Abstract: This dissertation discusses application of advanced power electronics in small size wind energy and hybrid systems. A new control method for maximum power tracking by employing a boost converter at a wind turbine system, using permanent magnet machine is introduced. Output voltage of the generator is connected to a fixed dc-link voltage through a rectifier and the boost converter. A maximum power-tracking algorithm calculates the reference speed as the control signal for the converter. The converter uses this signal to control the output power of the generator, by controlling the output voltage of the rectifier and input current of the converter. A current regulated voltage source inverter maintains the output voltage of the converter at a fixed value by balancing the dc-link input and output power. Moreover, a new speed estimator for maximum power tracking and a novel vector control approach are introduced. The speed estimator only needs two measurements to estimate the generator speed for maximum power-tracking. Furthermore, since the system maintenance is important and in wind energy systems the generator is not easily assessable, a robust technique for on-line condition monitoring of stator windings is introduced. In this technique the generator terminal voltage and current are utilized to monitor the stator winding condition to prevent catastrophic failure. Also a hybrid system consisting of a wind turbine, a photovoltaic, and a fuel cell is introduced. A simple control with dc-dc converter is used for maximum power extraction from the wind and sun. Due to the intermittent nature of both the wind and photovoltaic sources, the fuel cell unit is added to ensure continuous power flow. The fuel cell is controlled to provide the deficit power when the combined wind and photovoltaic sources cannot meet the net power demand. The proposed system is attractive owing to its simplicity, ease of control and low cost. Chapter 5 focuses on the design of a novel Power Conversion System to convert the energy from the hybrid system into useful electricity and provide requirements for power grid interconnections. The motivation behind developing this system is to reduce the overall cost of hybrid systems.
Keywords: Hybrid system,Power converter,Speed estimator, Wind energy