This investigates the voltage flicker problem of a large steel plant and presents the mitigation strategy by applying the static var compensator (SVC) and cogenerator. The fluctuation of real power and reactive power consumption by an arc furnace has been measured and recorded during the steel production process. The dynamic load model of the A/C arc furnace is derived based on the actual field data and has been included in the computer simulation by the CYME software package for load flow analysis. The block diagrams of SVC controller and the excitation system of cogenerators are considered to solve the response of reactive power compensation according to the voltage fluctuation of the control bus. To maintain the electric service reliability of arc furnace when an external utility fault occurs, the tie line tripping and load shedding is implemented to prevent the tripping of cogenerator after system disturbance. It is found that the dynamic load behavior of arc furnace in the isolated industrial power system can be well compensated by the cogenerator with adaptive control of exciter and governor to generate proper reactive power and real power according to the fluctuation of bus voltage and system frequency respectively.

This thesis discusses the modeling of a micro-grid with photovoltaic (PV)-wind-fuel cell (FC) hybrid energy system and its operations. The system consists of the PV power, wind power, FC power, static var compensator (SVC) and an intelligent power controller. Wind and PV are primary power sources of the system, and an FC-electrolyzer combination is used as a backup and a long-term storage system. A simulation model for the micro-grid control of hybrid energy system has been developed using MATLAB/Simulink. A SVC was used to supply reactive power and regulate the voltage of the hybrid system. To achieve a fast and stable response for the real power control, the intelligent controller consists of a Radial Basis Function Network-Sliding Mode Control (RBFNSM) and a General Regression Neural Network (GRNN) for maximum power point tracking (MPPT). The pitch angle of wind turbine is controlled by RBFNSM, and the PV system uses GRNN, where the output signal is used to control the DC/DC boost converters to achieve the MPPT.

Made available in DSpace on 2016-08-17T14:52:43Z (GMT). No. of bitstreams: 1 Gilson Soares da Silva Junior.pdf: 3373997 bytes, checksum: f03b490d45ba68e7ae2eacd3f33b718a (MD5) Previous issue date: 2008-02-15 / In this work is analyzed the influence of a static var compensator (SVC) on the electromechanical stability of the electrical energy system of the industrial consumer ALUMAR that has a cogeneration. The main considerations on cogeneration systems, the FACTS Controllers and the systems involved in the analysis are described. Moreover, it is discussed the modeling of electrical system of ALUMAR highlighting the modeling updated and validated by the National Electric System Operator (ONS) and the modeling of cogenerators. / Análise da influência de um compensador estático de reativos (SVC) na estabilidade eletromecânica do sistema de energia elétrica do consumidor industrial ALUMAR o qual possui cogeração. Descrevem-se as principais particularidades sobre os sistemas de cogeração, os controladores FACTS e sobre os sistemas envolvidos na análise. Discute-se, ainda, a modelagem do sistema elétrico da ALUMAR, destacandose a modelagem atualizada e validada pelo Operador Nacional do Sistema (ONS) e a modelagem dos cogeradores.

Modern interconnected power systems are becoming highly complex and sophisticated, while increasing energy penetrations through congested inter-tie lines causing the operating point approaching stability margins. This as a result, exposes the overall system to potential low frequency power oscillation phenomena following disturbances. This in turn can lead to cascading events and blackouts. Recent approaches to counteract this phenomenon are based on utilization of wide area monitoring systems (WAMS) and power electronics based devices, such as flexible AC transmission systems (FACTS) and HVDC links for advanced power oscillation damping provision. The rise of hybrid AC-DC power systems is therefore sought as a viable solution in overcoming this challenge and securing wide-area stability. If multiple FACTS devices and HVDC links are integrated in a scheme with no supervising control actions considered amongst them, the overall system response might not be optimal. Each device might attempt to individually damp power oscillations ignoring the control status of the rest. This introduces an increasing chance of destabilizing interactions taking place between them, leading to under-utilized performance, increased costs and system wide-area stability deterioration. This research investigates the development of a novel supervisory control scheme that optimally coordinates a parallel operation of multiple FACTS devices and an HVDC link distributed across a power system. The control system is based on Linear Quadratic Gaussian (LQG) modern optimal control theory. The proposed new control scheme provides coordinating control signals to WAMS based FACTS devices and HVDC link, to optimally and coherently counteract inter-area modes of low frequency power oscillations inherent in the system. The thesis makes a thorough review of the existing and well-established improved stability practises a power system benefits from through the implementation of a single FACTS device or HVDC link, and compares the case –and hence raises the issue–when all active components are integrated simultaneously and uncoordinatedly. System identification approaches are also in the core of this research, serving as means of reaching a linear state space model representative of the non-linear power system, which is a pre-requisite for LQG control design methodology.

The modern day power system is witnessing a tremendous change. There has been a rapid rise in the distributed generation, along with this the deregulation has resulted in a more complex system. The power demand is on a rise, the generation and trans-mission infrastructure hasn't yet adapted to this growing demand. The economic and operational constraints have forced the system to be operated close to its design limits, making the system vulnerable to disturbances and possible grid failure. This makes the study of voltage stability of the system important more than ever. Generally, voltage stability studies are carried on a single phase equivalent system assuming that the system is perfectly balanced. However, the three phase power system is not always in balanced state. There are a number of untransposed lines, single phase and double phase lines. This thesis deals with three phase voltage stability analysis, in particular the voltage stability index known as L-Index. The equivalent single phase analysis for voltage stability fails to work in case of any unbalance in the system or in presence of asymmetrical contingency. Moreover, as the system operators are giving importance to synchrophasor measurements, PMUs are being installed throughout the system. Hence, the three phase voltages can be obtained, making three phase analysis easier. To study the effect of unbalanced system on voltage stability a three phase L-Index based on traditional L-Index has been proposed. The proposed index takes into consideration the unbalance resulting due to untransposed transmission lines and unbalanced loads in the system. This index can handle any unbalance in the system and is much more realistic. To obtain bus voltages during unbalanced operation of the system a three phase decoupled Newton Raphson load ow was used. Reactive power distribution in a system can be altered using generators voltage set-ting, transformers OLTC settings and SVC settings. All these settings are usually in balanced mode i.e. all the phases have the same setting. Based on this reactive power optimization using LP technique on an equivalent single phase system is proposed. This method takes into account generator voltage settings, OLTC settings of transformers and SVC settings. The optimal settings so obtained are applied to corresponding three phase system. The effectiveness of the optimal settings during unbalanced scenario is studied. This method ensures better voltage pro les and decrease in power loss. Case studies of the proposed methods are carried on 12 bus and 24 bus EHV systems of southern Indian grid and a modified IEEE 30 bus system. Both balanced and unbalanced systems are studied and the results are compared.