Implementations and experiences of wide-area HVDC damping control in China Southern Power Grid

The weakly damped low frequency oscillation deteriorates the stability of some interconnected power systems. In order to suppress the swings more efficiently, the global dynamics of different areas are required, and then the synchrophasor measurement techniques are becoming necessary for real time and continuous control. In this paper, the design, implementation and commission of a coordinated wide-area adaptive damping control (WADC) system through the modulations of multiple HVDC links in China Southern Power Grid (CSG) are presented. Based on the calculations of observability and controllability, six phasor measurement units (PMU) and three HVDC links were chosen to be included in this system. The controllers were coordinated to damp two dominant inter-area oscillation modes. Another key issue for the wide-area control system is the random time delay and a solution using low-pass filter was proposed. Based on the improved online Prony identification, the controller parameters can be adapted according to the changes of the oscillation frequency. The above WADC were implemented and tested in the CSG real time digital simulations (RTDS) platform, which is composed of more than 10 racks of RTDS, real HVDC control and protection cubicles. After field debugging and trial operations, the WADC system was further validated in the practical CSG through artificial block and de-block of three different HVDC links and tripping a 500kV AC tie-line in the years of 2008 and 2009. The field test results show that the commission of WADC system can increase the damping ratio of the dominant modes more than 10%.