A switched dynamical system approach towards the economic dispatch of renewable hybrid power systems

Abstract

This paper considers an economic dispatch problem of renewable hybrid power systems. According to the analysis of the renewable hybrid power system dynamic behavior, the problem is modelled as an optimal control problem of switched dynamic systems. As is known to all, the frequent switching may cause that the engine wear is increased, and the service life is reduced. Then, some switching constraints are imposed to the switched dynamic system model. However, these switching constraints lead to a non-connected feasible region for the optimal control problem with unknown switching instants, integer variables, and continuous variables. Thus, it is difficult to solve such problem by using conventional optimization methods, such as sequential quadratic programming. To overcome this difficulty, by using the time-scaling transformation technology and introducing an auxiliary continuous vector derive a more tractable equivalent problem, in which the variable switching instants and the switching sequence are replaced with conventional continuous parameter variables. Then, based on an exact penalty function, an alternative computational method is developed for solving the problem. Finally, three numerical examples are solved by using the proposed algorithm. The numerical results show that although the optimal costs with switching constraints slightly higher than the optimal costs without switching constraints, the proposed algorithm can effectively avoid the additional switches. In addition, the numerical results also show that the switched dynamical system approach is low time-consuming and obtains a better cost function value than the existing approaches.