Research Of Shunt Active Harmonic Suppression System In Low Voltage Power Supply

As long as the wide use of power electronic device, more and more people pay attentions to the harmonic pollution. Active power filter will be one of the most important approaches to improve the power quality. But active power filter has not reached the mature stage in the domestic applications, and there are many problems to be studied and solved. Compared with passive power filter, active power filter still stay in less important position in actual application. For this purpose, some key technologies were researched, including harmonic current detection, the current tracking control, the inverter DC side capacitor voltage control and the selection of the main circuit parameters. The study was mainly aimed at shunt three-phase three-wire active power filter.Harmonic current detection is one of the key technologies of active power filter. Three kinds of simple and effective detecting methods were introduced, including: the detection method based on instantaneous reactive theory, the detection method based on the FBD theory, the. detection method based on the sliding Fourier transform. Simulations were constructed to verify the validity of the three kinds of detection methods.The parameters of active power filter main circuit, to a great extent, affect the performance of active power filter. Based on the analysis of relation between the parameters and the performance, the methods of the parameters' selection were researched. It is the base that the voltage of the capacitor was maintained constant, so the method to maintain the voltage constant was researched too. A method of the capacitor soft-start was introduced, and a simulation was constructed to verify the validity of the method.The control of current tracking is another key technology of active power filters, whose performance directly affects the filtering effect of the filter. Based on the mathematical description of the main circuit, two kinds of current tracing methods based on voltage space vector were introduced, and some simulations were constucted to verify the validity of the methods.