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Two recent enhancements to Distributed Heterogeneous Simulation (DHS) are variable communication rates and higher-order predictors. Variable communication automatically controls the communication interval between any two subsystems in an attempt to achieve a desired accuracy during transient periods and maximize speed during steady-state periods. Higher-order predictors can better estimate the values of exchanged variables between data exchange instances, which can improve accuracy and possibly require fewer exchanges. A comparison between a single-computer simulation of an aircraft electric power system and an equivalent three-computer DHS show that the variable communication technique enables more accuracy and higher speed distributed simulations than fixed-step communication. In addition, higher-order predictors are shown to increase accuracy in some cases.

In this paper, a recently-developed algorithmic method of deriving the state equations of power systems containing power electronic components is described. Therein the system is described by the pertinent branch parameters and the circuit topology; however, unlike circuit-based algorithms, the difference equations are not implemented at the branch level. Instead, the composite system state equations are established. A demonstration of the computer implementation of this algorithm to model a variable-speed, constant-frequency aircraft generation system is described. Because of the large number of states and complexity of the system, particular attention is placed on the development of a model structure which provides optimal simulation efficiency.

In this paper, a new technique useful for the numerical simulation of large-scale systems is presented. This approach enables the overall system simulation to be formed by the dynamic interconnection of the various interdependent simulations, each representing a specific component or subsystem such as electrical, mechanical, hydraulic, or thermal. Each simulation may be developed separately using possibly different commercial-off-the-shelf simulation programs thereby allowing the most suitable language or tool to be used based on the design/analysis needs. For the purpose of demonstration, this technique is applied to a detailed simulation of a representative aircraft power system. This system is comprised of ten component models each developed using MATLAB/Simulink™, EASY5™, or ACSL™.

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.

An Intermittent Megawatt Generator (IMG) has been designed by Innovative Power Solutions (IPS) to meet the needs of future directed energy loads on high-performance aircraft. These loads significantly impact the electrical, mechanical, and thermal performance of the generator, load, and aircraft. If representative simulation models of the generator and other important subsystems can be obtained, the impact on system performance can be analyzed and optimized before the generator is deployed. The objective of this work was to utilize various modeling techniques to obtain accurate electrical, thermal, and mechanical performance models of the IMG, and to apply these models to analyze dynamic response transients to sudden load changes as seen for directed energy loads. Additionally, the models have been used to optimize the IMG control to mitigate voltage transients during these load changes.

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.