Research On Single Phase Control Of Three Phase Four Bridge Active Power Filter In Distribution Power Network

In power distribution network, the distorted current and voltage cased by the power electronic equipment will deteriorate the quality of power supply. And the three-phase uneven load planning and random operation of single-phase load will lead to unbalanced three-phase load current, increasing the line loss. Among all those management method, three-phase four-wire active power filter is superior. Because they can flexibly and accurately compensate harmonics and reactive power in power system, and balance three phase load current.This paper first introduced three kinds of3P4W APF topologies:split capacitor, three-phase four-arm and3H-bridge topology. Their advantages and disadvantages were analyzed. And it turns out that the three-phase four-arm topology is more suitable for low-voltage power distribution network application with different phase compensate strategies were demanded.Then, using split phase harmonic detection to eliminate the influence to the calculation of harmonics caused by unbalanced three phase voltage. And then through the integration and subdivision of three phase active power, the three-phase current can be balanced. The phase lock characteristics respectively based on multiplication detector, delay construction detector and differential construction detector were analyzed. Compared with other detectors, the delay construction detector was found to be more suitable to use in the proposed harmonic detect method. The cascading combination of a trap filter and Butterworth low-pass filter was also used in the method to reduce the dynamic response time of frequency filter.And then, based on analyzing the compensation ability of active filter device and the characteristics of several kinds of traditional control method, a modified repetitive control method is designed for single phase control of3P4W APF. This method can compensate the control delay occurring in the control process, strengthen the high frequency disturbance resistance ability, and to overcome the traditional repetitive controller’s shortcoming:it cannot compensate within one period after load mutation. Simulation result verified the above characteristics of the improved repetitive controller.Finally, this paper puts forward a kind of four-bridge-arm APF control method in the ABC coordinate based on the zero inductance decoupling. Through feed forward decoupling to eliminate zero inductance coupling’s effects on ABC phase current control. Combining it with the proposed split phase detection technology, the nonlinear strong coupling APF was made into three single independent system to control, so the controller design becomes easier. The effect of inductance parameter error to the stability of decoupling control was analyzed. And the trend of decoupling effect influenced by the inductor error is given, so as to guide the engineering application. By simulation and experiment, the effectiveness of the proposed decoupling control method was validated.