Research On Three-Phase Three-Wire Shunt Active Power Filter Based On DSP

In the process of industrialization and urbanization in China, electric power industry has achieved considerable development. However, due to the use of a variety of power electronic devices, numerous reactive power consumption and harmonic pollution sources have emerged in the parts of generating and transmitting of electricity and power utilization terminals. Problems of harmonic suppression and reactive power compensation have become the hotspot of current research. As a comprehensive control device, active power filter has received extensive attention and research. This paper do systemic and deep research on the harmonic detection method, main circuit design method and current closed loop control in the three-phase three-wire active power filter.The reasonable harmonic detection algorithm should be confirmed first in the use of active power filter. This paper analyzed the mechanism of the SRF method and PQ method decomposition harmonic currents, summed up the advantages and disadvantages of the SRF method and PQ method in harmonic detection. Meanwhile, to deal with the time domain harmonic detection algorithm of active power filter, a high performance digital low-pass filter is present based on the comparison and analysis between infinite impulse response filter (IIR) and moving average filter (MA), which can satisfy the requirements of dynamic response and filtering accuracy simultaneously by cascaded MA filter and Butterworth filter optimally. The proposed high performance filter can make full use of Butterworth filter to achieve more precise filtering result and improve dynamic response by using MA filter with its narrow transition zone and fast dynamic response.Active power filter need reasonable main circuit design to ensure the current closed loop compensation effect. The detailed principle of LCL filter is introduced in this paper. Based on analyze of the influence of gird voltage on the LCL filter, the necessity and feasibility of grid voltage feed-forward control is present. To some extent, LCL filter design is difficulty, then the general design guidelines and procedures of LCL filter are introduced in this paper. LCL filter is designed in accordance with the actual needs. Furthermore, the mathematical model of APF based on the LCL filter in three phase static field is established.For grid connected inverters such as active power filter, the current loop control is the core issue. This paper present detailed analysis of the PID control in LCL filters control and obtained a stable PI controller through the root distribution analysis. Simulation results show that the PI controller is effective and practical. The experimental hardware platform and software processes are introduced briefly at the end of this paper. Experimental results show the active power filter technique route mentioned in this paper is effective and practical.