Mehmet Buyuk

Analysis and comparison of passive damping methods for shunt active power filter with output LCL filter

Recently, LCL filter which is commonly preferred in grid connected inverters has found its common usage in shunt active power filters. LCL filter can suppress the switching harmonic ripples effectively. However, it has resonance problem which results unstable system. The resonance problem can be solved with damping the resonance using passive damping methods. The design of LCL filter with using PD is a challenging issue because APF generates currents in a wide harmonic spectrum range to compensate harmonics. The aim of this paper is to present the design procedure of LCL filters with different passive damping methods for SAPF and analyze them in terms of damping performances and power losses. The performance and analysis of LCL filters designed for SAPF is performed with simulation model developed in MATLAB/Simulink.

Performance evaluation of LLCL filter for active power filter

Active Power Filter (APF) is an inverter based device that compensates the harmonic currents generated by nonlinear loads. Inverters release high frequency switching ripple harmonics. In early studies, APFs have been generally interfaced to the grid via a single L filter to reduce these harmonics. However, high order filters like LCL and LLCL filters have been recently used with APFs instead of L filter due to insufficient mitigation of L filter. LCL and LLCL filters have better attenuation of switching ripple harmonics at high frequencies. Attenuation performance of LLCL filter at switching frequency is superior to LCL filter. Since LLCL filter has resonance problem, a simple resistor is connected in series with parallel LC branch. The purpose of this paper is to evaluate the performance of LLCL filter for different damping resistor values when used with APF. In order to examine the performance of the LLCL filter, a simulation model is developed in Simulink/MATLAB.

EPLL based controller for voltage harmonic mitigation in grid connected wind systems

Voltage harmonics are very important voltage disturbances which induce overheating of transformer/generator, connection loss and rise of current rating in grid connected wind energy systems. In this paper, Enhanced Phase Locked Loop (EPLL) based controller method is proposed to generate reference signals of voltage harmonics at grid-side voltages. In order to achieve the harmonic compensation, EPLL based controller method is tested to compensate voltage harmonics for balanced and unbalanced conditions in Dynamic Voltage Restorer (DVR) tied grid-connected wind energy systems. The performance results of EPLL based controller demonstrate that it is a very effective technique for harmonic compensation under steady-state and transient conditions.

Survey of inverter topologies implemented in dynamic voltage restorers

Voltage disturbances which affect the stability of electrical networks are the most important power quality problems. The most known voltage disturbances are voltage sag and swell in distribution systems. Dynamic Voltage Restorer (DVR) is the most effective device to compensate these voltage disturbances among the custom power devices. The basic structure of a conventional DVR consists of an inverter, dc link capacitor, injection transformer and filter. The major component in DVR is inverter that generates controlled voltage to compensate voltage sag/swell and other problems such as flicker, interruption and harmonics. Each inverter implemented in DVR has individual properties such as voltage level, unbalanced compensation capability and/or dc link capacitor requirement. This paper aims a comprehensive review on different inverter topologies according to the number of phases, size, voltage level and structure of DVR. In addition, individual properties of inverters are presented in this study.

A notch filter based active damping of llcl filter in shunt active power filter

Shunt Active Power Filter (APF) is a custom power device applied in electric grid system in order to compensate harmonic currents generated by nonlinear loads. Shunt APF operates by firing power electronic devices of voltage source inverter (VSI) to produce the compensation currents. The VSI also generates high frequency switching ripple harmonics that distorts the source current. High order filters, such as LCL and LLCL, have been recently used with shunt APF to decrease the ripple harmonics and to couple shunt APF with the grid. Compared with LCL filter, LLCL filter has more effective attenuation performance at switching frequency because of demonstrating nearly zero impedance. As other high order filters, LLCL filter has resonance problem that leads the system to unstable condition. Passive damping or active damping method is exploited to mitigate the resonance impact and make the system stable. AD methods have more widespread applications and research due to no damping power losses. AD is fulfilled through making improvment in the control system. The objective of this paper is to point out notch filter based AD for shunt APF with output LLCL filter. The proposed system is constructed in Matlab/Simulink and the performance of the proposed system is investigated through simulation cases.

FFT based reference signal generation to compensate simultaneous voltage sag/swell and voltage harmonics

The most severe power quality problems are known as voltage sag, swell and harmonics. Series connected custom power device called as dynamic voltage restorer (DVR) is the most effective device used in electrical systems to compensate these power quality problems. Traditional DVR compensates only voltage sag/swell in electrical grids. The main contribution of this paper is that FFT based a novel reference generation method is used in DVR to compensate unbalanced voltage sag/swell and unbalanced voltage harmonics, simultaneously. In this study, FFT achieves both voltage sag/swell detection and voltage harmonics extraction at the same time. FFT controlled DVR compensates voltage sag/swell within 5 ms while unbalanced selective voltage harmonics (5th, 7th, 11th and 13th) are compensated in the system, simultaneously. The system is analyzed for various case studies. The performance of proposed controller method is presented and confirmed through simulation results using PSCAD/EMTDC.