Synchronization of PCP and VBC for xiamen bipolar MMC HVDC project

The MMC based converter interfaces with valve base controller (VBC) by using high speed Aurora communication protocol. The pole control and protection (PCP) system interfaces with VBC through High-level Data Link Control (HDLC) protocol. The HDLC communication mechanism is demonstrated in the controller hardware-in-loop (CHIL) test. However the asynchronous communication between PCP and VBC causes drifting for the firing numbers, which brings one frame period delay periodically. The delay is 100us and is equal to 1.8 degree phase shifting for 50Hz system, which causes the power transmission disturbance. This paper reveals and emphases the importance of synchronization between PCP and VBC for the first time. Several measures have been taken to mitigate the influence of the asynchronous communication. The testing results show the effectiveness of the proposed methods.