Next-Generation Smart Grids: Completely Autonomous Power Systems (CAPS)

Power systems are going through a paradigm change from centralised generation, to distributed generation, and further on to smart grids. A huge number of renewable energy sources, electric vehicles, and storage systems etc. are being connected to power systems. Moreover, various loads are being required to take part in demand response and to improve energy efficiency. These make it impossible to control and operate power systems in the conventional way, because of the difficulties in modelling the huge number of players in the system and in identifying a suitable mechanism to operate the system. In this lecture, we will present the architecture and its associated distributed control strategy for the next-generation smart grids, based on the inherent synchronisation mechanism of conventional synchronous generators. Inverters will be operated to behave like synchronous generators and rectifiers will be operated to behave like synchronous motors. Moreover, the dedicated synchronisation units, often phase-locked-loops, which are deemed to be a must-have component in grid-tied converters, will be removed. As a result, this architecture unifies the interface of all the different players with the transmission and distribution network so that the majority of the players, including all conventional power plants, new add-ons of suppliers and most loads, will be able to synchronise with each other to achieve autonomous operation and maintain system stability, without the need of a dedicated communication network. Most of the players will follow the same mathematical model of synchronous machines and hence the operation and analysis of the system is simplified considerably.