Study Of Direct Drive Permanent Synchronous Wind Power Generation Power Grid-connected System Based On Z Source Inverter

In recent years,along with the traditional energy is consumed and in the process of traditional energy consumed environmental pollution is becoming increasingly serious.Because of its many advantages,wind power has been paid more and more attention by the country as a kind ofefficiently clean renewable energy power generation.Wind power is the second-largest renewable clean energy following the hydropower,and wind power technology has become a focus for researchers,meanwhile,wind power generation technology has become more sophisticated.More and more scholars and institutions Direct-drive have realized the importance of the wind power converter system with PMSG because of its simple structure.It is one of the important research direction in the field of wind power.First,this paper is studying on the part of the grid connected inverter in wind power generation system.Aiming at the defects and deficiencies of traditional inverter,then a new inverter which is named Z-source inverter is discussed based on the analysis of limitation of the tradional inverter.The Z-source inverter constructed by adding Z type circuit grid to the tradional PWM inverter ha s some new features which tradional inverters doesn 't have.It employs a unique impedance network to couple the inverter main circuit to diode front end can be shoot through to boost the DC link voltage,so the widely range AC voltage can be obtained.A major feature of Z-source inverter is through the shoot through duty cycle adjustable voltage,so the modulation method of PWM is particularly important,many references has been described the modulation method of SPWM in detail,this paper will not repeat them,just introduced two kinds of modulation methods of SVPWM,simple and segmented.Because of the segmented SVPWM does not increase the switch frequency,the loss is decreased and with significant advantages,so this paper will use the method to be simulation.Through the analysis,the voltage and current double closed loop control of traditional still applies to the Z-source inverter.The inner current loop with direct current control based on d-q coordinate transformation,to achieve control of the network side current using state feedback coupling strategy.Due to the DC bus voltage of capacitor voltage is equal to the average value,Z network and Znetwork is introduced,the voltage can be maintained constant capacitor voltage outer loop control,to achieve the effect of the capacitor voltage is constant,ensure that the inverter output power quality,maintain the balance of power system.At the end of the main part of Z-source inverter circuit elements in the design parameters,selecting reasonable parameters,to build a direct drive wind power generation grid connected system simulation model of Z-source inverter based on the MATLAB/simulink environment,and the corresponding simulation,verified the feasibility of SVPWM modulation method and control strategy.