Hierarchical coordinated control for DC microgrid with crowbar and load shedding control

Abstract

Due to the challenge of energy demand, renewable energy sources are introduced to our daily life in order to satisfy the energy demand and reduce the emission of greenhouse gas. But the increasing penetration of renewable energy sources causes obvious impact on the conventional power systems especially the control strategies. In order to solve the problem, microgrid is introduced, which usually consists of distributed generators(DG), storage system, loads and converters. There are two kinds of microgrid: DC microgrid and AC microgrid. Compare with AC microgrid, the conversion loss and transmission loss of DC microgrid is lower, furthermore, its control strategy is less complex. Due to the advantages of DC microgrid, it has drawn increasing attention in recent years especially the coordinated control of DC microgrid, which is very essential for the correct operation of DC microgrid. The control methods of DC microgrid can be divided into two categories: centralized control and distributed control. Since centralized control strongly relies on communication system, it gradually replaced by the distributed control, which can further classified into many subcategories such as droop control and hierarchical control. Compared with centralized control and droop control, hierarchical control method is easier and reduce the dependence of communication system, so the reliability of this control method can be ensured. In this paper, a hierarchical control strategy is provided to improve the operation performance of DC microgrid. The crowbar control and load shedding control are also included in this hierarchical control strategy. In this paper, the DC microgrid is set up in PSCAD and the hierarchical control is verified for different operating scenarios.