The Simulation Research On Control Strategy Of Shunt Active Power Filter

The shortcoming of LC filter is serious and the technology of power electronic is developing rapidly, eliminating harmonic dynamically by using Active Power Filter (APF) becomes an important method.The topology and principle of classical APF are analyzed. For the detection of harmonic and reactive current method and the control of main circuit,which are the two important parts of APF's control strategy,are discussed in detail in the thesis. Aiming at the problem of detect methods of harmonic current existing in the single-phase system, a control strategy based on power equilibrium is designed, which only need to detect the load current and the voltage of the capacitor at the DC side of the inverter, without detecting harmonic current of the load and the phase-locked loop. It can make the line current of the power supply to be a standard sine wave,which has the same phase as the network voltage.To solve the problem of neutral line current,harmonic and reactive current and three-phase unbalance exiting in the distribution network, a control strategy for the three-phase four-wire active power filter based on synchronous reference frame transformation is designed, the method is more simple than former, main circuit with only three bridge legs, and the compensation goals can be chosen conveniently according to practical needs.The whole system of single-phase APF and three-phase four-wire APF are simulated respectively on computer using MATLAB 7.0 .The simulating results have demonstrated that this single-phase active power filter can compensate the harmonics and reactive component of load current effectively as well as good dynamic performance. The three-phase four-wire active power filter can compensate the neutral line current, harmonics and reactive component and three phase unbalance in transient state and steady state effectively.