Improving Grid-Connection Reliability and Safety of Synchronous Condensers With Start-Up Process Optimization

The new-type synchronous condenser uses the uncontrollable and irreversible freewheeling grid-connection mode during the start-up process, so that considerable rates of grid-connection failure could be observed in case of strict grid-connection criterions. Therefore, this paper proposes an optimized start-up process for the new-type synchronous condenser, with the effort to improving its grid-connection reliability and safety. This optimized process involves two new approaches, namely freewheeling speed ratio regulation and starting freewheel point setting, to adjust the covered range of the freewheeling speed over time, which indirectly expands the allowable initial phase angle difference and thus achieves an increased grid-connection success rate under strict grid-connection conditions. The effectiveness of the proposed optimized process incorporating the two new approaches is validated using statistical analysis in Matlab, as compared to the conventional freewheeling process without optimization. The results show that the successful grid-connection operations of the synchronous condensers can be guaranteed in strictest cases at the cost of a slight increase of the starting freewheeling point (from 105% to around 107%) with 99% rated freewheeling speed ratio.