Voltage stability limits the maximum utilisation of transmission line thermal capability. Planning studies by the national grid owner-operator, Transpower, show that the most cost-effective means of dealing with voltage stability and dynamic reactive power issues in New Zealand is to use dynamic shunt compensation, such as Static VAr Compensators (SVC), Static Synchronous Compensators (STATCOM) or synchronous condensers. However, this means that the number of reactive power devices will increase in major load areas, and coordinating numerous dynamic and static devices is difficult. A Reactive Power Controller (RPC) can be employed to ensure optimal coordination, but no suitable equipment existed for the New Zealand configuration. So Transpower commissioned Alstom Grid to design and develop an RPC that would be installed first in Christchurch and subsequently throughout the whole national network.
The final configuration will involve multiple systems hierarchically grouped by region and area, communicating with the national SCADA system. For Dr Wang’s design team, the main challenge was to “devise a generic principle in both control concept and engineering implementation so that the design can be rolled out easily to other parts of Transpower’s network without major hardware and software reengineering.” The control algorithm has to be independent of a given substation’s physical topology to be readily applicable to a wide range of installations.
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At the same time, control priorities have to be configurable to easily address the particular requirements of a given substation or area, or changed control strategies. In other words, what’s needed is what Dr Wang describes as “generic modularity”.
Islington HMI cubicles at the Christchurch substation.