A novel multi-stage fuel cost minimization in a VSC-based microgrid considering stability, frequency, and voltage constraints

This paper presents a multi-stage fuel consumption minimization method in an autonomous voltage source converter (VSC)-based microgrids considering microgrid small signal stability (SSS) margin, frequency and voltage regulation, and the minimum and maximum allowable range of active and reactive output power of VSCs. In VSC-based microgrid, the parameters of each VSC power sharing controller have significant influence on microgrid SSS margin, frequency and voltage regulation, and the ratio of active and reactive power shared between VSCs. Considering all of these effects in fuel consumption minimization method with straightforward technique leads to having a complicated constrained optimization problem, which cannot be solved in a short time. The computation time of solving this optimization problem is very important in practical applications. In order to eliminate this problem, a multi-stage method is developed in this paper. This method can optimize the fuel consumption and consider the output active and reactive power limit, SSS margin, and frequency and voltage regulation in different stages without significant interactions on each other. Hence, the computation time is strongly reduced. The simulation results in a microgrid, which has a wind turbine, two gas turbines, and a micro-turbine with heat load, demonstrate the effectiveness of the proposed method.