Applied Research Of Dynamic Reactive Power Compensation Device In HVDC Commutation Failure

Commutation failure is one of the most common and serious failures in HVDC system. It may result in the DC current rush-increasing, converter valve life shortening, DC transmission power reducing, AC system voltage instability in the inverter side weakening and other serious consequences. If improperly handled after the fault, it may lead to subsequent commutation failure, and continuous commutation failures could cause the converter station bipolar latching, eventually lead to the DC transmission power interruption.By making a analysis of HVDC commutation failure theory and researching the failure case in East China, we gain the conclusion that AC side voltage drop is the main reason for the accident. To suppress the commutation failure, this dissertation propose a method of configuring certain dynamic reactive power compensation devices in the inverter station bus. In order to send action commands to the dynamic reactive power compensation devices, we need to select quantitative criterion. Considering the symmetrical and asymmetrical faults and safety margin of safety measures taken for commutation failure, this dissertation proposes a quantitative criterion of taking measures to suppress commutation failure:0.1pu as commutation failure threshold voltage drop.After the analysis and comparison of related performance of the existing dynamic reactive power compensation devices, the option is STATCOM. Then analyze the demand principles of STATCOM, performance indicators, the main circuit topology and the equivalent model, at last propose a rational reactive capacity configuration, the main parameters, as well as control objectives and control strategies for the suppression of HVDC commutation failure. Based on the PSCAD/EMTDC software, put STATCOM into operation when different voltage drops. Simulation results show that STATCOM can provide dynamic voltage support, equivalently expand the bus voltage security operation range, and reduce the probability of communication failure and assist the bus voltage recovery.