Vsc-Hvdc Frequency Control Strategy For Dc-Segmented Multi-Infeed Lcc-Hvdc Systems

LCC-HVDC technology has been widely used in China, such as the Guangdong power grid, which is a typical multi-infeed LCC-HVDC system. However, since the inverters are located in close proximity, concurrent commutation failures of the multi-infeed HVDC system may happen during faults. In order to alleviate the problem, the dc-segmentation technique based on VSC-HVDC transmission technology is planned to be used in the Guangdong power grid. Since the frequency support strength of the sectors after segmentation is low, it is necessary for the VSC-HVDC system to participate in controlling the frequency. This paper proposes a frequency control strategy for improving the frequency stability of the system. The development of the control method includes two steps. First, the d-axis control scheme of the VSC station is proposed. Secondly, the q-axis auxiliary frequency control scheme is added to the VSC controller, which can further enhance the frequency stability of the system. The simulation tests are done in PSS/E and the results verify the validity of the control method.