A Review of DC Shipboard Microgrids Part II: Control Architectures, Stability Analysis and Protection Schemes

This paper presents a review of coordinated control strategies, stability analysis, and fault management for dc shipboard microgrids (dc-SMGs). As an emerging application, the dc-SMG lacks of a comprehensive summary on the control schemes. Considering the specific load profile in ships, this paper discusses the coordinated control strategies of diesel generators and energy storage system (ESS). Depending on the maritime conditions, different operation modes are switched by the energy management system (EMS). Due to the presence of high-bandwidth controlled constant power load (CPL) converters, negative impedance instability is induced. Meanwhile, the pulsed loads in dc-SMG may affect the voltage stability significantly. Small-signal and large-signal stability analysis can be used to evaluate the effect of these two types of loads. In the aspect of shipboard protection system, this paper presents the specific requirements of dc-SMG based on the standards. Lacking of ground in ships, solutions in designing the grounding system for dc-SMG is described. Besides, the short-circuit fault management consisting of fault detection, fault isolation, and reconfiguration in dc-SMGs are summarized. Finally, existing commercial dc ships are presented and compared to demonstrate the developing trends.