The correct operation of adjustable speed drives, which form part of a larger system, is often essential to the operation of the system as a whole. In certain applications the failure of such a drive could result in a threat to human safety and these applications are termed 'safety critical'. The chance of a component failure resulting in non-operation of the drive can be dramatically reduced by adopting a fault tolerant design. A fault tolerant drive must continue to operate throughout the occurrence of any single point failure without undue disturbance to the power output. Thereafter the drive must be capable of producing rated output indefinitely in the presence of the fault. The work presented in this thesis shows that fault tolerance can be achieved without severe penalties in terms of cost or power to mass ratio. The design of a novel permanent magnet drive is presented and a 'proof of concept' demonstrator has been built, based on a 20 kW, 13000 RPM aircraft fuel pump specffication. A novel current controller with near optimal transient performance is developed to enable precise shaping of the phase currents at high shaft speeds. The best operating regime for the machine is investigated to optimise the power to mass ratio of the drive. A list of the most likely electrical faults is considered. Some faults result in large fault currents and require rapid detection to prevent fault propagation. Several novel fault sensors are discussed. Fault detection and identification schemes are developed, including new schemes for rapid detection of turn to turn faults and power device short circuit faults. Post fault control schemes are described which enable the drive to continue to operate indefinitely in the presence of each fault. Finally, results show the initially healthy drive operating up to, through and beyond the introduction of each of the most serious faults.

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The research presented in this dissertation primarily focuses on providing analytical frequency-domain equations that use the system and controller parameters to accurately characterize the power conversion harmonics resulting from the deployment of hysteresis current-controlled inverters within the ac network. In addition, the ac and dc harmonic interactions under both ideal system conditions (constant dc excitation and pure sinusoidal ac voltages) and non-ideal system conditions (harmonic terms are added to the dc and ac sources) are derived for the fixed- and variable-band hysteresis current control. The spectral characteristics, such as frequency orders, spectral magnitude and bandwidth, are given in terms of line and control parameters, a development not only useful in analyzing the harmonic output sensitivity to line and controller parameter variations, but also in filter and system design. Various simulation studies compared results obtained from the developed models to those obtained from the Fourier analysis of MATLAB/Simulink output with very good agreement. The developed models proved their reliability and improved numerical efficiency in harmonic studies compared to those performed using time-domain simulations.

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This thesis presents the design of various closed-loop real-time control of a novel linear magnetostrictive actuator. The novel linear magnetostrictive actuator which uses Terfenol-D as the magnetostrictive material was developed by Sadighi. It solves the problem of power consumption in a conventional magnetostrictive actuator. However, the control system of this magnetostrictive actuator cannot control the current in the coils, which limits the performances of the real-time position control. In the closed-loop real-time control system proposed in this thesis, the controller is designed depending on the change of current. The closed-loop real-time control design focused on the position control of the active element in the novel linear magnetostrictive actuator. The closed-loop position-control system of the linear magnetostrictive actuator was successfully designed by implementing a closed-loop current-control system as an inner loop of the entire control system. This design offers the flexibility to design various position controllers in the closed-loop position-control system. The closed-loop current-control design uses pulse-width modulation (PWM) signal to change the current in the coils of the novel linear magnetostrictive actuator. By changing the duty ratio of the PWM signal, the current in the coils can be changed from zero to its maximum value. With a current controller using an integrator with a gain of 10, the current can be controlled with high response time and an error of /- 0.01 A. The position-controller design was successfully conducted by using four different approaches. First, a proportional-integral-derivative (PID) controller which was designed by relay-auto tuning method with experiments exhibited a position error of ±1 μm with a 5 μm peak-to-peak position noise. Second, a PID controller which was designed by root-locus can control the position with a position error of /- 3-4 μm with a 5 μm peak-to-peak position noise. Third, a linear variable velocity controller exhibited a position error of /-5 μm with a 5 mu m peak-to-peak position noise. Then, the sliding mode control (SMC) exhibited a position error of /-5 μm with a 5 μm peak-to-peak position noise.

Nowadays personal small electronic devices like cellphones are more and more popular, but the various batteries in need of charging become a problem. This thesis aims to explain a Lithium-ion charger which can control the current and voltage so that it can charge most kinds of popular batteries. More specifically, Li-ion battery charging is presented. The charging circuit design, simulation and the measurements will also be included.

High performance current control is critical to the success of the switched reluctance motor (SRM). Yet high motor phase nonlinearities in the SRM place extra burden on the current controller, rendering it the weakest link in SRM control. In contrast to linear motor control techniques that respond to current error, the deadbeat controller calculates the control voltage by the current command, phase current, rotor position and applied phase voltage. The deadbeat controller has demonstrated superior response in three-phase inverter current control, PM motor current control, and other relatively linear control applications. This study will investigate the viability and performance of a deadbeat controller for the highly nonlinear SRM. The need for an accurate deadbeat control model first motivates the investigation of experimental inductance measurement techniques. A deadbeat control law is then proposed through multiple revisions to demonstrate the benefit of the numerical method chosen to derive the controller and a current predictor that accounts for processor latency and PWM delay. The practical problems of loop delay, feedback noise, feedback filtering, and deadbeat controller parameter sensitivity are investigated by linear analysis, simulation, experimental implementation and nonlinear model analysis. Simulation and implementation verify deadbeat performance and various measures of transient performance are presented. To address the problem of SRM model error the study ends with a brief discussion of adaptive deadbeat control modifications for possible future research. / Master of Science

This research investigates the modeling and simulation, using the state transition approach to nonlinear system simulation, of a DC drive system. The drive system that was modeled is a closed loop system composed of a velocity loop with an inner current loop. The power stage is composed of a pulse generator module and a scr bridge, while the motor is a permanent magnet DC motor. A detailed development of each module model is included to reveal the open loop characteristics of the system. A total system state model was developed from each of the modules and closed loop simulations were run. The results show that the system may be modeled and simulated using this technique. However, the exactness of the simulation is heavily dependent on the DC motor parameters selected for the model. / Master of Science