A double switching table based direct power control strategy for three-phase voltage source PWM rectifiers

Firstly, an improved strategy of direct power control (DPC) is proposed to solve the complexity problem of sector determination and reactive power cyclical fluctuation problems under the traditional DPC strategy in three-phase voltage source pulse width modulation (PWM) rectifiers. The improved strategy adopts two switching tables and chooses the different ones in accordance with the reactive power errors. Then the new algorithm of sector determination is presented aiming at avoiding the complexities involved with coordinate transformation and arctangent function. Furthermore, the principle of selecting the switching tables is provided to reduce the switching losses and enhance the reactive power response speed. Finally, a simulation model is established under MATLAB/Simulink environment to compare with the results obtained from both the proposed and the traditional DPC strategies. The simulation results show that the proposed strategy has much lower total harmonic distortion (THD) rate at the AC side, meanwhile the response time for both active and reactive powers reaching the steady state is reduced by 38.5% as compared with the traditional approaches.