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Impedance (Z)-source inverter can provide stable output by smooth controlling of shoot-through duty cycle of any of the traditional PWM bridge inverters. In this paper a control system for impedance-source inverter is designed suitable for wind power conversion system. The main challenge in wind power system to maintain a constant voltage at the output with unpredictable variation in wind speed, is suitably taken care in steady state through buck-boost-capability of z-source inverter (ZSI). The shoot through state of ZSI is able to control and boost the output voltage when the wind generator voltage is not more enough to directly generate the desired output. Again, the nonshoot through state can control and buck the output voltage when the wind generator voltage is more than desired. So, the zsource PWM inverter replacing the conventional PWM inverter provides the unique output voltage regulation feature by making an appropriate choice of buck-boost factor. The closed loop controller carefully monitors the wind generator voltage and controls the shoot-through and non-shoot through duty cycles automatically. The whole system is simulated under arbitrary input variation condition and results are presented. A comparison between the traditional and z-source inverter based system is also presented, which clearly indicates the benefits of the proposed system. Index Terms--closed loop control, Impedance-source inverter, wind generator. VII. BIOGRAPHIES

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The variable wind generator output due to unpredictable variation in wind speed is suitably controlled through a closed loop system employing the buck-boost capability of quasi z-source inverter derived from traditional zsource inverter (ZSI) and is converted into a three phase power. The quasi z-source inverter inheriting all the advantages of the traditional ZSI replaces the conventional PWM inverter in the system. Additionally, the quasi ZSI has the unique advantages of lower component ratings and continuous dc current from the source. The closed loop controller carefully monitors wind generator voltage and controls the shoot-through duty cycles of the inverter employing third harmonic injection constant boost control to develop a three phase steady boosting voltage, which is not possible by conventional PWM control. The whole system is modeled, analysed and verified through simulation and hardware arrangement. It provides the unique output voltage regulation by making an appropriate choice of boost factor under both arbitrary generator voltage and variable load conditions. The proposed closed loop system, therefore, can be used for smooth and effective dynamic and steady state control maintaining the three phase output at a desired level.Keywords-Quasi z=source inverter, power converter, wind power,closed loop system.