An integrated starter/alternator (ISA) has been proposed for the future 42 V PowerNet, which combines both starter and alternator functions into a single electrical machine with bidirectional power flow ability. This thesis presents analysis, design, modeling and experimental results of the direct torque controlled ISA system based on a low voltage induction machine. The classical direct torque controlled ISA based on switching-table is systematically for an ISA evaluated in this thesis. The simulation and experimental results show that the direct torque control (DTC) concept can be successfully extended to the ISA application. An improved DTC of the ISA based on direct stator flux vector is presented to reduce the drawbacks of high torque and flux ripples of the classical DTC. Robust design of the controller ensures the system is not sensitive to the variation of rotor resistance. By controlling the electromagnetic torque of the induction machine quickly, the required dc bus voltage can be well regulated within the 42 V PowerNet specifications. Another improved DTC of the ISA with direct torque and flux control is also studied. Compared to the direct flux vector control scheme, the calculation of the commanded voltage vector in this scheme only requires the derivative of the stator flux magnitude, which is a dc quantity. In addition, both torque and flux are regulated directly with two independent closed-loops. This scheme is relatively insensitive to the noise. The thesis proposed compensation methods to reduce the effects of switch voltage drops and dead-time on the estimation of the stator flux. Experimental results confirm that the estimation error is reduced with compensation for both motoring and generating modes of the ISA. A closed-loop type of sliding mode flux observer is proposed to reduce the estimation error of the stator flux. Both Simulation and experimental results confirm that the proposed sliding mode observer is insensitive to the stator resistance variation and sensor offsets. A loss minimized scheme with power factor control for the ISA is proposed in this thesis. It provides a simple solution for the efficiency improvement of the induction machine without requiring any speed or load information. The effectiveness of the direct torque controlled induction machine for an integrated starter/alternator system has thus been confirmed and well supported by the studies presented in this thesis.

<p>The VAWT project at Uppsala University has successfully managed to develop a vertical axis wind turbine (VAWT). The VAWT has many benefits compared to the Horizontal axis wind turbines (HAWT) which are the most common wind turbine design today. One of the many advantages with the VAWT is that it allows the generator to be located on the ground level. That reduces the required tower strength. The wind turbine is not self starting, i.e. the turbine needs a certain speed before the wind can force the turbine to revolve. The wind turbine is therefore in need of special start procedure. During the start, power electronics is used to operate the generator as a motor. Today Hall latches are located in the air gap of the generator which provides the signals that govern the power electronics. However, there is a demand to have a start that does not require Hall latches. Such controller would increase the reliability of the starter system. The design of the wind turbine could be even more simplified. Hence, the diploma work treats a programmed microcontroller to control the start-up without using any sensors at all. A hub motor was obtained for laboratory work, a driver and an inverter were constructed to drive the motor using a microcontroller. The finished start-up program has the ability to start the hub motor both sensorless and using Hall sensors. The microcontroller controls the motor by measuring the phase voltages of the motor. This information is used to decide which phases of the motor the electric current should go through. The current to the motor is limited using pulse width modulation strategy (PWM). Current limitation is necessary to protect the power electronics and limit the torque during the start. The result of start-ups using both Hall sensor and sensorless showed that the two start strategies are able to accelerate the rotor at the same rate. However, the start-ups using Hall sensors reached a higher top speed than the sensorless starts. However, the wind turbine is not in need of a higher speed than what the sensorless start was able to reach. Thus, the sensorless start is considered to be as good as the start using Hall sensors.</p>

Synchronous machines provide a practical way to control reactive power consumption of a plant. One of the main advantages of using synchronous motors in a plant is their ability to generate reactive power for plant loads. A new control scheme for synchronous motor excitation systems is developed to automate reactive power consumption. The system performs adaptive control based on the real time data and keeps the power factor within a specified range. The system can also be used to improve voltage drop during large induction motor starts. Power system behavior as a result of applying the adaptive control is studied under different operating scenarios using power system analysis software. Results and conclusions are based on mathematical simulation and experimental measurements of a prototype system. / Graduation date: 2003

The VAWT project at Uppsala University has successfully managed to develop a vertical axis wind turbine (VAWT). The VAWT has many benefits compared to the Horizontal axis wind turbines (HAWT) which are the most common wind turbine design today. One of the many advantages with the VAWT is that it allows the generator to be located on the ground level. That reduces the required tower strength. The wind turbine is not self starting, i.e. the turbine needs a certain speed before the wind can force the turbine to revolve. The wind turbine is therefore in need of special start procedure. During the start, power electronics is used to operate the generator as a motor. Today Hall latches are located in the air gap of the generator which provides the signals that govern the power electronics. However, there is a demand to have a start that does not require Hall latches. Such controller would increase the reliability of the starter system. The design of the wind turbine could be even more simplified. Hence, the diploma work treats a programmed microcontroller to control the start-up without using any sensors at all. A hub motor was obtained for laboratory work, a driver and an inverter were constructed to drive the motor using a microcontroller. The finished start-up program has the ability to start the hub motor both sensorless and using Hall sensors. The microcontroller controls the motor by measuring the phase voltages of the motor. This information is used to decide which phases of the motor the electric current should go through. The current to the motor is limited using pulse width modulation strategy (PWM). Current limitation is necessary to protect the power electronics and limit the torque during the start. The result of start-ups using both Hall sensor and sensorless showed that the two start strategies are able to accelerate the rotor at the same rate. However, the start-ups using Hall sensors reached a higher top speed than the sensorless starts. However, the wind turbine is not in need of a higher speed than what the sensorless start was able to reach. Thus, the sensorless start is considered to be as good as the start using Hall sensors.

The present work proposes a new computational algorithm for analyzing Morton Effect using a Successive Iterative Synchronous Response Algorithm (SISRA). Previous studies on the Morton Effect were based on Eigen or Nyquist analysis for stability studies and predicted only an onset speed of instability. The outcome of SISRA is the convergence of response to a steady state orbit in a finite number of iterations. A progressive increase in the response with increasing running speed indicates the former instability. SISRA predicts both the synchronous response for the speed range of concern plus the speed where the response becomes divergent. SISRA is implemented in a Timochenko-beam-based finite-element rotordynamics software suite. SISRA analyzes the Morton Effect as a synchronous response problem with excitations from: (1) mechanical imbalance, (2) induced thermal bent shaft moments, and (3) mechanical imbalance that is induced by thermal bow. A general elliptical orbit can be decomposed into the sum of forward and backward circular orbits. As input, SISRA requires that, at a specified speed, equilibrium position, and orbit: (1) the predicted maximum differential temperature, and (2) the angle between hot spot (position of maximum temperature) and position of minimum film thickness. Two examples from the published literature are considered. SISRA predicted higher vibration levels, even before the motion diverges due to Morton Effect. In some cases, the synchronous response of the system due to Morton Effect is orders of magnitude greater than the response due only to mechanical imbalance. The combined effects of: (1) mechanical imbalance with induced thermal bent shaft moments, and (2) mechanical imbalance with thermally induced mechanical imbalance are also studied. The impact of induced thermal bent shaft moments is found to be greater than the mechanical imbalance induced by thermal bow. A parametric investigation on the impact of the changes of (1) bearing length to diameter ratio, (2) reduced viscosity of the lubricant, (3) bearing radial clearance to radius ratio and (4) overhung mass magnitude is performed to consider their respective impacts on synchronous response. Based on the available input data and the cases considered, reducing viscosity and reducing the overhung mass are found to be the best remedies to alleviate problems arising from the Morton Effect.

No description available.

Thesis (M.S.)--Ohio University, November, 1981. / Title from PDF t.p.

Thesis (M.E.)--University of Adelaide, Dept. of Electrical Engineering, 1970.

Thesis (M.Eng.Sc.)--University of Western Australia, 2007.

Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 134-135).