Research and Implementation of Control Strategies for Multiple Transmission Modes in Yongren-Funing HVDC

The ± 500 kV Yongren-Funing HVDC transmission project is the first HVDC whose sending and receiving ends are both located in the same province, its inverter station is required to transmit power to different AC asynchronous grids according to the different requirements of the grid operation. The present control and protection system of HVDC cannot adapt to and meet the technical requirements of multiple power transmission modes. In order to achieve this goal, the control system of HVDC must be capable of automatic discrimination and sequential control, selecting the correct strategy of reactive power control (RPC), which is essential for the stable operation of the HVDC system. Therefore, based on the operating conditions of the HVDC system and the switch configuration of the AC switch yard of the inverter station, the principle, process and interlocking conditions of automatic switching between different transmission modes are systematically analyzed. Effects on RPC, last breaker and the over voltage protection of AC busbar are researched. The control strategies for multiple transmission modes have great significance for the similar HVDC/UHVDC transmission projects in the future.