<p>Controlling the power flow in transmission systems has recently gained increased interest. The difficulties of building new lines and the pressure of having a high utilization of existing assets, makes the flexibility of grid systems increasingly important.</p><p>This master thesis work investigates induction regulators as control devices for active power flow in a transmission system. A small change in angle of the rotor affects both the amplitude and the phase of the voltage. The magnetic coupling in the induction regulator can be controlled by changing the permeability of a thermo magnetic material such as gadolinium and can hence give a second independent controlling parameter. An analytical model and calculations in the</p><p>FEM software AceTripleC together with Matlab, is used to simulate the influence of the regulators connected to a simple grid in case1, a 400 kV scenario and case 2, a 45 kV scenario.</p><p>The analysis was carried out on a small transmission system consisting of two parallel transmission lines connected to source and load. The induction regulators are connected to one of the parallel transmission lines. The regulators modelled in case 1 must be able to control the active power flow in the regulated line to vary between 50 and 150 % of the original power flow through this line.</p><p>This shall be done over a range of 0 to 800 MW transmitted power. The regulators modelled in case 2 must be able to control the active power flow in</p><p>the regulated line to vary between 0 and 30 MW, if this does not cause the power flow in the parallel line to exceed 30 MW. This shall be done over a range of 0 to</p><p>50 MW transmitted power.</p><p>The regulators are designed as small and inexpensive as possible while still fulfilling requirements regarding the active power flow controllability in the grid, current density in windings and maximum flux density in core and gap.</p><p>The results indicate that the size of the 400 kV solution has to be reduced to become competitive whereas for the 45 kV solution the relative difference to existing solution is smaller. Advantages with the proposed design over a phase shifting transformer are mainly a simpler winding scheme and the absence of a tap changer.</p>

Controlling the power flow in transmission systems has recently gained increased interest. The difficulties of building new lines and the pressure of having a high utilization of existing assets, makes the flexibility of grid systems increasingly important. This master thesis work investigates induction regulators as control devices for active power flow in a transmission system. A small change in angle of the rotor affects both the amplitude and the phase of the voltage. The magnetic coupling in the induction regulator can be controlled by changing the permeability of a thermo magnetic material such as gadolinium and can hence give a second independent controlling parameter. An analytical model and calculations in the FEM software AceTripleC together with Matlab, is used to simulate the influence of the regulators connected to a simple grid in case1, a 400 kV scenario and case 2, a 45 kV scenario. The analysis was carried out on a small transmission system consisting of two parallel transmission lines connected to source and load. The induction regulators are connected to one of the parallel transmission lines. The regulators modelled in case 1 must be able to control the active power flow in the regulated line to vary between 50 and 150 % of the original power flow through this line. This shall be done over a range of 0 to 800 MW transmitted power. The regulators modelled in case 2 must be able to control the active power flow in the regulated line to vary between 0 and 30 MW, if this does not cause the power flow in the parallel line to exceed 30 MW. This shall be done over a range of 0 to 50 MW transmitted power. The regulators are designed as small and inexpensive as possible while still fulfilling requirements regarding the active power flow controllability in the grid, current density in windings and maximum flux density in core and gap. The results indicate that the size of the 400 kV solution has to be reduced to become competitive whereas for the 45 kV solution the relative difference to existing solution is smaller. Advantages with the proposed design over a phase shifting transformer are mainly a simpler winding scheme and the absence of a tap changer.

As novas tecnologias FACTS aplicadas ao sistema de transmissão, com base em eletrônica de potência, podem também ser úteis à distribuição. Para tal é preciso conduzir um procedimento de consolidação da utilização e do desempenho destas, para sua aplicação sem riscos. Neste trabalho, dois aspectos serão contemplados. O primeiro se refere à aplicação do dispositivo FACTS atuando como um capacitor série. Em se tendo controle de módulo e da fase da tensão inserida em série com a linha pode-se fazê-la comportar-se como uma queda em uma reatância série capacitiva ou indutiva. O controle dessa reatância série (aumentando/diminuindo) permitirá a aplicação do conceito de compensação série em qualquer ponto do sistema de distribuição, provendo benefícios de um controle contínuo da tensão e também do controle do fluxo de carga no sistema independente da corrente. O segundo aspecto refere-se ao uso dos dispositivos na conexão de alimentadores controlando a potência ativa entre eles. Para esta operação outro dispositivo UPFC, com conceito similar ao descrito acima, entretanto atuando na fase da tensão entre 2 barras, comporta-se como um transformador defasador com variação contínua de ?taps?, podendo controlar a potência ativa entre os alimentadores. A aplicação destas tecnologias propiciarão vários benefícios para a expansão da distribuição tais como, flexibilização do uso da rede, interligação de alimentadores permitindo manobras de blocos de energia sem ?pisca?, ajuste contínuo do suporte de reativos durante a operação, controle dinâmico do fluxo de potência. O objetivo deste trabalho é estudar a aplicabilidade da tecnologia FACTS e estender este conceito para aplicação em sistemas de distribuição e conduzir simulações digitais em redes de distribuição (15kV) identificando o desempenho e os benefícios atingidos. O programa de simulação utilizado é o ATP (Alternative Transients Program). / The new FACTS technologies applied to the transmission system, based on power electronics, can also be useful to the distribution. For that, it is necessary to drive a procedure to consolidate the use and the performance for their application without risks. In this work two aspects will be approached. The first refers to the application of a FACTS device acting as series compensator. This device will be able to control the voltage in module and phase in order to act as a voltage drop in a serie reactance with capacitive or inductive features. The control of this series reactance (increasing/ decreasing) will allow the application of series compensation concept to any point of the distribution system, providing the benefits of continuous control of the voltage added to the load flow control in the system independent of the current. The second aspect refers to its use in the connection of two feeders controlling the active power between them. For this operation other device, UPFC, with similar concept as described previously, acts mainly in the phase of the injected voltage in the line, performing as a phase-shift with continuous taps variation and is able to control the active power flow between feeders. The application of this technology will provide several benefits for the distribution expansion, such as, a greater flexibility in the use of the network, connection of feeders without load flow interruption, continuous adjust of reactive power during the operation and dynamic control of power flow. The purpose of this work is to study the applicability of the FACTS technology, to extend this concept for the application in the distribution system by using digital simulations in distribution network up to 15kV identifying the performance and the reached benefits.

The objective of the research is to develop a cost-effective, dynamic grid controller called the controllable network transformer (CNT) that can be implemented by augmenting existing load tap changing (LTC) transformers with an AC-AC converter. The concept is based on using a fractionally rated direct AC-AC converter to control the power through an existing passive LTC. By using a modulation strategy based on virtual quadrature sources (VQS), it is possible to control both the magnitude and the phase angle of the output voltage of the CNT without having any inter-phase connections. The CNT architecture has many advantages over existing power flow controllers, like absence of low frequency storage, fractional converter rating, retro-fitting existing assets and independent per-phase operation making it potentially attractive for utility applications. The independent control of the magnitude and the phase angle of the output voltage allow independent real and reactive power flow control through the CNT-controlled line. In a meshed network with asymmetric network stresses this functionality can be used to redirect power from critically loaded assets to other relatively under-utilized parallel paths. The power flow controllability of CNT can thus be used to lower the overall cost of generation of power. The solid state switches in the CNT with fast response capability enable incorporation of various additional critical functionalities like grid fault ride through, bypassing internal faults and dynamic damping. This bouquet of features makes the CNT useful under both steady state and transient conditions without compromising the grid reliability.

A low-cost power router (PR), capable of dynamic, independent control of active- and reactive-power flows on meshed grids is presented. The operating principle, detailed schematics, and various possible implementations of the proposed power router are discussed. Various operating modes are identified and a control algorithm has been proposed and verified through simulations. Small-signal and frequency-domain models of the power router from basic time-domain equations are developed. A three-tier protection system based on the fail-normal switch to avoid single point-of-failure is presented. The operation of proposed protection system in isolating the converter and the grid in the event of faults is verified through simulation. An analytical method to evaluate the stability of a system with multiple power routers is proposed. Necessary conditions for the PR-controller design to ensure stable operation of a system with multiple power routers is proposed. These necessary conditions are verified through simulation studies. Potential applications of proposed power router in distribution system and the associated challenges in implementation are presented. The functionality and advantages of the proposed power router are experimentally demonstrated at 13 kV, 1 MVA. The proposed power router can result in a low cost power routing solution that can reduce electric grid congestion and efficient implementation of RPS mandates.

As novas tecnologias FACTS aplicadas ao sistema de transmissão, com base em eletrônica de potência, podem também ser úteis à distribuição. Para tal é preciso conduzir um procedimento de consolidação da utilização e do desempenho destas, para sua aplicação sem riscos. Neste trabalho, dois aspectos serão contemplados. O primeiro se refere à aplicação do dispositivo FACTS atuando como um capacitor série. Em se tendo controle de módulo e da fase da tensão inserida em série com a linha pode-se fazê-la comportar-se como uma queda em uma reatância série capacitiva ou indutiva. O controle dessa reatância série (aumentando/diminuindo) permitirá a aplicação do conceito de compensação série em qualquer ponto do sistema de distribuição, provendo benefícios de um controle contínuo da tensão e também do controle do fluxo de carga no sistema independente da corrente. O segundo aspecto refere-se ao uso dos dispositivos na conexão de alimentadores controlando a potência ativa entre eles. Para esta operação outro dispositivo UPFC, com conceito similar ao descrito acima, entretanto atuando na fase da tensão entre 2 barras, comporta-se como um transformador defasador com variação contínua de ?taps?, podendo controlar a potência ativa entre os alimentadores. A aplicação destas tecnologias propiciarão vários benefícios para a expansão da distribuição tais como, flexibilização do uso da rede, interligação de alimentadores permitindo manobras de blocos de energia sem ?pisca?, ajuste contínuo do suporte de reativos durante a operação, controle dinâmico do fluxo de potência. O objetivo deste trabalho é estudar a aplicabilidade da tecnologia FACTS e estender este conceito para aplicação em sistemas de distribuição e conduzir simulações digitais em redes de distribuição (15kV) identificando o desempenho e os benefícios atingidos. O programa de simulação utilizado é o ATP (Alternative Transients Program). / The new FACTS technologies applied to the transmission system, based on power electronics, can also be useful to the distribution. For that, it is necessary to drive a procedure to consolidate the use and the performance for their application without risks. In this work two aspects will be approached. The first refers to the application of a FACTS device acting as series compensator. This device will be able to control the voltage in module and phase in order to act as a voltage drop in a serie reactance with capacitive or inductive features. The control of this series reactance (increasing/ decreasing) will allow the application of series compensation concept to any point of the distribution system, providing the benefits of continuous control of the voltage added to the load flow control in the system independent of the current. The second aspect refers to its use in the connection of two feeders controlling the active power between them. For this operation other device, UPFC, with similar concept as described previously, acts mainly in the phase of the injected voltage in the line, performing as a phase-shift with continuous taps variation and is able to control the active power flow between feeders. The application of this technology will provide several benefits for the distribution expansion, such as, a greater flexibility in the use of the network, connection of feeders without load flow interruption, continuous adjust of reactive power during the operation and dynamic control of power flow. The purpose of this work is to study the applicability of the FACTS technology, to extend this concept for the application in the distribution system by using digital simulations in distribution network up to 15kV identifying the performance and the reached benefits.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第16855号 / 工博第3576号 / 新制||工||1540(附属図書館) / 29530 / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 引原 隆士, 教授 木本 恒暢, 教授 小野寺 秀俊 / 学位規則第4条第1項該当

An important issue in today's power system is the need to analyse and determine the adequacy of transmission capacity. There is a need for approaches to increase transmission system capacity without construction of new transmission facilities, all while assuring secure operation of the grid. New technologies can enhance efficiency and reliability, increase capacity utilization, enable more rapid response to contingencies, and increase flexibility in controlling power flows on transmission lines. Distributed Series Reactor (DSR) control is a new smart grid technology that can be applied to control flows in the transmission system. DSRs can be used to balance phase flows in a single line as well as to control the distribution of flow in parallel flow paths. This dissertation investigates the Design of Distributed Series Reactors (DSRs) on transmission lines and provide guidelines and considerations for their implementation in bulk power system transmission networks to control power flow to: increase the exisiting transmission capacity utilization, alleviate overloads due to load growth and contingencies, and mitigate the effects of unbalanced voltages, unbalanced transmission line impedances and unbalanced loads by balancing flows in the phases of an unbalanced line. This dissertation provides several DSR System Design aspects; for a single line by performing an experiment for EHV and high voltage three parallel transmission lines, and for lines within the boundaries of a power system by deployment of DSRs over the IEEE 39 bus system that is modified and modelled as a 3-phase unbalanced transmission model with 345 kV lines that accounts for tower geometry and as a balanced, 3-phase model that is derived from the unbalanced, 3-phase model, and finally for lines within a control area and a set of tie lines among control areas by deployment of DSRs over a real system control area and the tie lines connecting this area to other power pool areas. For all experiments and simulations in this dissertation lines are modelled as 3-phase lines. The DSR system design for Unbalanced vs. Balanced 3-phase systems (Unbalanced immittance, Unbalanced load) are examined. Also the Distributed vs. Lumped models for 3-phase systems are tested. Comparison between DSR system design and transposition for voltage balancing was performed. The effect of bundling the conductors for DSR system design was investiagted. In this dissertation an economic evaluation of DSR System Design for parallel lines and for the IEEE 39 bus three-phase unbalanced line model for N-1 criterion contingency with load growth is performed. The economic evaluation performed for the DSR system design of a power system versus new transmission line construction showed that DSRs can be cost effective in managing load increases from year to a year, and thus avoid larger investments in new line construction until load expectations are proven to be true. Thus, a major value of DSRs is handling load growth in the short term, delaying larger investments. Although many aspects of DSR control implementation have yet to be explored, this work has demonstrated the fundamental concept is sound and the economics are compelling. / Ph. D.

Distributed Series Reactors (DSRs) can be used to control power flow to more fully utilize the capacity of a transmission network, delaying investment in new transmission lines. In this study the IEEE 39 bus standard test system is modified to a 3-phase, unbalanced model consisting of 230 kV, 345 kV and 500 kV lines, where lines of different voltage run in parallel. This model is used to study load growth and the effect of adding DSRs to alleviate resulting overloads, and in particular to alleviate overloads on lines of different voltage running in parallel. The economic benefit of adding DSRs to the network is compared to the addition of new transmission lines in the network. In the second part of the work, the effect of unsymmetrical operation of DSRs on a single transmission line is studied and compared to the symmetrical operation of DSRs. It is found that the unsymmetrical operation of DSRs is more economical. Finally the unsymmetrical operation of DSRs to reduce voltage imbalance in the network is considered. / Master of Science

The objective of the proposed research is to develop a cost-effective power flow controller to improve the utilization and reliability of the existing transmission, sub-transmission, and distribution networks. Over the last two decades, electricity consumption and generation have continually grown at an annual rate of around 2.5%. At the same time, investments in the Transmission and Distribution (T&D) infrastructure have steadily declined. Further, it has become increasingly difficult and expensive to build new power lines. As a result, the aging power-grid has become congested and is under stress, resulting in compromised reliability and higher energy costs. In such an environment it becomes important that existing assets are used effectively to achieve highest efficiency. System reliability is sacrosanct and cannot be compromised. Utility system planners are moving from radial towards networked systems to achieve higher reliability, especially under contingency conditions. While enhancing reliability, this has degraded the controllability of the network, as current flow along individual lines can no longer be controlled. The transfer capacity of the system gets limited by the first line that reaches the thermal capacity, even when majority of the lines are operating at a fraction of their capacity. The utilization of the system gets further degraded as the lines are operated with spare capacity to sustain overloads under contingencies. Market efficiency is also sub-optimal, with congestion on key corridors restricting the low-cost generators to connect to the end users, resulting in higher electricity prices for the consumers. The proposed technology offers the capability to realize a controllable meshed-network, with the ability to utilize static and dynamic capacity of the grid to provide system-wide benefits, including- increased line and system-capacity utilization, increased reliability, improved operation under contingencies, and rapid implementation. It would allow a broadening of the energy market, permitting owners to direct how energy flows on their wires, and making it easier to connect to new sources of generation.