An optimised variable structure control of a shunt active filter

This paper presents a modeling and a nonlinear control of three-phase voltage source shunt active filter. The modeling is based on the abc/dq transformation of the AC system variables. The currents injected by the active filter are controlled in the synchronous orthogonal dq frame using a decoupled nonlinear control strategy. The reference harmonic components are extracted from the sensed nonlinear load currents by applying the synchronous reference frame method, where a three-phase thyristor bridge rectifier with R-L load is taken as the nonlinear load. The voltage level of the DC side is regulated using a linearizing feedback control. The reference current needed to maintain a regulated DC voltage is added to the current loop reference. The transfer functions of the two loops are developed and synthesized to obtain the desired stability and dynamic response. Simulation results confirm the performances considered theoretically for the shunt active filter topology.

This paper present the mitigation of line current harmonics using control of shunt active power filter (SAPF). The three phase system is connected to nonlinear load which cause harmonics to affect the power system. The control of shunt active power filter is not only compensating harmonics but also compensate reactive power. Voltage source inverter(VSI) at using SAPF reference current control strategies; instantaneous real and reactive power theory (p-q theory), modified synchronous rotating reference frame theory(Modified d- q theory) with PI control and current control method at using hysteresis current control and SPWM controller. The different control technique of SAPF is based on reference current generation and current control method simulated by using MATLAB Simulink.

Usage of Active power filters is increased in this moderen era as they are capable to reduce harmonics effectively. Shunt Active Filters are proven to diminish harmonics compared to all other devices. Many control strategies has been developed till date to control Shunt Active Power filter. In soft computing techniques generally fuzzy logic has been used with mamdani type of fuzzy logic controller. This paper presents comparison of mamdani and TS type fuzzy logic controller to control the three-phase shunt active power filter. Fuzzy logic method is used to tune PID controller to autotune controller. Instantaneous Reactive Power theory is implemented to generate reference currents. Simulation is done in MATLAB to verify the results.

FLC based shunt active filter (p–q and Id–Iq) control strategies for mitigation of harmonics with different fuzzy MFs using MATLAB and real-time digital simulator

Active power filters have been used in practice to suppress the harmonic interference in power systems. To compensate for harmonic currents of loads active power filters are usually connected to power systems in parallel with the loads. These filters which are called shunt active filters here are very effective to loads that can be considered as current sources, such a thyristor rectifiers with large DC reactances. Many papers have covered the shunt active filters applied to these currentsource loads. No paper, however, has discussed characteristics of the shunt active filters when they are applied to voltage-source loads.On the other hand, since more and more diode rectifiers with capacitive DC filters are used recently, harmonics generated by which become an issue.The diode rectifier with capacitive DC filters behaves like a voltage source rather than a current source. When a shunt active filter is applied to such a diode rectifier, the current injected from the shunt active filter may flow into the diode rectifier. As a result, harmonics of the source current cannot be reduced effectively, and harmonic current flowing into the diode rectifier increases largely.This paper reveals the above-mentioned problem of shunt active filters analytically and experimentally. Then a series active filter is proposed to suppress harmonic current of the diode rectifiers. The features, operating conditions, and considerations of shunt active filters and series active filters are described analytically and demonstrated experimentally. Taking a diode rectifier with capacitive DC filter as a typical voltage-source load, compensation characteristics of shunt active filters and series active filters are discussed by experiment and simulation. The validity of the series active filters is illustrated experimentally.

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

This paper proposes a very accurate harmonic current control for shunt active filters (SAF) using resonant compensators. The resonant control compensator based on sinusoidal internal model principle is introduced into the control system design in order to improve the control accuracy and performance for ac input signal. The proposed current control system is designed to operate with a single dq reference frame, synchronous with the 50 Hz supply voltage, for the compensation of all main harmonic currents, 5th, 7th, 11th and 13th. The principle of the proposed control method and the design procedure is presented. Experimental results confirm the accuracy and effectiveness of the suggested approach. Excellent harmonic current tracking performance can be achieved. Another major advantage of this strategy is the ability to eliminate the effect of an ac external disturbance from the harmonic components caused by the power supply

This paper discusses automatic gain adjustment in a fully‐digital‐controlled shunt active filter intended for installation on power distribution systems. This is the first step in cooperative control of multiple shunt active filters based on voltage detection for harmonic damping throughout power distribution systems. In general, an optimal control gain is equal to the characteristic impedance of a distribution line. However, it is difficult to know the circuit parameters of a real distribution line, which depend strongly on feeder connections, shunt capacitors, and loads. Therefore, the main purpose of the gain adjustment is to help the active filter to damp out harmonic propagation without considering the circuit parameters. Moreover, the gain adjustment can reduce the compensating current and losses in the active filter. The active filter having the function of automatic gain adjustment is experimentally compared to that with a constant gain. Experiment results verify the effectiveness of the active filter having the function of automatic gain adjustment. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 142(4): 56–65, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10094

This paper presents an indirect current control scheme, developed using the single-phase synchronous d-q reference frame method, for single-phase shunt active power filter (APF). To formulate d-q transformation for single-phase system an imaginary vector is considered and achieved by providing a π/2 delay to the original signal. The real-time implementation of single-phase d-q frame based shunt APF system is discussed in detail. The performance of shunt APF to compensate load current harmonics under sinusoidal and distorted supply voltage conditions is evaluated. Both simulation and digital signal processor (DSP) based experimental results are discussed.

This paper describes a three-phase four-wire shunt active power filter using a conventional three-leg converter, without the need of power supply at DC bus. Two approaches have been developed to control the active filter. Both control strategies consider harmonics and zero sequence components in the voltage and current simultaneously. The first one provides constant power and the second one sinusoidal current to the source, even under unbalanced voltage conditions. Simulation results from a complete model of shunt active filter are presented to validate and compare the control strategies.

Harmonics in the power system can be reduced and thus power quality can be improved with the use of Active power filter. In this literature, fixed switching frequency single phase shunt active filter based on sliding mode controller is modeled and analyzed using MATLAB. Control law is designed to generate both continuous and discontinuous component of the control signal. Pulse width modulated switching signals to the shunt active power filter are generated from the Control output of the sliding mode controller. DC link capacitor voltage is controlled using PI controller which gives the reference source current. Performance of single phase shunt active power filter with nonlinear and combined nonlinear and linear load is demonstrated with the help of simulation results.

This paper describes a novel control strategy for shunt active filters the sinusoidal Fryze currents control strategy. The control strategy considers the presence of harmonics in the system voltage and load current simultaneously. Although the fundaments of the pq theory is used to better explain the proposed control strategy, it is not directly used, since the Clarke transformation (abc to /spl alpha//spl beta/0 transformation) is avoided. In fact, the fundaments of the pq theory is inserted in a minimization method - the generalized Fryze currents, which together with a robust synchronizing circuit (PLL control circuit), form a concise controller for shunt active filter. The shunt active filter provides current compensation, such that the compensated current drawn from the network is sinusoidal and balanced, corresponding to the fundamental positive-sequence component of the load current, plus an additional fundamental positive-sequence component to cover losses in the power circuit of the shunt active filter. Simulation results are presented to validate the control strategy.

This paper is focused on a single phase shunt active filter based on detection of harmonic voltages at the point of installation; the mission of the active filter is to eliminate these harmonic voltages implementing a repetitive-based control. The active filter is a single-phase voltage-controlled voltage source inverter controlled so to generate a harmonic voltage in phase with the one detected at the point of installation. The proposed repetitive-based control regulates the power at the fundamental frequency so to maintaining the dc voltage of the capacitor placed on the dc side of the filter close to a reference; such an issue is faced implementing the self-charging functionality or supplying real power to the grid when the active filter is a distributed generation solution. Numerical results are provided so to demonstrate the effectiveness and the feasibility of the proposed repetitive-based control in compensating harmonic voltages in an electrical power distribution system.

This paper presents a precise harmonic current control for shunt active filters (SAF) based on the robust control design. To ensure robust stability causing by system uncertainties and tracking performance, the robust control employing a two-degree-of-freedom ℋ ∞ control method is designed to accurately track harmonics generated by nonlinear loads in power system. The controller is synthesized by using mixed sensitivity loop shaping. The principle of the proposed control method and the design procedure are described. Robustness to parameter uncertainties can be achieved. The excellent control performance has been carried out by simulations.

This paper deals with the harmonic mitigation and reactive power compensation using Shunt Active filter. The performance of the Shunt active filter depends on the design and current control technique for generating a reference current. The design of the filter involves the iterative procedure for choosing the filter components so that it compensates the harmonics and reactive power for maximum load condition. The current controller method adopted for indirect current control technique where the reference signal is similar to the supply current signal. The Adaptive filter used in current controller mitigates harmonics and reactive power and voltage control loop of SAF balancing the active power between the load and supply unit. The learning rate is fixed by repeated simulation. The SAF active filter is tested in four load condition ie., nonlinear load(37% Total Harmonic Distortion(THD)),highly nonlinear load(>100% THD), linear load(<8% THD, power factor(pf) <0.5) and both nonlinear and linear load(37% THD and 0.7 pf). The study is carried out in MATLAB Simulink and the results are presented.