Conversion of Retired Coal-fired Plant to Synchronous Condenser to Support Weak AC Grid

A proposal of using phased-out coal-fired generation as synchronous condensers in a power system with weak interconnection to large Type-3 wind farms exporting energy to remote load centers through Line Commutated Converter (LCC) High Voltage Direct Current (HVDC) transmission is investigated. The frequency nadir (i.e, the minimum post-contingency frequency) and the rate of change of frequency in such systems following disturbances like loss of generation due to a single point failure are analyzed. LCC-HVDC rectifier is used for secondary frequency control in the weak AC system. Time-domain and frequency-domain analyses are performed on a 4-machine 2-area system connected to two remote wind farms on the rectifier side of the LCC-HVDC, which compare different scenarios and develop deeper insights into the root-cause of the frequency dynamics.