Coordinated Frequency Control for Multiple Microgrids in Energy Internet: A Stochastic H∞ Approach

Abstract

This paper deals with the coordinated frequency regulation problems for multiple AC microgrids (MGs) interconnected via energy routers (ERs) within the scenario of an energy Internet (EI). We assume electric power is transmitted between MGs with DC transmission technology, thus the AC bus frequency in each single MG is independent. It is assumed that these multiple MGs (MMs) are not connected with the main power grid. We take the power stochasticity of renewable distributed energy resources (DERs) and loads into consideration, and we formulate the dynamics of each MG’s components as a combination of ordinary differential equations (ODEs) and stochastic differential equations (SDEs). Then the coordinated frequency regulation problem regarding each MG’s AC bus is formulated as a stochastic $H_{\infty }$ control problem. A state feedback controller is designed, such that a prescribed $H_{\infty }$ performance is satisfied. In case that the obtained controller is over strong, a constraint is implemented to ensure the rationality of the designed controller. The linear matrix inequality (LMI) and semi-definite programming (SDP) approaches are developed to solve the aforementioned problems. Simulations are provided to demonstrate the effectiveness of the proposed approach.