An improved direct power control of PWM rectifier with active power ripple minimization

This paper presents an improved direct power control (DPC) to achieve active power ripple minimization for three-phase PWM rectifiers. Conventional switching-table-based DPC (STDPC) selects only one voltage vector from a heuristic switching table for the whole control period, leading to high power ripples at steady state. Contrary to STDPC, the proposed DPC divides the control period into two intervals: one for the active vector from a switching table and another for a null vector. The principle of active vector selection is discussed in detail based on geometry illustration and mathematical analysis. The duration of the active vector is analytically obtained based on the principle of active power minimization. Simulation and experimental results prove that, compared to conventional STD-PC, the proposed DPC achieves much lower power ripples and less line current harmonics at steady state, even if the sampling frequency is halved. Meanwhile, the merits of decoupled active and reactive power control and fast response of conventional STDPC is maintained.