Synchronous islanded operation of isolated power system areas

• Main Author: Best, Robert J.
• Published: Queen's University Belfast 2008
• Subjects: 621.31
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492340

The increasing capacity of installed distributed generation has stimulated interest in the possibility of using power system islanding to improve distribution system security and prevent blackout. Several challenges must be addressed for islanding to become viable, but perhaps the most serious issue is out-of-synchronism re-closure of the island onto the main power system. The associated transient current, torque and voltage deviation can cause damage and malfunction of generators, protective devices, and power system loads. This thesis explores a solution to the issue of out-of-synchronism re-closure, called synchronous islanded operation, whereby the island is kept in synchronism with the main power system at all times while not being electrically connected. The physical process and effect of out-of-phase synchronisation is investigated by simulation and experimental tests on a salient-pole alternator. The many variables that affect the process are identified and examined. The results suggest that it would be acceptable for the maximum synchronisation angle of distributed generation to exceed current limits. This work is of interest for applications that can benefit from rough synchronisation, such as power system islanding. A suitable control algorithm that enables distributed generation to remain in-phase with the power system is developed and tested. A practical demonstration is perfonned on a diesel generator using a radio-frequency communications link. The results show stable perfonnance is achievable and that phase difference error can be removed following disturbances. Time-stamped synchronised phasor measurements are proposed as a universal control solution. The error introduced by variability of cross-system voltage phase shift is evaluated through observations from the all-Ireland power system. Additional requirements for a multiple-set implementation are investigated by simulation, including control, power quality and load sharing. From this work it is envisaged that synchronous islanded operation could fonn an important part of the control scheme in any future active distribution network. Supplied by The British Library - 'The world's knowledge'