This article examines the trade space between the resilience and cost of an island microgrid. The article presents two models for the resilience and the cost of the microgrid. The resilience model considers the invulnerability and recoverability of the microgrid and represents the power balance of the microgrid, energy storage, and maintenance policies. The cost model adapts the levelized cost of energy measure to the context of island microgrids. We conduct experiments to investigate two microgrid architecture decisions of how much excess generation capacity and redundancy to provide. The experiments show that redundancy of generative sources provides greater resilience for similar cost, and resilience improves quickly as excess power capacity is added while the cost grows more slowly. Case studies for island microgrids show how a redesign of the microgrid can improve resilience without increasing costs. The article contributes to the literature a model for decisions makers to evaluate the tradeoffs between resilience and cost for island microgrids that must depend on their own distributed energy resources.

This paper presents a novel power flow control system for a remote military microgrid with hybrid energy storage. A combination of batteries and supercapacitors (SCs) is managed by the novel control system to increase the battery life by redirecting the higher frequency current that would have to flow in the battery if SCs weren't present. This work offers a practical solution to manage the SC current and ensure that the SCs are never overcharged or commanded to support the system when they are discharged to the lower operating limit chosen. The new controller allows the independent selection of the low pass filter parameter and the number of SCs. By making the most out of these two degrees of freedom, we investigate different configurations, identifying the one achieving the highest cash flow for the overall system. Modeling, simulations and experimental verification are presented and linked to the sensitivity analysis of the economics of the military microgrid.

This article develops a method to model, analyze, and design military microgrids with the objective to improve their resilience in the face of disconnections from the larger electrical grid. Military microgrids provide power to installation and base facilities to enable base mission objective accomplishments that are related to national security. Previous research, tools, and methods for microgrid design and assessment do not adequately address resilience in terms of accomplishing mission objectives and instead primarily focus on economic outcomes. This article proposes a novel metric to quantify microgrid resilience in terms of its ability to minimize the impact of power disruption on missions supported by the microgrid. The metric is used in a novel design method to ensure an islanded military microgrid can continue operations while disconnected for a two-week duration. Our model examines the ability to continue mission operations subject to various microgrid disruptions as well as equipment reliability.

A mathematical model that Is developed for a generalized drive system, including common-mode passive and active elements, is used to explore the issues of paralleling soft-switched resonant dc-link drive systems. Differences between the modulation pattern for each drive system cause common voltage disturbances, which lead to significant circulating currents between the drive systems. Control methods for actively compensating for common-mode circulating currents or reducing the common- mode voltage disturbances are investigated. Practical modifications to the drive system controls are implemented to reduce the circulating currents between paralleled systems.

This paper presents two current control methods to attenuate the common mode (CM) conducted emissions in three-phase four-wire four-pole inverters connected to an AC distribution bus and operating in grid-following mode. Delta modulation and model predictive control both achieve elimination of the common mode voltage at the output of the three-phase four-pole inverter and meet the requirements of the military standard 461G without a full-size CM choke. The differential mode performance is comparable to that achieved with the benchmark three-dimensional space vector modulation, which does not cancel the CM voltage. A physics-based model of the system was developed to simulate the conducted emissions and DM performance of the two proposed methods. As the CM voltage cancellation methods result in increased switching frequency, wide bandgap devices were used to build a laboratory prototype, on which the simulated results were successfully validated.

This paper presents a novel power flow control strategy, combined with an economic analysis, for an energy management system (EMS) involving a hybrid energy storage. The EMS operates a remote microgrid and directs the power flow to either batteries or supercapacitors to increase the life of the batteries. This paper demonstrates how the use of supercapacitors increases the lifetime of the batteries and ultimately how it affects the economics of the system. The proposed EMS controller also compensates for the 120-Hz ripple on the dc bus. Modeling, simulations, and experimental verification are presented together with the procedure to perform the assessment of the battery lifetime, according to the tuning parameters of the controller.