Improved Direct Power Control of Three-Phase PWM Converters

This paper proposes a new direct power control (DPC) strategy for a three-phase PWM converter with constant switching frequency. Similar to an electrical machine, source and converter flux which equal the integration of the respective source and converter voltage are used to define the active and reactive power flow. Different from conventional look-up-table based DPC, the required converter voltage vector with a fixed half switching period is calculated from the active and reactive power errors. With such a configuration, a constant switching frequency is readily achieved, which eases the design of the power converter and the AC harmonic filter. Both simulations and experimental results are provided to demonstrate the effectiveness and robustness of the proposed control strategy during active and reactive power steps, and line inductance variations. Compared to conventional DPC, it not only facilitates a constant switching frequency, but also results in less power ripple and current distortion.