A Fuzzy fault tolerant controller design based on virtual sensor for a DC microgrid

In this paper, a fault tolerant control (FTC) method is presented for a DC microgrid with constant power loads (CPLs) which is prone to sensor faults. The main idea of this FTC method is based on hiding the sensor faults from the controller point of view using a suitable virtual sensor. After presenting the nonlinear model of the system, the model is then converted to a Takagi-Sugeno (TS) fuzzy representation. The nominal controller is designed for the fuzzy model in the form of a state feedback and the states are estimated using a suitable observer. In the event of a sensor fault detection, the effects of the fault in the control loop are compensated by a virtual sensor. The gains of the controller, the virtual sensor and the observer are designed using related linear matrix inequalities (LMIs) and applying some appropriate LMI regions to achieve appropriate performance. The proposed method is an active fault tolerant control (AFTC) strategy in which the virtual sensor hides the sensor faults from the controller and the observer. In this method, from the controller's point of view, the faulty system plus the virtual sensor acts like a healthy system, and the nominal controller continues to its work without the need to be reconfigured. The efficiency of the proposed method is demonstrated in a constant-load DC microgrid modelled using electrical elements.