Harmonic Detection Of Active Power Fliter And Harmonic Impedance Estimation

The extensive use of non-linear loads have seriously affected the quality of public power grid. Active power filter(APF) which has good dynamic response and precision compensation is becoming a valid harmonic suppression device. And APF has been further applied in engineering practice.The paper makes analysis on topology, structure and working principle of the shunt active power filter on detail.The mathematical models of shunt active power filter are respectively established under in abc three-phase stationary coordinate system, αβtwo-phase stationary coordinate system and dq two-phase rotating coordinate system.This paper also analyzes the coupling relationships involved in control strategy and studys two harmonic extraction algorithms based on instantaneous reactive power theory of active power fliter.This two detection algorithms are compared by simulation.Besides, the paper designs dual-loop control strategy including outer voltage loop and inner current loop is adopted for the employed active power filter.This study is verified by simulations which are based on the MATLAB.Based on the research of active power filter, this paper presents a new method to estimate harmonic impedance using active power filter. Its mathematical model is established and the influence of the phase processing of sampled signals is analyzed. The estimation algorithm is designed on the basis of research. Simultaneously, the impedance estimation applied on islanding detection of distributed generation system is studied.This paper puts forward a new method that by using active power filtero compensate harmonic current caused by nonlinear loads and considering compensation current of APF as a disturbance, islanding mode is judged by detecting the change of the equivalent impedance of the APF port. The equivalent model of distributed generation system with nonlinear load is established and the detect algorithm is designed. Due to regarding compensation current as disturbance, the power quality can be improved and islanding detection can be finished simultaneously. The simulation verifies the feasibility of proposed method.Finally, this paper accomplishs the hardware implementation of the shunt active power filter. Bsaed on TMS320F28335, control system is designed. The software code is completed by development tools. On the basis of experimental setup of active power filter,the experiment of harmonic impedance estimation is achieved. At the same time, theexperimental study of islanding detection method of distributed generation system based on active power filter is accomplished. The experimental results demonstrates the feasibility of the proposed method.