Chris S. Edrington

Making the case for applications of switched reluctance motor technology in automotive products

Switched reluctance machines (SRM) offer attractive attributes for automotive applications. These include robustness to harsh operational conditions, rugged structure, fault resilient performance, and a wide range of speed. The main debate over the adequacy of switched reluctance drives in automotive applications has often focused on efficiency and position sensorless control over the entire speed range, adaptation of control algorithms in the presence of parameter variations, and high levels of acoustic noise and vibration. The present paper demonstrates three key technologies developed over the past few years that have resulted in tangible improvements in the performance of SRM/generators (SRM/G) as related to the above areas of interest. This paper intends to illustrate the new possibilities and remaining challenges in applications of SRM in automotive industry. The proposed technologies have been validated by simulation and experimental results

A Megawatt-Scale Power Hardware-in-the-Loop Simulation Setup for Motor Drives

We report on the application of a 5-MW variable voltage source (VVS) amplifier converter for utilization in power hardware-in-the-loop (PHIL) experiments with megawatt-scale motor drives. In particular, a commercial 2.5-MW variable speed motor drive (VSD) with active front end was connected to a virtual power system using the VVS for integrating the drive with a simulated power system. An illustrative example is given, whereby a 4-MW gas turbine generator system, including various loads, is simulated and interfaced with the VSD hardware in the lab through the VVS using current feedback to the simulation. Mechanical loading is applied to the motor via an identical 2.5-MW dynamometer connected to the same shaft. This paper first describes the PHIL facility, illustrates the challenges of powering a motor drive from a controlled voltage source converter at the multimegawatt scale, and provides experimental results from dynamic simulations. While certain challenges remain with the accuracy of the interface, it is concluded that PHIL simulations at the megawatt power level are possible and may prove useful for validating models of drive systems in the future.

Bipolar Switched Reluctance Machines: A Novel Solution for Automotive Applications

Current vehicle architectures utilize belt driven components such as the coolant pump, air-conditioner, power steering pump, etc. However, the trend toward more electric vehicles requires electromechanical energy conversion devices to replace these inefficient mechanical components. It is essential that electrical machines used in automotive applications to be compatible with the corresponding mechanical and electrical terminals. Furthermore, replacement of belt driven components with electrical drives should be performed as efficient and cost effective as possible. Bipolar switched reluctance machines (SRM) are both cost effective and very robust to the effects of temperature variation. They also offer a very wide speed range and an excellent mechanical integrity, which optimally suits a range of automotive applications including electric propulsion. This paper presents a detailed investigation of the performance indices for bipolar SRM drives. Using a Maxwell stress method, variations of radial and tangential force components due to saliency of the machine and saturation have been studied. Access to distribution of the force components acting on the rotor and stator enables us to provide a more accurate picture of the torque generation and vibration in this family of electric machines. Furthermore, distribution of magnetic forces under multiphase excitation has been studied in detail. Our findings show that bipolar excitation of SRM phases, resulting in a short flux path magnetic circuit, favors its efficiency and power quality while generating higher torque with less pulsation. This is a significant improvement, particularly for automotive applications where the difference in the required number of power electronics components can be justified. An experimental, 2-kW, 42-V, 8/6 SRM drive which has been designed and manufactured in our energy system laboratory was targeted for this study. In addition to our extensive finite-element (FE) analysis, experimental results have been provided to prove theoretical claims.

Prediction of rotor position at standstill and rotating shaft conditions in switched reluctance machines

Development of a reliable, smooth, and precise position sensorless startup routine is an integral part of the switched reluctance machine (SRM) control. The proposed sensorless startup method presented in this paper presents high grade performance and does not require additional hardware or memory. Further, the proposed sensorless technique is extended to rotating shaft conditions. These capabilities are highly demanded by automotive applications such as starter/alternator and electric power steering systems. An assessment of the impact of motor parameters and diagnostic signal measurement on the quality of the sensorless startup method is also included. This will help practicing engineers to make judicious selections for implementation of the proposed technique. Experimental and theoretical results are included to validate our claims.

Real-Time Emulation of a High-Speed Microturbine Permanent-Magnet Synchronous Generator Using Multiplatform Hardware-in-the-Loop Realization

This paper demonstrates a multiplatform hardware-in-the-loop (HIL) approach to observe the operation of a high-speed permanent-magnet synchronous generator coupled with a microturbine in an all-electric-ship power system. The mathematical model of the gas turbine and the dynamic equations of the high-speed generator are implemented in real time on a field-programmable gate array (FPGA). This real-time simulation interfaces with hardware via a serial peripheral interface to a supervisory digital signal processor (DSP) of a three-phase voltage source inverter. The inverter output load is virtually emulated in the FPGA using received hardware measurements from the DSP. A user input interface is introduced using dSPACE on a personal computer to acquire data and adjust the speed reference of the generator system through a serial communication interface to the DSP. The real-time simulation and HIL experimental setup are validated in a scaled medium voltage dc ship power system.

An Autocalibrating Inductance Model for Switched Reluctance Motor Drives

Development of a precise dynamic model is a critical step in design and analysis of optimal control strategies for switched-reluctance machines (SRM). This paper is focused on important issues concerning the development of such models and their subsequent use in designing control strategies for SRM drives. The main goal in modeling is to provide a good accuracy over the entire speed and torque range. To achieve this objective, the following requirements need to be met: 1) a good accuracy in matching the inductance of each stator phase; 2) inclusion of mutual effects when significant overlap among phases exists; 3) inclusion of short flux-path operation in each electrical cycle when significant overlap among adjacent phases exists; and 4) capability for autocalibration to cope with parameter variations incurred by manufacturing imperfections and operational conditions. In this paper, in addition to an in-depth discussion of the above factors, a practical modeling approach along with an autocalibration strategy is presented. A simple test collects the necessary data in developing the proposed model. Inherent separation among mechanical, electrical, and control time constants has been used to develop the autocalibration process. Experimental results are presented to validate the proposed method.

Analysis and Control of a Photovoltaic System: Application to a High-Penetration Case Study

This paper explores a two-stage, multistring photovoltaic system connected by a common dc bus to a centralized inverter, interfaced with a utility grid. The centralized inverter is controlled via a decoupled current control method and interfaced to the utility grid through a distribution transformer. Inverter control is completely independent of maximum power point control of the boost converter, used to step up the photovoltaic (PV) array voltage. Modeling and stability analysis of the photovoltaic system interfaced with the IEEE 14 bus grid system via a double circuit transmission line are presented. A control strategy is developed to overcome instability problems associated with the series compensated transmission connecting the photovoltaic system to the grid. Studies are also conducted that explore the transient response of the photovoltaic system following a three-phase and single-line to ground fault on the transmission line. Additionally, participation factor analysis is applied to a small signal model of the entire system to identify the parameters that have the most influence on the system stability. The developed models and analysis are validated through detailed simulation studies. The results obtained from this paper reveal the importance of conducting system level analysis when characterizing grid-connected PV systems.

Power Flow Control and Network Stability in an All-Electric Ship

The concept of an all-electric ship, while offering unprecedented advantages from the point of view of efficiency and flexibility of operation, has introduced new challenges in terms of stability and power flow control. The advent of a full power electronics power system has raised new questions from the point of view of system dynamics, particularly when dealing with the new medium-voltage direct current distribution. The overall goal of guaranteeing a secure operation of the power system has brought researchers to consider two main approaches: reducing the dynamics of the large load to operate in a range of dynamics compatible with traditional generation systems, or making the generator set smarter through its power electronics interface. This paper compares these approaches to stable operation, focusing on the latter considered more in line with the progress of technology and in general more appealing.

Application of Artificial Intelligence to Real-Time Fault Detection in Permanent-Magnet Synchronous Machines

This paper discusses faults in rotating electrical machines in general and describes a fault detection technique using artificial neural network (ANN) which is an expert system to detect short-circuit fault currents in the stator windings of a permanent-magnet synchronous machine (PMSM). The experimental setup consists of PMSM coupled mechanically to a dc motor configured to run in torque mode. Particle swarm optimization is used to adjust the weights of the ANN. All simulations are carried out in MATLAB/SIMULINK environment. The technique is shown to be effective and can be applied to real-time fault detection.

A review of PHEV grid impacts

This paper is a literary review of the benefits and barriers of PHEV deployment in the U.S., along with the proposed solutions to the setbacks that may occur. The review aims at identifying the energy requirements of PHEVs, the impact of PHEVs on the grid, and solutions to the shortcomings of the electrical grid, such as vehicle to grid and smart grids.