Design And Implementation Of Digital Controlled Three-phase Three-wired Shunt Active Power Filter

With the proliferation of nonlinear loads, the amount of harmonic current has increased. This causes the power quality beyond acceptable level in many situations. Therefore, the active power filter (APF) with its predominant compensate performance, has been a hot research spot in power electronics area. The shunt active power filter plays the most important role in the past or future.Firstly, this thesis has presented the system structure and operation principles of three-phase three-wire parallel APF. The analysis of harmonic detection and current control is based on mathematic model of APF.Real-time and accurate harmonic detection is the key for practical active filter implementation. Specified introductions of the three current detection ways based on instantaneous reactive power theory are given, and finally the d-q detection method based on Park transformation is used in our design. This thesis has presented a specified theory analysis of FFT, the summary of the rule of FFT calculation, the advantages of FFT calculation by using DSP, and the program flow chart of APF contains FFT.The SVPWM digital control is used in the current loop . PI controller is usually the core of control, but there is the limitation of pure PI controller in active filtering. In order to achieve better characteristics in the steady state of APF, this thesis has proposed a way of adding the repetitive control technology to the digital current loop. In this control strategy, the proportion-integral control is used to guarantee system dynamic performance and the repetitive control loop is to improve current waveform quality. The feed forward of network voltage and output current is proposed to decrease the impaction of voltage fluctuation on the performance of active power filter.This thesis has proposed the design of switch mode power supply. The experiment has proved that the system has a highly stability, a lower output ripples and a great practical value.In terms of the proposed control approaches and operation principle, a three-phase three-wire shunt active power filter is established and corresponding experiment and simulation studies are done. Through the simulation and experiment, it can be verified that the key techniques for APF described in this paper, including control strategy, main circuit design, harmonic detection and application solutions, etc, is viable and effective, which ensures the performance of active power filter.