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The performance of a more-electric aircraft (MEA) power system electrical accumulator unit (EAU) architecture consisting of a 57000 rpm induction machine (IM) coupled to a controllable shaft load and controlled using direct torque control (DTC) is examined through transient modeling and simulation. The simplicity and extremely fast dynamic torque response of DTC make it an attractive choice for this application. Additionally, the key components required for this EAU system may already exist on certain MEA, therefore allowing the benefits of EAU technology in the power system without incurring a significant weight penalty. Simulation results indicate that this architecture is capable of quickly tracking system bus power steps from full regenerative events to peak load events while maintaining the IM's speed within 5% of its nominal value.

A primary challenge in performing integrated system simulations is balancing system simulation speeds against the model fidelity of the individual components composing the system model. Traditionally, such integrated system models of the electrical systems on more electric aircraft (MEA) have required drastic simplifications, linearizations, and/or averaging of individual component models. Such reductions in fidelity can take significant effort from component engineers and often cause the integrated system simulation to neglect critical dynamic behaviors, making it difficult for system integrators to identify problems early in the design process. This paper utilizes recent advancements in co-simulation technology (DHS Links) to demonstrate how integrated system models can be created wherein individual component models do not require significant simplification to achieve reasonable integrated model simulation speeds.

Numerous modern military and commercial vehicles rely on portable, battery-powered sources for electric energy. Due to their highly specialized functions these vehicles are typically custom-designed, produced in limited numbers, and expensive. To mitigate the power system's contribution to these undesirable characteristics, this paper proposes a modular power system architecture consisting of “smart” power battery units (SPUs) that can be readily interconnected in numerous ways to provide distributed and coordinated system power management. The proposed SPUs contain a battery power source and a power electronics converter. They are compatible with multiple battery chemistries (or any energy storage device that can produce a terminal voltage), allowing them to be used with both existing and future energy storage technologies.

Integration of Directed Energy Weapons (DEW) into future aircraft presents significant challenges. Principally, the need for generating and managing copious amounts of power into the Megawatt class is foreseen. Probably, the most critical and challenging area for supporting a DEW system on an aircraft is the Megawatt Class Electric Power System (MCEPS) and its associated Thermal Management Systems (TMS). MCEPS converts the aircraft fuel’s chemical energy into useable power for the load or system and the TMS disposes of the waste energy, all within the extremely challenging constraints (volume, weight, EMI, etc.) For the purposes of our studies, the MCEPS consists of the following subsystems: Engine, Power Generation, Power Conditioning, Distribution, Control, and Protection. The TMS manages Component Heat Extraction, Thermal Energy Storage, and Waste Heat disposal.

An alternative approach for producing variable speed constant frequency (VSCF) constant voltage power is the use of a resonant link power system. This system uses a permanent magnet (PM) generator and a resonant link solid state power converter. An electrically isolated PM generator may also be required for protection depending upon the final control topology. The use of a resonant link allows bi-directional power flow for engine start capability. Also, the resonant link allows the power semiconductor devices to be switched during the high frequency link zero crossings to reduce device stresses and improve reliability. The resonant link VSCF system is under investigation by the GE Corporate Research and Development group under contract #F33615-87-C-2806 to the Air Force.

Brushless Variable Speed Constant Frequency (VSCF) electric power generation may be obtained using cascaded symmetrically wound machines. The feasibility of using these machines as the basis for a stand-alone aircraft generator system was investigated by the USAF Aero Propulsion Laboratory. The concept is attractive as the system operates without hydraulics and employs a solid state power converter which operates at a fraction of the system output power and frequency. These factors combine to offer a system of relatively low complexity with the potential for high-reliability operation. This paper will discuss the operation of the cascaded doubly fed VSCF generator system and microprocessor control unit.

The Air Force Research Laboratory is currently funding efforts under the More-Electric Aircraft (MEA) Generation II Study for developing a preliminary design of an electrical power generation and distribution system (EPGDS) for flight demonstration of an Internal Starter/Generator (IS/G) for the main engine on an advanced fighter-class aircraft. The MEA Initiative is a phased, goal-oriented, effort that develops technologies to enable the use of electrical power to perform aircraft functions that historically have been powered hydraulically, mechanically, or pneumatically. The use of electrical power for these functions has the potential for enhanced aircraft performance through improved efficiency, reliability, maintainability, and supportability. Today, the MEA effort is in its second phase, with an anticipated technology availability date of 2005.

The movement to more-electric architectures during the past decade in military and commercial airborne systems continues to increase the complexity of designing and specifying the electric power system. In particular, the electrical power system (EPS) faces challenges in meeting the highly dynamic power demands of advanced power electronics based loads. This paper explores one approach to addressing these demands by proposing an electrical equivalent of the widely utilized hydraulic accumulator which has successfully been employed in hydraulic power system on aircraft for more than 50 years.