Wind is an inexhaustible natural energy source that human beings has used in one way or another for millennia. At present wind power plant which used wind energy to generate electricity were operated around the world. A great many wind farms with large numbers of wind turbines has been constructed in recent years around the world, and offshore wind farms were the becoming popular. A commonly used WG control system is based on the WG optimal power versus the rotating speed characteristic, which is usually stored in a microcontroller memory.The WG rotating speed was measured then the optimal output power were calculated and compared to the actual WG output power. The resulting error has used to control a power interface. In the same way the WG output power was measured and the target rotor speeds for optimal power generation were derived from the WG optimal power versus rotor-speed characteristic. The target rotor speed has compared to the actual speed and the error was used to control a dc/dc power converter. In permanent-magnet (PM) WG systems, the output current and voltages are proportional to the electromagnetic torque and rotor speed respectively.
The rotor speed was calculated according to the measured WG output voltage, while the optimal output current is calculated using an approximation of the current versus the rotational-speed optimal characteristic. So that different types of controller are used to get the better operation characteristics. PI controller was eliminated forced oscillations and steady state error resulting in operation of on-off controller and P controller respectively. PD controller was Often derivative not taken from the error signal but from the system output variable. This was done to avoid effect of the sudden change of the reference input that would cause sudden change in the value of error signal. PID controller has all the necessary dynamics: fast reaction on change of the controller input (D mode), increase in control signal to lead error towards zero (I mode) and suitable action inside control error area to eliminate oscillations (P mode).
PID controller is often used in industry, but also in the control of mobile objects (course and trajectory following included) when stability and precise reference following were required. Conventional autopilot was the foremost part PID type controllers. The general Z – source inverter network employed a unique impedance circuit to couple the converter main circuit to that of the power source in order to obtain the unique features that cannot be achieved using conventional VSI or CSI. The Z-source inverter (ZSI) has the capability of voltage boost and inversion in a single stage.
The unique feature about Z- source inverter was that the output voltage could be anywhere from zero to infinity. The inverter could perform both buck and boost operation and provide a wide range of output voltage which was not possible in conventional voltage source and current source inverters. The Z source inverter has nine permissible switching states which has an extra state compared to the conventional inverters. The extra switching two switches of the same leg is switched ON and conduct simultaneously which is not possible in conventional inverters.
