Research And Design Of Shunt Active Power Filter In Three-phase Four-wire System

With extensive application of power electronic devices in production and life, they make power energy conversion and application easily, but also lead to the serious harmonic pollution in the power system. At present, the shunt active power filter (SAPF) has been an effective way to dynamically compensate reactive power and harmonic. In addition to these problems, the load unbalance is more and more serious in three-phase four-wire system, therefore, SAPF applied to three-phase four-wire system is researched and designed to solve these problems in this paper.For the harmonic current detection of SAPF in three-phase four-wire system, the i_p-i_qalgorithm based on the instantaneous reactive theory is detailedly derived, and this algorithm is demonstrated it could be directly applied to three-phase and four-wire system without being improved. Hysteresis-band comparison method is chosen as compensation current control strategy. The four-leg converter which has clear division is adopted as the main circuit, and the working model and switching coefficient of four-leg converter is deduced. The main parameters of 5kVA SAPF are analyzed and calculated in detail. Besides, the control system with DSP TMS320F2812 as the core is designed, and functions of various circuits are introduced. The PCB of control system is made, and the results of debugging hardware circuits show that control board works well and meets the design requirements.At the end of the paper, the simulation platform is built by use of MATLAB/Simulink software. The output inductance parameter and soft-start scheme are simulated respectively. The results prove that output inductance parameter is reasonable and the soft-start scheme is feasible. Then, the integrated simulation for SAPF and compensation system is carried out. Finally, simulation results show that SAPF has a good compensation characteristic for the harmonic produced by the balance and unbalance nonlinear loads, and balances three-phase loads in three-phase and four-wire system. At the same time, simulation results show that harmonic detection method is correct and the control strategy is proper.