Research On Theory And Application Of Four-switch Three-phase Shunt Active Power Filter

With the development of power electronics technology, all kinds of large power capacity switching components are widely used. On the one hand, they made Power energy transformation and application conveniently, on the other hand, they lead to the serious reactive power and harmonic current pollution in the power system. The functions of active power filter(APF) to compensate the reactive power and harmonic current is recognized in common, and it has been a key project in power electronics application technology to study the active power filters. But APF has not reached the mature stage in the domestic applications, and there are many problems need to be studied and improved, such as how to get a more economic APF solution to adapt to the low-voltage power grid, how to ensure the effective operation of APF in a abnormal condition, how to realize the product of APF faster, how to deal with the engineering problems in the application of APF, etc.Based on the background above, this paper analyse the typical topology clearly, and a new categories method is presented in accordance with the demand of the detail market. Consider of the product-forming and economic benefits, A four-switch three- phase shunt APF is presented to fit for the harmonic and reactive power control with medium and small capacity in low-voltage. The detecting, control, production realization and application technologies are studied deeply, the result of these research proved the availability of the function and performance. A new idea and approach in the economic studies and engineering applications is represented in the study. There are great importance in theory and practice to the development of APF.This paper discussed the method to obtain the direction current of APF, and a direction current calculation method based on the DC bus voltage is presented. This method use the positive sequence fundamental current as the direction current for APF. The response time and adaptability is improve by the apply of fuzzy-PI controller. The correction loop for amplitude of positive sequence fundamental current is studied, and phase angle detection of fundamental positive sequence voltage is designed. The designed mentioned above determines that APF can work safely and effectively with unbalance voltages and short time faulting of power grid. A DC bias voltage compensator based proportional control algorithm is researched, which ensures that mid-point of DC voltage is balanced. Simulation and experiment results proved the feasible and effective of the direction current calculation method.The space vector PWM (SVPWM) technique of output current modulation is studied in this paper. Firstly, the basic theory of the SVPWM algorithm based on six-switch three-phase shunt APF is elaborated. Then the algorithm is extended to the four-switch three-phase system. A new SVPWM algorithm is proposed based on four-switch three-phase shunt APF current modulation. The six-switch three-phase SVPWM modulation algorithm can not be applied in the four-switch three-phase system directly. The SVPWM algorithm fit for four-switch three phase modulation is acquired through the obtain of the equivalent zero vector. Simulation and experiment results proved the feasible and effective of the algorithm.The product design and implementation methods of APF is discussed in this paper. The way of system constitutes of four-switch three-phase APF is given. The key technology including the choose of power switching component, the parameters design of the buffer circuit, the design of the DC capacitor, the output filter, the hardware and the software design of control system are researched deeply. The design principle of the key parameters and the selection method of the key components are presented.The functions and performance of four-switch three-phase APF are verified effectively through the experimental study. First of all, the experimental platform and key equipments are introduced. Then, the experiment of DC bus voltage stability, Steady-state and dynamic-state compensation experiment, the influence of different control algorithm to the compensate are performed. The perfect compensation effect of four-switch three-phase shunt APF in different parameter and environment is verified.At the end of the paper, the engineering application case of four-switch three-phase APF is introduced and analyzed in detail. The analysis about the largest value of harmonic current injected into the point of common coupling proved the necessary of harmonic control. The THD of the voltage harmonic and current harmonic reduced obviously after APF put into operation. The application results proved the correctness, the feasibility and the effectiveness of the design about four-switch three-phase shunt APF.