Reseach On Multi-objective Hierarchical Coordinated Control For DC Microgrid

Fossil fuel such as oil and coal is facing two major problems: resource depletion and environmental pollution. Renewable energy is now been widely developed. In order to improve power quality, grid security and stability of the renewable generation system, foreign and domestic scientists have studied extensively on these issues and proposed the concept of “Microgrid”.Microgrid can be divided into AC and DC microgrid according difference power bus categories. Compared to AC microgrid, the control problem of voltage phase and frequency is eliminated because of the unique structure in DC microgrid. Reactive power loss can be reduced and the limitation of natural power can be overcome in DC microgrid. DC microgrid topology and control strategies are different from the traditional power system. Constructing a reasonable overall model, studying the coordination control theory and ensuring normal working condition of each unit are some important issues of DC microgrid safe operation. And they are of great significance to the development of DC microgrid.Existing control strategies of DC microgrid have several limitations. The control objective is simple and sigle. Storage capacity is not regarded as the measure of load capacity. The storage capacity is not initialized under grid-connect mode.Aiming at the existing problems of DC microgrid, this paper first studies the multiple objectives of DC microgrid. The DC bus voltage stability is set as the core objective. Load, generation and storage module are considered in the secondary objectives. Concept of hierarchical control is adopted and then this paper proposes the hierarchical coordinated control strategy. Main work of this paper can can be divided into three parts. The first part discusses the references of module selection, and discusses working principle and operating characteristics of the selected modules. The second part particularly discusses the hierarchical coordinated control scheme of the DC microgrid. By using MATLAB/SIMULINK, The third part builds the model of the entire DC microgrid and verifies the effectiveness of the proposed control strategy using modular and systematic simulation methods.