Control Of Shunt Active Power Filter Research Articles

Novel Control Strategy for a UPQC under Distorted Source and Nonlinear Load Conditions

This paper proposes a novel control strategy for a unified power quality conditioner (UPQC) including a series and a shunt active power filter (APF) to compensate the harmonics in both the distorted supply voltage and the nonlinear load current. In the series APF control scheme, a proportional-integral (PI) controller and a resonant controller tuned at six multiples of the fundamental frequency of the network (<TEX>$6{\omega}_s$</TEX>) are performed to compensate the harmonics in the distorted source. Meanwhile, a PI controller and three resonant controllers tuned at <TEX>$6n{\omega}_s$</TEX>(n=1, 2, 3) are designed in the shunt APF control scheme to mitigate the harmonic currents produced by nonlinear loads. The performance of the proposed UPQC is significantly improved when compared to that of the conventional control strategy thanks to the effective design of the resonant controllers. The feasibility of the proposed UPQC control scheme is validated through simulation and experimental results.

Approximated fuzzy logic controlled shunt active power filter for improved power quality

AbstractShunt active power filters have been widely used for power quality improvement. With the advancement in artificial intelligence techniques, the applications of fuzzy logic‐based control systems have increased manifolds. This paper proposes a reduced rule fuzzy logic controller (FLC) in the voltage control loop of a shunt active power filter (APF), which is approximating a conventional large rule FLC. The difference between the controlled outputs of two controllers is compensated by proposed compensating factors. The dynamic response and harmonic compensation performance of proposed 4‐rule approximated fuzzy logic controller (AFLC) is compared with 25‐rule FLC. A three‐phase shunt APF is used for harmonic and reactive power compensation. The proposed scheme is tested with randomly varying single and multiple non‐linear loads. The simulation results presented under transient and steady‐state conditions confirm that the proposed 4‐rule AFLC efficiently approximates the 25‐rule FLC. The proposed control methodology takes less computational time and computational memory as the numbers of rules are reduced significantly.

Artificial neural network-based harmonics extraction algorithm for shunt active power filter control

This paper presents a harmonics extraction algorithm using artificial neural network methods. The neural network algorithm was used due to the simpler calculation process compared with conventional method such as fast Fourier transform (FFT). Two types of neural network, i.e., multi-layer perceptron (MLP) and radial basis function (RBF) were employed to extract harmonics current component from its distorted wave current. Further, the extracted harmonics current was used as reference current for shunt active power filter (APF) control. This paper compared the performance of MLP and RBF for harmonics extraction. The advantages of RBF are simpler shape of the network and faster learning speed. Unfortunately, the RBF need to be trained recursively for various harmonics component. MLP can be used to extract various harmonics component in specific data range but need large number of data training hence slower training process.

A Novel Control Strategy of Three-phase, Four-wire UPQC for Power Quality Improvement

The current paper presents a novel control strategy of a three-phase, four-wire Unified Power Quality (UPQC) to improve power quality. The UPQC is realized by the integration of series and shunt active power filters (APF) sharing a common dc bus capacitor. The realization of shunt APF is carried out using a three-phase, four-leg Voltage Source Inverter (VSI), and the series APF is realized using a three-phase, three-leg VSI. To extract the fundamental source voltages as reference signals for series APF, a zero-crossing detector and sample-and-hold circuits are used. For the control of shunt APF, a simple scheme based on the real component of fundamental load current (I CosΦ) with reduced numbers of current sensors is applied. The performance of the applied control algorithm is evaluated in terms of power-factor correction, source neutral current mitigation, load balancing, and mitigation of voltage and current harmonics in a three-phase, four-wire distribution system for different combinations of linear and non-linear loads. The reference signals and sensed signals are used in a hysteresis controller to generate switching signals for shunt and series APFs. In this proposed UPQC control scheme, the current/voltage control is applied to the fundamental supply currents/voltages instead of fast-changing APF currents/voltages, thus reducing the computational delay and the required sensors. MATLAB/Simulink-based simulations that support the functionality of the UPQC are obtained.

Approximated Simplest Fuzzy Logic Controlled Shunt Active Power Filter for Current Harmonic Mitigation

This paper examines the size reduction of the fuzzy rule base without compromising the control characteristics of a fuzzy logic controller (FLC). A 49-rule FLC is approximated by a 4-rule simplest FLC using compensating factors. This approximated 4-rule FLC is implemented to control the shunt active power filter (APF), which is used for harmonic mitigation in source current. The proposed control methodology is less complex and computationally efficient due to significant reduction in the size of rule base. As a result, computational time and memory requirement are also reduced significantly. The control performance and harmonic compensation capability of proposed approximated 4-rule FLC based shunt APF is compared with the conventional PI controller and 49-rule FLC under randomly varying nonlinear loads. The simulation results presented under transient and steady state conditions show that dynamic performance of approximated simplest FLC is better than conventional PI controller and comparable with 49-rule FLC, while maintaining harmonic compensation within limits. Due to its effectiveness and reduced complexity, the proposed approximation methodology emerges out to be a suitable alternative for large rule FLC.

병렬 능동전력필터 위치에 따른 전기철도 AT급전 시스템의 전기품질 비교

This paper presents a power quality compensation of the autotransformer-fed railway system using Matlab/SimPowerSystem and especially investigates two installation methods of the shunt active power filter (SAPF) along the autotransformer-fed railway systems; one configuration describes the SAPF installed at the substation and the other is the SAPF at the sectioning post. Also, the novel SAPF control algorithms based on the synchronous reference frame are proposed. A comparative study on two SAPF configurations and the corresponding control algorithms is investigated comprehensively through the case study.

A control strategy based on UTT and I Cos&amp;#920 theory of three-phase, fourwire UPQC for power quality improvement

This paper presents a control strategy for a three-phase four-wire Unified Power Quality (UPQC) for an improvement of different power quality (PQ) problems. The UPQC is realized by integration of series and shunt active power filters (APFs) sharing a common dc bus capacitor. The shunt APF is realized using a thee-phase, four leg voltage source inverter (VSI) and the series APF is realized using a three-phase, three legs VSI. A control technique based on unit vector template technique (UTT) is used to get the reference signals for series APF, while ICosO theory is used for the control of Shunt APF. The performance of the implemented control algorithm is evaluated in terms of power-factor correction; load balancing, neutral source current mitigation and mitigation of voltage and current harmonics, voltage sag and swell and voltage dips in a three-phase four-wire distribution system for different combination of linear and non-linear loads. In this control scheme, the current/voltage control is applied over the fundamental supply currents/voltages instead of fast changing APFs currents/voltages, thereby reducing the computational delay and the required sensors. MATLAB/Simulink based simulations results are obtained, which support the functionality of the UPQC.

A Control Strategy Based on UTT and ISCT for 3P4W UPQC

This paper presents a novel control strategy of a three- phase four-wire Unified Power Quality (UPQC) for an improvement in power quality. The UPQC is realized by integration of series and shunt active power filters (APFs) sharing a common dc bus capacitor. The shunt APF is realized using a thee-phase, four leg voltage source inverter (VSI) and the series APF is realized using a three-phase, three leg VSI. A control technique based on unit vector template technique (UTT) is used to get the reference signals for series APF, while instantaneous sequence component theory (ISCT) is used for the control of Shunt APF. The performance of the implemented control algorithm is evaluated in terms of power-factor correction, load balancing, neutral source current mitigation and mitigation of voltage and current harmonics, voltage sag and swell in a three-phase four-wire distribution system for different combination of linear and non-linear loads. In this proposed control scheme of UPQC, the current/voltage control is applied over the fundamental supply currents/voltages instead of fast changing APFs currents/voltages, there by reducing the computational delay and the required sensors. MATLAB/Simulink based simulations are obtained, which support the functionality of the UPQC. MATLAB/Simulink based simulations are obtained, which support the functionality of the UPQC.

Fuzzy logic controller for three-level shunt active filter compensating harmonics and reactive power

In this paper, the three-level inverter is used as a shunt active power filter, making use of the multilevel inverter advantages of low harmonic distortion, and reduced switching losses. This PWM inverter is employed as shunt APF compensating reactive power and suppresses harmonics drawn from a nonlinear load. Most previously reported three-phase active power filters are based on two-level inverters with conventional controllers requiring a complex and a complicated mathematical model. In order to overcome this problem a fuzzy logic controller applied and extended to a three level shunt APF is proposed. In this paper, fuzzy logic control algorithm is proposed for harmonic current and inverter dc voltage control to improve the performances of the three levels active power filters. The MATLAB Fuzzy Logic Toolbox is used for implementing the fuzzy logic control algorithm. The obtained results showed that, the proposed shunt active power filter controller have produced a sinusoidal supply current with low harmonic distortion and in phase with the line voltage.

New digital reference current generation for shunt active power filter under distorted voltage conditions

In this paper, a new reference current computation method suitable for shunt active power filter control under distorted voltage conditions is proposed. The active power filter control is based on the use of self-tuning filters (STF) for the reference current generation and on a modulated hysteresis current controller. This active filter is intended for harmonic compensation of a diode rectifier feeding a RL load under distorted voltage conditions. The study of the active filter control is divided in two parts. The first one deals with the harmonic isolator which generates the harmonic reference currents and is experimentally implemented in a DS1104 card of a DSPACE prototyping system. The second part focuses on the generation of the switching pattern of the inverter by using a modulated hysteresis current controller, implemented in an analogue card. The use of STF instead of classical extraction filters allows extracting directly the voltage and current fundamental components in the α–β axis without phase locked loop (PLL). The performances are good even under distorted voltage conditions. First, the effectiveness of the new proposed method is mathematically studied and verified by computer simulation. Then, experimental results are presented using a DSPACE system associated with the analogue current controller for a real shunt active power filter.

A New Approach for Optimal Shunt Active Power Filter Control Considering Alternative Performance Indices

A new steady-state approach for determining the optimal shunt active power filter (APF) reference compensation current injections to control harmonic currents generated by the nonlinear load and for reactive power compensation under ideal or nonideal supply voltages are presented in the paper. Conventionally, the compensation currents injected by the shunt APF are determined to eliminate harmonic currents of the load. However, when considering different APF performance indices such as minimizing source current distortion and maximizing compensated load power factor, the issues related to sizing the APF to meet IEEE-519 harmonic current limits and other constraints such as current imbalance limits and minimum load power factor requirement are rarely investigated. In the paper, a new theory of APF control in the a-b-c reference frame is proposed to determine the APF current injections to meet different constraints with an optimal APF size, where the filter control strategy is formulated as a nonlinear programming problem and is solved to find the optimal current injections. Results obtained by simulations with Matlab/Simulink show that the proposed approach is more flexible and effective than the conventional approaches on compensating reactive power and harmonic currents of the load.

Optimisation-based strategy for shunt active power filter control under non-ideal supply voltages

A new theory and a conceptual design for the three-phase shunt active power filter (APF) control strategy under imbalanced and distorted supply voltages are presented. Conventionally, the compensation currents injected by the APF are determined according to reference frame transformation-based approaches, where the load instantaneous real and reactive powers are calculated in the new reference frame. The APF injection currents are then computed to maintain the balanced and sinusoidal source currents, as well as the least active power consumption by the APF. However, if current harmonics set by harmonic standards or other constraints are considered, the load harmonic currents after APF compensation can be controlled to meet the requirements. Therefore, the APF may have an adjustable performance. An optimal algorithm for the APF control in steady state is proposed, in which the individual and total harmonic current distortion limits, the minimum load power factor, levels of current imbalance and the size of the APF can be taken into account. The planned APF does not consume or produce active power and only the passive energy-storage elements are required in the new APF design. Results obtained by simulations with Matlab and Simulink show that the proposed approach is more flexible than conventional approaches for compensating reactive power and harmonic/neutral currents of the load, even if the source voltages are severely distorted and imbalanced. The new control strategy is very suitable for planning the APF when several alternative objective functions and constraints are under considerations.

A Dedicated Microcontroller based Fuzzy Controlled Shunt Active Power Filter

Abstract This paper presents a dedicated micro-controller based fuzzy logic controller for three-phase shunt active power filter. It is used to improve power quality by compensating harmonics and reactive power requirement of non-linear loads. The compensation process proposed is simple, which is based on sensing line currents and regulating the do link voltage. It operates without sensing the harmonic or reactive volt-ampere requirement of the load. Fuzzy logic control is used to regulate the do link voltage in place of the conventional PI controller, as the fuzzy control is based on simple linguistic variables and does not require the mathematical model of the system. Response of the fuzzy controller is compared with the conventional PI controller by simulation study. An attempt is made to implement a complex control like fuzzy logic on an inexpensive 8-bit micro-controller (INTEL 8031). Various experimental results are presented under steady state and transient conditions.

A Novel Reference Compensation Current Strategy for Shunt Active Power Filter Control

The shunt active power filter has proved to be a useful device to eliminate harmonic currents and to compensate reactive power for linear/nonlinear loads. This paper presents a novel approach to determine reference compensation currents of the three-phase shunt active power filter (APF) under distorted and/or imbalanced source voltages in steady state. The proposed approach is compared with three reviewed shunt APF reference compensation strategies. Results obtained by simulations with Matlab and Simulink show that the proposed approach is more effective than the reviewed approaches on compensating reactive power and harmonic/neutral currents of the load, even if the source voltages are severely distorted and imbalanced. In addition, the proposed approach yields a simpler design of the shunt APF controller.

Simulation Results of a Shunt Active Power Filter with Control Based on p-q Theory

The present paper describes a shunt active power filter with a control system based on the p-q theory, and studies its performance through simulation results obtained with different types of loads. It is explained, in a brief form, the p-q theory and its application in the control of a shunt active power filter. Matlab/Simulink was the simulation tool, used in the study, development, and performance evaluation of the shunt active power filter controller. The simulations were carried out for different loads, of linear and non-linear types. The shunt active power filter allows compensating harmonic currents, reactive power, unbalanced loads, and zero-sequence currents, presenting a good dynamic and steady-state performance, as it can be observed in the simulation results.

Fuzzy logic controlled shunt active power filter for power quality improvement

The simulation and experimental study of a fuzzy logic controlled, three-phase shunt active power filter to improve power quality by compensating harmonics and reactive power required by a nonlinear load. The advantage of fuzzy control is that it is based on a linguistic description and does not require a mathematical model of the system. The fuzzy control scheme is realised on an inexpensive dedicated micro-controller (INTEL 8031) based system. The compensation process is based on sensing line currents only, an approach different from conventional methods, which require harmonics or reactive volt-ampere requirement of the load. The performance of the fuzzy logic controller is compared with a conventional PI controller. The dynamic behavior of the fuzzy controller is found to be better than the conventional PI controller. PWM pattern generation is based on carrierless hysteresis based current control to obtain the switching signals. Various simulation and experimental results are presented under steady state and transient conditions.