Current Predictive Control Research In Active Power Filter

Now, with the rapid development of power electronic technology, as well as improved requirement of electrical equipment to the electric power quality, the problems of harmonic suppression and improvement of reactive power compensation have gotten more attention. As a dynamic compensation equipment, active power filter(APF) has more advantages than other passive filter devices. Compared with other kinds of APF, this paper chooses three phase shunt APF as the research object and proposes a design scheme of shunt active power filter.This paper firstly introduces the harmonic source and harm, and analyzes the current research status of APF. Through its mathematics model, the structure of APF is presented. APF mainly includes harmonic detection, current control and dc side voltage control.The instantaneous reactive power theory is widely used in harmonic detecting, and the pq method and ip-iq method based on instantaneous reactive power theory are deduced in this paper. Calculation shows that ip-iq method can also accurately detect the harmonic current in grid distortion circumstance. this detection algorithm can be applied directly into asymmetric three-phase four wire system and won't produce zero sequence leak error.In the harmonic detection, second-order Butterworth low-pass filter is modified in view of its shortcomings. Butterworth low-pass filter and average current filter are serried in this paper. Simulation results show that the effect of improved low-pass filter is better than Butterworth low-pass filter.Real time and accurate harmonic current control is the key of APF. A harmonic current control based on predictive control is presented in this paper. Based on current predictive control, this paper builds system structure and carries on detailed mathematical analysis. including the design of given input smoothness, calculation of the next moment output value with forecasting model, introducing feedback correction and the building of performance index. Through calculation we can get the controller transfer function. Besides, the effects of parameters between the stability of system and dynamic response performance.After the completion of each link design etc, APF system is set up under the simulation model based on MATLAB/Simulink. Simulation results show that current predictive control system has good tracking recision and dynamic response performance. Compared with current hysteresis control, both have the same dynamic response performance. But, current predictive control is obviously superior to current hysteresis control in the control accuracy and robustness of the control system. Finally, this paper gives the APF software process based on DSP of TMS320F2812.