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This dissertation is to investigate the power system service quality of a Mass Rapid Transit (MRT) system and derive the proper transformer planning to enhance the system operation efficiency. The transformer loading factor is improved by proper capacity planning by considering the power demand according to the growth of ridership. To mitigate the harmonic distortion, the installation location and capacity of harmonic filters are designed and verified by computer simulation. In this dissertation, the software programs for the AC/DC load flow study and harmonic analysis have been developed and integrated to simulate the MRT power system. To enhance the accuracy of computer simulation for the system operation with multiple trains on the main lines, the effect of voltage fluctuation to the traction effort of a train set is considered in the AC/DC load flow analysis. The mathematical model of 12-pulse uncontrolled rectifiers without interphase transformers has been derived and implemented in the programs to obtain more accurate simulation results. To achieve better cost effective capacity planning of main transformers, the unit commitment is applied to derive the optimal transformer capacity to meet the annual peak demand and provide reserve for service reliability. The power consumption of an MRT system is varied with the train operation modes and the route gradient, curvature of MRT networks. The motion equation of train sets has been applied to find the dynamic power consumption and travel distance for each time snapshot. The AC/DC load flow analysis is performed to find the annual power loading of traction substations and whole Taipei MRT network. The energy loss, investment cost of main transformers, and the system service reliability are used to define the equivalent cost of all feasible states for each dynamic programming stage. According to the computer simulation, significant cost saving has been obtained by the proposed methodology for transformer capacity planning of Taipei MRT network. Due to the dynamic load behavior of train sets, the stochastic harmonic distortion of an MRT system is simulated. The mathematical model of the 12-pulse uncontrolled rectifiers without interphase transformers is considered in the harmonic load flow analysis to solve the power demand and harmonic injection currents at traction substations for each time snapshot. According to the mean values and standard deviation of injection harmonic currents, the stochastic harmonic load flow analysis is executed to find the average value and the confidential interval of harmonic voltage distortion for all system buses. By this method, the system voltage harmonic distortion can be evaluated more accurately to provide better guidance for the strategy of harmonic mitigation. According to the results of the stochastic harmonic load flow, different strategies of harmonic distortion mitigation are investigated. Both the fixed type and switching type of passive filters are considered to be implemented. The cost function of filter investment and the harmonic distortion are used in the objective function by considering the regulation of harmonic distortion and system voltages as the constraints. By performing the nonlinear programming, the proper capacity of harmonic filters for each harmonic order and the corresponding switching time of unit commitment is determined. To further improve the power quality, the hybrid filter is also proposed for better distortion mitigation. The analysis of distortion mitigation by harmonic filters are performed to demonstrate the effectiveness of the hybrid filters to improve the power quality of MRT systems.

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The main goal of this thesis is to improve the efficiency of power consumption for single train and propose the effects of the voltage variation to AC/DC power flow. This thesis establishes a simplified mathematic model for motor drivers with the magnetic vector control laws. Furthermore, it designs the framework of the motor drives model with the power system blockset of the MATLAB/SIMULINK. The mass rapid transit(MRT) power system framework are also introduced in the thesis. Besides the power and propelment system model are developed. Due to the differences of the load pattern for the MRT system and the other customers, the analysis can be separated into static station load and dynamic load during the train operations. Static station load is constant and easy to measure. But dynamic load leads to some extent of variation depended on the MRT network characteristics and the headway of trains. The power consumption for dynamic load is about 60-70% of the whole MRT power consumption. The whole process of starting, acceleration, coasting and stopping are realistically concerned for the simulation of MRT operation. In this thesis, the DC system is composed of a 12 pulse rectifying transformer, a conductor rail, motor-driven induction drive control, VVVF inverter, and a 3-phase motor-driven induction electric power model. The performance for single train can be obtained very efficiently with the rate curves. To perform the MRT power system simulation, an AC/DC load flow analysis has been developed with Matlab. The power system model of an simulation for Taipei MRT system has been created, the AC/DC load flow analysis is executed to analyze the effects of traction substation, voltage fluctuation, and various load under the dynamic operation for multiple trains. The efficiency of proposed methodology to solve the optimal MRT operation is verified by comparing to the results of Train Performance Simulator (TPS), which has been used by Taipei MRT project. It is suggested that the proposed rigid modeling of propulsion driving system can enhance the accuracy of system simulation and provide the tool to achieve better planing of MRT operation.

With the rapid growth of load demand, the distribution system is becoming very complicated such that the operation efficiency and service quality are deteriorated during recent years. Engineers have to solve the problems by applying new technologies to enhance the efficiency of distribution system. In this thesis, an immune algorithm(IA) based on weighting selection as a decision maker is proposed to reach the desired switching operations such that transformer and feeder loading balance can be achieved. The IA antigen and antibody are equivalent to the objective and the feasible solution for a conventional optimization method. The concept of the information entropy is also introduced as a measure of diversity for the population to avoid falling into a local optimal solution. This algorithm prevents the possibility of stagnation in the iteration process and achieves the fast convergence for the global optimization. With the object-orient programming(OOP), this research project is to create the relationship of distribution element objects and encapsulation of data with all 22KV underground systems in Taichung district. The OOP does provide an effective tool for the management of distribution system database and the fault detection, isolation, and service restoration(FDIR) function of feeders and main transformers. According to the attributes of line switches, we can create the 22KV distribution system configuration with the topology processor. In order to calculate the current flows of line switches, this project will also execute the three phase load flow program with the customer information system(CIS), load survey, outage management information system(OMIS), and the data of all feeders and main transformers. In this thesis, the IA is used to solve the optimal switching problem by considering the customer load characteristics for the normal operation and the overload contingency of the distribution system. The efficiency of immune algorithm to solve the problem is verified by comparing to the computing time of the conventional binary integer programming for decision making of switching operation. A Taichung district distribution system is selected for computer simulation to demonstrate the effectiveness of the proposed methodology for solving the optimal switching operation of distribution system. The result of this thesis will be an important reference for distribution automation in Taiwan.

No / In this study, a new methodology to optimally allocate wind turbines (WTs) in distribution networks is proposed. A market-based optimal power flow is used to determine the optimal numbers and capacities of WTs in a way that maximises the social welfare. The method is conceived for distribution network operators to strategically allocate WTs in distribution networks. The proposed method by yielding location-specific WTs capacity settlement both in terms of cost reduction and consumers' benefits is consistent with distribution network topology and constraints. The method is solved by using step-controlled primal dual interior point method considering network constraints. The effectiveness of the proposed method is demonstrated with two radial distribution systems including an 84-bus 11.4 kV and a 69-bus 11 kV network.

<p>U disertaciji je predstavljen postupak GSSKN (generalizovani postupak sumiranja<br />struja i korekcija napona) integrisan u DMS. Integracija postupka GSSKN u DMS se<br />sastoji od sledećeg: 1) postupak GSSKN se naslanja na jedinstvenu bazu podataka DMS i<br />2) rezultati dobijeni proračunom tokova snaga korišćenjem postupka GSSKN koriste<br />se u velikom broju ostalih funkcija DMS. Standardni postupak BFS (čišćenje<br />unaprjed/unazad), koji je razvijen za proračun tokva snaga uravnoteženih<br />distributivnih mreža u simetričnim režimima, u ovoj disertaciji je generalizovan na<br />uravnotežene mreže u nesimetričnim režimima, neuravnotežene distributivne mreže<br />(u nesimetričnim režimima), sa obuhvaćenim miksovanim mrežama, a da su pri tome u<br />potpunosti zapaženi robustnost, efikasnost i brzina u odnosu na ostale postupke.<br />Odnosno, u ovoj disertaciji je predložen GSSKN za proračun bilo kako složenih<br />slaboupetljanih distributivnih mreža s distributivnim generatorima, koji ima sve<br />osobine i prednosti u odnosu na ostale postupke, kao što su ih imali standardni<br />postupci BFS za proračun tokova snaga uravnoteženih slaboupetljanih<br />distributivnih mreža sa distributivnim generatorima u simetričnim režimima.<br />Dakle, osnovni cilj ove disertacije glasi: pokazati da standardne postupke BFS ne<br />samo da ne treba napuštati prilikom proračuna tokova snaga neuravnoteženih<br />slaboupetljanih aktivnih mreža (uključene miksovane), već da je to napuštanje<br />kontraproduktivno, bar sa aspekta postupaka koji su do sada objavljeni u literaturi.</p> / <p>The dissertation presents GBFS (General Backward/Forward Sweeping) procedure<br />which is integrated in DMS. The integration of the GBFS procedure in DMS<br />consists of the following: 1) the GBFS procedure is based on the unique DMS<br />database and 2) the results obtained from load flow calculation by application of<br />GBFS procedure are used in many other DMS applications. The standard BFS<br />procedure (Backward/Forward Sweeping), developed for the load flow calculation<br />of balanced distribution networks in symmetrical states, in this dissertation is<br />generalized to balanced networks in asymmetrical states, unbalanced distribution<br />networks (in asymmetrical states), including mixed networks. In addition, the<br />robustness, efficiency and speed comparing to other procedures, have been saved.<br />In other words, this dissertation proposes the GBFS procedure for calculation of<br />any composite weakly meshed distribution networks with distribution generators. It<br />has all the properties and advantages as compared to other procedures, like<br />standard BFS procedures applied for load flow calculation of balanced weakly<br />meshed distribution networks with distribution generators in symmetrical states.<br />Therefore, the basic objective of this dissertation is as follows: to show that the<br />standard BFS procedures should not be abandoned when performing the load flow<br />calculation of unbalanced weakly meshed active networks (mixed included), and<br />that, on the contrary, abandoning them would be counterproductive, at least from<br />the aspect of procedures published so far.</p>

Installation of reactive compensators is widely used for improving power system voltage stability. Reactive compensation also improves the system loading margin resulting in more stable and reliable operation. The improvements in system performance are highly dependent on the location where the reactive compensation is placed in the system. This paper compares three load flow analysis methods - PV curve analysis, QV sensitivity analysis, and Continuation Load Flow - in identifying system weak buses for placing reactive compensation. The methods are applied to three IEEE test systems, including modified IEEE 14-bus system, IEEE 30-bus system, and IEEE 57-bus system. Locations of reactive compensation and corresponding improvements in loading margin and voltages in each test system obtained by the three methods are compared. The author also analyzes the test systems to locate the optimal placement of reactive compensation that yields the maximum loading margin. The results when compared with brute force placement of reactive compensation show the relationship between effectiveness of the three methods and topology of the test systems.

The number of integrated wind farms into the power system is increasing as well as the total installed wind power capacity, which may cause voltage stability concerns. Additionally, there are European Transmission System Operators (TSOs) that do notinvolve wind farms in contributing to the voltage control in any significant extent. In the on-going project by the European Network of Transmission System Operators for Electricity (ENTSO-E), to update the European grid requirements, this will probably be changed. The aim of this Master thesis is to demonstrate the voltage variations in the high voltage grid during different operational conditions. Thereafter, clarify when high voltages may occur at the connection point of the studied wind farm. Furthermore, it is investigated whether the wind farm is able to regulate the voltage in the cases when high voltages occur. The load flow and switching studies are performed with the software tool Power System Simulator for Engineering (PSS/E) version 32.1.1. The grid model represents a part of the Swedish high voltage grid. Since voltage stability often is a local issue, special modelling aspects has been performed at the hydropower generators in the close-located area of the wind farm. The main conclusions of this Master thesis are that high voltages is associated with low load situations, i.e., mostly during summer nights. Furthermore, the studied close-located reactor is not able to keep the voltage within desired level by itself. Finally, it has been shown that the wind farm is technically able to contribute to the voltage stability in the close-located area. But since wind power is an intermittent power source it makes the voltage regulating capacity less reliable compared to hydropower. The results and conclusions given in this Master thesis have also been summarized in a conference paper for The 11th International Workshop on Large-Scale Integration of Wind Power into Power Systems as well as on Transmission Networks for Offshore Wind Power Plants, see Lidström et al [35].