On control strategy of Z-source inverter for grid integration of direct-driven wind power generator

In order to improve operation stability of grid-connected direct-driven wind power generators, the control strategy of Z-source inverter for grid integration and its low-voltage ride-through (LVRT) ability are studied. The boost control of Z-source inverter is investigated, and the possible operation ranges for voltage gain and modulation index, taking voltage stress on the devices into account, are given. According to the power balance principle of traditional grid-connected inverter, the power capacity of Z-source inverter is proposed and the theoretical formulation for active and reactive power limits is given. The control system of Z-source grid-connected inverter consists of control of capacitor voltage on Z-source network and control of power delivered to the grid, in which a low-voltage ride-through control strategy is proposed for direct-driven wind power generators using Z-source inverter. The simulation results show that the capacitor voltage on Z-source network can be stabilized so that the LVRT operation of direct-driven wind power generators can be effectively realized.