed.
Based on a new definition of nonactive current/power, this paper presents the application of a parallel active filter for the compensation of nonperiodic currents. Analysis of the compensation characteristics required for a variety of nonperiodic currents such as those associated with arc furnaces is presented. In addition, the corresponding current rating and energy storage requirements of the compensator are also presented.
This paper proposes a novel power compensation algorithm in
three-phase four-wire power systems by using p-q-r theory. P-q-r theory
is compared with two previous instantaneous power theories, p-q theory
and cross-vector theory. P-q-r theory provides two-degrees of freedom to
control the system currents by only compensating the instantaneous
imaginary power without using any energy storage element. The definition
of powers maintains conservatism, and agrees well with the general
understanding of power. Simulation results show the superiority of p-q-r
theory both in definition and compensation
Many definitions have been formulated to characterize nonactive
power for nonsinusoidal waveforms in electrical systems, and no single,
universally valid power theory has been adopted as a standard for
nonactive power. Most of the nonactive power theories formulated thus
far have had a particular type of compensation in mind, which has
influenced the conventions used in the development of the definitions.
Because nonsinusoidal loads are expected to continue to proliferate
throughout electrical distribution systems, nonactive power theories
will only grow in importance for applications such as nonactive power
compensation, harmonic load identification, voltage distortion
mitigation, and metering. This paper presents a comprehensive technical
survey of the published literature on the topic and briefly outlines the
salient points of each of the different theories as well as each one's
applicability to active power filtering
Before the area of power electronics was developed, nonperiodic
currents occurred in distribution systems, apart from arc furnaces
supply, mainly during switching and faults. Now, such currents are
produced at normal operation of some power electronics equipment. Power
electronics enables very fast control of processes and energy flow.
Nonperiodic currents are a by-product of such a fast control.
Identification of nonperiodic currents and their compensation is the
subject of this paper. The paper discusses the main properties of
nonperiodic currents, provides their classification and introduces a
concept of coperiodic, noncoperiodic and quasi-periodic currents as well
as the concept of interharmonic noise and quasi-harmonics. The paper
provides fundamentals of quasi-periodic current compensation and
discusses a hybrid control algorithm of a hybrid compensator
This paper presents a discussion about the use of the
instantaneous active and reactive power theory (p-q theory) for the
compensation of nonperiodic currents in three-phase circuits. First, the
concept behind the term nonperiodic is discussed. A summary of the basic
points of the instantaneous power theory is presented and them some
examples of nonperiodic currents and their identification and
compensation by active filters are presented. This paper shows that it
is not possible to have at the same time a perfect compensation, where
the source currents are purely sinusoidal and the power flowing in the
circuit is constant. The user has to decide which condition has higher
priority and adapt the compensation characteristics of the active filter
This paper describes power electronics technology relevant to
active filtering and energy storage for the purpose of power
conditioning. The combination of active filtering and energy storage
leads to a versatile system in terms of compensation under nonperiodic
conditions. However, energy storage is much more difficult and costly in
realization than active filtering because modern science offers only
chemical action, electromagnetic or electrostatic field, and kinetic or
potential energy as viable ways of energy storage. This paper is focused
on the present status of active filters, and energy storage systems for
power conditioning, along with a 200 MJ/20-MW flywheel energy storage
system which was commercially installed on a 66 kV power system for the
purpose of line-frequency regulation in 1996
The paper deals with a comparison between AC and DC arc furnaces
taking into account power quality indices. The study is performed using
computer simulation based on the ATP program, assuming as reference a
real AC arc furnace plant. Flicker phenomenon, harmonic and
interharmonic distortion are evaluated for both DC and AC arc furnaces
Operation of rapidly varying loads such as AC and DC arc furnaces
in large industrial power systems will cause voltage flicker on the
utility system. System planning will help in determining the available
short-circuit duty at the point-of-common-coupling to keep the voltage
flicker within acceptable limits. Perceptible flicker limit curves are
useful in determining the amount of flicker in a system. Short-circuit
voltage depression calculation is one technique to estimate the amount
of expected flicker in a system. On-site field tests with equipment that
will accurately capture multiple frequencies will aid in measuring the
existing voltage flicker. The authors discuss flicker estimation and
field tests as well as harmonic filter tuning effects on voltage
flicker. The ultimate determination whether unacceptable voltage flicker
exists in a system will be complaints from customers served by the
utility system actually experiencing objectionable or noticeable flicker
This paper proposes a novel power compensation algorithm in three-phase four-wire systems by using p-q-r theory. The p-q-r theory is compared with two previous instantaneous power theories, p-q theory and cross vector theory. The p-q-r theory provides two-degrees of freedom to control the system currents by only compensating the instantaneous imaginary power without using any energy storage element. The definition of powers maintains power conservation, and agrees well with the general understanding of power. Simulation results show the superiority of p-q-r theory both in definition and compensation.
Flicker is a power quality problem that affects our daily lives. In this paper, the authors describe how voltage fluctuations may originate in the power system, but most frequently they are generated by the equipment or load connected to it, for example, arc furnaces, welders, etc.
Flicker is a power quality problem that affects our daily lives. In this paper, the authors describe how voltage fluctuations may originate in the power system, but most frequently they are generated by the equipment or load connected to it, for example, arc furnaces, welders, etc.
The conventional reactive power in single-phase or three- phase circuits has been defined on the basis of the average value concept for sinusoidal voltage and current waveforms in steady states. The instantaneous reactive power in three-phase circuits is defined on the basis of the instantaneous value concept for arbitrary voltage and current waveforms, including transient states. A new instantaneous reactive power compensator comprising switching devices is proposed which requires practically no energy storage components.
A generalized theory of instantaneous reactive power for
three-phase power systems is proposed in this paper. This theory gives a
generalized definition of instantaneous reactive power, which is valid
for sinusoidal or nonsinusoidal, balanced or unbalanced, three-phase
power systems with or without zero-sequence currents and/or voltages.
The properties and physical meanings of the newly defined instantaneous
reactive power are discussed in detail. A three-phase harmonic distorted
power system with zero-sequence components is then used as an example to
show reactive power measurement and compensation using the proposed
theory
Generalized instantaneous reactive power theory for three-phase power systemsSurvey of active and nonactive power definitions
- F Z Peng
- J S Lai
- L M Tolbert
- T G Habetler
F. Z. Peng and J. S. Lai, "Generalized instantaneous reactive power theory for three-phase power systems," IEEE Trans. Instrum. Meas., vol. 45, pp. 293–297, Feb. 1996. [9] L. M. Tolbert and T. G. Habetler, "Survey of active and nonactive power definitions," in Proc. IEEE Int. Power Electronics Congress, Acapulco, Mexico, 2000, pp. 73–79.
Definitions and compensation of nonactive current in power systems
- peng