Control of bidirectional DC/DC converter for back to back NPC-based wind turbine system under grid faults

Viability and reliability of the wind power has made Wind Turbine Systems (WTSs) a popular renewable energy resource. A bidirectional DC/DC converter is proposed in this study for the WTS. The proposed DC/DC converter controls the DC-link voltage by injecting the difference between the extracted power from permanent magnet synchronous generator (PMSG) and the output power of the grid-tied inverter, to the energy storage system. The proposed DC/DC converter controller compensates the shortage of extracted active power from PMSG under wind reduced speed condition in order to inject the constant power to the grid during normal operation. The back to back (BTB) neutral point clamped (NPC) converter is proposed to extract the maximum power from PMSG and inject the extracted power to the grid. The proposed WTS structure achieves fault ride through capability and it can inject reactive power to the grid in order to enhance the PCC voltages under voltage sags. The proportional resonant (PR) current controller is implemented for both rectifier and grid-tied inverter due to its fast response and low steady state error. The adaptive space vector modulation (ASVM) is used to generate the switching signal while balances the DC-link capacitor voltages. The performance of the proposed controller is investigates under grid faults as well as reduced wind speed condition and results have proven the applicability of the proposed controller.