Master-slave second order sliding mode control for microgrids

This paper deals with the design of advanced control strategies of sliding mode type for microgrids. Each distributed generation unit (DGu), constituting the considered microgrid, can work in both grid-connected and islanded operation mode. The DGu is affected by load variations, nonlinearities and unavoidable modelling uncertainties, because of the presence of a voltage-sourced-converter (VSC) as interface with the main grid. This kind of uncertainty terms makes the sliding mode controller perfectly fitting the control problem to solve. In particular, a second order sliding mode (SOSM) control scheme, belonging to the class of Suboptimal SOSM control, is proposed. Moreover, in order to face some undesired overshoot on the currents fed into the load, due to the reconnection to the main grid, as well as to step variations of current references, a constrained SOSM control is designed. Simulation results confirm that the proposed robust controllers provide closed-loop performance complying with the IEEE recommendations for power systems.