Academic literature on the topic 'Reactive Power Optimization (RPO)'

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.

Growth in Distributed Energy Resources (DERs) and low-inertia renewable energy sources in smart grids require imperative Volt-VAR Control (VVC). Moreover, this growth combined with increasing deployment of information technologies in smart grids fuels communication uncertainties and reveals transient stability challenges for Distributed Network Operators (DNOs). Innovative approaches have been proposed to use the inherent thermal inertia of buildings to provide ancillary services to the grid to tackle the problems posed by the increasing trend of volatile DERs. Although numerous approaches harness traditional VVC devices to compensate for voltage violations, synthetic inertia and control of Energy Storage System (ESS) exist to improve transient stability with an increase of DERs. While ample strategies tackle these two problems separately, the ability of smart buildings to provide active and reactive power support simultaneously has not yet been exploited. This study explores the concurrent effects of modulating loads’ apparent power consumption on the grid’s frequency and voltage profile. A Distributed Model Predictive Control (DMPC) strategy for voltage and frequency control in the DN is employed by using smart buildings and sensitivity analysis without compromising customers’ climate control performance in smart buildings. The robustness of this strategy is validated on a modified IEEE 13 bus system modelled in MathWorks Simulink.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010.<br>Committee Chair: Begovic, Miroslav; Committee Member: Divan, Deepak; Committee Member: Harley, Ron; Committee Member: Petit, Marc; Committee Member: Verriest, Erik. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Ocean wave as a renewable energy source possesses great potential for solving the world energy crisis and benefit human beings. The total theoretical potential wave power on the ocean-facing coastlines of the world is around 30,000 TWh, although cannot all be adopted for generating electricity, the amount of the power can be absorbed still can occupy a large portion of the world's total energy consumption. However, multiple reasons have stopped the ocean wave energy from being widely adopted, and among those reasons, the most important one is immature of the Power Take-off (PTO) technology. In this dissertation, a self-reactive two-body wave energy point absorber that is embedded with a novel PTO using the unique mechanism of Mechanical Motion Rectifier (MMR) is investigated through design, analysis and testing to improve the energy harvesting efficiency and the reliability of the PTO. The MMR mechanism can transfer the reciprocated bi-directional movement of the ocean wave into unidirectional rotation of the generator. As a result, this mechanism brings in two advantages towards the PTO. The first advantage it possess is that the alternating stress of the PTO is changed into normal stress, hence the reliability of the components are expected to be improved significantly. The other advantage it brings in is a unique phenomenon of engagement and disengagement during the operation, which lead to a piecewise nonlinear dynamic property of the PTO. This nonlinearity of the PTO can contribute to an expanded frequency domain bandwidth and better efficiency, which are verified through both numerical simulation and in-lab experiment. During the in-lab test, the prototyped PTO achieved energy transfer efficiency as high as 81.2%, and over 40% of efficiency improvement compared with the traditional non-MMR PTO under low-speed condition, proving the previously proposed advantage. Through a more comprehensive study, the MMR PTO is further characterized and a refined dynamic model. The refined model can accurately predict the dynamic response of the PTO. The major factors that can influence the performance of the MMR PTO, which are the inertia of the PTO, the damping coefficient, and the excitation frequency, are explored through analysis and experiment comprehensively. The results show that the increase on the inertia of the PTO and excitation frequency, and decrease on the damping coefficient can lead to a longer disengagement of the PTO and can be expressed analytically. Besides the research on the PTO, the body structure of the point absorber is analyzed. Due to the low-frequency of the ocean wave excitation, usually a very large body dimension for the floating buoy of the point absorber is desired to match with that frequency. To solve this issue, a self-reactive two-body structure is designed where an additional frequency between the two interactive bodies are added to match the ocean wave frequency by adopting an additional reactive submerged body. The self-reactive two-body structure is tested in a wave to compare with the single body design. The results show that the two-body structure can successfully achieve the frequency matching function, and it can improve more than 50% of total power absorption compared with the single body design.<br>Doctor of Philosophy<br>Ocean wave as a renewable energy source possesses great potential for solving the world energy crisis and benefit human beings. The total theoretical potential wave power on the ocean-facing coastlines of the world is around 30,000 TWh, although impossible to be all transferred into electricity, the amount of the power can be absorbed still can cover a large portion of the world's total energy consumption. However, multiple reasons have stopped the ocean wave energy from being widely adopted, and among those reasons, the most important one is immature of the Power Take-off (PTO) technology. In this dissertation, a novel two body wave energy converter with a PTO using the unique mechanism of Mechanical Motion Rectifier (MMR) is investigated through design, analysis, and testing. To improve the energy harvesting efficiency and the reliability of the PTO, the dissertation induced a mechanical PTO that uses MMR mechanism which can transfer the reciprocated bi-directional movement of the ocean wave into unidirectional rotation of the generator. This mechanism brings in a unique phenomenon of engagement and disengagement and a piecewise nonlinear dynamic property into the PTO. Through a comprehensive study, the MMR PTO is further characterized and a refined dynamic model that can accurately predict the dynamic response of the PTO is established. The major factors that can influence the performance of the MMR PTO are explored and discussed both analytically and experimentally. Moreover, as it has been theoretically hypothesis that using a two-body structure for designing the point absorbers can help it to achieve a frequency tuning effect for it to better match with the excitation frequency of the ocean wave, it lacks experimental verification. In this dissertation, a scaled two-body point absorber prototype is developed and put into a wave tank to compare with the single body structure. The test results show that through the use of two-body structure and by designing the mass ratio between the two bodies properly, the point absorber can successfully match the excitation frequency of the wave. The highest power capture width ratio (CWR) achieved during the test is 58.7%, which exceeds the results of similar prototypes, proving the advantage of the proposed design.

Distributed generators (DGs) are proposed as a possible solution to supply economic and reliable electricity to customers. It is adapted to overcome the challenges that are characterized by centralized generation such as transmission and distribution losses, high cost of fossil fuels and environmental damage. This work presents the basic principles of integrating renewable DGs in low voltage distribution networks and particularly focuses on the operation of DG installations and their impacts on active and reactive power. In this thesis, a novel technique that applies the stochastic approach for the operation of distribution networks with considering active network management (ANM) schemes and demand response (DR) within a joint active and reactive distribution market environment is proposed. The projected model is maximized based on social welfare (SW) using market-based joint active and reactive optimal power flow (OPF). The intermittent behaviour of renewable sources (such as solar irradiance and wind speed) and the load demands are modelled through Scenario-Tree technique. The distributed network frame is recast using mixed-integer linear programming (MILP) that is solved by using the GAMS software and then the obtained results are being analysed and discussed. In addition, the impact of wind and solar power penetration on the active and reactive distribution locational prices (D-LMPs) within the distribution market environment is explored in terms of the maximization of SW considering the uncertainty related to solar irradiance, wind speed and load demands. Finally, a realistic case study (16-bus UK generic medium voltage distribution system) is used to demonstrate the effectiveness of the proposed method. Results show that ANM schemes and DR integration lead to an increase in the social welfare and total dispatched active and reactive power and consequently decrease in active and reactive D-LMPs.<br>Ministry of Higher Education and Scientific Research - Iraq<br>The selected author's publications, the published versions of which were attached at the end of the thesis, have been removed due to copyright.

Este trabalho propõe uma metodologia para enumerar soluções, que indiquem a barra e a compensação de potência reativa necessária para o sistema elétrico sob análise, que atendam aos requisitos avaliados pela função objetivo e as restrições. Nessa alocação de compensação ótima de potência reativa, obtemos as melhores barras e configurações de potências e tecnologias de dispositivos de compensação, minimizando as perdas totais de potência ativa da rede. Em redes fracas com conversores de frequência (por exemplo, para conexão de fontes renováveis, ou interligações utilizando conversores HVDC), esta metodologia proposta busca a melhor relação de curto-circuito trifásico (SCR) no ponto de conexão do conversor de frequência, melhorando a conexão da barra de interesse. O método busca soluções para alocar um único dispositivo de compensação, e soluções alocando simultaneamente dois dispositivos. A metodologia proposta baseia-se na enumeração exaustiva das soluções, e o estudo de caso nos sistemas de 14 e 30 barras do IEEE mostrou a aplicabilidade e funcionalidade da metodologia proposta.<br>This work proposes a methodology to enumerate solutions, which indicate the bar and the reactive power compensation required for the electrical system under analysis, that meet the requirements evaluated by the objective function and the constraints. In this allocation of optimal compensation of reactive power, we obtain the optimal bars and technologies of compensation devices, minimizing the total losses of active power of the network. In weak networks with frequency converters (e.g. for connection of renewable sources, or interconnections using HVDC converters), the proposed methodology seeks the best threephase short-circuit (SCR) relation at the connection point, improving the connection of the new generation. The method looks for solutions to allocate a single compensation device, and solutions to allocate two devices simultaneously. The proposed methodology is based on the exhaustive enumeration of the solutions. A case study carried out in the IEEE 14 and 30 bus systems shows the applicability and performance of the proposed methodology.

Attempts to reduce greenhouse gas emissions are promising with the recent dramatic increase of installed renewable energy sources (RES) capacity. Integration of large intermittent renewable resources affects smart grid systems in several significant ways, such as transient and voltage stability, existing protection scheme, and power leveling and energy balancing. To protect the grid from threats related to these issues, utilities impose rigorous technical requirements, more importantly, focusing on fault ride through requirements and active/reactive power responses following disturbances. This dissertation is aimed at developing and verifying the advanced and algorithmic methods for specification of protection schemes, reactive power capability and power control requirements for interconnection of the RESs to the smart grid systems. The first findings of this dissertation verified that the integration of large RESs become more promising from the energy-saving, and downsizing perspective by introducing a resistive superconducting fault current limiter (SFCL) as a self-healing equipment. The proposed SFCL decreased the activation of the conventional control scheme for the wind power plant (WPP), such as dc braking chopper and fast pitch angle control systems, thereby increased the reliability of the system. A static synchronous compensator (STATCOM) has been proposed to assist with the uninterrupted operation of the doubly-fed induction generators (DFIGs)-based WTs during grid disturbances. The key motivation of this study was to design a new computational intelligence technique based on a multi-objective optimization problem (MOP), for the online coordinated reactive power control between the DFIG and the STATCOM in order to improve the low voltage ride-through (LVRT) capability of the WT during the fault, and to smooth low-frequency oscillations of the active power during the recovery. Furthermore, the application of a three-phase single-stage module-integrated converter (MIC) incorporated into a grid-tied photovoltaic (PV) system was investigated in this dissertation. A new current control scheme based on multivariable PI controller, with a faster dynamic and superior axis decoupling capability compared with the conventional PI control method, was developed and experimentally evaluated for three-phase PV MIC system. Finally, a study was conducted based on the framework of stochastic game theory to enable a power system to dynamically survive concurrent severe multi-failure events, before such failures turn into a full blown cascading failure. This effort provides reliable strategies in the form of insightful guidelines on how to deploy limited budgets for protecting critical components of the smart grid systems.

Orientador: Luiz Carlos Pereira da Silva<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação<br>Made available in DSpace on 2018-08-04T07:50:24Z (GMT). No. of bitstreams: 1 Alcantara_MarcioVenicioPilar_M.pdf: 1100908 bytes, checksum: 0913d60c47bc87e4c67320408f6905af (MD5) Previous issue date: 2005<br>Resumo: É sabido que o maior volume de perdas ocorre nos sistemas de distribuição de energia elétrica. Capacitores shunt são largamente utilizados nos alimentadores primários dos sistemas de distribuição para compensar potência reativa e conseqüentemente obter melhor perfil de tensão, reduções das perdas de potência e energia, e aumento da capacidade da rede de distribuição em atender carga ativa. A decisão do local ótimo de instalação de bancos de capacitores corresponde a um problema de programação matemática combinatorial. A determinação da influência da modelagem da carga na solução do problema, a inclusão de objetivos técnicos relacionados ao controle de tensão, custos de operação e de manutenção, e perdas de potência e energia, resultando numa nova formulação multi-critério com critérios conflitantes para o problema, e a viabilidade da aplicação de algoritmos genéticos como método de solução dessa nova formulação justificaram o desenvolvimento desta pesquisa. A definição do problema, e o desenvolvimento de modelagens matemáticas podem ser encontrados na primeira parte do trabalho. Na segunda parte apresentam-se os métodos de resolução utilizados nesse trabalho, são eles: heurísticos, e um método meta-heurístico. Um dos métodos heurísticos utiliza fatores de participação reativos da teoria de estabilidade de tensão para resolução do problema. O método meta-heurístico é um algoritmo baseado em algoritmos genéticos que resolve a formulação matemática apresentada anteriormente. Os métodos são testados utilizando-se uma rede real de 70 barras. Efeitos de cargas dependentes da tensão no problema são avaliados<br>Abstract: It is well known that the major portion of active power losses happen in the electric power distribution feeders. Shunt capacitors are broadly used in the primary feeders to compensate reactive power and consequently to obtain better voltage profile, reductions of power and energy losses, and increase the distribution network capacity in supplying active power demand. The decision of the optimal capacitors banks installation corresponds to a combinatorial mathematical programming problem. The determination of the influence of the load modeling in the solution of the problem, the inclusion of technical objectives relating to voltage control, costs of operation and maintenance, and cost of power and energy losses, resulting in a new multi-criteria formulation with conflicting criteria to the problem, and the viability of the application of genetic algorithms as method of solution of that new formulation justified the development of this research. The definition of the problem and the development of mathematical models can be found in the first part of the work. In the second it is presented the resolution methods, they are: heuristic, and a meta-heuristic method. One of the heuristic methods uses reactive participation factors commonly applied for voltage stability analysis of power systems. The meta-heuristic method is an algorithm based on genetic algorithms that solve the mathematical formulation previously presented. The methods are tested by using a real network of 70 bars. Effects of voltage dependent loads in the problem are quantified<br>Mestrado<br>Energia<br>Mestre em Engenharia Elétrica