Unknown input observer-Model predictive control scheme for state and disturbance estimation of 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.

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 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.

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.

This paper shows the method of improving the power quality using voltage source inverter based shunt active power filter. The procedure uses a simple method named synchronous reference current generation for reference current extraction .The proposed topic comprises of PI controller, high pass filter, phase locked loop, dc link capacitor. The switching signal generation for filter is from hysteresis current controller techniques. With the all these element shunt active power filter reduce the total harmonic distortion. This paper represents the simulation and analysis of the using three phase three wire system active filter to compensate harmonics .The proposed shunt active filter model uses balanced non-linear load. This paper successfully lowers the THD within IEEE norms and satisfactorily works to compensate harmonics. The model is made in MATLAB / SIMULINK and successfully reduces the harmonic in the source current.

This paper presents a novel control scheme for unified power quality conditioner (UPQC) based on three-level neutral point clamped (NPC) inverter using fuzzy logic and Ann's for controlling respectively series and shunt APFs. The proposed UPQC is able to mitigate source current harmonics and compensate all voltage disturbances. It is designed by the integration of series and shunt active filters (AFs) sharing a common DC bus capacitor. The DC voltage is maintained constant using proportional integral voltage controller. The synchronous reference frame (SRF) theory is used to get the reference signals for the shunt APF and the power reactive theory (P-Q theory) for the series APF. The shunt and series active power filter (APF) reference signals derived from the control algorithm and sensed signals are injected in two intelligent controllers to generate switching signals. The performances of the proposed UPQC system are evaluated using Matlab-Simulink software and SimPowerSystem Toolbox. The simulation results show the performance of the proposed UPQC at the common connection point of the non-linear load to improve the power energy quality.

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

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.

The extensive use of power electronics devices in power systems, including rectifiers and inverters, presents considerable issues regarding power quality. One problem is the creation of current and voltage harmonics, which result in load waveform distortion, voltage fluctuation, voltage drop, and equipment overheating. Harmonic current sources are prevalent in commercial, institutional, and medical establishments, encompassing computer power supplies, fluorescent lights with electronic ballasts, elevator motors, and electrical devices using switch-mode power supplies. Active power filters (APF) represent the most effective method for harmonic reduction and may be used across many applications. This study employs a digital active power filter to eliminate harmonics from the source current in a grid system characterized by non-linear demand. Nonlinear loads are essential components of every power system. The advent of power electronics has resulted in switching components constituting a substantial portion of electrical demand. These features create discontinuities in lines, exacerbating line losses and diminishing power quality and sine wave integrity. Passive filters effectively eliminate harmonics at specified frequencies within the design. Active filters, conversely, operate in accordance with the prevailing harmonics. This work develops a shunt active power filter that mitigates current harmonics generated by non-linear loads. The active filter includes a voltage source converter (VSC) that functions in conjunction with a DC coupling capacitor. The VCS delivers power at the point of common coupling (PCC). The reference current is obtained by the instantaneous power theory. The instantaneous power theory, or PQ theory, has been enhanced with the FIS control system to optimize DC voltage generation over the DC link capacitor. The fuzzy system substituting the PI controller has a 49-rule base structure organized in a 7x7 configuration for the generation of error signals. A comparative study of DC voltage and total harmonic distortions (THDs) is conducted using MATLAB software and the FFT analysis tool..

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

The use of active power filters is widely accepted and implemented as a solution to the power quality problems in utility, industry and commercial applications. This paper presents an optimisation based control algorithm for determining the reference compensation currents of shunt active power filter (SAPF) to maintain sinusoidal source currents supplied to non-linear loads and to maintain the total harmonic distortion (THD) less than 5% according to IEEE-519 standard and improve power factor. Optimisation is due to the combined effect of perfect harmonic cancellation (PHC) and unity power factor (UPF) strategies. Reference compensation current is calculated through MATLAB using discrete Fourier transform. The optimisation-based control algorithm gives the best power factor while satisfying the constraints such as THD limits and average power balance of source currents. It is also flexible to adopt different compensation characteristics based on the supply voltage conditions. The proposed technique is implemented using MATLAB/Simulink and optimisation tool boxes for both balanced and unbalanced load conditions. The algorithm is validated by using a prototype of digital signal processor (TMS320F2812) based SAPF. Detailed experimental results are presented.

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 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 modified hybrid Controller based on instantaneous power-fuzzy controller (IPFLC) for a shunt active power filter (SAPF). The current produced by the AC source is polluted by harmonics injected by the non-linear loads. The supply system requires filtering by suppressing harmonic currents to improve power quality at interface bus. The filtering system consists of an LC filter and a SAPF. The proposed IPFL Controller for the SAPF is based on a combination of the p-q instantaneous power and the fuzzy logic strategy. In this part, two cases are studied, first the active filter is connected only to a capacitor by its dc side, and second case where the active filter is connected to a photovoltaic source or to a battery. The effectiveness, robustness and the dynamic speed of the proposed controller is validated and assessed using dynamic digital simulation. Digital Simulation results validated also the effectiveness of the active filter scheme with modified controller in reducing the source current THD from 25.87% to 0.83% which largely meets the standards of IEEE STD and International Electro-technical Commission (IEC). Digital Simulation and validation used MATLAB-SIMULINK Software Environment.