New Active Power Filter Based On Soft-switch Technology Research

Active power filter is a new device which could suppress harmonicdynamically and compensate reactive power at the same time, it becomes themost effectively method for the suppression of harmonic. The function andperformance of the detection mode and modulation strategy determine thecompensation effect directly. The researcher study out various advanced andaccurate detection modes and modulation strategies, but the application of theseis limited seriously by the technical level. The mall capacity of compensation,the high cost, the EMI and switching loss caused by high switching frequency ofsingle AFP became series difficulty problems. In the paper, based on theresearch and comparative analysis,proposed a new circuit topology to solvethese new problems.First of all, the paper introducesp qand based on the instantaneousreactive power theory, using a i p iqalgorithm without PLL, this algorithmmay reduce the influence of frequency fluctuating of network voltage effectively,and simplified the circuit structure. Built a three-phase power system simulationmodel,then make a simulation research on the cut-off frequency of the LPFwhich has an important influence of the detection precision.Secondly, on the study and analysis of the traditional multi-level circuitcombined with the soft-switching technology, put forward a novel three-phaseand single-phase cascaded inverter topological structure with auxiliary resonantcircuit. According to the structural characteristics of the novel inverter put ahybrid triangle carrier modulation strategy. The switching frequency of2H-bridge is low an order of magnitude than three-phase bridge, thus couldreduce the switching-loss of the whole inverter. The three-phase bridge unit isbearing the main output power, and the2H-bridge used as auxiliary supplementof switching frequency. An auxiliary resonant pole circuit is applied in thehigh-frequency three-phase unit to reduce the switching loss furthermore, and itwould not affect the independence of each phase. Then make a simulationresearch with the software of Matlab, the result of the simulation show that the peak-current on the turn-on time and the tail current on the turn-off time wereinhibited effectively. So the validity and efficiency of the novel topology wasproved by the simulation.Finally, the novel inverter is applied to the main circuit of active powerfilter, using the software Matlab/Simulink make a simulation research for theactive power filter with new-topology. It proved that the novel active powerfilter can be working effectively.