Wind Power Grid-Connected System With Dual Half Quasi-Z-Source Inverter

As a green,non-pollution renewable energy generation method,wind power generation has become an effective way to mitigate global environmental pollution and energy crisis.Direct-drive permanent magnet wind power generation system has become a major development trend of wind power generation due to its high efficiency,simple structure and good stability.The grid-connected inverter is the core of the direct-drive permanent magnet wind power generation system,and its topology improvement has been widely studied by scholars all over the world.The impedance source inverter provides a new idea for direct-drive permanent magnet wind power generation due to its single-stage control and allowing the inverter bridge arm to shoot through.Based on the direct-drive permanent magnet wind power generation system,this paper proposes a dual half quasi Z source network inverter topology,which is applied to the direct-drive permanent magnet wind power generation system to realize the grid-connected operation of the system.The main work has been done includes:(1)A dual half quasi Z source inverter is proposed in this paper,and the relationship between boost voltage gain,modulation factor and shoot through duty ratio is analyzed.The small-signal model of the system is established,and the relationship between the inductors and capacitors of dual half quasi Z source network and system performance is analyzed.(2)Based on the space vector six-segment shoot through PWM strategy,the inductor current and capacitor voltage ripple of the dual half quasi Z source network,the voltage and current stress of the impedance source network diode,and the voltage and current stress of the inverter bridge switch are analyzed.It provides the theoretical basis for device parameter selection of dual half quasi Z source network inverter.(3)In order to meet the grid-connected requirements of direct-drive permanent magnet system based on dual half quasi Z source network inverter,the mathematical model of DHQZSI-based direct-drive permanent magnet wind power grid-connected system in different coordinate systems is analyzed.According to the characteristics,a DHQZSI-based direct-drive permanent magnet wind power generation grid-connected control method is proposed,and the effectiveness of the method is verified by RT-LAB.(4)Taking the energy storage crowbar as an example,the voltage stress,boost ratio and stability of the switching device of the crowbar circuit are analyzed by comparing the different access points of the crowbar circuit under the grid voltage fault.It provides a theoretical basis for the selection of the Crowbar circuit access point under the grid voltage fault of the direct-drive permanent magnet wind power grid-connected system.