System restoration using the [ldquo ]black start[rdquo ] capability of the 500MW Eirgrid east-west VSC-HVDC interconnector

Abstract

This paper presents the capability of the East - West Interconnector (EWIC) to act as a “black start” generator and its application to provide rapid restoration following a widespread system shut-down. During the development of the EWIC control and protection system, the algorithms for black start were evolved and the operating parameters for real and reactive power support were determined. A digital study was implemented in a time-domain software tool (PSCAD/EMTDC), which simulated the progressive energisation of the islanded Irish network and confirmed the functionality of the black start regime. The paper will show extracts from this study. During the commissioning trials of the interconnector, a test was performed to confirm the black start capability of the scheme. This involved isolating about 230km of the Irish 400kV transmission network from the Woodland sub-station to a remote 300MW coal-fired generator (Moneypoint), which was disconnected from the grid. The EWIC was energised at the rated DC voltage (±200kV) from the GB terminal, with the main circuit breaker at the Irish terminal open. Starting from 0MW and 0Mvar, the interface transformer was energised, allowing the converter station auxiliary load to be supplied from a tertiary winding rather than back-up sources. The main AC circuit breaker was closed and transmission lines, transformers and shunt reactors were progressively energised, with the EWIC automatically picking up the reactive power demand and the real power demand, which was mainly system losses. The 20MW auxiliary load of the generating station was supplied, allowing the generator to be run up to speed and finally synchronised with the transmission system. At this point, the generator picked up the system load and the converter station automatically reverted to power export mode. The paper will present some of the results from this successful commissioning trial. Now that the HVDC converter station is a recognised black start “generator” on the Irish network, a repeat test is performed on an annual basis, to ensure that the network operators are well trained for black start operation. A similar black start application is possible for the GB network and the potential for the Shotton converter station to operate in the wider voltage and frequency ranges required during system restoration conditions will be described in the paper.