The HVDC Inter-Island bipole link between Benmore and Haywards dates back to 1965. At the time the technology was based on mercury arc valves (MAV) and was rated for 600MW. In 1992 the link was reconfigured with a thyristor based Pole 2 joining the original MAV Pole 1. In 2012 Pole 1 was decommissioned and replaced in 2013 by Pole 3. The HVDC Pole 3 Project was built in two stages resulting in a 1200MW capacity for the overall HVDC link. A third future stage will enable the bipole capacity to be increased to 1400 MW. The Pole 3 Project also included replacement of the control
system for the existing Pole 2.
The HVDC link connects two small AC island systems where the voltage and frequency can fluctuate widely on the two islands when compared to a large interconnected grid. Because of the relatively low
short-circuit levels at the Haywards converter station and other unique features of the New Zealand power grid, additional controls and runbacks were implemented. A unique reactive power control (RPC) system was developed to provide coordinated control of all reactive power plant, on-load tapchangers and a STATCOM. Additionally, Round Power logic had to be implemented that allows the bipole power to smoothly change direction through 0 MW.
There were multiple phases in verification and commissioning of the Pole 3 project. The off-site control system Factory Acceptance Tests (FAT) covering both functional and dynamic performance, were followed by the system tests on-site in New Zealand. The off-site tests provided confirmation of the functional operation of the new control system, including all operational sequences and the fault recovery performance of the overall interconnected ac and HVDC system. This ensured that the supplier met contractual obligations to Transpower, confirmed dynamic performance and models relevant to system security and ensured that protection systems functioned correctly and met performance requirements. Various test environments were utilised to support the FAT testing including PSCAD, the suppliers real time digital simulator (RTDS) environment, and Transpower’s RTDS simulator.
The on-site testing continued on from this off-site FAT testing to validate the results against the real system and to provide an end-to-end system test, including the integration of the new control system with the existing Pole 2. During this phase, Transpower’s RTDS simulator was used for the development of test plans and the verification of fixes to defects identified during the on-site testing. The project was successful in testing multiple project stages, performing adequate testing of the new RPC, Round Power and other complex controls utilising different test platforms, and then commissioning the control systems onto both new and existing primary plant within the constraints of an electricity market. This paper highlights the approach and some of the challenges associated with the Factory Acceptance Testing and the on-site commissioning tests.
D. Crawshay, W. Otto, R. Sherry, D. Kell, Presented at the CIGRÉ Canada Conference on Power Systems, Winnipeg, Canada, Sep. 2015, paper CIGRE 673
KEYWORDS: HVDC, Commissioning, Functional Testing, Dynamic Performance Testing, Validation, Roundpower, Reactive Power Controller, Market Environment, RTDS, PSCAD