Wind Power And The Network Side Of The T-filter Design And Control Strategy

In grid-connected system of wind power generation, the development of grid converter is the core technology. The traditional grid converter use single inductor filter, which require large inductance and high cost in high power grid-connected systems whose switching frequency is low and small power ones as well whose grid current is low. Because of superior high-frequency characteristics and requiring small inductance, T-filter is going to replace the L filter. On the other hand, the control algolithm of T-inverter is much more complex due to the increase of filter's order and the appearance of resonance.To illustrate the working principle of PWM inverter, This paper analyses commutation process of single phase PWM inverter with L-filter, and then establishes the mathematical model of single phase PWM inverter with T-filter. In addition, this paper analyses the impact on the grid current's harmonic, AC side current ripple and resonance frequency with the varied combination of T-filter's parameters. Then provide the optimal method of designing T-filter's parameters. Moreover, to eliminate the resonance of T-filter, this paper quotes the passive damping method and active damping method previous scholars proposed, by which decreases the transmission gain on the resonance frequency and improves the system's stability.Different current-feedback control strategies are discussed and the performance are compared. Using MATLAB's Simulink toolbox, this paper simulates the single phase grid-connected inverter with L filter and LCL filter separately, compares the grid current's harmonic, and the result prove the validity of theoretical analysis above. In addition, this paper sets up experimental platform of single phase grid inverter and finishes the grid experiment respectively based on L-filter and T-filter and then analyzes the grid current of both.