Active Damping Method Using Grid-Side Current Feedback for Active Power Filters with LCL Filters

In allusion to the difficulty of achieving accurate mathematical model of active power filter (APF), the Takagi-Sugeno (TS) fuzzy control is led into DC voltage control of APF. To solve the problem of control system stability, the control approach based on Lyapunov stability theory is applied to the current control. Both methods can ensure the control accuracy and stability. By means of adaptive fuzzy neural system in Matlab/Simulink the parameters of TS fuzzy controller are optimized and experiments are performed. Results show that under the time-varying load and variation of power system parameters both robustness and control accuracy of the control system can be ensured by the proposed control method.

This paper presents a synchronous detection with Fourier analysis (SDFA) method. The proposed method is used to calculate the reference current of single-phase shunt active power filters. The SDFA method is operated bases on a synchronous detection (SD) and the sliding window with Fourier analysis (SWFA) technique. The harmonic elimination in single-phase power system is considered in this paper. The performance comparison of the SD and SDFA methods is also presented. The simulation results by using the Simulink program confirm that the SDFA method can provide the better performance compared with the SD method. Furthermore, the total harmonic distortion percentage (%THD) of the source current after compensation is satisfied under the IEEE std 519–2014.

An advanced active power filter for the compensation of instantaneous harmonic current components in nonlinear current loads is presented in this paper. A novel signal processing technique using an adaptive neural network algorithm is applied for the detection of harmonic components generated by nonlinear current loads and it can efficiently determine the instantaneous harmonic components in real time. The validity of this active filtering processing system to compensate current harmonies is substantiated via simulations.

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.

A comparative study of shunt hybrid and shunt active power filters for single-phase applications: Simulation and experimental validation

For a single-phase Shunt Active Power Filter (SAPF) with a two-step prediction, this research presents a modified current control based on a Model Predictive Current Control (MPCC) technique. An H-bridge inverter, a DC link capacitor, and a filter inductor comprise the single-phase SAPF topology. The SAPF reference current is computed using the DC-link capacitor voltage regulation-based PI control technique. The weighting factor-based model predictive current controller is used to track the current commands. The essential dynamic index for evaluating waveform quality is the Total Harmonic Distortion (THD) of a source current and switching frequency of power switches. The conventional methods the THD and switching frequency are not considered as an objective function, so that a weighting factor-based MPCC technique is used to obtain a good compromise between the THD of the source current and switching frequency of power switches. Through MATLAB simulation and experimentation with the Cyclone-IV EP4CE30F484 FPGA board, the usefulness of the proposed control technique is proven. As compared with hysteresis, predictive PWM, and conventional MPCC control methods, the cost function-based MPCC algorithm provides a lower switching frequency (13.4 kHz) with an optimal source current THD value.

This paper presents a three-level three-phase diode clamped inverter that uses an auxiliary circuit to equalize its DC-bus capacitor voltages. The proposed converter is used in an Active Power Filter (APF) and a controller is designed for this new APF. A state space model of this filter is obtained first. Three single input single output (SISO) robust controllers are designed to compensate the load current harmonics, to regulate the DC-bus voltage and to equalize the capacitor voltages. The effectiveness of this control strategy is guaranteed by the fact that each of the SISO controllers is provided with appropriate nonlinear terms that compensate the interactions among the filter sub-modules. The APF performance is evaluated. The results demonstrate that load current harmonics are very well compensated, the converter DC-bus voltage is maintained at its reference value and capacitor voltages remain equal despite load variations.

Due to the proliferation of non-linear modern power electronics, currents and voltages produced by non-linear loads have lead to the deterioration and distortion of the output sine wave forms of the source currents and voltages. These distortions have resulted in the power quality problems. The non-linear load draws reactive power and harmonics from the ac source in the fundamental current. The harmonics in power system caused by non-linear loads such as, arc furnaces, switch mode power supply, fluorescent lamps rectifiers etc all are the main sources of harmonics, as a result of these non-linear loads the supply system lead to overheating of cables and conductors, electromagnetic interference to nearby communication facilities etc. Therefore, as a result of theses harmonics, a traditional passive filters are used to suppressed the integer multiple fundamental frequencies, but due to the passive filter draws back in producing series or parallel impedance with the supply impedance and heavy in sized, its limitations in service becomes an old scheme. The application of shunt active power filter in mitigating these harmonics problems supersedes the used of passive filter. This paper, presents the modeling and simulation of single-phase shunt active power filter controlled with fuzzy logic controller (FLC) to mitigate the harmonics drawn by non-linear loads. The proposed scheme is performed by using MATLAB fuzzy tool box environment. Simulation results obtained by the proposed control algorithm found to be satisfied and within the recommended imposed IEEE 519-1992 harmonic standard limit.

This paper presents the design and simulation of a single-phase shunt active power filter for harmonic and power factor compensation of multiple nonlinear loads. The system is modeled in Matlab Simulink to consist of an uncontrolled rectifier and an AC controller as the nonlinear loads, with an active filter to compensate for the harmonic current injected by the load. The active filter is based on a full-bridge single-phase inverter. The design of the active filter controller is based on time-domain method that consists of three main tasks; to identify the harmonic content and form a synchronized reference, to provide closed-loop control to force the current of the active filter to follow the reference and to regulate the capacitor DC voltage. The spectral analysis of the supply current shows the harmonics produced by the load has been successfully compensated by the active filter. The effect of varying the switching frequency on the performance of the active filter is also presented.

Shunt active power filters (SAPFs) are considered as an effective and practical solution for growing power quality problems. The purpose of the SAPF is to generate and inject the appropriate current into the power system to eliminate the load harmonics and obtain the unit power factor. In this paper, a single-phase power system with pure sinusoidal voltage source and nonlinear load with single-phase SAPF is studied. The reference currents of the filter are obtained by conservative power theory (CPT) and constructed using the model predictive control (MPC) switching algorithm which is applied to the conventional two-level inverter. This study is verified by both simulation and experimental results. Also, the results of this study are compared with those of hysteresis switching algorithm.

This paper presents some effects that contribute to performance degradation of grid-connected systems, when they are subjected to operate under distorted reference phase-angle signals. In many power electronics applications, grid-tied systems are developed on the synchronous reference frame (SRF) and make use of the synchronous unit vector coordinates to compute their control references. Usually, the unit vector coordinates are generated from the estimation of the utility phase-angle, which is obtained by means of phase-locked loop (PLL) schemes. Thus, static and dynamic disturbances present in the utility voltage can generate distorted phase-angle signals, and, hence, can affect the quality of the synchronous unit vector coordinates. In this paper, two single-phase SRF-based PLL schemes, which operate under distorted utility voltage conditions, as well as distinct bandwidth PI controllers, are used to generate the current control references of a single-phase shunt active power filter (S-APF). Experimental results based on digital signal controller are used to evaluate the problems that can interfere on the S-APF performance.

Cascaded controller for single-phase shunt active power filter and STATCOM

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.

Ahlstrom Corp, Finland

In this paper, a least-mean-squares (LMS) finite memory (FM) estimator for a stochastic discrete-time state space model is obtained by taking the conditional expectation of the estimated state given a finite number of inputs and outputs measured on the recent finite horizon. Any a priori state information is not involved and any arbitrary constraints are not imposed. For a general discrete-time state space model with both system and measurement noises, the LMS FM estimator is represented in a closed-form. It turns out that the proposed LMS FM estimator has the unbiased property and the linear structure with respect to inputs and outputs on the recent finite horizon.