Flexible Grid-connection Technique of Quasi-Z Source Photovoltaic Power Generation System based on Direct Power Control

To make the Quasi-Z-source inverter applied in photovoltaic systems better, a flexible grid-connection method based on direct power control is proposed. The proposed method adopted grid power to control APF directly, thus the detection of harmonics and reactive current of loads is omitted. Moreover, space vector modulation(SVM) is adopted to keep switching frequency constant and improve dynamic performance. In this paper, the reference value of power control loop is acquired from the Quasi-Z source network and the power compensation required by maximum power point tracker(MPPT) is also considered. Therefore a comprehensive optimization of active power loss and the compensational performance is achieved. Besides, the control reliability is improved and the cost is reduced. Simulation results verified the validity and feasibility of the approach.