On-board microgrids for the More Electric Aircraft: technology review

This paper presents an overview of technology related to on-board microgrids for the More Electric Aircraft. All aircraft use an isolated system, where security of supply and power density represent the main requirements. Different distribution systems (AC and DC) and voltage levels coexist, and power converters have the central role in connecting them with high reliability and high power density. Ensuring the safety of supply with a limited redundancy is one of the targets of the system design, since it allows increasing the power density. This main challenge is often tackled with proper load management and advanced control strategies, as highlighted in this paper

Fault detection and location in DC systems from initial di/dt measurement

The use of DC for primary power distribution has the potential to bring significant design, cost and efficiency benefits to a range of power transmission and distribution applications. The use of active converter technologies within these networks is a key enabler for these benefits to be realised, however their integration can lead to exceptionally demanding electrical fault protection requirements, both in terms of speed and fault discrimination. This paper describes a novel fault detection method which exceeds the capability of many current protection methods in order to meet these requirements. The method utilises fundamental characteristics of the converter filter capacitance’s response to electrical system faults to estimate fault location through a measurement of fault path inductance. Crucially, the method has the capability to detect and discriminate fault location within microseconds of the fault occurring, facilitating its rapid removal from the network

Demonstration of sustained and useful converter responses during balanced and unbalanced faults in microgrids

In large power grids where converter penetration is presently low and the network impedance is predominantly reactive, the required response from converters during faults is presently specified by phrases such as “maximum reactive output”. However, in marine and aero power systems most faults are unbalanced, the network impedance is resistive, and converter penetration may be high. Therefore a balanced reactive fault current response to an unbalanced fault may lead to over-voltages or over/under frequency events. Instead, this paper presents a method of controlling the converter as a balanced voltage source behind a reactance, thereby emulating the fault response of a synchronous generator (SG) as closely as possible. In this mode there is a risk of converter destruction due to overcurrent. A new way of preventing destruction but still providing fault performance as close to a SG as possible is presented. Demonstrations are presented of simulations and laboratory testing at the 10kVA 400V scale, with balanced and unbalanced faults. Currents can be limited to about 1.5pu while still providing appropriate unbalanced fault response within a resistive network

From Barracks to the Battlefield: Clean Energy Innovation and America's Armed Forces

Details how innovations in clean energy, renewable sources, and energy efficiency technologies could help the Department of Defense reduce the risks associated with dependence on fossil fuels, as well as what DoD could do to spur energy innovation

Hybrid Maritime Microgrids: A Quest for Future Onboard Integrated Marine Power Systems

The following is a comprehensive analysis which details potential ways for the maritime industry to begin to phase out AC power generation and distribution on new vessels over a short period of time. Therefore, the vessels of the future should consider transitioning into DC power generation and distribution. During the transition from AC shipboard systems to DC shipboard systems, there will be a time during which the vessels will be run by “hybrid” shipboard power systems, which utilize a mixture of AC and DC power. These systems are known as integrated marine power systems (IMPS) or hybrid maritime microgrid architectures, since they represent a distribution system or a part thereof. This study presents a state of the art of maritime systems, emphasizing on the design aspects of hybrid maritime microgrids, summarizing the advantages, disadvantages, and the challenges that planners may face when it comes to the vessels of the future. This study also reviews remedies that have been recently proposed in the literature to overcome such challenges. In addition, this work reports on the problem of service restoration of shipboard power systems and introduces directions on how to enhance the survivability of maritime power systems using techniques based on distribution system reconfiguration

Next-Generation Shipboard DC Power System: Introduction Smart Grid and dc Microgrid Technologies into Maritime Electrical Networks

In recent years, evidence has suggested that the global energy system is on the verge of a drastic revolution. The evolutionary development in power electronic technologies, the emergence of high-performance energy storage devices, and the ever-increasing penetration of renewable energy sources (RESs) are commonly recognized as the major driving forces of the revolution. The explosion in consumer electronics is also powering this change. In this context, dc power distribution technologies have made a comeback and keep gaining a commendable increase in research interest and industrial applications. In addition, the concept of flexible and smart distribution has also been proposed, which tends to exploit distributed generation and pack together the distributed RESs and local electrical loads as an independent and self-sustainable entity, namely a microgrid. At present, research in the area of dc microgrids has investigated and developed a series of advanced methods in control, management, and objective-oriented optimization that would establish the technical interface enabling future applications in multiple industrial areas, such as smart buildings, electric vehicles, aerospace/aircraft power systems, and maritime power systems

Adaptive Control of Surge Impedance for Electric Motors in Motor Drive Systems

This article studies the possibility of controlling the surge impedance of the electric motor in motor drives. The existing solution to suppress (or eliminate) the reflected wave impact on the motor insulation run by a Si-IGBT or SiC-MOSFET-based drive is to use either a sinewave filter or dv/dt filter. The alternative solution suggested in this article is to implement a high-bandwidth electronic circuit at the end of the cable or at the motor terminals to match the surge impedance of the cable and motor. The high-frequency voltage ringing due to the reflected waves in motor drives is around 1 MHz, depending on the cable parameters and the length of the cable. In the proposed method, the electronic circuit can quickly detect the dv/dt rise and fall edges and adjust the electronic circuit equivalent impedance when pulses arrive the motor terminals. Thus, the cable and motor surge impedances can be matched over a short time to prevent reflected waves. As a result, the leakage currents passing through the ball bearing and overvoltage stress on the motor insulation can be suppressed significantly