38 research outputs found
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Rotating Machine Technologies for Integration of Pulsed and High Power Loads in Naval Electric Power Systems
Advanced electric sensors and weapons are placing increasing demands on the electric power distribution systems of future naval vessels and energy storage is viewed as a critical technology for effective integration of IPS architectures in these platforms. This paper shows that kinetic energy storage, i.e. stored in the angular momentum of a rotating mass, can be applied in differing topologies to address a range of ship power system applications. Rotating machine technologies are presented for UPS and load leveling applications as well as for high cycle rate pulsed power applications.Center for Electromechanic
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Modeling of Electric Ship Power Systems
The central element of a ship power system model is typically a circuit model. This level of modeling has been valuable in evaluating architectures for future electric ships as it provides initial power flow and stability information as well as performance specifications, perhaps most notably overall efficiency. This circuit model is typically the middle layer in what is a three layer approach. At the more basic level, the physics of the components and processes is captured. In a power system, there are interactions among the electromagnetic, mechanical, and thermal behaviors. The third level is even more approximate than the circuit level. It includes such models as cost-of-ownership models, models of physical layout and integration of the power system with the balance of plant. These models are critical in the design process and depend on the circuit model to specify components and their interconnections. Incorporating breakdown physics demonstrates the linkage between the basic physics and the circuit models. Rotor dynamics provides examples of phenomena that cannot be captured in a circuit model. The design of insulation systems is an example of a field in which the circuit modeling may lead to less costly electrical systems for future electric ships.Center for Electromechanic
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High speed induction motor and inverter drive for flywheel energy storage
The use of flywheels to store energy is a technology which is centuries old. The confluence of several modern technologies has resulted in flywheels becoming a viable solution for the needs of the transportation, electric utility, and aerospace industries. This paper discusses a high-speed induction motor and its associated inverter drive which were developed for the Federal Railroad Administration’s “Advanced Locomotive Propulsion System.” The design of the induction motor provided several significant challenges. A megawatt rated, 12,000 rpm motor operating at a rotor surface velocity speed of 230 m/s required a unique mechanical configuration to withstand the centrifugal forces as well as an electromagnetic design, which produced a high efficiency at 200 Hz. Extending the design practices used in smaller motors would not achieve the goals required for a megawatt size machine. Similarly, the inverter was developed using a soft switching technique in order to meet the demands of high power output in a compact package. Application requirements, electrical and mechanical features of the motor, design strategy for the inverter, and test results are all presented in this paper.Center for Electromechanic
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Cross-platform validation of notional baseline architecture models of naval electric ship power systems
To support efforts in assessing the relative merit of alternative power system architectures for future naval combatants, the Electric Ship Research and Development Consortium (ESRDC) has developed notional baseline models for each of the primary candidate architectures currently considered, medium-voltage DC (MVDC), conventional 60 Hz medium-voltage (MVAC), and high-frequency medium-voltage (HFAC). Initial efforts have focused on the development of a consistent set of component models, of which the system models can be comprised, and the basic definition of the system models. The broader objectives of the consortium, however, go beyond the definition of the baseline models. The focus is on the process by which the models are implemented in software and validated, the process by which the performance of the disparate system models are objectively and quantitatively assessed and compared, and, ultimately, the process by which the relative merits of the architectures may be assessed. This paper focuses specifically on cross-platform component validation.Center for Electromechanic
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Waveform-level time-domain simulation comparison study of three shipboard power system architectures
Detailed waveform-level modeling and simulation of three alternative shipboard power system architectures is presented herein. The three system architectures are based on conventional 60Hz medium-voltage ac (MVAC), higherfrequency 240Hz medium-voltage ac (HFAC) and mediumvoltage dc (MVDC) technologies. To support the quantitative assessment and comparison of these three different power system architectures, each technology was modeled using a common representative, notional baseline ship. The baseline ship represents a multi-mission destroyer fitted with an 80MW next generation integrated power system (NGIPS). Modeling of each power system architecture is set forth along with simulation studies for three fault scenarios. Each of the three power system architectures was implemented within the MATLAB/ Simulink environment. Continuity of service was evaluated for each architecture along with a fault scenario using an operability metric. After a brief description of the three power system architectures and the operability metric, quantitative results are presented.Center for Electromechanic
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Dynamic Load and Storage Integration
Modern technology combined with the desire to minimize the size and weight of a ship’s power system are leading to renewed interest in more electric or all electric ships. An important characteristic of the emerging ship power system is an increasing level of load variability, with some future pulsed loads requiring peak power in excess of the available steady– state power. This inevitably leads to the need for some additional energy storage beyond that inherent in the fuel. With the current and evolving technology, it appears that storage will be in the form of batteries, rotating machines, and capacitors. All of these are in use on ships today and all have enjoyed significant technological improvements over the last decade. Moreover all are expected to be further enhanced by today’s materials research. A key benefit of storage is that, when it can be justified for a given load, it can have additional beneficial uses such as ride-through capability to restart a gas turbine if there is an unanticipated power loss; alternatively, storage can be used to stabilize the power grid when switching large loads. Knowing when to stage gas turbine utilization versus energy storage is a key subject in this paper. The clear need for storage has raised the opportunity to design a comprehensive storage system, sometimes called an energy magazine, that can combine intermittent generation as well as any or all of the other storage technologies to provide a smaller, lighter and better performing system than would individual storage solutions for each potential application.Center for Electromechanic
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Dynamic Simulations of a Large High-Frequency Power System
Dynamic simulations to assess performance aspects of a large high-frequency power system have been conducted. The analysis uses a model of an 80-MW power system for an all-electric ship. The model, developed in the Matlab/Simulink environment, includes several power generation units, two propulsion power trains, an energy storage system, a high-power pulse load, and several service loads. Three case studies were addressed. The first considers the response of the power system to a high-power step load, representing a sudden request for acceleration of the ship. The second deals with the effects of a partial loss of generation during operation. The third addresses the effects of load drop on the power system.Center for Electromechanic
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Uncertainty Analysis of Large-scale Power Systems Using Collocation
Collocation algorithms for efficiently solving stochastic differential equations arising from modeling uncertainty in large-scale systems are presented. The resulting solutions are integrated to compute statistical moments, from which sensitivity can be inferred, and interpolated to propagate PDF’s. We give a detailed exposition of this approach, focusing on the dimension-adaptive algorithm of [10]. We give applications on a double pendulum, an integrated shipboard power system, and a pulse power system.Center for Electromechanic
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Variable Speed Operation of Turbogenerators to Improve Part-load Efficiency
Our investigation of variable speed operation of turbogenerators, including both single-shaft and twin-shaft variants, shows significant opportunities to improve part-load efficiency in those certain electrical power generation applications that permit variable speed operation. Efficiency improvement increases as load decreases and the improvement is larger for single-shaft engines than for twin-shaft engines. For example, when operating at 20% loading, adjusting the engine speed can improve fuel efficiency by 14% for single-shaft gas turbines, and by 2% for twin-shaft gas turbines. In addition, we present a semi-theoretical analysis that provides a procedure to obtain the gas turbine optimal efficiency and its corresponding optimal speed as a function of shaft load. Simulation results of part-load variable speed modeling of gas turbines further confirmed the theoretical analysis. This has important practical implications. An analysis of fuel consumption by a gas turbine that operates with a load profile representative of a typical propulsion profile for a DDG51 ship, shows a 15% reduction in fuel consumption when variable speed operation is used, as compared to fixed speed operation. In addition, the analysis presented in this paper provides a general method to evaluate the steady-state performance of gas turbines operating with variable speed.Center for Electromechanic
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Large area black body source for ITER ECE in situ calibration
Development and testing of a hot calibration source for the ECE systems on ITER is underway. The source is intended to meet the requirements described in DDD55 Overview of Diagnostics. The requirement is for two 200 mm diameter sources. One will operate at atmospheric pressure and be well removed from the experiment. The other will operate in vacuum near the plasma. Both will operate at temperatures up to 800 °C. Here we report on the development of a prototype hot calibration source and of a realistic thermal model of the hot calibration source that will be used in simulations of the thermal properties of the source. Selection of a reliable heating method is challenging. Heating methods under consideration will be discussed.Center for Electromechanic