Research And Applicationon Key Technologies Of Active Power Filter

With the development of modern power electronic and control technology, a large amount of power electronic equipments are widely used, which also bring serious power quality problem into the electric power system. Active power filter (APF) is one of the most effective methods to improve the power quality and reduce the distortion of power system. However, as lacking in maturity of APF in our country, there are still a number of problems need to be solved. For this purpose, it makes a study around the harmonic detection, current and voltage control technique of APF. The settings of important parameters and the designment of the main circuits are discussed deeply.It is critical to detect harmonic current accurately and rapidly for the compensation performance of APF. In this paper, a comparative study is made on the type selection, filter order, passing frequency and realization of low pass filter. By using coefficients quantitative analysis approach, a rapid and stable digital low pass filter designment is proposed and its rationality is verified by simulations and experiments. To improve the dynamic response and reduce steady-state error, via analyzing the relation between the pole-zero location and the dynamic performance of harmonic detection, the paper proposes a design method of elliptical digital low pass filter with a lead-lag correction network. To get a better detecting performance at same sampling frequency, the paper proposes a harmonic detection method based on compressive sensing. Firstly, it makes a compressive sampling on original harmonic signal based on compressive sensing theory. Then, compressive sampling matching pursuit (CoSaMP) method is used with a sample sequence to detect and reconstruct harmonic. The results show that the method proposed can reduce the response time, improve the accuracy of harmonic detection and compensation performance of APF.In this paper, fuzzy control based variable bandwidth hysteresis current control strategy is presented for the problem that the hysteresis current controllers with fixed bandwidth for APF have limited compensation capability. By discussing relation between the harmonic current compensation capability and the bandwidth of the hysteresis control, the fuzzy rules are established according to the error and its changing rate of compensation current, which can improve the compensation capability and solve the problem that the current tracking capability is inadequate at the crossing zero and vertex points of harmonic current. Moreover, by analyzing the existing DC-bus voltage control methods, a nonlinear method is proposed to discuss the stability of the system focusing on the limiter which is a key part of the control loop. And an effective limiter is designed to regulate the DC-bus voltage with fuzzy theory. At last, for eliminating the undesirable impact of the coupling between the DC-bus voltage and the compensation current, a multivariable adaptive control method for nonlinear system based on data driven and multiple models is also proposed to deal with the nonlinear problem and system modeling of APF. The switching mechanism can make a switchover between the linear adaptive controller and the data driven nonlinear multivariable adaptive controller according to the system operation condition. While the linear controller ensures the system is stable, the nonlinear controller can identify the non-modeling parts and improve the dynamic performance. Then, the stability of closed loop and the convergence of the method are also proved in the paper. The simulations and experiments show that the control method can meet the requirements of APF system designment, and make the system have better dynamic performance and anti-disturbance capability.This paper makes a further study on the important parameters and circuits of three-phase three-wire shunt voltage type APF. It carefully discusses the parameter setting principle of DC bus voltage, DC capacity and AC inductance. It selects the type of IGBT and drive circuit by comparison. The paper also optimizes the parameter of RCD and PLL, then designs the soft-start circuit and system protection circuit. Based on the analysis and designment ahead, it sets up a 100kVA APF experimental prototype and carries out experiments. The results of simulation and experiment show that the designment of APF is logical and effective. These can produce a positive effect on the research and production of APF.