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

Abstract

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 a comprehensive summary of 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 highbandwidth 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.

Effect of Magnetic Field on Partial Discharge Dynamics in Insulation Systems of Transportation Power Devices

“…In maritime applications, onboard DC grids are developed in the form of modular power system platforms that are comprised of modules of power sources; these may include variable-speed > REPLACE THIS LINE WITH YOUR MANUSCRIPT ID NUMBER (DOUBLE-CLICK HERE TO EDIT) < generators, energy-storage units, fuel cells, or auxiliary systems. Currently, a low-voltage DC system architecture is usually adopted for ships that require less than 1 MW; larger ships that demand more than 10 MW need an MVDC architecture [34]. Therefore, the on-board voltage level for small ships, ferries, and short-sea vessels is around 1kV, while a medium voltage is applied (above 3kV) for larger ships (which still need diesel generators or LNG (liquefied natural gas) generators to be the main power sources).…”

Power Distribution and Propulsion System for an All-Electric Short-Range Commuter Aircraft—A Case Study

“…Most promising are so-called hybrid circuit breaker, which are a combination of solid-state switches for arc-free switching and mechanical switches for providing galvanic isolation [77]. Compared to passive/active resonance DC circuit breaker, hybrid circuit breaker offer faster response times and have less risk of arcing [78]. A hybrid circuit breaker with galvanic sepa-ration and fail-safe functionality is especially suitable for the application between two high voltage DC-buses to avoid Single Point of Failure (SPOF).…”

“…In order to protect crew or passengers from leakage current, RCD are mandatory in aircraft designs. A type B RCD, which is able to detect the leakage current with DC components is recommended for DC grids in [78]. For future application, advanced RCD solutions with real-time leakage current monitoring function are expected for electric aircraft system architecture [84].…”

A Centralized Shifted Power Control Scheme for Isolated Bidirectional DC-DC Converter in Standalone DC Distribution System

“…In the stand-alone DC distribution system, the balance between power generation and load consumption is rather important [7]. Due to mismatched output impedances of energy sources and unpredictable power fluctuations in loads, instantaneous power imbalance may occur and affect the stable operation of the DC system [8]. Thus, an appropriate EMS control scheme is essential to mitigate the power sharing error and compensate deficient power for system stability [2].…”