A control strategy for shunt active filter

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

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.

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.

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 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.

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.

In this paper the performances of a new shunt active filter control are presented. The proposed variable structure control strategy aims to reduce voltage distortion at the connection point of the nonlinear load and to cancel harmonic components from the system side. A switching optimisation circuit based on a digital switching table is added to the variable structure control. This control method permits a reduction of the switching frequency with an insignificant deterioration of the active filter performances. Simulation results on SABER program and experimental results show the effectiveness of the optimised variable structure control strategy.

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 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 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 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.

This paper presents a shunt active power filter for four-wire power systems with unity power factor control (UPF), which operates in unbalanced and nonsinusoidal conditions. In these power systems it is interesting to use four-branch voltage source inverters (VSI) because they are capable of compensating load currents of nonzero average value. Most four-branch VSI control methods are based on a space vector generalization using Clarke's transformation. The switches of these inverters operate at variable frequency with the well-known disadvantages that this supposes. Here a fixed frequency current controller applied to four-branch VSI is presented. It is based on an extension of the space vector modulation from two-dimensional space to three-dimensional space using Clarke's transformation. With it, a fixed switch switching frequency is obtained that causes line current ripples to have a fixed frequency. These current ripples can be easily attenuated by means of appropriate filters. This current controller also is able to decrease the relationship between DC and AC voltages at a greater rate than the one in and at a much greater rate than the ones in. For obtaining the reference currents starting from load currents the UPF control method based on the domain analysis is used.

SummaryShunt active power filters have been introduced as a way to overcome the power quality problems caused by nonlinear and reactive loads [9, 14, 23]. These power electronics devices are designed with the goal of obtaining a power factor close to 1 and achieving current harmonics and reactive power compensation [5, 6, 15]. The usual approaches [5, 15] for the control of shunt active filters are based on two hierarchical control loops: an inner one that assures the desired current and an outer one in charge of determining its required shape and the appropriate power balance as well. The control structure followed in this Chapter is the one in [7], in which the current controller is composed of a feedforward action that provides very fast transient response, and also of a feedback loop which includes an odd-harmonic repetitive control that yields closed-loop stability and a very good harmonic correction performance. In turn, the outer control law is based on the appropriated computation of the amplitude of the sinusoidal current network and, aiming at a robustness improvement, this is combined with a feedback control law including an analytically tuned PI controller.

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

Shunt active power filters are proved a useful elements to correct the distorted currents caused by nonlinear loads in power distribution systems. This work presents an all digital approach, based on the repetitive control technique, for their control and a design is performed for the particular case of single-phase shunt active filters with a full-bridge boost topology. Several experimental results are also presented to show the behavior of the closed loop system.