Adaptive type-2 fuzzy PID controller for LFC in AC microgrid

An AC microgrid (MG) system links the distributed generation (DG) based on renewable energy resources and local electrical loads in modern power systems. Intermittent characteristics of wind and solar resources influence not only the availability of energy but also the stability of the entire AC microgrid. This matter as well makes a challenge on the load frequency control (LFC) problem in an islanded MG system, and consequently, the fixed structure controllers are unable to provide a proper performance over a wide range of operating conditions. Therefore, it is required to design a dedicated controller for LFC to ensure the capability of maintaining a generation–load balance by managing the intermittent resources. In this paper, an adaptive type-2 fuzzy PID (T2FPID) controller is suggested for LFC in an AC MG system to enforce the frequency deviation to zero by supplying the load demands. The designed T2FPID controller is a nonlinear controller that can handle the system nonlinearities and uncertainties in the MG system in a better way. Using a Lyapunov function, the stability of the system is evaluated and parameter tuning laws for the T2FPID controller are derived using this function. It has been illustrated that the adaptive parameters are bounded and the frequency deviation reaches to zero properly. The proposed adaptive T2FPID controller has been applied for LFC of a MG system, and the simulation results have been compared with those obtained by type-1 fuzzy (T1F) PI and nonadaptive fuzzy PID controllers, which is the latest research in the problem in hand. The simulation results indicate the efficiency of the proposed adaptive controllers in dealing with intermittent resources and changing in the power system parameters.