Investigation of transient overvoltage issues due to commutation failure at inverter side of parallel ±660kv LCC HVDC transmission lines in pakistan

摘要

This Paper investigates the transient overvoltage (TOV) issues due to the commutation failure at inverter side of AC system. It’s a case study of 1st HVDC project that is in construction phase in Pakistan. The Project is Parallel ±660kV LCC HVDC transmission Links to transmit Bulk amount of Power from south to North of the country. As the rectifier converter station of two transmission line are very close to each other, commutation failure on inverter side AC system of any transmission line causes TOV issues on rectifier side AC system of both Transmission lines. PSCAD based model is designed to study the steady states and transient states (TOV and Commutation Failure) of the system. The main focus of the study is to understand when a commutation failure is occurred at inverter side AC system then how it will affect the TOV at both rectifier side AC systems and how the variation of SCR at rectifiers of both transmission lines reduce the TOV issues. By the simulation based study of PSCAD model it’s found that commutation failure at inverter side of AC system of transmission line 1 or transmission line 2 has a prominent effect on the Transient over Voltage issues of rectifier side AC system of both lines. Similarly it is observed that by keeping the SCR at rectifier side AC system of one transmission line constant and increasing the SCR at rectifier side of ac system of other transmission lines much reduces the transient over voltage issues.