Stochastic Robust H∞ Control Strategy for Coordinated Frequency Regulation in Energy Internet Considering Time Delay and Uncertainty

In this article, we consider the coordinated frequency control issues for energy Internet (EI) within a certain area. We assume multiple AC microgrids (MGs) are interconnected via energy routers (ERs) and electricity is transmitted between MGs via DC transmission technology, in the sense that the AC bus frequency in each individual MG is independent. In addition, the scenario of EI is presumed to be disconnected with the main grid. We formulate a generalized connection topology for the considered EI scenario. Each MG is assumed to be composed of a combination of distributed wind turbine generators (WTGs), photovoltaic (PV) units, micro-turbines (MTs), fuel cells (FCs), battery energy storage (BES) devices and local loads. Then we formulate the dynamics of the above components as a class of ordinary differential equations (ODEs) and stochastic differential equations (SDEs) with parameter uncertainty and time-varying delay in the state. To alleviate frequency fluctuation in each individual MG, the coordinated frequency control problem is formulated as problems of robust stabilization and robust H-infinity control. The linear matrix inequality (LMI) approach is applied to solve these two problems sufficiently with desired state feedback controllers obtained. Numerical simulations are illustrated to show the effectiveness of the proposed method.