Colin Coates

Performance evaluation of a nine-phase synchronous reluctance drive

This paper describes the performance of an experimental 5 kW nine-phase synchronous reluctance motor (Syncrel) drive. Increasing the number of phases of the Syncrel above three allows the stator MMFs to be shaped, producing significantly greater torque/RMS ampere in the same volume machine. Generalized d-q voltage and torque equations are derived for the nine-phase Syncrel. These demonstrate that harmonic direct and quadrature components of current contribute to torque production in the machine and can be controlled by applying appropriate stator voltages. A field-oriented controller is described and implemented using a TMS320C32 digital signal processor board. The controller designates portions of the stator winding as supplying either direct or quadrature excitation. A simple inverter switching strategy is used to control the phase currents to their reference values. Experimental current regulation, speed response and torque measurements are presented from the drive. These results validate the system model and demonstrate the drive capability.

Opportunities and challenges in the application of advanced control to power electronics and drives

Control technology underpins the operation of many, and arguably all, modern high technology systems. Such systems include transportation (aircraft, high speed trains, marine vessels, automobiles), telecommunication systems, electricity networks, mining, minerals processing and agriculture. A particular area where control is playing an increasingly important role is industrial electronics. In this paper we will adopt a control engineering perspective to reflect on the opportunities and challenges that exist in the application of advanced control to these systems.

An introduction to the control of switching electronic systems

Control technology underpins the operation of many, and arguably all, modern high technology systems. Such systems include transportation (aircraft, high speed trains, marine vessels, automobiles), telecommunication systems, electricity networks, mining, minerals processing and agriculture. A particular area where control is playing an increasingly important role is industrial electronics. In this paper we will give a tutorial introduction to the application of control engineering concepts to such systems and reflect on the opportunities and challenges that exist in this area.

Low cost wind turbine controller

A significant market exists for small (<20 kW) wind turbines in both remote communities and also in grid connected applications as individuals seek to reduce their CO2 emissions. A low cost wind turbine controller is presented based around a standard electric drive circuit. This allows significant cost savings over current commercially available devices. Functions of maximum power tracking, dynamic braking of the turbine and output voltage regulation are achieved in the controller. The implementation of a 5 kW prototype is presented.

Behaviour of microgrids in the presence of unbalanced loads

In a low voltage distribution network there is the increased likelihood of significant load imbalance between phases. This is undesirable as the resulting voltage imbalance can cause damage to equipment such as motors. This paper presents simulations of the behaviour of a microgrid employing droop type controllers in combination with unbalanced loads, showing that significantly unbalanced voltages can occur in the system. The paper details a controller which addresses this problem by controlling the negative sequence components associated with load imbalance. This concept is then integrated into a droop controller and is shown to significantly reduce voltage imbalance across the load.

Ironless axial flux permanent magnet motor control with multilevel cascaded H-bridge converter for electric vehicle applications

The Ironless Axial Flux Permanent Magnet (IAFPM) machine, also referred to as air-cored or coreless machine is a variant of the AFPM machine with the iron removed from the stator. This allows the efficiency and power density of the machine to be further improved [1]-[4]. However, IAFPM motors generally have very low inductance (< 50μH) due to their ironless nature [5], which increases the design complexity of the drive system as the motor currents becomes difficult to control. If neglected, the large current ripple will produce significant torque ripple. The Multilevel Cascaded H-bridge (MLCHB) converter topology could potentially address this issue. This paper first provides an analysis of the IAFPM motor characteristics and control method, then it provides a review of topologies currently used to control IAFPM motors. Lastly the application of a MLCHB converter for the control of low inductance motors is introduced. Simulation results of an IAFPM motor with 5μH line inductance driven by a MLCHB converter are presented with comparisons made to existing strategies.

Modelling of Single Phase Induction Machines

Abstract This paper considers a novel model of a single phase, capacitor start induction motor that is based on the use of an ideal rotating transformer (IRTF). The model is an extension of the IRTF based model already used for modelling three phase and DC machines. The paper outlines the new model and discusses an application of the model. A TRIAC is connected in series with the machine as to allow control of the motor speed. Experimental and simulation results of the new model confirm the validity of the work carried out.

Performance of a nine-phase synchronous reluctance drive

This paper describes the performance of an experimental 5 kW nine-phase synchronous reluctance motor (Syncrel) drive. Increasing the number or phases or the Syncrel above three allows the stator MMFs to be shaped, producing significantly greater torque/RMS ampere in the same volume machine. Generalized dq voltage and torque equations are derived for the nine-phase Syncrel. These demonstrate that harmonic direct and quadrature components of current contribute to torque production in the machine and can be controlled by applying appropriate stator voltages. A field-oriented controller is described and implemented using a TMS320C32 digital signal processor board. The controller designates portions of the stator winding as supplying either direct or quadrature excitation. A simple inverter switching strategy is used to control the phase currents to their reference values. An alternative control strategy based on the transformed d-q harmonic components of stator current and voltage is also presented. Experimental and simulation results are provided for both controllers.

Renewable energy source emulator

Small scale solar and wind turbines are finding increased application in stand-alone, grid-connected and micro grid scenarios. New controllers for these devices are continually being developed. This paper documents the design and development of a low cost circuit to emulate the electrical characteristics of both photovoltaic arrays and wind turbines. The emulator circuit is intended as a tool to aid in the development of new wind turbine and photovoltaic controllers. The emulator consists of a DC / DC converter controlled by a microprocessor. A separate Maximum Power Point Tracking (MPPT) module is also described.

A High Performance Drive For the Rotary Coal Breaker Application

This paper considers recent advances made within the field of electric drives and how this new technology might be best applied within the mining industry. A case study is presented showing simulated results of the performance of the electric drives in a coal preparation plant. The various starting methodologies (resistance starting, fluid coupling, V/f=const and vector control) are compared within this application. The merits of each method are then discussed with regard to the specific application and other more generic applications within the mining industry. Application of a rotor flux orientation control drive is substantiated, its superior performance under start and stall conditions to that of the currently implemented system is confirmed by theoretical analysis and simulations. Experimental results for a scale model of the candidate system are presented that agree with the main conclusions of the paper.