Active damping control of PMSG with LCL filter in tidal generation system

This paper has researched on the control strategy of PMSG direct-drive tidal generation system with LCL filter. Firstly, the model of PMSG (permanent magnet synchronous generator) with LCL filter is established in dq-frame, and then according to the analysis of the model, the equivalent circuit and admittance seen from the converter side in dq-frame is obtained. The bode figure shows that the LCL filter may resonance the harmonic current and even break the stability of whole system. One way to restrain the resonance is in parallel or in series a resistance with the capacitor in AC filters which is called passive damping. However, the physical resistance in passive damping will cause the energy loss. So an active damping strategy using a virtual resistance parallel with capacitor in LCL filter is proposed to restrain the resonance and reduce the stator current THD. Based on the active damping, the control system of PMSG is designed, in which the rotor speed is controlled and the unity power factor is realized. Finally, the simulation results have verified the effectiveness of the proposed control strategy.