Assessment of Reactive Power Reserve for DC Continuous Commutation Failure

Abstract

Real-time assessment of the risk of continuous commutation failure of the thyristor-based phase-controlled commutation direct current transmission system (LCC-HVDC) and timely preventive control measures are of great significance to ensure the safe and stable operation of the large power grid. This paper proposes a method for evaluating effective dynamic reactive power reserve of generators to deal with DC continuous commutation failure. The maximum reactive power increment of the generator corresponding to the secondary drop of the converter bus voltage is defined as the effective dynamic reactive power reserve. The effective dynamic reactive power reserve at the critical point is called the maximum effective dynamic reactive power reserve. When the system dynamic reactive power reserve is less than the reserve capacity threshold, a two-stage preventive control measure searching method is adopted. First, increase the terminal voltage of the generator and the static reactive power compensation. If the requirements are still not met, the start-up unit measures will be adopted. An example of an actual power grid verifies the effectiveness of the method.