Rapid synchronisation of fast instantaneous reserves CAES generator

Abstract

Electric power systems maintain system security by keeping instantaneous reserves that can substitute for a credible loss of generation. Instantaneous reserves are fast responding generators that maintain electric power system frequency immediately following a sudden mismatch between generation and load, and these are an indispensable system security tool. These are typically offered by partially or unloaded generators which are already synchronised to the AC network. The reserve requirement constrains generator operation, and reduces system flexibility and efficiency. These are important issues in a renewables-based power system. A compressed air energy storage and hydraulic actuation system is proposed to provide instantaneous reserves without constraining existing generators. By rapidly accelerating and synchronising a generator to the AC grid through a pressurised hydraulic drive, the cost of running unloaded or under-loaded spinning generators can be eliminated. This paper presents a novel hydraulic actuation system which is capable of achieving simultaneous frequency and phase matching between the power system and a 100kW generator within 1s. The hydraulic drive system, instrumentation, and the nonlinear controller design are described. In simulations, successful synchronisation is achieved under a wide range of system uncertainties.