Analysis on the VSC based controller for damping SSR in multi-generator system

With the continuous expansion of the power system and the construction of the series compensator devices in Northwest China, interactions between the generators and the power grid become more complicated while the problem of sub-synchronous resonance (SSR) is more prominent. To deal with this problem, a controller named subsynchronous resonance dynamic suppressor (SSRDS) based on voltage source converter (VSC) for damping SSR of multi-generator system is proposed. Meanwhile, this study also presents an analysis of the control strategy of SSRDS and the method of connecting the power grid. The damping characteristics of SSRDS and the interaction between SSRDS and grid are analyzed by the complex torque coefficient method. A detailed electro-magnetic transient simulation model based on the expansion topology of future Jinjie Power Plant in northern China is established to verify the analytical results. The results show that the proposed control strategy can effectively suppress SSR in the system of six generators and six modes through one-to-many control method. Compared to the traditional thyristor controlled reactor-subsynchronous damping controller (TCR-SSDC), the controller can achieve the same effect with a smaller capacity, a faster response and less harmonic pollution.