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Abstract
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.
... It is possible thanks to that, opposite to the CPC theory [9], the GNP theory is formulated in the time domain. Thus, let us suppose that the load current in unbalanced non-sinusoidal systems with also non-periodic load current disturbances can be decomposed into the following components L L a L n L a L 1 r (12) where i L1r is the reactive current associated with the fundamental harmonic only, i L1u is the fundamental harmonic unbalanced current, i Lh is the harmonic current, and i Lnp is the non-periodic current containing all remaining non-active disturbances (subharmonics, interharmonics, stochastic). The question is whether the non-periodic load current components can be detected with reasonable accuracy by using the GNP theory. ...
... It was theoretically as well as in some experiments proofed [12]- [17] that the precision of the calculation of the currents i La , i Ln by using (6), (9) in unbalanced nonsinusoidal systems with non-periodic load currents is sufficient if T C is chosen to be 5-10 times that of the fundamental period. Contrary to that, for T C decreasing under 5 times that of the fundamental period (T c =T/2 is the lowest possible value), the non-periodic component of the load current is more and more pronounced in the current i La . ...
... 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). ...
... 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. ...
... where n is the order of existing harmonics in the current and voltage (odd numbers for power system), and m is the order of existing harmonics in the modulating signal (odd numbers for regular modulating signal), ∆ω(= 2πf m ) is the modulation frequency, and ω 0 is the power system frequency. The equivalent conductance of the load is calculated using equation Part I- (28). In this equation the denominator is always constant, assuming the calculation window (T ) is an integer multiple of the power system frequency period (T = lT 0 ). ...
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.
... It was shown [17] that the precision of the calculation of the currents i a , i n by using (2), (5) in unbalanced nonsinusoidal systems with non-periodic load currents is sufficient if T C is chosen to be 5-10 times that of the fundamental period. Let us demonstrate some basic attributes of the GNP theory on an example of the one phase voltage and current ...
... As for subharmonics, the lower their frequency is, the higher the value of T C should be for a sufficient compensation, Fig. 1. The full compensation of the subharmonic with the frequency ∆ω needs the averaging time interval T C = 2π/∆ω which, on the other hand, restricts the compensation dynamics in case of transient processes [17]. Another thing is that the energy storage requirement on a power electronics-based compensator is higher for lower T C . ...
The principle and analysis of usage of the generalized non-active power theory for the parallel compensation of periodic and non-periodic current disturbances is presented in the paper. A non-linear unbalanced load generating periodic as well as non-periodic stochastic currents connected to an unsymmetrical non-sinusoidal voltage source is considered.
... Different non-active power theories in the time domain have been discussed in [23]. The generalized non-active power (GNAP) theory was applied for the compensation of the periodic and non-periodic load current with the parallel AF [24][25][26], the static synchronous compensator (STATCOM) [27] and voltage and current unbalance compensation using an active filter [28]. The theory does not specify the characteristics of the voltage and current, they can theoretically be any waveshape. ...
... The fourth leg reference voltage v * no is defined by Eq. (21) to achieve the optimum switching sequence using an offset voltage concept [32]. Then, all the inverter phase output terminal reference voltages (v * ao , v * bo , v * co ) with respect to the virtual dc-link midpoint of the split capacitor ("o" point) are defined in Eq. (24). ...
... Também Tolbert et. al. [21] e Xu et. ...
... Non-linear non-stationary currents (also known as non-periodic currents) are known to be problematic to power systems. Arc furnaces, cycloconverters, adjustable speed drives, as well as transient disturbances are the typical sources that generate non-linear nonstationary currents [Czarnecki, 2000; and Tolbert et al., 2003]. This also includes currents with sub-harmonics as well as super-harmonics [Tlusty et al., 2012]. ...
This paper describes an active power filter (APF) control strategy, which
eliminates harmonics and compensates reactive power in a three-phase four-wire
power system supplying non-linear unbalanced loads in the presence of
non-linear non-stationary currents. Empirical Mode Decomposition (EMD)
technique developed as part of the Hilbert-Huang Transform (HHT) is used to
singulate the harmonics and non-linear non stationary disturbances from the
load currents. The control strategy for the APF is formulated by hybridizing
the so called modified p-q theory with the EMD algorithm. A four-leg
split-capacitor converter controlled by hysteresis band current controller is
used as an APF. The results obtained are compared with those obtained with the
conventional modified p-q theory, which does not possess current harmonics or
distortions separation strategy, to validate its performance.
... If a shunt active filter is used as the compensator, then it must inject the current components that are the difference between the desired source current and the demanded load current. The work here defines active and nonactive currents from a compensation point of view and, in particular, examines how to apply this definition when nonperiodic load currents are present in the power system [12], [13]. ...
The STATCOM based on voltage source converter is used for voltage regulation in transmission and distribution systems. In this paper, the integration and control of energy storage systems such as supercapacitor into a distribution system STATCOM (D-STATCOM) with voltage controller is developed to enhance power quality and improve distribution system reliability. This paper develops the control concepts to charge/discharge the supercapacitor by the D-STATCOM, and validates the performance for an integrated D-STATCOM/supercapacitor system for improving distribution system performance. The potential performance improvements are verified by simulation results for rapidly varying arc-furnace loads for voltage flicker mitigation, by supplying fluctuating real power by the D-STATCOM/supercapacitor system.
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 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
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.
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.
Evaluation of instantaneous power terms in multi-phase systems: techniques and application to power conditioning equipment ETEP Reactive power and harmonic compensation based on the generalized instantaneous reactive power theory for three-phase power systems
- L Rossetto
- P Tenti
L. Rossetto, P. Tenti, " Evaluation of instantaneous power terms in multi-phase systems: techniques and application to power conditioning equipment, " ETEP, vol. 4, no. 6, Nov./Dec. 1994. F. Z. Peng, J. S. Lai, " Reactive power and harmonic compensation based on the generalized instantaneous reactive power theory for three-phase power systems, " Proceedings of the 7th Intemational Conference on Harmonics and Quality of Power, Las Vegas, USA, 1996, pp. 83-89.
Survey of active and non-active power Acapulco IEEE Intemational Power Electronics Congress Instantaneous Power Compensation in Three-phase Systems by Using p-q-r Theory
- L M Tolbert
- T G H Habetler
- F Kim
- B Blaabjerg
- J Bak-Jensen
- Choi
L. M. Tolbert, T. G. Habetler, " Survey of active and non-active power Acapulco, Mexico, 2000, pp. 73-79. definitions, " IEEE Intemational Power Electronics Congress, [lo] H. Kim, F. Blaabjerg, B. Bak-Jensen, J. Choi, " Instantaneous Power Compensation in Three-phase Systems by Using p-q-r Theory, " ZEEE Transactions on Power Electronics, vol. 17, no. 5, Sep. 2002, pp. 701-710.
Reactive power and harmonic compensation based on the generalized instantaneous reactive power theory for threephase power systems
- F Z Peng
- J S Lai
F. Z. Peng, J. S. Lai, " Reactive power and harmonic compensation
based on the generalized instantaneous reactive power theory for threephase power systems, " Proceedings of the 7th International Conference
on Harmonics and Quality of Power, Las Vegas, USA, 1996, pp. 83-
89.