Dynamic Analysis of Power Systems with Multiterminal HVDC Links and Static Compensators

The paper presents a generalized small signal model of a multinode power system having multiterminal HVDC links and thyristor controlled static compensators. This model is suitable for the application of modal control techniques for centralised dc power modulation to improve the dynamic stability of the ac-dc system. For practical implementation of the centralised controller, proportional-plus derivative feedback of the output states have been used to shift the dominant modes to prescribed locations. Further a decentralised control scheme based on the control of the static compensator alone and a combination of both static compensator and dc power modulation have been presented in this paper to bring out the differences between the two approaches. An eigenvalue search has been used to optimize the controller gains. Simulation results for a 3-terminal system are presented to highlight the important features of both the modal control and dc power modulation along with reactive power control schemes.