Michael Corbett, Jessica Williams, Mitch Wolff, E. A. Walters, J. R. Wells, PC Krause and Associates, Inc; Peter Lamm, U.S. Air Force Research Laboratory Aircraft power demands continue to increase with the increase in electrical subsystems. These subsystems directly affect the behavior of the power and propulsion systems and can no longer be neglected or assumed linear in system analyses. The complex models designed to integrate new capabilities have a high computational cost. This paper investigates the possibility of using a hardware-in-the-loop (HIL) analysis with real time integration. A representative electrical power system is removed from a turbine engine model simulation and replaced with the appropriate hardware attached to a 350 horsepower drive stand. In order to update the model to proper operating conditions, variables are passed between the hardware and the computer model. Using this method, a significant reduction in runtime is seen, and the turbine engine model is usable in a real time environment. Scaling is also investigated for simulations to be performed that exceed the operating parameters of the drive stand. Similar results are generated with and without the scale factor implemented. Excellent agreement is shown between the HIL and stand alone model results. These results validate the capability of HIL experimentation and provide the opportunity for significant future propulsion configuration studies with minimal cost. 2006 SAE Power Systems Conference, November 7–9, 2006, New Orleans, LA. Paper...
Read MoreAn Observer-Based Automated Averaging Technique for Power Electronic Circuits
E. A. Walters, O. Wasynczuk, J. V. Jatskevich, C. E. Lucas, PC Krause and Associates, Inc. Average-value models are commonly used in the design and analysis of power electronic-based systems as a method of portraying the overall system dynamics while neglecting discontinuities that arise from switching. Although numerous averaging methodologies have been developed to eliminate discontinuities, they are typically limited to specific circuits operating in specific modes. Therefore, substantial analytical effort is generally required to select an appropriate averaging technique and develop the corresponding average-value model that is valid for a given converter. To reduce this effort, an automated averaging technique is set forth in which an averaged model is established via coupling with a detailed simulation of the system. The structure of the averaged model is based upon state-space averaging with the detailed simulation used to calculate state models for each switching topology, the time spent per cycle in each topology, and the operating mode (continuous or discontinuous) of the circuit. However, since classical state-space averaging is not applicable to circuits with state-dependent switching logic and does not portray high- frequency dynamics associated with discontinuous states, a state feedback loop is introduced such that the high-frequency dynamics associated with state- dependent switching or discontinuous modes are accurately portrayed. To demonstrate the new technique, to example systems are examined, a PWM-controlled buck converter operating in both continuous and discontinuous modes and buck converter with a hysteresis current controller. The new averaging technique is verified by comparison with established analytical and numerical methods. SAE Transactions Journal of Aerospace, sec. 1, set 3, Month 2000, pp....
Read MoreImprovements in the Distributed Heterogeneous Simulation of Aircraft Electric Power Systems
B. P. Loop, C. E. Lucas, E. A. Walters, M. Hasan, PC Krause and Associates, Inc; S. Field , N. Kumbar, Naval Air Systems Command 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. 2006 SAE Power Systems Conference, November 7–9, 2006, New Orleans, LA. Paper...
Read MoreHardware-in-the-Loop Power Extraction Using Different Real-Time Platforms
John McNichols, Caleb Barnes, Mitch Wolff, T. Baudendistel, PC Krause and Associates, Inc; Michael Corbett, Peter Lamb, U.S. Air Force Research Laboratory Aircraft power demands continue to increase with the increase in electrical subsystems. These subsystems directly affect the behavior of the power and propulsion systems and can no longer be neglected or assumed linear in system analyses. The complex models designed to integrate new capabilities have a high computational cost. Hardware-in-the-loop (HIL) is being used to investigate aircraft power systems by using a combination of hardware and simulations. This paper considers two different real-time simulators in the same HIL configuration. A representative electrical power system is removed from a turbine engine simulation and is replaced with the appropriate hardware attached to a 350 horsepower drive stand. Variables are passed between the hardware and the simulation in real-time to update model parameters and to synchronize the hardware with the model. Real-time simulation platforms from dSPACE and National Instruments (NI) are utilized for this investigation. Similar results are obtained when using HIL and a simulated load. Initially, noticeable differences are seen when comparing the results from each real-time operating system. However, discrepancies in test results obtained from the NI system can be resolved. This paper briefly details the underlying problem and its solution before discussing test results which show that both dSPACE and NI can be configured to match the baseline Simulink data. American Institute of Aeronautics and Astronautics 6th International Energy Conversion Engineering Conference, July 2008. Contact information:...
Read MoreMulti-Fidelity Modeling of Wound-Rotor Synchronous Machines
B. P. Loop, M. Hasan, M. Gualtieri, E. A. Walters, PC Krause and Associates, Inc. In this paper, methods for transitioning between different types of wound-rotor synchronous machines models are examined. The specific transitions investigated are (1) finite element to circuit-based machine models and (2) circuit-based to average value models of machine/rectifier systems. Good agreement between simulation results obtained using the different model types is achieved. This work sets the stage for a software environment that enables both component and system level analysis of electrical power systems. 2008 Electric Machines Technology Symposium, August 12-13, 2008, Philadelphia,...
Read MoreWater-Cooled Load Bank for Aircraft Power Systems Analysis
C. Barnes, G. Diehl, T. Baudendistel, PC Krause and Associates, Inc; J. Potter, L. Burich, U.S. Air Force Research Laboratory Using an air-cooled load bank in the high speed drive stand room at AFRL Building 18b Room 15 has presented several problems. It required significant floor space. It was designed only for 270VDC. It raised the temperature of the room to a high level due to its 82.5KW resistive load. Lastly, it applies a load in large 2.7kW steps. This presentation will cover a new 150KW load bank developed to address these issues. The new load bank that was developed is water cooled to transport heat out of the drive stand room by using 30 5KW heater elements configured in three banks of 10. Each element is switched on or off by a controller built into the load bank to meet the loading requirements. Three of the elements are controlled by a Pulse Width Modulation (PWM) circuit to provide 20W steps in loading. The load bank is equipped with rectifiers and adaptor plates to accommodate various generator configurations including single phase AC, 3-phase AC, and DC voltages. In order to minimize floor space used, the load bank is wall mounted above the drive stand. 2008 SAE Power Systems Conference, November 11-13, 2008, Bellevue,...
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