Control Strategy Of Electrically Excited Direct-driven Wind Power Generation

The back-to-back inverter control technology applying in renewable energy has been studied in this thesis. The research object is the electric excitation direct drive wind power system. The grid-connection control strategy of steady state and transient state of the converter has been mainly researched, and simulations and experiments are also provided in this thesis. The main research contents are as follows:Firstly, the models of grid-side converter in the static coordinate system and synchronous rotating coordinate system are built; Study one of phase locked loop technique which can separate the positive and negative sequence contents from input signals so that apply to the power grid voltage unbalance control; Perfect grid inverter control scheme is given by reasonable selection of phase-locked loop and current regulator.Secondly, this thesis builds mathematical model of the electric excitation synchronous motor in synchronous rotating coordinate system and MT system, and studies on the air gap flux linkage oriented vector control strategy of synchronous motor with flux observer based on low-pass filter compensation integrator.Then, the thesis introduces voltage sags as the grid faults. The electric excitation direct drive wind power system characteristics are analyzed during voltage sags, symmetric, asymmetric and voltage drop of electric excitation wind power system low voltage through schemes have been given.Finally, a experiment platform containing one capacity of25kW electric excitation synchronous generator dragged by a asynchronous motor has been built. Many experiments including the positive and negative sequence separation phase-locked loop based on reduced order resonance controller, the electric excitation direct drive wind power system interconnecting to grid, machine side converter harmonics suppression, low voltage ride through were done.