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.

Voltage stability studies (VSS) of the electric network is a crucial factor to make the system operate in stable region and to prevent power blackouts. There are several commercial tools available for VSS of electric transmission systems (TS) but not many for distribution systems (DS). With increasing penetration of distributed renewable generations and meshed network within DS, shipboard power system (SPS) and microgrid, these VSS tools need to be extended for DS. Due to inherent characteristic like high R/X ratio, three phase and unbalanced operation, DS or SPS requires different mathematical approach than TS. Unbalanced three phase power flow and continuation power flow tools were developed using current injection and corrector predictor methods in this work for VSS. Maximum loading point for given DS or SPS can be computed using developed tools to guide required preventive and corrective actions. Developed tool was tested and validated for several different test cases.

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.

abstract: The combined heat and power (CHP)-based distributed generation (DG) or dis-tributed energy resources (DERs) are mature options available in the present energy mar-ket, considered to be an effective solution to promote energy efficiency. In the urban en-vironment, the electricity, water and natural gas distribution networks are becoming in-creasingly interconnected with the growing penetration of the CHP-based DG. Subse-quently, this emerging interdependence leads to new topics meriting serious consideration: how much of the CHP-based DG can be accommodated and where to locate these DERs, and given preexisting constraints, how to quantify the mutual impacts on operation performances between these urban energy distribution networks and the CHP-based DG. The early research work was conducted to investigate the feasibility and design methods for one residential microgrid system based on existing electricity, water and gas infrastructures of a residential community, mainly focusing on the economic planning. However, this proposed design method cannot determine the optimal DG sizing and sit-ing for a larger test bed with the given information of energy infrastructures. In this con-text, a more systematic as well as generalized approach should be developed to solve these problems. In the later study, the model architecture that integrates urban electricity, water and gas distribution networks, and the CHP-based DG system was developed. The pro-posed approach addressed the challenge of identifying the optimal sizing and siting of the CHP-based DG on these urban energy networks and the mutual impacts on operation per-formances were also quantified. For this study, the overall objective is to maximize the electrical output and recovered thermal output of the CHP-based DG units. The electrici-ty, gas, and water system models were developed individually and coupled by the devel-oped CHP-based DG system model. The resultant integrated system model is used to constrain the DG's electrical output and recovered thermal output, which are affected by multiple factors and thus analyzed in different case studies. The results indicate that the designed typical gas system is capable of supplying sufficient natural gas for the DG normal operation, while the present water system cannot support the complete recovery of the exhaust heat from the DG units. / Dissertation/Thesis / Ph.D. Electrical Engineering 2013

No description available.

No description available.

Based on the load survey study, a stratified sampling method is proposed to select the proper size of customers so that the load patterns derived can represent the load behavior of whole customer population. In this study there are 1315 customers out of Taipower customers over various service classes are selected for the installation of intelligent meters in the field to measure the power consumption within every 15 minutes. The bad data detection is performed to identify the abnormal power consumption by executing the Chi-square test. The standardized daily load pattern of each customer class has been derived with the mean per-unit method of customer load. The billing data are retrieved from the customer information system and applied to derive the customer daily load pattern by considering the customer load patterns. According to the total power consumption by all customers within the same class and considering the corresponding daily load pattern, the daily load profile of the customer class is then determined. By aggregating the load profiles of all customer classes, the daily load composition and load model of each service district can therefore be solved. By the same manner, the daily load pattern of whole Taipower system can be derived and it can be used to support the proper design of tariff structure according to the respective contribution of system power demand by each customer class. To investigate the overloading of distribution main transformers during the summer season, the correlations analysis of customer power consumption and temperature is performed. The effect of temperature change to the power consumption of each customer class is solved by multiple regression analysis with 95% confidential level. Based on the temperature sensitivity and the corresponding load composition, the load change due to temperature rise for various customer classes can be estimated. To demonstrate the impact of temperature change to distribution system operation, considering the temperature sensitivity of power consumption and load composition solves the power demand at each load bus. By updating the bus load demand due to temperature change, the feeder loading and power loss is therefore derived. To resolve the over loading problem of distribution feeders and main transformers during the summer season, a temperature adaptive switching operation has been proposed to perform the proper load transfer among the feeders/main transformers. In this dissertation, the effect of temperature change to the time varying characteristics of load buses and power transmission in Taipower is investigated. The dc circuit model of Taipower system and the temperature effect of customer power consumption are considered in the stochastic load flow analysis. With the temperature rise, the power demand of northern buses is increased dramatically and more power has to be transmitted from the southern region. The large voltage angle difference is significantly various between system buses during the summer peak period. It is suggested that the safety margin assessment of system operation has to be executed by considering the temperature effect to the bus loading of power systems.

The aim of this study is to analyse the voltage regulation of a power grid when wind power parks are connected to an existing power grid. Secondary the project have studied the placement of these wind power parks and costs related to connecting them to the grid. The goal was to achieve this grid with a smaller than 5% voltage margin and preferably a low phase deviation. The power grid is located in the area around Lule älven. Several issues with constructing and connecting windpower parks to an electrical grid have been studied by numerical analysis of a fictive grid but with real world variables. A balanced and stable grid is achieved with wind and hydro power and is able to successfully operate without non-renewable energy sources.The data was simulated in Matlab to analyse the power grid and the modification of it when connecting the wind power parks. The method used is power flow analysis through Matlab. All required unknown voltages and phase angles are determined and whether they are within given specifications. This entails that a stable electrical grid can be constructed

The increasing number of electric vehicles (EVs) in the transport sector has rendered the conventional fuel-based vehicles obsolete along with the fuel filling stations. With the growth in EVs, there has been an increase in the public charging infrastructure with fast charging equipment being used to charge the EVs in least possible time and also address the issue of ‘range anxiety’ among the EV owners. Many countries like South Korea and Germany has seen policies being implemented to install fast chargers for EVs in existing fuel filling stations. This study aims conduct a techno-economic feasibility to analyse the potential of implementing Electric Vehicle Supply Equipment (EVSE) with fast charging capacity into existing fuel filling stations. The potential of using solar photovoltaic system (PV) and battery storage systems (BESS) to reduce the load from the grid is also explored. Scenarios are developed considering different configurations of the EVSE, PV and BESS and an in-depth economic analysis is conducted to analyse the economic feasibility of the configurations. The impact on the electricity grid is also analysed in this thesis by conducting a load flow analysis on the CIGRE Low voltage network for Europe using Python.The proposed design enables selection of techno-economically feasible configurations of EVSE, BESS and PV. The results of the design are explained with the UK as a case study. It is observed that the configurations with 3 EVSE, BESS and 8 hours and the configuration with 3 EVSE, 1 BESS and 1 PV system for 8 hours of operation are economically viable. The proposed design shows that though the connection cost is the dominant factor affecting the feasibility, use of BESS with or without PV can reduce the connection cost by almost 90% depending on the number of BESS. Load flow analysis is conducted for the different configurations of EVSE, BESS and PV on the CIGRE LV network on Pandapower in Python. The results indicate that the existing network needs to be reinforced to facilitate the connection of EV fast chargers into the grid. Upgrading the network cables and increasing the slack voltage to a value of 1.05 or 1.1 Volts per unit, are the two strategies that have been suggested in this study to prevent any undervoltage that may occur as a result of connecting the EVSE to the electricity grid. The simulations conducted for the two strategies highlight that by implementing these strategies into the electricity grid network, the undervoltage issues in the transmission network can be mitigated. / Det ökande antalet elfordon inom transportsektorn har gjort de konventionella bränslebaserade fordonen föråldrade tillsammans med bränslepåfyllningsstationerna. Med ökningen av elbilar har det skett en ökning av den offentliga laddningsinfrastrukturen med snabbladdningsutrustning som används för att ladda elbilarna på åtminstone möjlig tid och också ta itu med frågan om ’range anxiety’ bland elägare. Många länder som Sydkorea och Tyskland har sett politik införas för att installera snabbladdare för elbilar i befintliga bensinstationer. Denna studie syftar till att genomföra en teknisk-ekonomisk genomförbarhet för att analysera potentialen för att implementera elfordonstillförselutrustning (EVSE) med snabb laddningskapacitet i befintliga bensinstationer. Potentialen med att använda solcellssystem (PV) och batterilagringssystem (BESS) för att minska belastningen från nätet undersöks också. Scenarier utvecklas med beaktande av olika konfigurationer av EVSE, PV och BESS och en djupgående ekonomisk analys genomförs för att analysera konfigurationernas ekonomiska genomförbarhet. Effekten på elnätet analyseras också i denna avhandling genom att genomföra en belastningsflödesanalys på CIGRE lågspänningsnät för Europa med Python.Den föreslagna designen möjliggör val av tekno-ekonomiskt genomförbara konfigurationer av EVSE, BESS och PV. Resultaten av designen förklaras med Storbritannien som en fallstudie. Det observeras att konfigurationerna med 3 EVSE, BESS och 8 timmar och konfigurationen med 3 EVSE, 1 BESS och 1 PV-system för 8 timmars drift är ekonomiskt lönsamma. Den föreslagna designen visar att även om anslutningskostnaden är den dominerande faktorn som påverkar genomförbarheten, kan användning av BESS med eller utan solceller minska anslutningskostnaden med nästan 90% beroende på antalet BESS. Lastflödesanalys utförs för de olika konfigurationerna av EVSE, BESS och PV på CIGRE LV-nätverket på Pandapower i Python. Resultaten visar att det befintliga nätverket måste förstärkas för att underlätta anslutningen av EV-snabbladdare till nätet. Uppgradering av nätverkskablarna och ökning av spänningen till 1,05 eller 1,1 volt per enhet är de två strategier som har föreslagits i denna studie för att förhindra underspänning som kan uppstå till följd av att EVSE ansluts till elnätet. Simuleringarna för de två strategierna lyfter fram att genom att implementera dessa strategier i elnätet kan underspänningsfrågorna i överföringsnätet mildras.

This master thesis is focused on analysis of reactive power flow in LV and MV networks. In the first part there is a definition of reactive power and description of individual parts of electrical networks that contribute with their reactive power to distribution network. The second part is dedicated to calculation of power flow in simulation software PSS® Sincal where on numerical models of network different types of network configuration are tested and consequently its influence on reactive power flow is evaluated. A more detailed analysis is dedicated to reactive power compensation in networks with distributed generation equipped with Volt-Var regulation and its possible negative mutual influence. This thesis also includes general recommendation on the basis of network simulation analysis concerning installation of compensating systems in distribution transformer station.