This Thesis Research involves the analysis, simulation and design alternatives for an industrially-relevant voltage regulator. An initial prototype circuit, designed by Texas Instruments Inc., is simulated and analysed in detail. Then an alternative circuit is derived which improves the circuit performance by implementing different compensation techniques and some transistors modifications. The final circuit has excellent phase margin, transient response and load regulation.

Voltage sags are short duration of voltage reduction caused by system faults, overloads and starting of large motors. Voltage sags are the main causes of trips of various sensitive equipment. In order to understand the voltage-tolerance performance of some process control equipment, this thesis presents test results of some sensitive equipment (such as computers, AC contactors, high intensity discharge lamps and programmable logic controller) and provides their voltage tolerance curves. A number of magnitudes and durations recommended by IEC 61000- 4- 11 are used to perform the tests. With the performance information in hands, power quality requirements of different types of equipment and customer, and area of vulnerability for sensitive loads could be estimated.

Increasing power consumption and heat dissipation are becoming urgent challenges for processors today and in the future. Digital power control architectures in which processors closely interact with voltage regulators are becoming necessary to enhance system energy efficiency. Digital techniques offer advantages such as flexibility, fewer external components and reduced overall cost as compared to conventional analog techniques. The primary objective of this thesis is to develop new digital control architecture for processor voltage regulators with low complexity and high dynamic performance. A digital control technique to naturally implement the desired output impedance is proposed. In this technique, Adaptive Voltage Positioning (AVP) is implemented by generating a dynamic voltage reference and a dynamic current reference to achieve the desired output impedance. A dual-voltage-loop control with dynamic reference step adjustment, non-linear control and a dedicated transient detection circuit is proposed to improve the dynamic performance. The dynamic reference step adjustment method lowers the high speed requirement of reference update clock; the non-linear control minimizes the transient-assertion-to-action delay and maximizes the inductor current slew rate; and the transient detection circuit recognizes the load transient state in a manner adaptive to the amount and slew rate of load transient. Theoretical, simulation and experimental results prove the effective operation and excellent performance of the controller. Finally, the dynamic performance of the voltage regulator with the proposed digital controller under large-step load oscillations is proven by simulation and experimental results. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2008-07-31 13:14:52.149

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Recent events, such as the Northeast Blackout of 2003, have highlighted the need for accurate real-time stability assessment techniques to detect when an electric power system is on the brink of voltage collapse. While many techniques exist, most techniques are computationally demanding and cannot be used in an on-line application. A voltage stability index (VSI) can be designed to estimate the distance of the current operating point to the voltage marginally stable point during the system operation. In this research work, a new VSI was developed that not only can detect the system voltage marginally stable point but also is computationally efficient for on-line applications. Starting with deriving a method to predict three types of maximum transferable power of a single source power system, the new VSI is based on the three calculated load margins. In order to apply the VSI to large power systems, a method has been developed to simplify the large network behind a load bus into a single source and a single transmission line given the synchronized phasor measurements of the power system variables and network parameters. The simplified system model, to which the developed VSI can be applied, preserves the power flow and the voltage of the particular load bus. The proposed voltage stability assessment method, therefore, provides a VSI of each individual load bus and can identify the load bus that is the most vulnerable to voltage collapse. Finally, the new VSI was tested on three power systems. Results from these three test cases provided validation of the applicability and accuracy of the proposed VSI.

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