Digital control of a single-phase 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.

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 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

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.

Current Control of the Isolated Self-Excited Induction Generator using Shunt Active Filter

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.

This paper describes a single-phase modified packed U-cell seven-level multilevel inverter (MPUC7) with finite control set model predictive control (FCS-MPC) for a single phase shunt active power filter application. The shunt active filter can directly inject the harmonic load current and compensate for the reactive power of the load and thus, make the grid current sinusoidal and in-phase with the grid voltage. The active filter improves the power factor and THD of current at point of common coupling (PCC). The MPUC7 is a six switch seven level inverter with only two dc-link capacitors. The mathematical model of shunt connected MPUC7 converter is explained for derivation of the next sample prediction required for FCS-MPC. The cost function for the constraint of tracking current and regulating the two dc-link voltage is mentioned. The filter reference currents are derived using direct control method. The single-phase active filter application is simulated in the Matlab/Simulink to validate the operation and robustness of the FCS-MPC current controller. Various non-linear load changes are simulated to verify the effect on dynamic operation.

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.

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

The distribution system's nonlinear loads cause low total harmonic distortion (THD), low distortion power factor, and localized communication interference, among other poor power quality metrics. Shunt active power filter (SAPF) capacity to function depends on the controller's ability to follow the reference signal. To manage larger systems with several inputs and outputs, it would be challenging task to design PID controllers, because excessive controller gains would need to be tuned. Also, every control loop would operate independently of one another, as if there were no interactions between the two loops. This paper proffers Model prediction control for Shunt active power filter (SAPF), which can manage systems with several inputs and outputs that may interact with one another. Luenberger observer (LO) and Proportional Integral observer (PIO) fail to estimates the actual states of SAPF to SAPF, as shown even in the presence of three unknown disturbances, i.e step, triangular and noise type. The proposed unknown input observer (UIO) in the presence of three unknown disturbances perfectly tracks the reference signal. Apart from state estimation, the proposed observer also estimates all the unknown disturbances, when compared to PIO. The results have been simulated in MATLAB environment.

This chapter explains excellent performance of shunt active power filter (SAPF) integrated with photovoltaic source, for considerable energy management, harmonic alleviation, and reactive power recompense. The solar plant produces extreme or equal power essential to the load requirement, hence the coordination with grid is complex. The PV module is designed with INC-MPPT technology, and the shunt active power filter is connected at the AC side of the inverter integrated with a nonlinear load. Here, the shunt active power filter design depends on PI controller whose gains are selected arbitrary. In the first study, the total harmonic distortion (THD) is calculated with no filter and nonlinear load. Then, THD analysis is performed with SAPF. Further to pick up the recital of shunt active power filter, a new PSO optimization technique is applied to select the proper value of PI gains R and L of nonlinear load. The simulation result depicts that the optimized shunt active filter reduces harmonics to a great extent. The results of SAPF, PSO-SAPF, APSO-SAPF, and TCPSO-SAPF are compared.

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 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.

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