Study Of Active Power Filter For Micro Grid

As an efficient supplement of normal grid, micro grid has many merits and huge developing potential, at the same time, its power quality problems are quite different.Aiming at harmonic current suppression and reactive power compensation of micro grid, an Active Power Filter suitable for micro grid is proposed in this paper.The characteristics and improve methods of micro grid power quality problems are introduced, the feasibility of harmonic current suppression and reactive power compensation with APF is analyzed, and a general mathematical model of APF is built. Two common harmonic current abstract methods of APF: p-q method andp qi-i method based on the instantaneous reactive power theory are introduced, and the performances of both methods are analyzed. The Phase-Locked Loop of APF is introduced, the capabiliti’s difference of two common software Phase-Locked Loops: Single Synchronous Reference Frame Software Phase Locked Loop(SSRF-SPLL) and Decoupled Double Synchronous Reference Frame Software Phase Locked Loop(DDSRF-SPLL) is dicussed. Three classical current tracking control methods:Triangle-carrier Control, Hysteresis Current Control and Space Vector Pulse Width Modulation(SVPWM) based on voltage feedforward are analyzed, and their characteristics are discussed,then, some advanced harmonic current abstracting methods based on Artificial Neural Network and Wavelet Transform and some advanced current tracking control methods like One Cycle Control and Fixed-Frequency Hysteresis Control are introduced.Three main modules of APF: Phase-Locked Loop, harmonic current abstract method,current tracking control method are simulated on the platform of MATLAB/Simulink. The fact of DDSRF-SPLL’s performance is better than SSRF-SPLL,p qi-i method’s robustness is better than p-q method, SVPWM based on voltage feedforward control is more suitable for micro grid than Hysteresis Current Control are certified by simulation results, the results also provides an important reference of designed APF prototype’s module select.An APF prototype based on TMS320F28335 DSP is designed; an experimental platform is built to monitor three most common load situations of micro grid: symmetrical-load,variable-load and unsymmetrical-load, the compensating performance of APF prototype is tested in each situation. After test, a series of satisfactory results are obtained, but the improving of compensating accuracy is needed.