Study Of Active Power Filter Based On Improved Hysteretic Current Control

With the rapid development and wide application of the nonlinear and time-variable power electronic equipments, a great quantity of harmonic and reactive currents are injected in power system, which results in a serious impact to the power system security and power quality improvement. As an effective device of harmonic suppression, the Active Power Filter (APF) has become a research focus currently.This paper firstly introduces the producing cause, hazard and management strategy of power system harmonic, and then analyzes the development status, classification, common current tracking control mode and its research status of APF. Next the paper discusses mainly the fundamental structure and working principle of the three-phase three-wire shunt APF. Common harmonic current detection algorithm and the target of current tracking control for APF are expounded as well.Through comparing the advantages and disadvantages of Triangular Wave Comparison Mode and Hysteresis Comparison Mode, the latter is selected usually. Based on establishing the mathematical model of the main circuit of APF, the relationship between hysteresis band, compensation current, switching frequency, power system voltage, voltage of DC side and inductance of AC side is analyzed. Aimed at the shortcoming of traditional hysteresis current control mode, the two improvement thoughts are put forward in this paper.This paper chooses and simulates variable-band hysteresis current control mode as current tracking control for APF. The fundamental principle, overall structure, band regulation and circuit structure of this control mode is analyzed firstly. On this basis, the paper investigates hardware design of variable-band hysteresis current control mode, which includes basicl structure of PWM inverter, selection of device and inductance on AC side.By taken PSIM6.0as simulation experiment platform, the simulation model of the APF is put up. Based on same experimental parameters except hysteresis band, simulation experiment is carried out. With the contrastive analysis of simulation results made, which show that the effectiveness and feasibility of variable-band hysteresis current control mode.Finally, the main research contents of this paper are summarized and some suggestions for the further research are put forward.