Study Of Direct Drive Square Wave Permanent Synchronous Wind Power Generation System Based On Z Source Inverter

In this paper, a direct driven square wave permanent synchronous wind power generation system based on Z source inverter is presented. Z source inverter is a new power conversion. The Z source inverter employs a unique impedance network to couple the inverter main circuit to the diode front end and can be shoot through to boost the DC link voltage, so the widely range AC voltage can be obtained.The direct-drive permanent magnet synchronous wind generation system are attracting increasing attention. Becauce the system leaves out the gearbox, and that has greatly improved the stability and reliability of whole generation system. The aim of the electric control of direct drive wind power generation is mainly to speed of genetator and grid-connected inverter. The control of speed of genetator is aiming at the maximum power point tracking. A novel MPPT strategy is proposed in this paper. The output current of rectifier can be controlled by the shoot-through duty cycle of Z source inverter, so the armature current and electromagetic can be regulated , and the control of speed of generator is achived. When wind speed increases, the output current of rectifier should be decreased to keep electromagetic large, so the speed of generator can increase rapidly. So as to increase the output current of rectifier when wind speed decreases, the maximum power point can be tracked.The voltage and current double closed-loop controlling method can be still used for the three-phase Z source grid-connected inverter. The current inner loop uses direct current control based on rotating coordinate transformation and decoupled d-q axis current to ensure system working in unit power factor. According to the average voltage in the inverter dc-bus is equal to the capacitor voltage of the Z source inverter, the capacitor voltage of the Z source inverter is introduced in the control unity. To maintain capacitor voltage of Z source inverter and the system power dynamical equilibrium, the system continually regulates the output of activer power of inverter to guarantee the quality of output power.MATLAB/Simulink tool box is employed to construct the dynamic simulation modul for whole stall regulation wnd turbine generator system so that the dynamic operation of the system may be simulated, and the experiment results validate the operating principle.