A novel coordinated control strategy for improving the stability of frequency and voltage based on VSC-HVDC

At the early stages of electric network restoration, the capacity of power system is relatively small, and adding large power load to such a power system will result in severe fluctuation of system frequency and voltage. Thus the stable operation and the restoration speed of power system will be affected seriously. VSC-HVDC (voltage source converter based HVDC) can control active and reactive power injected into network independently and rapidly. Based on the characteristics of VSC-HVDC, a coordinated control method between VSC-HVDC and conventional speed governing system is proposed to maintain the stability of frequency at the early stage of network restoration. Similarly, a coordinated control method between VSC-HVDC and automatic voltage regulator (AVR) is proposed to maintain the stability of bus voltage. The whole system model is established in RTDS environment. Simulation results show that the fluctuations of frequency and voltage are diminished remarkably, and the stability is improved by adopting the method proposed. It´s conducive to expediting the restoration process of power system.