N. Wu, O. Wasynczuk, Purdue University; E. A. Walters, C. E. Lucas, PC Krause and Associates, Inc; Peter T. Lamm, U.S. Air Force Research Laboratory Power systems that include regulated power-electronic sources and/or loads are susceptible to potentially destabilizing interactions between these components. A variety of techniques and methodologies have been developed to characterize the small- and large displacement stability of such systems. Perhaps the most common approach is to establish the input/output impedance-versus-frequency characteristics of all sources and loads, whereby Nyquist- and/or Bode-inspired criteria may be used to characterize interconnected system stability. Essential to this methodology is a means of accurately and efficiently determining the input and/or output impedance-versus-frequency characteristics of the power electronic components that comprise the overall system. These frequency-domain characteristics can be established by (1) direct measurement, (2) exercising detailed simulations, or, more commonly, (3) using state-space average-value models. The primary disadvantage of using direct measurements is that the hardware must be available a-priori which makes it difficult and/or expensive to change or tailor the impedance characteristics if instabilities occur. Calculation of the impedance characteristics from detailed simulations is generally time consuming, especially if the low-frequency characteristics are needed, and little insight is gained as to how the impedance characteristics are affected by the various design parameters. Average-value models overcome the previous disadvantages; however, they introduce a new one. In particular, the derivation of an average value models is typically time consuming, especially if the circuit topology is complex and/or the power converter exhibits multiple load-dependent modes of operation. In this paper, an automated approach of establishing average-value models of power electronic converters of arbitrary complexity is set forth. The user-supplied inputs consist of a standard Spice-like circuit description (branch parameters and network graph) whereupon the input/output impedance-versus frequency characteristics are automatically and rapidly established. In addition to eliminating the need for the analytical derivation of average-value models, this technique readily permits the inclusion of secondary effects such as conduction losses, switching losses, and magnetic nonlinearities, to name a few. This technique has been successfully applied to characterize the output impedance of a one-quadrant dc/dc buck converter and a three-phase generator/rectifier source. Proceedings 3rd International Energy Conversion Engineering Conference, August 15-18, 2005, San Francisco,...
Read MoreAverage-Value Model of a High-Frequency Six-Phase Generation System
Juri Jatskevich University of British Columbia; E. A. Walters, C. E. Lucas, PC Krause and Associates, Inc; Peter T. Lamm U.S. Air Force Research Laboratory In this paper, a parametric average-value modeling approach is applied to a high-frequency six-phase aircraft generation subsystem. This approach utilizes a detailed switch-level model of the system to numerically establish the averaged dynamic relationships between the ac inputs of the rectifier and the dc-link outputs. A comparison between the average-value and detailed models is presented, wherein, the average-value model is shown to accurately portray both the large-signal time-domain transients and the small-signal frequency-domain characteristics. Since the discontinuous switching events are not present in the average-value model, significant gains can be realized in the computational performance. For the study system, the developed average-value simulation executed more than two orders of magnitude faster than the detailed simulation. SAE Transactions Journal of Aerospace, July 2005, pp. xxx, and 2004 SAE Power Systems Conference, November 2-4, 2004, Reno, NV, Paper...
Read MoreAutomated Evolutionary Design of a Hybrid-Electric Vehicle Power System Using Distributed Heterogeneous Optimization
Dionysios C. Aliprantis, O. Wasynczuk, Purdue University; N. Wu and C. E. Lucas, PC Krause and Associates, Inc; M. Abul Masrur, U.S. Army RDECOM-TARDEC The optimal design of hybrid-electric vehicle power systems poses a challenge to the system analyst, who is presented with a host of parameters to fine-tune, along with stringent performance criteria and multiple design objectives to meet. Herein, a methodology is presented to transform such a design task into a constrained multi-objective optimization problem, which is solved using a distributed evolutionary algorithm. A power system model representative of a series hybrid-electric vehicle is considered as a paradigm to support the illustration of the proposed methodology, with particular emphasis on the power system’s time-domain performance. 2006 SAE Power Systems Conference, November 7–9, 2006, New Orleans, LA. Paper #...
Read MoreDistributed Heterogeneous Simulation of a Hybrid-Electric Vehicle Drive System Using the Simplorer Software Product
N. Wu, C. E. Lucas, Curtis Rands, I. E. Simpson, PC Krause and Associates, Inc; Dionysios C. Aliprantis, Purdue University; M. Abul Masrur; U.S. Army RDECOM-TARDEC To support research and analysis requirements in the development of future hybrid-electric drive systems, a flexible and efficient means of predicting the dynamic performance of large-scale multi-disciplinary systems prior to hardware trials is crucial. With the development of Distributed Heterogeneous Simulation (DHS), the technology now exists to enable this type of investigation. Previously, DHS was shown to allow the interconnection of component simulations running on a single computer or networked computers and developed using any combination of a variety of commercial-off-the-shelf software packages. The US Army is interested in using the Simplorer software product from Ansoft Corporation to model various subsystems that are incorporated with such vehicle system simulations. In this paper, the DHS technique is expanded to support the Simplorer software package; thus, allowing subsystem models developed using this tool to be interconnected to form a dynamic system simulation. A representative hybrid-electric vehicle has been selected as a study system and includes propulsion, generation, weapon, and payload subsystems. Models of the components/subsystems that comprise the power system have each been developed in MATLAB/Simulink or Simplorer. Utilizing the system simulation, studies have been performed to illustrate the dynamic interactions between the subsystems when simulated on a computer network containing Windows based personal computers. 2006 SAE Power Systems Conference, November 7–9, 2006, New Orleans, LA. Paper #...
Read MoreCoupled-Circuit Modeling of 3, 6, and 9-Phase Induction Machine Drive Systems
Juri Jatskevich, University of British Columbia, Canada; E. A. Walters, C. E. Lucas, PC Krause and Associates, Inc. This paper describes a coupled-circuit physical-variable modeling of multiphase induction motors. The presented modeling interface makes it straightforward to implement an induction machine with arbitrary number of phases and/or phase groups on the stator and the rotor. The 3-, 6-, and 9-phase motors are simulated and compared. It is shown that machines with higher number of phases have less severe torque pulsation and the stator current increase following a loss of one phase. For the 9-phase machine, several studies involving loss of multiple phases are also presented, wherein the relative location of the faulted phases is shown to have a significant impact on redistribution of currents and resulting electromagnetic torque. The proposed models can be used to represent induction motors and generators for transient studies involving multiple faults, system-level reconfiguration, and survivability. 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....
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