The synchronous machine is one of the critical components of electric power systems. Modeling of synchronous machines is essential for power systems analyses. Electric machines are often interfaced with power electronic components. This work presents an advanced synchronous machine modeling, which emphasis on the modeling and simulation of systems that contain a mixture of synchronous machines and power electronic components. Such systems can be found in electric drive systems, dc power systems, renewable energy, and conventional synchronous machine excitation. Numerous models and formulations have been used to study synchronous machines in different applications. Herein, a unified derivation of the various model formulations, which support direct interface to external circuitry in a variety of scenarios, is presented. Selection of the formulation with the most suitable interface for the simulation scenario has better accuracy, fewer time steps, and less run time. Brushless excitation systems are widely used for synchronous machines. As a critical part of the system, rotating rectifiers have a significant impact on the system behavior. This work presents a numerical average-value model (AVM) for rotating rectifiers in brushless excitation systems, where the essential numerical functions are extracted from the detailed simulations and vary depending on the loading conditions. The proposed AVM can provide accurate simulations in both transient and steady states with fewer time steps and less run time compared with detailed models of such systems and that the proposed AVM can be combined with AVM models of other rectifiers in the system to reduce the overall computational cost. Furthermore, this work proposes an alternative formulation of numerical AVMs of machine-rectifier systems, which makes direct use of the natural dynamic impedance of the rectifier without introducing low-frequency approximations or algebraic loops. By using this formulation, a direct interface of the AVM is achieved with inductive circuitry on both the ac and dc sides allowing traditional voltage-in, current-out formulations of the circuitry on these sides to be used with the proposed formulation directly. This numerical AVM formulation is validated against an experimentally validated detailed model and compared with previous AVM formulations. It is demonstrated that the proposed AVM formulation accurately predicts the system's low-frequency behavior during both steady and transient states, including in cases where previous AVM formulations cannot predict accurate results. Both run times and numbers of time steps needed by the proposed AVM formulation are comparable to those of existing AVM formulations and significantly decreased compared with the detailed model.

In this dissertation, several volt-var optimization methods have been proposed to improve the expected performance of the distribution system using distributed renewable energy sources and conventional volt-var control equipment: photovoltaic inverter reactive power control for chance-constrained distribution system performance optimisation, integrated distribution system optimization using a chance-constrained formulation, integrated control of distribution system equipment and distributed generation inverters, and coordination of PV inverters and voltage regulators considering generation correlation and voltage quality constraints for loss minimization. Distributed generation sources (DGs) have important benefits, including the use of renewable resources, increased customer participation, and decreased losses. However, as the penetration level of DGs increases, the technical challenges of integrating these resources into the power system increase as well. One such challenge is the rapid variation of voltages along distribution feeders in response to DG output fluctuations, and the traditional volt-var control equipment and inverter-based DG can be used to address this challenge. These methods aim to achieve an optimal expected performance with respect to the figure of merit of interest to the distribution system operator while maintaining appropriate system voltage magnitudes and considering the uncertainty of DG power injections. The first method is used to optimize only the reactive power output of DGs to improve system performance (e.g., operating profit) and compensate for variations in active power injection while maintaining appropriate system voltage magnitudes and considering the uncertainty of DG power injections over the interval of interest. The second method proposes an integrated volt-var control based on a control action ahead of time to find the optimal voltage regulation tap settings and inverter reactive control parameters to improve the expected system performance (e.g., operating profit) while keeping the voltages across the system within specified ranges and considering the uncertainty of DG power injections over the interval of interest. In the third method, an integrated control strategy is formulated for the coordinated control of both distribution system equipment and inverter-based DG. This control strategy combines the use of inverter reactive power capability with the operation of voltage regulators to improve the expected value of the desired figure of merit (e.g., system losses) while maintaining appropriate system voltage magnitudes. The fourth method proposes a coordinated control strategy of voltage and reactive power control equipment to improve the expected system performance (e.g., system losses and voltage profiles) while considering the spatial correlation among the DGs and keeping voltage magnitudes within permissible limits, by formulating chance constraints on the voltage magnitude and considering the uncertainty of PV power injections over the interval of interest. The proposed methods require infrequent communication with the distribution system operator and base their decisions on short-term forecasts (i.e., the first and second methods) and long-term forecasts (i.e., the third and fourth methods). The proposed methods achieve the best set of control actions for all voltage and reactive power control equipment to improve the expected value of the figure of merit proposed in this dissertation without violating any of the operating constraints. The proposed methods are validated using the IEEE 123-node radial distribution test feeder.

Power system faults normally result in system damage, profit loss and consumer dissatisfaction. Consequently, there is a strong demand on precise and fast fault location estimation for power system to minimize the system restoration time. This paper examines a method to locate short-circuit faults on a distribution system with unbalanced loads without fault type information. Bus impedance matrix technique was harnessed in the fault location estimation algorithm. The system data including line impedances, source impedance and distribution system layout was assumed to be known factors, hence pre-fault bus impedance can be calculated and implemented into the algorithm. Corresponding methods to derive system matrix information were discussed. Case studies were performed to evaluate the accuracy of the fault location algorithm and illustrate the robust performance under measurements errors influences, load variation impacts and load compensation implementations. Traditional fault location methods involve current and voltage measurements mandatorily locating at each ends of faulted section to locate the fault. The method examined finds fault location for distribution system utilizing impedance matrix accompanied with sparse measurements in the power network. This method fully considers the unbalance of distribution system.

Renewable energy is one of the most reliable resource that can be used to generate the electricity. It is expected to be the most highly used resource for electricity generation in many countries in the world in the next few decades. Renewable energy resources can be used in several purposes. It can be used for electricity generation, water desalination and mining. Using renewable resources to desalinate the water has several advantages such as reduce the emission, save money and improve the public health. The research described in the thesis focuses on the analysis of using the renewable resources such as solar and wind turbines for desalination plant. The output power from wind turbine is connected through converter and the excess power will be transfer back to the main grid. The photo-voltaic system (PV) is divided into several sections, each section has its own DC-DC converter for maximum power point tracking and a two-level grid connected inverter with different control strategies. The functions of the battery are explored by connecting it to the system in order to prevent possible voltage fluctuations and as a bu er storage in order to eliminate the power mismatch between PV array generation and load demand. Computer models of the system are developed and implemented using the PSCADTM / EMTDCTM software.

The work presented in this thesis is a frequency adaptive tracking filter that can be used in exact tracking of power frequencies and rejection of unwanted harmonics introduced during power disturbances. The power synchronization process includes power converters and other equipment that have many non-linear components that introduce unwanted harmonics. This new design is motivated by the requirement of a filter that can filter all the harmonics and exactly track a rapidly varying fundamental frequency with little time delay and phase error. This thesis analyzes the proposed filter mathematically based on Lyapunov theory and simulations are presented to show the performance of the design in rapid frequency variations.

As renewable energy plays an increasingly important role in the power system, the addition of PV systems to the distribution network has become a major trend in the current power system development. However, if a PV system with excessive capacity is added to the distribution network, voltage problems may occur in the system. Hence, it is important to determine the capacity of the PV system that can be added at the distribution system. The thesis aims to identify the major factors that affect the PV hosting capacity of distribution systems. The thesis studies various scenarios for the IEEE-123 test network PV system and evaluates the PV hosting capacity of the distribution system based on simulation tools including Matlab and Opendss software.

Current differential protection principle is superior in terms of sensitivity and speed of operation in comparison with other protection principle used in power systems. From the last five decades, various current differential protection schemes are widely used to protect busbars, transformers, and short-transmission lines. The deployment of high capacity microwave and optical fiber technologies redefined the line protection systems by facilitating the use of current differential protection schemes for long transmission lines. The common application issue of these schemes is mis-operation due to current transformer (CT) saturation during close-in external faults. Moreover, transformer differential protection schemes face mis-trip due to inrush current during energization. The techniques presented in the literature to address those issues, de-sensitize protection function and increase the time of operation. A comprehensive fault discrimination algorithm and an inrush current detection algorithm are highly demanded for current differential protection schemes. The purpose of this dissertation is to optimize the performance of differential schemes applied to protect busbar, transformer and line. This research derives the mathematical model of saturated secondary current of CT and introduces the concept of Partial Operating Current (POC). Based on these mathematical developments, the characteristics of POC are identified for all three types of differential zones like busbar, transformer and line protection. A new inrush current blocking algorithm is developed for transformer differential protection. A new time-domain CT saturation detection algorithm is also proposed. Based on these new developments, three separate differential schemes are designed for busbar, transformer, and line protection, respectively. The proposed schemes provide complete immunity against the mis-operations due to CT saturation during close-in external faults and transformer inrush current without sacrificing the sensitivity for internal faults. The speed of operation is also improved. The model for each scheme is built in Matlab platform and the performance is validated using the test system simulated in Electro-Magnetic Transient Program (EMTP) for all possible fault scenarios. Documented results show the improved performance of the proposed schemes when compared to traditional differential schemes in terms of reliability, sensitivity, selectivity, and speed

Various directional comparison bus protection methods including widely used superimposed directional element method need to have both voltages and currents from all feeders connected to the zone of protection to find the direction of current for detecting a bus fault or a line fault. The purpose of the thesis is to present a new technique for directional comparison bus protection to discriminate a bus fault from line fault and normal condition. The new technique, which is implementing superimposed directional element method to modify partial operating current characteristics (POC) method to superimposed POC (SPOC) method, does not use voltages from feeders, hence capacitor voltage transformers (CVTs) are no longer needed in the zone of protection. The proposed technique was implemented in 4-bus and IEEE 14-bus test system and was tested using different fault cases including CT saturation and high impedance fault. The proposed technique, SPOC method was compared with POC method with both methods implemented in same test systems and tested with same fault cases. The results show that the proposed technique is successful to detect bus faults with high accuracy and high speed.

Fault location reveals the exact information needed for utility crews to timely and promptly perform maintenance and system restoration. Therefore, accurate fault location is a key function in reducing outage time and enhancing power system reliability. Modern power systems are witnessing a trend of integrating more distributed generations (DG) into the grid. DG power outputs may be intermittent and can no longer be treated as constants in fault location method development. DG modeling is also difficult for fault location purpose. Moreover, most existing fault location methods are not applicable to simultaneous faults. To solve the challenges, this dissertation proposes three impedance-based fault location algorithms to pinpoint simultaneous faults for power transmission systems and distribution systems with high penetration of DGs. The proposed fault location algorithms utilize the voltage and/or current phasors that are captured by phasor measurement units. Bus impedance matrix technique is harnessed to establish the relationship between the measurements and unknown simultaneous fault locations. The distinct features of the proposed algorithms are that no fault types and fault resistances are needed to determine the fault locations. In particular, Type I and Type III algorithms do not need the information of source impedances and prefault measurements to locate the faults. Moreover, the effects of shunt capacitance are fully considered to improve fault location accuracy. The proposed algorithms for distribution systems are validated by evaluation studies using Matlab and Simulink SimPowerSystems on a 21 bus distribution system and the modified IEEE 34 node test system. Type II fault location algorithm for transmission systems is applicable to untransposed lines and is validated by simulation studies using EMTP on a 27 bus transmission system. Fault area identification method is proposed to reduce the number of line segments to be examined for fault location. In addition, an optimal fault location method that can identify possible bad measurement is proposed for enhanced fault location estimate. Evaluation studies show that the optimal fault location method is accurate and effective. The proposed algorithms can be integrated into the existing energy management system for enhanced fault management capability for power systems.

The general trends in the past decade of increasing solar cell efficiency, decreasing PV system costs, increasing government incentive programs, and several other factors have all combined synergistically to reduce the barriers of entry for PV systems to enter the market and expand their contribution to the global energy portfolio. The shortcomings of current inverter functions which link PV systems to the utility network are becoming transparent as PV penetration levels continue to increase. The solution this thesis proposes is an approach to control the inverters real and reactive power output to help eliminate the problems associated with PV systems at their origin and in addition provide the grid with ancillary support services. The design, modeling, and analysis of a grid-tied PV system was performed in the PSCAD software simulation environment. Results indicate that in the presence of grid disturbances the smart inverter can react dynamically to help restore the power system back to its normal state. A harmonic analysis was also performed indicating the inverter under study met the applicable power quality standards for distributed energy resources.