Shunt Active Power Filter

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

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

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 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.

This paper presents the analysis of a three-phase active filter (AF), which establishes the superiority of PI control over other existing control techniques for power factor compensation and load balancing. A three-phase IGBT-based voltage source inverter with a DC bus capacitor is used as an active filter. An hysteresis-based carrierless PWM current control over the supply currents is employed resulting in reduction of load current sensors and derived gating signals are fed to the devices of AF. Thereby AF currents are such that they force supply currents to remain sinusoidal under varying load conditions. Continuously varying unbalanced lagging power factor load is considered as a sample load. A detailed dynamic model of the complete system is developed to study the steady state and transient behaviour of the active filter. This type of AF is also capable of converting single phase large RL loads into three phase balanced loads and eliminates the use of a transformer. Simulated results for the cases of single-phase, two-phase and three-phase loading are presented and discussed in detail to demonstrate the reactive power compensation and load balancing capabilities of the AF. The response of proposed AF with PI control is quite fast. It is envisaged that this compensator has great potential in several applications like supply utilities, process industries and cavity power generation systems.

We present an energy-based approach for the control of shunt active power filters based on voltage source inverters. These are commonly used to compensate for current harmonics, unbalance and reactive power produced by nonlinear, time-varying and fluctuating loads. The main control issues on these applications arise from the possible presence of unknown dynamics and parameter uncertainties in the load and in the power line. This, however, is often the case when active filters are used not only to compensate a specific distorting load, but also to handle a group of loads. We explore the effectiveness of a family of controllers based on the generalized averaging techniques and on notions of incremental energy and dissipativity. We obtain a compensation strategy that allows stable active filter operation regardless of line and load parameter variations. Moreover, an adaptive procedure, which allows precise reference tracking, is also presented. Simulation results indicate the effectiveness and validity of the proposed method.

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 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 presents different compensation characteristics that can be applied in the control of parallel active filters or combined systems for parallel active and passive filters, in both cases considering the active part working as a current source in parallel with the power system. These control strategies, with their base in p-q theory and its extension, allow the compensation of harmonic currents, harmonic currents plus reactive power at fundamental frequency, and the last two and plus zero sequence components. In the case of combined filter systems, the reactive power at fundamental frequency and the very high harmonics are operated for passive filters; therefore the parallel active part presents low nominal rate. The aim is to combine passive filter robustness with active filter performance, improving system reliability. The analyses shown in the paper are practical alternatives to improve power quality.

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

Now-a-days, decadence of power quality is foremost issue of electrical society. In practice, utility of switching device is increased in industrial as well as in domestic applications. Non-linearity causes adverse effects on system efficiency, utility of the power supply, power factor, etc. As reduction in power factor increases reactive power which does not have any contribution in energy transfer so its compensation is needed. So efforts are made to upgrade power quality, concept of Filter is in demand. In contrast to passive filter, active filters are popular due to its smaller size and weight. In this paper, work is done on shunt active power filter (SAPF) using P-Q theory for current harmonic mitigation and reactive power compensation. Here the simulation as well as its parameters, with or without active filter is well presented. We commence the paper with power quality issues then better understanding of PQ theory, simulation circuits, results, comparison and finally ended with conclusion. An effort is made to achieve THD value of source current below 5% to meet the required IEEE standards.

This paper presents an analysis of the modeling of reactive power compensation using renewable energy from sunlight through photovoltaic to eliminate harmonic signals in the electricity network with a three-phase active power system filter. Electric energy supply comes from three-phase electricity sources in the form of a sinusoid. Non-linear loads such as electronic devices and electrical equipment connected to the grid generate harmonics signals; can make the format of electrical energy distorted. This nonlinear load draws electric current in the form of non-sinusoid. This format increases Total Harmonic Distortion (THD), thereby worsening the performance of electrical equipment. An active power filter is a very effective method in reducing harmonics signals and increasing the quality performance of electricity. This power filter works by injecting compensation current into the grid. The energy that is injected comes from the direct current output voltage (DC) of the photovoltaic link stored in the capacitor via a Voltage Source Inverter (VSI) switch. The compensation current has the same format as the harmonics current but differs in 180°. The main parts of this power filter include the Reference Signal Generating Unit, PI Controller, VSI Switch Signal Ignition Gate Generator, Energy Storage Circuit (Battery), and Photovoltaic. Simulation modeling using Matlab Simulink Tools to reduce THD levels by IEEE 519 standards. Simulation results show a significant decrease in Total Harmonic Distortion (THD), where the grid before compensation contains THD of 29.74% and after injection of 2.25%. So this modeling is worth proposing as an active filter in a power system.

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.

Reactive power compensation devices are widely used: thyristor-control reactors (TCR) and thyristor-switched capacitors (TSC). The TCR disadvantages are discussed. The TSC disadvantages are: influence of higher harmonics on nonsinusoidal voltage power system, the inability to ensure the smooth regulation. The proposed reactive power compensator consists of series with active filter and capacitors with step switch. Reactive power compensator’s control system is proposed. Hysteretic control of the inverter with current feedback is applied. DC-voltage regulator provides balance of active power. The control system allows overcompensation or undercompensation of reactive power modes. Reactive power distribution regulator performs the redistribution of power between switching capacitors and active filter. Minimization condition of this regulator is active filter’s power. Adjustment properties of reactive power compensator are analyzed. The choice of relations between the capacitors TSC steps to minimize the installed capacity of the active filter and the number of stages in TSC is considered. The approach that makes possible to «isolate» capacitors from harmonic currents and provide smooth control of reactive power is proposed