Improved Synchronous Detection Algorithm And Its Applied Research, Active Power Filter

Accompanied with the development of the technology of electrical power & electronics, all kinds of transducer, converter and switch power are widely applied on every areas of modern society. As a result, the harmonic problem of electricity net becomes worse and worse. As an effective tool of restraining harmonics and compensating reactive power, the active power filter (APF) is developed and applied widely, because of its excellent compensating performance and uninfluenced by the impedance and status of electricity.The algorithm of detecting harmonics and reactive components, the mathematic basis of APF, determined the performance of APF. In three-phase distorted and unbalanced systems, the conventional instantaneous reactive power theory and synchronous detecting method all have limitation. In the thesis, an advanced synchronous detecting method is proposed, which replaces the phase voltage by fundamental positive sequence voltage. It can overcome the limitations of conventional methods. The theoretical analysis and simulation verified the feasibility of this method. And then the performance of low pass filter is analyzed, which plays an important role in the performance of the whole algorithm. In order to improve the performance, a method to improve low pass filter is given in this article. Because the advanced synchronous detecting method should be applied on three-phase four-wire system, the thesis does deeper research on three-phase four-wire parallel active power filter, which is the physical equipment to achieve the algorithm. The influence of the parameters and the control strategy to the performance of compensating is analyzed by a series of simulations. At last, this thesis introduces the design of hardware and software system of APF, which based on the digital signal processor TMS320VC5402 and advanced synchronous detecting method. The result of the experiment verified the feasibility of the method.