1,746 research outputs found

    Three-Phase Power Converter Based Real-Time Synchronous Generator Emulation

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    To bridge the gap between power system research and their real application in power grids, a Hardware Test-Bed (HTB) with modular three-phase power converters has been developed at the CURENT center, the University of Tennessee, Knoxville, to emulate transmission level power systems with actual power flowing. This dissertation focuses on the development and verification of a real-time synchronous generator (SG) emulator in the HTB. The research involved in this dissertation aims at designing a proper control to achieve emulator performance goal and investigating the sources of error and its influence on interconnected SG-emulator networks. First, different interface algorithms (IAs) are compared and the voltage type ideal transformer model (ITM) is selected considering the accuracy and stability. At the same time, closed-loop voltage control with current feed-forward is proposed to decrease the error caused by the non-ideality of the power amplifier. The emulation is then verified through two different ways. First, the output waveforms of the emulator in experiment are compared with the simulation under the same condition. Second, a transfer function perturbation (TFP) based error model is obtained and redefined as the relative error for the amplitude and phase between the emulated and the target system over the frequency range of interest. The major cause of the error is investigated through a quantitative analysis of the error with varying parameters. Third, the stability issue associated with the interconnection of two SG emulators is studied. The small signal models of the two-generation system with constant current and constant impedance load are developed, and the main reasons that cause instability are researched and verified. The developed SG emulator is also verified in the two-area system by comparing the system dynamics visually. At last, the 6th-order SG model including transformer voltages and saturation effect is applied in the three-phase symmetrical fault scenario. Control parameters are designed based on the TFP error evaluation of the fault condition. The developed SG emulator is then tested and verified in line-to-line fault condition. In addition, the stability of the new SG emulator is studied again and compared with the previous emulation

    Power-Electronics-Based Mission Profile Emulation and Test for Electric Machine Drive System:Concepts, Features, and Challenges

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    Design, Modelling and Verification of Distributed Electric Drivetrain

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    The electric drivetrain in a battery electric vehicle (BEVs) consists of an electric machine, an inverter, and a transmission. The drivetrain topology of available BEVs, e.g., Nissan Leaf, is centralized with a single electric drivetrain used to propel the vehicle. However, the drivetrain components can be integrated mechanically, resulting in a more compact solution. Furthermore, multiple drivetrain units can propel the vehicle resulting in a distributed drive architecture, e.g., Tesla Model S. Such drivetrains provide an additional degree of control and topology optimization leading to cheaper and more efficient solutions. To reduce the cost, the drivetrain unit in a distributed drivetrain can be standardized. However, to standardize the drivetrain, the drivetrain needs to be dimensioned such that the performance of a range of different vehicles can be satisfied. This work investigates a method for dimensioning the torque and power of an electric drivetrain that could be standardized across different passenger and light-duty vehicles. A system modeling approach is used to verify the proposed method using drive cycle simulations. The laboratory verification of such drivetrain components using a conventional dyno test bench can be expensive. Therefore, alternative methods such as power-hardware-in-the-loop (PHIL) and mechanical-hardware-in-the-loop (MHIL) are investigated. The PHIL test method for verifying inverters can be inexpensive as it eliminates the need for rotating electric machines. In this method, the inverter is tested using a machine emulator consisting of a voltage source converter and a coupling network, e.g., inductors and transformer. The emulator is controlled so that currents and voltages at the terminals resemble a machine connected to a mechanical load. In this work, a 60-kW machine emulator is designed and experimentally verified. In the MHIL method, the real-time simulation of the system is combined with a dyno test bench. One drivetrain is implemented in the dyno test bench, while the remaining are simulated using a real-time simulator to utilize this method for distributed drivetrain systems. Including the remaining drivetrains in the real-time simulation eliminates the need for a full-scale dyno test bench, providing a less expensive method for laboratory verification. An MHIL test bench for verification of distributed drivetrain control and components is also designed and experimentally verified

    Propulsion Powertrain Real-Time Simulation Using Hardware-in-the-Loop (HIL) for Aircraft Electric Propulsion System

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    It is essential to design a propulsion powertrain real-time simulator using the hardware-in-the-loop (HIL) system that emulates an electrified aircraft propulsion (EAP) systems power grid. This simulator would enable us to facilitate in-depth understanding of the system principles, to validate system model analysis and performance prediction, and to demonstrate the proof-of-concept of the EAP electrical system. This paper describes how subscale electrical machines with their controllers can mimic the power components in an EAP powertrain. In particular, three powertrain emulations are presented to mimic 1) a gas turbo-=shaft engine driving a generator, consisting of two permanent magnet (PM) motors with brushless motor drives, coupled by a shaft, 2) a motor driving a propulsive fan, and 3) a turbo-shaft engine driven fan (turbofan engine) operation. As a first step towards the demonstration, experimental dynamic characterization of the two motor drive systems, coupled by a mechanical shaft, were performed. The previously developed analytical motor models1 were then replaced with the experimental motor models to perform the real-time demonstration in the predefined flight path profiles. This technique can convert the plain motor system into a unique EAP power grid emulator that enables rapid analysis and real-time simulation performance using hardware-in-the-loop (HIL)

    Modeling and Control of Diesel-Hydrokinetic Microgrids

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    A large number of decentralized communities in Canada and particularly in Québec rely on diesel power generation. The cost of electricity and environmental concerns suggest that hydrokinetic energy is a potential for power generation. Hydrokinetic energy conversion systems (HKECSs) are clean, reliable alternatives, and more beneficial than other renewable energy sources and conventional hydropower generation. However, due to the stochastic nature of river speed and variable load patterns of decentralized communities, the use of a hybrid diesel- hydrokinetic (D-HK) microgrid system has advantages. A large or medium penetration level has a negative effect on the short-term (transient) and long-term (steady-state) performance of such a hybrid system if the HKECS is controlled based on conventional control schemes. The conventional control scheme of the HKECS is the maximum power point tracking (MPPT). In the long-term conditions, the diesel generator set (genset) can operate at a reduced load where the role of the HKECS is to reduce the electrical load on the diesel genset (light loading). In the short-term, the frequency of the microgrid can vary due to the variable nature of water speed and load patterns. This can lead to power quality problems like a high rate of change of frequency or power, frequency fluctuations, etc. Moreover, these problems are magnified in storage-less DHK microgrids where a conventional energy storage system is not available to mitigate power as well as frequency deviations by controlling active power. Therefore, developing sophisticated control strategies for the HKECS to mitigate problems as mentioned above are necessary. Another challenging issue is a hardware-in-the-loop (HIL) platform for testing and developing a D-HK microgrid. A dispatchable power controller for a fixed-pitch cross-flow turbine-based HKECS operating in the low rotational speed (stall) region is presented in this thesis. It delivers a given power requested by an operator provided that the water speed is high enough. If not, it delivers as much as possible, operating with an MPPT algorithm while meeting the basic operating limits (i.e., generator voltage and rotor speed, rated power, and maximum water speed), shutting down automatically if necessary. A supervisory control scheme provides a smooth transition between modes of operation as the water speed and reference power from the operator vary. The performance of the proposed dispatchable power controller and supervisory control algorithm is verified experimentally with an electromechanical-based hydrokinetic turbine (HKT) emulator. The permanent magnet synchronous generator (PMSG) is preferred in small HKECSs. So, a converter-based PMSG emulator as a testbed for designing, analyzing, and testing of the generator’s power electronic interface and its control system is developed. A 6-switch voltage source converter (VSC) is used as a power amplifier to mimic the behaviour of the PMSG supplying linear and non-linear loads. Technical challenges of the PMSG emulator are considered, and proper solutions are suggested. Finally, an active power sharing control strategy for a storage-less D-HK microgrid with medium and high penetration of hydrokinetic power to mitigate: 1) the effect of the grid frequency fluctuation due to instantaneous variation in the water speed/load, and 2) light loading operation of the diesel engine is proposed. A supplementary control loop that includes virtual inertia and frequency droop control is added to the conventional control system of HKECS in order to provide load power sharing and frequency support control. The proposed strategy is experimentally verified with diesel engine and HKT emulators controlled via a dSPACE® rapid control prototyping system. The transient and steady-state performance of the system including grid frequency and power balancing control are presented

    Implementation of Real-Time Hardware in the Loop Simulation for WAVE Instrument Avionics

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    The Regolith and Environment Science and Oxygen and Lunar Volatile Extraction (RESOLVE) payload will lead the Resource Prospector rover to hydrogen-rich locations on the moon supporting NASA's in-situ resource utilization (ISRU) mission. The Water Analysis and Volatile Extraction (WAVE) system will be responsible for heating up regolith samples and analyzing their volatiles in a vaporized state. Given the space environment, testing flight hardware and software using the scientific instruments can be costly and time consuming, which can hold back progress involving the instruments. A hardware-in-the-loop (HITL) simulation will test the Avionics Data Acquisition as well as the Instrument Interface Unit, through simulating sensors and actuators involved in supporting the WAVE instruments. HITL is a platform for testing and developing WAVE's avionics and software, where the simulation plant will imitate the LAVA and OVEN instruments, thus allowing for an accessible, efficient, and replicable testing environment

    Virtual Synchronous Generator Operation of Full Converter Wind Turbine ‒ Control and Testing in a Hardware Based Emulation Platform

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    Wind is one of the most promising renewable energy forms that can be harvested to into the electrical power system. The installation has been rising worldwide in the past and will continue to steadily increase. The high penetration of wind energy has bought about a number of difficulties to the power system operation due to its stochastic nature, lack of exhibited inertia, and differing responses to the traditional energy sources in grid disturbances. Various grid support functions are then proposed to resolve the issues. One solution is to allow the renewable energy sources to behave like a traditional synchronous generator in the system, as a virtual synchronous generator (VSG). On the other hand, testing the control of the future power grid with high penetration renewable often relies on digital simulation or hardware-based experiments. But they either suffer from fidelity and numerical stability issues, or are bulky and inflexible. A power electronics based power system emulation platform is built in the University of Tennessee. This Hardware Testbed (HTB) allows testing of both system level and component level controls, with a good balance between the fidelity of the hardware-based testing platform, and the coverage of the digital simulation.This dissertation proposal investigates the VSG operation of the full converter wind turbine (FCWT), focusing on its control and testing in the HTB. Specifically, a FCWT emulator was developed using a single converter to include its physical model and control strategies. The existing grid support functions are also included to demonstrate their feasibility.The comprehensive VSG controls are then proposed for a FCWT with short term energy storage. The dynamic response of the FCWT can be comparable to the traditional generation during grid disturbance. The control can also allow the FCWT to be dispatched by the system operator, and even operate stand-alone without other grid sources.To study the system response under faults, a short circuit fault emulator was developed in the HTB platform. Four basic types of the short circuit faults with various fault impedance can be emulated using the emulator. The power system transient stability in terms of critical clearing time can be measured using the developed fault emulator
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