Space vector pulse-width modulation algorithm and DC-side voltage control strategy of three-phase four-switch active power filters

A space vector pulse-width modulation (SVPWM) algorithm and a DC-side voltage control strategy for three-phase four-switch shunt active power filters are proposed. The basic principle of three-phase four-switch inverters to output three-phase balanced voltages is investigated in detail. Based on an advanced coordinate transformation, the proposed algorithm ensures basic voltage vectors to be right on the coordinate axes of αβ-coordinate system, which has the advantages of less computation and higher accuracy than the traditional. It synthesises zero vectors by equalising the duration time of two basic voltage vectors, which are equivalent in amplitude and opposite in phase, to simplify control logic and decrease harmonics of output voltages. To stabilise the DC bus voltage and balance the DC-side capacitor voltages, a DC-side voltage control strategy is presented. The former objective is obtained by controlling the active partition of the output currents, and the latter one by adapting the direct partition of phase C output current. An overall control method combining the proposed SVPWM algorithm with the DC-side voltage control strategy is presented. Experimental results have shown the validity and feasibility of the proposed algorithm and strategy.