Philip A Commins

Analytical Nonlinear Reluctance Model of a Single-Phase Saturated Core Fault Current Limiter

A saturated core fault current limiter (FCL) is a device that is designed to limit the fault currents in electrical energy networks and consequently, protect existing network equipment from damage. Due to complex nonlinear magnetic properties, the performance of saturated core FCLs has largely been characterized through experimentation and finite-element analysis simulations. Although both of these techniques are quite accurate, they are time consuming and do not describe the behavior of FCLs in actual electrical networks. This has led to an increasing demand for an accurate analytical model that is suitable for transient network analyses. This paper presents the development of an analytical model of a single-phase open-core FCL, which accurately describes the nonlinear magnetic properties of the FCL through a reduced reluctance approach. The extension of this model to other saturated core FCL arrangements (such as closed core) is also discussed.

Design considerations in MgB2-based superconducting coils for use in saturated-core fault current limiters

Saturated-core fault current limiters (FCLs) are devices that have many applications and potential for use within power networks. At a commercial scale, these devices require high H-field magnets to saturate the steel core, which can typically only be achieved through the use of superconducting coils. Here, we present several challenges that arise in the application of superconducting coils in FCLs and discuss how to address these issues through a case study MgB2-based coil. It is found that significant ac magnetic fields, Lorentz forces, and Joule heating in components occur during normal and fault operations; however, these issues can be mitigated when properly addressed.

Three phase saturated core fault current limiter performance with a floating neutral

High power demands in electricity grids are continually increasing. This increasing trend coupled with the introduction of renewable energy sources, which require energy storage devices, poses significant problems to fault current levels. To improve network availability and grid resilience, superconducting saturated core Fault Current Limiters (FCL) are a suitable solution to reduce high fault currents in distribution level electricity grids. These devices have the characteristic of low impedance to the network during normal operation and high impedance during a fault event. However, this change in impedance is nonlinear and can lead to an imbalance in a three phase saturated core FCL. In this paper, the effects on fault current limiting performance due to the unbalanced instantaneous impedance between the 3 phases are investigated. The FCL fault transients of a grounded fault and a floating fault are simulated and compared using Finite Element Analysis (FEA) techniques. The presented results are also validated against a real world distribution level saturated core FCL under high power testing.

Novel tooth design for a tubular linear motor for machine tool axis

Permanent magnet tubular linear motors have shown potential for use as direct drives in high precision machine tools. These devices are capable of replacing the traditional ball screw, given their ability to overcome or reduce many of the fundamental mechanical properties that limit the precision performance of the ball screw. However, given the desire from industry to increase speed and acceleration, the physical size of the motor must be minimised while maintaining high force output to increase bandwidth in high precision applications. This paper presents a new optimal tooth design to reduce the frame size of a slotted tubular linear motor. Several design aspects of the optimal tooth are considered and general solutions are derived. Data from finite element analysis and from an experimental machine is presented to validate the new designs.

Transient Modeling of Saturated Core Fault Current Limiters

A saturated core fault current limiter (FCL) essentially utilizes the dynamic and nonlinear magnetic behavior of steel cores to operate as a variable reactor. However, the nonlinear characteristic of magnetic materials has made modeling this unique device a difficult task. Hence, experimental measurements and finite-element method (FEM) analysis are the most common techniques used to characterize the transient behavior of the device. Both of these techniques, while accurate, cannot be used to analyze the transient electrical behaviour of FCLs in complex power systems, particularly when investigating power system switchgear behavior during fault events. FEM-based FCL modelling, despite its usefulness as a design verification tool, cannot be easily coupled to all electromagnetic transient programs that are in use today. This paper presents two modeling approaches to represent the saturated core FCL in transient network simulators: 1) the nonlinear reluctance model and 2) the nonlinear inductance model. Both models are implemented in PSCAD/EMTDC and are validated by experimental results of a single-phase prototype saturated core FCL, where excellent agreement between the experimental and the modelling approaches is achieved.

Framework for implementation of higher-level control for over-actuated electric vehicles

This paper will outline the development of a vehicle dynamics simulation framework using Matlab/Simulink and SimScape utilising the block based system modelling technique. This framework is used for implementing higher-level control architectures for distributed drive and torque vectoring strategies for Over Actuated Electric Ground Vehicles (OAEGV). Research and development of OAEGVs has been increasing over recent years, as such the work presented in this paper aims to produce a baseline framework for the simulation of important vehicle performance indicators to aid in the design process. A block based solution using Matlab/Simulink and SimScape also allows for a parametric, broad purpose simulation framework with hardware and software in the loop capabilities for rapid deployment of code.

Applicability of nonlinear reluctance model to a closed core Fault Current Limiter

A saturated core Fault Current Limiter (FCL) is a fault current reducing device that has attracted significant attention from both researchers and electricity utilities. The behaviour of saturated core FCLs has so far been characterised largely through experimentation and/or Finite Element Analysis (FEA) simulations, primarily due to the intricate nonlinear magnetic characteristics of the device. Both these techniques, while accurate, fail to demonstrate the behaviour of FCLs in actual electrical networks. Hence there is an increasing need for an accurate model of the FCL that can be easily incorporated into transient network analysers. This paper presents the development and applicability of an analytical model of a single-phase FCL with a closed core topology, which accurately describes the nonlinear magnetic properties of the FCL through a reduced reluctance approach. The model is implemented in an electromagnetic transient network simulation package and the simulation results are validated against experimentally measured data.

Synchronous reluctance tubular linear motor for high precision applications

This paper presents a novel Synchronous Reluctance Tubular Linear Motor (SyncRTLM) for high precision motion control applications, such as machine tools. Finite Element Analysis (FEA) of the motor is conducted to simulate the motor performance and to analyse the magnetic fields in the motor. The design and development of the built motor is outlined, where a novel construction technique is described. The position, velocity and force performance is measured using a modified servo current control algorithm.

Tubular linear motor position detection by hall-effect sensors

The Permanent Magnet Tubular Linear Motor (PMTLM) system using Hall-effect sensors as the position feedback devices is discussed in this paper. In order to have high precision position detection, simulation by the Finite Element Analysis (FEA) software Flux 2D and real experimentation are conducted. By choosing suitable Hall-effect sensor mounting positions, detecting the axial and radial directions of magnetic field and using double Hall sensors, high precision results are obtained. The results show the possibility of using Hall-effect sensors for linear motor position detection especially for low-cost linear servo systems.

State and Parameter Estimation of EVs

Abstract This chapter covers the implementation of state- and parameter-estimation techniques for electric vehicles (EVs) in both a mathematical and practical sense. First the reasoning behind such action will be discussed including the uses for EVs and the unique factors that give rise to a demand for such state and parameter estimation. Then highly desirable states and parameters are outlined, followed by an in-depth explanation of the assumption, equations, models, and algorithms required in order to estimate these states and parameters so that they can be utilized by the corresponding control systems implemented in EVs. The key states and parameters that will be discussed are vehicle velocity, vehicle slip angle, road–tire friction coefficient, road gradient, and vehicle mass.