Abstract:
Taking the three-phase voltage source pulse width modulation (PWM) rectifier as the research target, a direct power control (DPC) strategy based on new switching table is proposed in this paper. Firstly, according to the mathematical model of rectifier in two-phase rotating
dq coordinate, the control amplitude of switching vector to active power and reactive power is calculated, and normalized value is utilized for quantitative analysis. Based on this, the 12 sectors of traditional DPC are subdivided into 24 sectors. Then an active power differential interval judge is designed to construct a new switching table to achieve accurately control of active power, in which the optimal switching vector in current sector can be selected according to output value
Cp of designed judge, the output value
Sp,
Sq of active power and reactive power hysteresis comparator. Simulation comparison indicates that the new switching table not only overcomes the shortcomings of the traditional switching table in terms of poor control of reactive power, but also improves the current total harmonic distortion (THD) on grid side and reduces the output DC voltage fluctuation and active and reactive power ripple. Finally, an 800W three-phase voltage PWM rectifier prototype is built to verify the correctness and effectiveness of the proposed control strategy through comparison experiments.