Investigation Of Current Source Grid-Connected Inverter For Small-scale Wind Turbine

Wind energy is the abundant renewable clean energy. Wind generator and its grid-connected inverter become the hot topic at present, and small-scale wind power generation system is the focus of the study. Most of the small-scale permanent magnet (PM) wind turbine has small inductance, which has the disadvantage of small operating range of wind speed. Along with the change of wind speed, the output current from a small-scale PM wind turbine with large-inductance can be kept the same. This makes them have the advantage of large operating range of wind speed. Therefore, this thesis studies the current source grid-connected inverter for large-inductance small-scale PM wind turbine.Firstly the classification of small-scale PM wind turbine according to the inductor size was introduced in this thesis. Then four topological structures of grid-connected inverter for small-scale PM wind turbine were analyzed. Based on above analysis, the current grid-connected inverter topological structure for the large-inductance small-scale PM wind turbine was proposed and its control strategy was studied. This topological structure has the advantages of easy control and low cost since it uses less electronic devices. In order to verify the correctness of this topological structure, a simulation model of the grid-connected inverter in PSIM simulation environment was built. The simulation results show that this small-scale PM wind turbine has the constant current characteristics in a wide speed range and the proposed grid-connected inverter can output the grid-connected current waveform. In order to reduce the harmonics in grid current, the feed-forward control strategy of grid-connected inverter was studied. Simulation results show that it can further improve the output current waveform.To further validate the feasibility of the inverter topological structure, the hardware experimental platform based on dsPIC30F4011was established and the control program was debugged in the MPLAB IDE v7.62environment. It includes current switching modulation circuit, unfolding circuit, triggering circuit, isolating drive circuit and zero-crossing detecting circuit, etc. Preliminary experiments show that the grid-connected inverter topology presented in this thesis can achieve the expected functionality.