Minimum loss control of a variable speed offshore interior permanent magnet wind generator integrated to a weak grid by a voltage source - High Voltage Direct Current link

The paper presents a speed and current controller design that provides the maximum power from the wind turbine and minimizes copper loss of the generator under varying wind speed. The paper also presents a grid side inverter controller design which keeps the DC link voltage of the inverter constant and controls reactive power flow to maintain unity power factor. Additionally, an estimated frequency controller is presented to provide estimated grid frequency to the gird side system. A copper loss minimization technique that maintains the maximum torque of two mass model wind turbine and the maximum power point tracking under varying wind speed are applied in the generator side controller design to obtain optimal speed and current for the generator. The inner and outer loop controller design is applied to the rectifier controller at the machine side and the gird side inverter controller. The phase lock loop controller is designed to estimate grid frequency for the grid side system. Simulation results are presented to show that the designed controller at both machine side and grid side track their reference values and confirm good performance of the controller design.