Distributed frequency regulation system for interconnected microgrids based on heterogeneous agent theory

Abstract

Abstract. The increase in the use of distributed energy resources such as photovoltaic panels and wind turbines and the development of most efficient energy storage systems has allowed the implementation of microgrids. This concept includes a geographical area in which storage, generation, and loads can be operated connected or islanded of the distribution network. A microgrid can be AC or DC according to the current in the common bus. In an AC microgrid inverters are required due to the nature of some distributed energy resources; this implies the regulation of voltage and frequency. It can be done either using a centralized method which involves the use of a very reliable communication system or using an entirely decentralized model in which each agent (in this case each inverter) do not communicate with the others. An intermediate approach allows each agent communicate with its neighbors without the needing of a complex communication network. Frequency regulation must guaranty the same value for the whole system, for this purpose consensus equation is used. This method is used to regulate not only the frequency and the voltage for the inverters inside a microgrid but the frequency in several interconnected microgrids. This consensus approach supposes that each agent is identical to the others without having into account the particularities of each one. A frequency regulation method for a microgrids cluster is simulated and verified using a non-identical agent approach.

Resumen El aumento en el uso de fuentes distribuidas de energía y recursos de almacenamiento distribuido en las últimas décadas tales como paneles solares, turbinas de viento y bancos de baterias, ha permitido el desarrollo del concepto de Microrred. Una microrred, que agrupa generadores y almacenamiento distribuidos, puede funcionar en AC o DC dependiendo del su bus común. La microrred es definida por un área geográfica capaz de suplir su propia demanda incluso cuando funciona desconectada del sistema de potencia convencional. En un escenario futuro, varias microrredes en modo isla, podrán conectarse entre ellas formando un grupo o 'cluster'. En este trabajo se presenta un sistema de regulación de frecuencia para un grupo de microrredes. Se propone un control jerárquico distribuido basado en teoría de agentes heterogéneos, es decir, agentes no-idénticos. Este control permite la conexión y desconexión de microrredes en el nivel más alto, o la conexión y desconexión de inversores en un nivel inferior. El sistema y sus controladores son verificados por simulación.