Fig 1 - uploaded by Sergio Augusto Oliveira da Silva
Content may be subject to copyright.
Conventional PLL structures a Block diagram of the PLL basic scheme b Power-based pPLL for three-phase systems (3pPLL) c Control model of the 3pPLL
Source publication
This study proposes phase-locked-loop (PLL) algorithms, which are employed to improve the performance related to the estimation of the phase angle, as well as the frequency, in three-phase systems under utility voltage disturbances. The proposed PLL schemes are based on the three-phase instantaneous active power (3pPLL), which is composed of non-au...
Contexts in source publication
Context 1
... block diagram of a conventional PLL structure is shown in Fig. 1a, where v i , v d , v f and v o represent, respectively, the PLL input reference, the phase error, the voltage controlled oscillator (VCO) input and output signals. It is basically composed of three distinct parts: the phase-detector (PD), the loop filter and the VCO [28]. In most cases, PLL algorithms differ from each other in the way ...
Context 2
... conventional three-phase power-based PLL (3pPLL), which is based on the instantaneous active power theory for three-phase systems is shown in Fig. 1b, in which its operating principle consists in cancelling the DC component ( p ′ ) of the fictitious instantaneous power p′. It means that, when the DC component of p ′ is equal to the PLL reference ( p* = 0), the currents i ′ a and i ′ c will be in quadrature with the respective fundamental components of the input line-to-neutral ...
Context 3
... measured three-phase voltages (v a, b, c ) represent the input signals of the 3pPLL system, as shown in Fig. 1b. The dynamic of the PLL system will set the output of the PI controller to the angular frequency reference ( ˆ v = 2p f s ), where f s is the utility nominal frequency. The anglê u pll is obtained by the integration of the angular frequency referencê v that will be identical to the utility frequency ω s . Thus, the anglê u pll is used ...
Context 4
... the simplified 3pPLL model is shown in Fig. 1c, which replaces the 3pPLL control diagram of Fig. 1b. For small values of Δθ, the term sin(Δθ) behaves linearly, that is sin(Δθ) ≅ ...
Context 5
... the simplified 3pPLL model is shown in Fig. 1c, which replaces the 3pPLL control diagram of Fig. 1b. For small values of Δθ, the term sin(Δθ) behaves linearly, that is sin(Δθ) ≅ ...
Context 6
... most applications involving power line conditioning, the harmonic components existent in the utility grid voltage should be rejected. Since the 3pPLL algorithm shown in Fig. 1b has limited harmonic rejection capability, AFs can be used as a way of improving the 3pPLL robustness associated with the utility grid harmonic ...
Context 7
... section, the proposed AF-PSD-3pPLL schemes shown in Figs. 2c and d are experimentally evaluated by using the digital signal processor (DSP TMS320F28335, floating-point, 150 MHz), operating with a sampling frequency of 60 kHz. The performances of the AF-PSD-3pPLL algorithms are compared with the performance obtained from the conventional 3pPLL (Fig. 1b). In the experimental setup, a personal computer (PC) is used to generate the programming codes related to the PLL algorithms, as well as the communication with the DSP during the programme execution. Additionally, the PC is used to configure the AC power source in order to emulate the utility grid disturbances. The following utility ...
Citations
... It has been noted that a lot of emphasis is given to the proper design of filter and PD blocks (which helps extract the fundamental positive sequence component) while tuning these advanced PLLs (i.e., MRF-PLL, DDSRF-PLL, and MSRF-PLL). However, under high grid perturbations, proper phase sequence signal extraction is not feasible due to non-linearity that is discovered during signal alterations [21]. ...
Keywords: Modified synchronous reference frame Negative feedback phase-locked loop Power quality Shunt active power filter Total harmonic distortion A B S T R A C T The use of nonlinear devices introduces current and voltage harmonics into power distribution networks. The presence of harmonics, an undesirable power quality issue, causes transformer overheating, malfunctioning of sensitive loads, power losses, and significantly reduced distribution system efficiency. Therefore, harmonics mitigation in power systems has become absolutely essential and is widely addressed, utilizing shunt active power filters (SAPFs) around the globe. The performance of SAPF in generating adequate compensating current depends on the working of three control loops used for the purpose of reference current generation, dc-link voltage control, and switching pulse generation. The existing approaches for reference current generation suffer from inherent complexity and the inability to extract positive sequence signals required for obtaining synchronizing angle during source disturbance conditions. Therefore, this paper proposes a novel negative feedback phase-locked loop-based modified synchronous reference frame technique to overcome the drawback of the existing approaches. The effectiveness of the proposed approach is investigated under ideal and non-ideal grid voltage conditions with different load perturbations. The proposed control strategy is first tested using a number of simulation-based experiments and, thereafter, validated using OPAL-RT 4510 real-time digital simulator. Compared to other existing approaches, the proposed technique has offered improved results in terms of reduced total harmonics distortion.
... The PLL is one of the best control systems to synchronise the converter to the grid. Regardless of its ease of implementation, the PLL can be customised to deal with disturbances such as dc offset, harmonics, and unbalanced grid voltage sags [10]- [12]. Under unbalanced grid faults, the second harmonic oscillations (2ω 0 ) can be observed, which cannot be entirely attenuated by PI controllers, and causes steadystate errors. ...
As the number of converter-based renewable generations in the power system is increasing, the inertia provided by the synchronous generators is reducing, which in turn is reducing the stability margins of the power system. In order to assess the large-signal stability, it is essential to model the wind power plant connections accurately. However, the actual EMT models are often unavailable, black-boxed, or computationally too heavy to model in detail. Hence, simplified reduced-order models (ROMs) resembling the actual system behaviour have gained prominence in stability studies. In this regard, an improved WT ROM was proposed to investigate large signal stability during unbalanced grid faults. The methodology presents a systematic way to model the coupled sequence components of the WT ROM for various grid faults. Based on the studies carried out in this paper, it is observed that post unbalanced grid disturbances the proposed WT ROM correctly tracks the angle and frequency, and its trajectory is a good match when compared to a detailed simulation model in PSCAD.
... The FFCLs were experimentally evaluated using a UPQC prototype setup based on the power circuit shown in Fig. 1(a). Digital signal controllers (DSC TMS320F28335) were used in the UPQC implementation in which all the controllers, algorithms for generating the control references, and the phaselocked loop system [16] were embedded. The power circuits of the series and parallel inverters were composed of IGBT modules (SK40GB 123 Semikron) and their drivers. ...
This paper proposes feed-forward control loops that accelerate the dynamic responses of both the dc-bus voltage and the compensated grid/input currents of a three-phase unified power quality conditioner (UPQC) under the occurrence of voltage sags/swells. The strategy adopted in this paper to control the UPQC is implemented by controlling the input currents and the output voltages for being in phase with their respective input voltages (grid voltages). Since the input currents and voltages are in phase, the UPQC series converter will furnish active power to the system during voltage sags. Thus, to maintain the system power balance, this active power is absorbed by the UPQC parallel converter. In contrast, under a voltage swell event, the series converter absorbs active power and furnishes it to the load through the parallel converter. Therefore, in both mentioned power quality events, the amplitudes of the UPQC input currents must be controlled appropriately to regulate the dc-bus voltage, prevent sudden dc-bus voltage transients, and perform the system power balance as fast as possible. Simulation and experimental results are achieved to present the effectiveness of the proposed feed-forward control loops.
... The mathematical modeling of inverters, these particular algorithms, voltage controllers (DC bus and parallel converter) in addition to current controllers (series converters) are shown in detail in [41,58]. The phase locked loop (PLL) strategy, that is utilized for the useful detection and synchronization of the phase angle, is described in [63]. ...
This paper presents a comprehensive study that includes the sizing and power flow by series and parallel inverters
in a distributed generation system (DGs) that integrates the system of hybrid wind photovoltaic with a unified
power quality conditioner (UPQC). In addition to supplying active power to the utility grid, the system of
hybrid wind photovoltaic functions as a UPQC, compensating reactive power and suppressing the harmonic load
currents. Additionally, the load is supplied with harmonic-free, balanced and regulated output voltages. Since PV�Wind-UPQC is established on a dual compensation scheme, the series inverter works like a sinusoidal current
source, while the parallel inverter works like a sinusoidal voltage source. Consequently, a smooth alteration from
interconnected operating modes to island operating modes and vice versa can be achieved without load voltage
transients. Since PV-Wind-UPQC inverters handle the energy generated through the hybrid wind photovoltaic
system and the energy demanded through the load, the converters should be sized cautiously. A detailed study of
the flow of power via the PV-Wind-UPQC is imperative to gain a complete understanding of the system operation
and the proper design of the converters. Thus, curves that allow the sizing of the power converters according to the
power flow via the converters are presented and discussed. Simulation results are presented to assess both steady
state and dynamic performances of the grid connected hybrid system of PV-Wind-UPQC. This investigation is
verified by simulating and analyzing the results with Matlab/Simulink.
... (1) e current i L d consists of the harmonic and active constituents of the load currents, where cosθ and sinθ are the coordinates of the rotating unit vector. A PLL [52] is utilized to evaluate the phase angle of the line voltage θ � θ pll . e average value of i L d (i L d dc ) is obtained with a low pass filter (LPF), so that i L d dc in SRF are active constituents of abc load currents. ...
... where v dc 1 and v dc 2 represent the dc bus voltage of NPC inverter, while i wind−pv represents the current of the wind photovoltaic system; and V s pk and I s pk are peak magnitude of mains voltage and current, correspondingly, so that V s pk is assessed using the PLL scheme [52]. ...
This work presents a distributed generation system (DG) that combines system of a wind turbine (WT) and photovoltaic (PV) using a unified power quality conditioner (UPQC). Along with providing active power (AP) to the utility grid, Wind-PV-UPQC improves PQ indicators, for example, voltage drops/surges, harmonics of grid voltages, and PF. Since Wind-PV-UPQC depends on dual compensation scheme, the parallel converter works as a sinusoidal voltage source, while the series converter works as a sinusoidal current source. In this way, a smooth transition from grid operation to island operation and vice versa can be achieved without load voltage transitions. In addition, in order to overcome the problems through abrupt solar radiation or wind speed variations, a faster power balance is achieved between the wind turbines, the PV array, and the grid, as FFCL pursue the production of the current references of series converter. Consequently, the dynamic reactions of the converter currents and the voltage of dc bus are enhanced. A comprehensive analysis of flow of the AP through the converters is done to ensure a proper understanding of how Wind-PV-UPQC works. Finally, the simulation results are shown to estimate the dynamic and static performance of Wind-PV-UPQC in conjunction with the power distribution system.
... The current i Ld s formed by the load current harmonic and real components, here cosθ and sinθ are the coordinates of the rotating unit vector. A PLL [44] is using to gauge the phase angle of the voltage of source θ = θ pll . The mean of i Ld (i Ld dc ) is attained with a low pass filter (LPF) such that i Ld dc are real components of the abc load currents. ...
Emerging trends and advances in techniques in power electronics, Unified Power Quality Conditioner (UPQC) has a superior performance compared to other methods. The paper proposes the application of a ANN based UPQC to enhance the power quality of a three-phase Low-voltage network connected to a hybrid distribution generation (DG) system. The proposed work emphases the detailed performance analysis of a distributed generation system that integrates a solar PV and wind energy system by utilizing Unified Power Quality Conditioner (UPQC) with an artificial neural network (ANN) controller with respect to proportional-integral (PI) controller. The core objective of the proposed ANN is to offer good steady and dynamic state performance compared to the PID controller. The system called UPQC-ANN-RE feeds energy generated by a photovoltaic array and a wind turbine into the electrical grid and loads attached to a system of 3-phase 4-wire electrical distribution. In addition to inserting active/real power in the utility grid, the system of UPQC-ANN-RE functions as a UPQC, improving power quality signs e.g., voltage and current harmonics and power factor. A detailed analysis of the active-real power flow by converters is carried out to allow a good understanding of the operation of the UPQC-ANN-RE. The simulation outcomes are presented to assess the dynamic and steady state performance of the system of UPQC-ANN-RE connected to an electrical distribution system and to compare the consequences with the PI controller.
... The dqCDSC is used to tackle harmonic rejection using five types of DSC operators in the dq-frame [16]. Each type rejects a specific pattern of harmonics, from which dqCDSC 4,8,16,32 and dqCDSC 2,4,8,16,32 have the best capability for harmonic rejection, but they suffer from the slow transient response. With the aim of overcoming this problem, a proportional-integral-derivative (PID) controller is used in [16] to improve the dynamic response and increase bandwidth without affecting stability. ...
... The PLL introduced in [19] is based on a hybrid filter with dual adaptive notch filters (DNANF) to reject the DC offset and a dqCDSC 4,24 to separate either the positive or negative sequences of the grid voltage and reject the high-frequency harmonics. The dqCDSC 4,24 can eliminate the fundamental frequency negative sequence (FFNS) and the non-triple odd harmonics faster than dqCDSC 2,4,8,16,32 [19]. Nevertheless, it cannot reject the odd triple harmonics; its dynamic response is relatively slow. ...
The cascaded delayed signal cancelation (CDSC) method has attracted much attention recently as an efficient filtering technique to improve synchronous reference frame phase-locked loop (PLL) performance in grid synchronization under adverse grid conditions. The CDSC-based PLL suffers from slow transient response. Therefore, this study proposes a solution for grid synchronization under abnormal conditions utilizing an arbitrary time-delay operator to mitigate the DC offset and frequency adaptive CDSC operators for harmonic filtering. An accurate small-signal model was derived, opening the door to design the loop filter. The coefficient diagram method was adopted to systematically design the gains of the proportional–integral controller and a lead–lag compensator, yielding a faster dynamic response than the symmetrical optimum method-based design. The proposed PLL effectiveness was verified numerically under abnormal conditions, showing better dynamic and steady-state performance than other related PLLs. The proposed PLL requires less than two grid cycles to synchronize without ripples, meeting the grid code's requirement.
... The range of phase error δ is (−0.00960 • , 0.00244 • ), which confirms the accuracy of the simplified Equation (8). When the grid frequency is equal to the nominal value, the phase error δ is equal to 0. The output phase error of the PLL in Figure 8 is equal to ∠G . ...
... Define ω g = ω n + Δω g , where Δω g denotes the deviation of the grid angular frequency ω g from the nominal value. According to (8), the phase corrector can be approximated as ...
The fourth‐order generalised integrator is very suitable for single‐phase phase‐locked loop because it can provide orthogonal signal conveniently and block harmonic voltages effectively. In the conventional fourth‐order generalised integrator based phase‐locked loop, the resonance frequency of fourth‐order generalised integrator needs to be adjusted according to the grid frequency. To improve the phase‐locked loop performance, a non‐adaptive fourth‐order generalised integrator is suggested for single‐phase system, and this paper presents a correction method. According to the estimated grid frequency, the amplitude imbalance and phase error caused by non‐adaptive fourth‐order generalised integrator can be calculated, and two adaptive units are added to deal with the problems. Moreover, the small‐signal model of the proposed phase‐locked loop is carried out, and the control parameters are tuned. Compared to conventional fourth‐order generalised integrator based phase‐locked loop, the proposed phase‐locked loop shows a better performance, which is verified through simulation and experimental results.
... In the present study, φ is estimated using the three-phase power phase-locked loop (PLL), as proposed in. 27 This PLL-based tool is generally referred to as AF-PSD-3pPLL. In this scheme, three adaptive filters (AF) and a positive sequence detector (PSD) are functioning concurrently with the power PLL tool. ...
Stabilization of DC‐link voltage is indispensable for the satisfactory operation of three‐phase electronically coupled photovoltaic (PV) system. Practically, a challenge is to promptly and effectively settle the DC‐link voltage with minimum peak magnitude and settling time to its pre‐disturbance level when exposed to disturbances in the load and solar insolation level. The classical methods of DC‐link voltage stabilization employ a proportional‐plus‐integral (PI) compensator, and its gain coefficients are modulated through a cumbersome trial‐and‐error approach. Nevertheless, this approach does not yield superior results, especially under the wide interruptions in operating conditions due to nonlinear and time‐varying characteristic of the PV module. These concerns have resulted in the emergence of multiple meta‐heuristic techniques to optimally tune PI compensator gain coefficients. Nevertheless, most of these methods call for the ingrained paradox between computational efficiency and dynamic performance. Driven by this drawback, a proposal based on grey wolf optimizer (GWO‐PI) is described in this paper to serve the following control targets: (a) be able to improve harmonic filtering with computational effectiveness, and (b) to ensure superior performance under exposure to interferences in the load and solar insolation level. Good agreement in MATLAB/Simulink simulation studies and experimental evaluations establish that the proposed GWO‐PI outperforms the existing standardized optimization techniques such as particle swarm optimization (PSO‐PI) and gravitational search algorithm (GSA‐PI) in aspects of peak magnitude and settling time. Besides, it practically enables an improved harmonic filtering feature and complies with stringent harmonic distortion limit recommended in the IEEE revised standard 519‐2014.
... As a result, the conventional modified PLL circuit has very poor performance for highly distorted and unbalanced system voltages. Additionally, proper extraction of phase sequence signal is not feasible through adaptive filter-based phase detector (Bacon and da Silva, 2015;Yang et al., 2013) under extreme grid perturbations as nonlinearity is detected during signal alteration. With aforesaid views, this paper suggests a reorganization of the conventional modified PLL structure by means of a feedback integral loop present in low pass filter and a nonlinear adaptive-filter type phase detector circuit existing in the phase detector block in UPQC. ...
This paper proposes a hybrid fuzzy control strategy comprising both Takagi-Sugeno fuzzy and Mamdani fuzzy along with novel feedback integral phase-locked loop based modified synchronous reference frame for unified power quality conditioner for power quality enhancement in power distribution network. The hybrid fuzzy controller can vary the gain nonlinearly for controlling dc-bus capacitor voltage of unified power quality conditioner, which limits the dc-bus voltage deviations during the load and supply voltage turbulences. Moreover, the proposed novel feedback integral phase-locked loop system is employed to improve the grid synchronization performance of unified power quality conditioner by considering the feedback integral loop and nonlinear adaptive-filter type phase detector approach. As a consequence, the proposed feedback integral phase-locked loop system can extract the positive sequence signal perfectly during power system disturbances. Additionally, the novelty of modified synchronous reference frame control technique relies upon nonintervention with low pass filter as well as high pass filter. Hence, the proposed control technique quickly and accurately extracts the reference signal from the distorted power system. The efficacy of the proposed control technique is justified through a real-time Opal-RT Hardware underneath different states of power system and compared with both conventional modified phase locked loop system and Takagi-Sugeno fuzzy with synchronous reference frame-based control system.
