Investigation on SSCI between PMSGs-based wind farm and AC network

摘要

The sub-synchronous control interaction (SSCI) has frequently occurred in the direct-drive permanent magnetic synchronous generators (PMSGs) based wind farm integrated to the weak AC network. The system strength, i.e. short-circuit ratio (SCR) has been believed as the critical factor so far. However, the impedance-frequency characteristics of the practical network exhibit a strong resonance that might have impacts on the SSCI as well. In this study, considering the network resonance, the eigenvalue- and impedance-based analyses are conducted to study the SSCI phenomenon in the grid-connected PMSG system. The impacts on SSCI from system strength, network resonance and network-resonant frequency are investigated firstly. Then, the parameter limits of PMSG control for the stable region are calculated to discuss the effects of network resonance on the parameter design. The results show that the network resonance plays a critical role in the SSO mode. When the network resonance is considered in the PMSG system, the SSO would arise more easily, and the stable region of the control parameter will be reduced. Meanwhile, the frequency of the SSO mode matches well with the network resonance frequency in dq frame. The analytical results are all verified by simulation.