Topology and SVPWM modulation strategy of the improved bi-directional z-source converter for energy storage

To overcome the shortcomings of traditional Z-source inverter such as high capacitor voltage stress, high inrush current in start-up process, presence of abnormal working state, and unidirectional power flow, we have proposed a topology of improved high-performance bi-directional Z-source converter by replacing the diode with a full-controlled switch which has an anti-paralleled diode. By controlling this switch, the inductor current of Z source can flow reversely, and the inductor voltage is clamped to capacitor voltage. This method eliminates abnormal state at light load or small Z-source inductor conditions in traditional Z-source or improved Z-source inverter, and keeps DC link voltage stable. In addition, the proposed converter can implement dual power flow control by controlling the direction of the inductor current. On the basis of theoretical analysis, we put forward an improved space vector pulse width modulation strategy. The simulation results indicate that the proposed topology not only reserves the advantages of low capacitor voltage stress and small start-up inrush current, but also realizes the operation at reactive load and dual power flow.