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02145 Estimation of switching transient peak overvoltages during transmission line energization using artificial neural network
06 Electrical power supply and utilization (economics, policy, supplies, forecasts)
06
ELECTRICAL P O W E R SUPPLY A N D UTILIZATION Scientific, technical
06/02144 A power flow solvability identification and calculation algorithm Echavarren, F. M. et al. Electric Power Systems Research, 2006, 76, (4), 242 250. This paper presents a continuation and optimization based algorithm to detect power flow unsolvability. In addition, the algorithm obtains the power flow solution, if it exists, no matter how ill-conditioned the power system is. The proposed algorithm is based on the parameterization of the distance from the starting point to the real power flow to be solved, using a convergence margin. The performance of the algorithm is illustrated considering a highly loaded scenario of the operation of the Spanish power system.
06•02145 Estimation of switching transient peak overvoltages during transmission line energization using artificial neural network Thukaram, D. et al. Electric Power Systems Research, 2006, 76, (4), 259 269. Overvoltages are one of the most frequently encountered problems during line energization. At the time of restoration transmission line switching is also one of the major causes, which creates overvoltage. The magnitude and shape of the switching overvoltages vary with the system parameters and network configuration and the point-on-wave where the switching operation takes place. Though detailed electromagnetic transient studies carried out for the design of transmission systems, such studies are not common in a day-to-day operation of power system. However it is important for the operator to ensure that peak overvoltages resulting from the switching operations are well within safe limits. This paper presents an Artificial Neural Network (ANN)-based approach to estimate the peak overvoltage generated by switching transients during line energization. In proposed methodology Levenberg-Marquardt method is used to train the multilayer perceptron. The developed ANN is trained with the extensive simulated results, and tested for typical cases. The simulated results presented clearly show that the proposed technique can estimate the peak values of switching overvoltages with good accuracy.
06/02146 Micro-cogeneration system for a small passenger vessel operating in a nature reserve Bidini, G. et al. Applied Thermal Engineering, 2005, 25, (5 6), 851-865. Saving energy and money is one of the main concerns of many industrial and service firms. Reducing energy consumption means reducing environmental impact, related to the considered activity, and in some cases this entails also economical benefits. Environmental impact reduction becomes of main importance if the device operates in a nature reserve. In this work the possibility to install a microcogeneration system has been studied, for a small passenger vessel, by recovering a fraction of the heat rejected by the existing, fossil-fuelled, on-board engines, instead of the actual auxiliary fossil-fuelled heating system. These systems are necessary for supplying thermal demands to the pilot cockpit and to the passenger cabin, during the cold period of the year. The boat operates on Lake Trasimeno, which belongs to an Italian nature reserve. Thermal features of the boat structure have been carefnlly examined and evaluated, Experimental analysis of the amount of heat and temperature available from the engine has been carried out with the aid of a thermocouple and a non-intrusive ultrasonic flow-meter. The heat recovery system was designed and the capital cost estimated. An environmental and economical benefit anaiysis was also carried out.
06/02147 Novel reactive power controllers for the STATCOM and SSSC E1-Moursi, M. S. and Sharaf, A. M. Electric" Power Systems Research, 2006, 76, (4), 228 241. The paper investigates the dynamic operation of both static synchronous compensator (STATCOM) and static synchronous series compensator (SSSC) based on a new model comprising full 48-pulse GTO voltage source converter for combined reactive power compensation and voltage stabilization of the electric grid network. These key FACTS devices are power electronic GTO converters connected in parallel or series with the power system grid and are controlled by novel decoupled controllers. The complete digital simulation of the STAT-
COM and SSSC within the power system is performed in the MATLAB/Simulink environment using the power system blockset (PSB). The STATCOM scheme and the electric grid network are modelled by specific electric blocks from the power system blockset while the control system is modelled using Simulink. Two novel controllers for the STATCOM and SSSC are presented in this paper based on a decoupled current control strategy to ensure stable operation of the STATCOM under various load excursions. A novel control scheme for the static synchronous series compensator (SSSC) is also implemented to provide a full controllable series compensating (buck/boost) injected voltage over a specified capacitive and inductive range, independently of the magnitude of the transmission line current. The series reactive compensation scheme with an external dc power supply can also compensate for any voltage drops across resistive component of the transmission line impedance. The novel decoupled controller uses a phase locked loop (PLL) with a novel reduced inherent time delay to improve the transient performance of the SSSC. The performance of both STATCOM and SSSC schemes connected to the 230 kV grid are evaluated. The proposed novel control schemes for the STATCOM and SSSC are fully validated by digital simulation.
06102148 Optimum transient security constrained dispatch in competitive deregulated power systems Lin, X. J. et al. Electric Power Systems Researeh, 2006, 76, (4I, 209-216. The ongoing deregulation of the energy market needs to consider commercial implications when generators are re-dispatched to eliminate potential transient instability after a contingency to ensure transient security. A further complication is that different candidate contingencies may motivate different re-dispatch strategies because the advanced (critical) generator group is different in each case, or the sensitivity of the stability margin to power exchanges between generators is different. This paper develops a generalized approach that attempts to address all of these important issues in competitive deregulated power systems.
06/02149 Time stepping finite element analysis of a variable speed synchronous generator with rectifier Thorburn, K. et al. Applied Energy, 2006, 83, (4), 371 386. Several applications for renewable energy conversion make use of variable speed generators. A conversion from variable frequency to grid frequency is therefore essential. One part of the converter is a rectifier. A rectifier model is presented, which is integrated in a time stepping finite element simulation environment where the generator and circuit equations are solved simultaneously. The model handles bidirectional alternator speeds as the application is a linear generator for ocean wave energy conversion. The rectifier model is extended with a load model, consisting of R, L and E, and simulations show what impact the rectifier has on the generator's behaviour.
Economics, policy, supplies, forecasts 06•02150 A law enforcement perspective of electricity deregulation Horowitz, I. Energy, 2006, 31, (6-7), 905 907. In April 2004, the California Attorney General's (AG) office issued a white paper that provided a 'law enforcement perspective of the California energy crisis'. Three aspects of that paper are summarized: notably, the deficiencies in market oversight and enforcement that left the deregulated market prone to potential abuse, the principal modus operandi that some market agents used to exploit those deficiencies without fear of retribution, and the AG's 'recommendations for improving enforcement and protecting consumers in deregulated energy markets'.
06/02151 A novel method for fast computation of saddle node bifurcation in power systems using an optimization technique Karbalaei, F. et al. Energy Conversion and Management, 2006, 47, (5), 582 589. In this paper, a new method for computation of saddle node bifurcation is presented. In this method, initially, the problem is converted to an optimization problem, then solving the optimization problem, the obtained optimum point is the saddle node bifurcation. Here, instead of calculating several power flows, with very few iterative solutions of the optimization equations, which are similar to power flow equations, the saddle node bifurcation is obtained. The number of iterations in which the optimization problem is solved depends directly on the number of reactive power resources reaching their limits before saddle node bifurcation occurs. In the proposed method, for the increase of active power at PV buses, the loss function has been
Fuel and Energy Abstracts September 2006 331
06
ELECTRICAL P O W E R SUPPLY A N D UTILIZATION Scientific, technical
06/02144 A power flow solvability identification and calculation algorithm Echavarren, F. M. et al. Electric Power Systems Research, 2006, 76, (4), 242 250. This paper presents a continuation and optimization based algorithm to detect power flow unsolvability. In addition, the algorithm obtains the power flow solution, if it exists, no matter how ill-conditioned the power system is. The proposed algorithm is based on the parameterization of the distance from the starting point to the real power flow to be solved, using a convergence margin. The performance of the algorithm is illustrated considering a highly loaded scenario of the operation of the Spanish power system.
06•02145 Estimation of switching transient peak overvoltages during transmission line energization using artificial neural network Thukaram, D. et al. Electric Power Systems Research, 2006, 76, (4), 259 269. Overvoltages are one of the most frequently encountered problems during line energization. At the time of restoration transmission line switching is also one of the major causes, which creates overvoltage. The magnitude and shape of the switching overvoltages vary with the system parameters and network configuration and the point-on-wave where the switching operation takes place. Though detailed electromagnetic transient studies carried out for the design of transmission systems, such studies are not common in a day-to-day operation of power system. However it is important for the operator to ensure that peak overvoltages resulting from the switching operations are well within safe limits. This paper presents an Artificial Neural Network (ANN)-based approach to estimate the peak overvoltage generated by switching transients during line energization. In proposed methodology Levenberg-Marquardt method is used to train the multilayer perceptron. The developed ANN is trained with the extensive simulated results, and tested for typical cases. The simulated results presented clearly show that the proposed technique can estimate the peak values of switching overvoltages with good accuracy.
06/02146 Micro-cogeneration system for a small passenger vessel operating in a nature reserve Bidini, G. et al. Applied Thermal Engineering, 2005, 25, (5 6), 851-865. Saving energy and money is one of the main concerns of many industrial and service firms. Reducing energy consumption means reducing environmental impact, related to the considered activity, and in some cases this entails also economical benefits. Environmental impact reduction becomes of main importance if the device operates in a nature reserve. In this work the possibility to install a microcogeneration system has been studied, for a small passenger vessel, by recovering a fraction of the heat rejected by the existing, fossil-fuelled, on-board engines, instead of the actual auxiliary fossil-fuelled heating system. These systems are necessary for supplying thermal demands to the pilot cockpit and to the passenger cabin, during the cold period of the year. The boat operates on Lake Trasimeno, which belongs to an Italian nature reserve. Thermal features of the boat structure have been carefnlly examined and evaluated, Experimental analysis of the amount of heat and temperature available from the engine has been carried out with the aid of a thermocouple and a non-intrusive ultrasonic flow-meter. The heat recovery system was designed and the capital cost estimated. An environmental and economical benefit anaiysis was also carried out.
06/02147 Novel reactive power controllers for the STATCOM and SSSC E1-Moursi, M. S. and Sharaf, A. M. Electric" Power Systems Research, 2006, 76, (4), 228 241. The paper investigates the dynamic operation of both static synchronous compensator (STATCOM) and static synchronous series compensator (SSSC) based on a new model comprising full 48-pulse GTO voltage source converter for combined reactive power compensation and voltage stabilization of the electric grid network. These key FACTS devices are power electronic GTO converters connected in parallel or series with the power system grid and are controlled by novel decoupled controllers. The complete digital simulation of the STAT-
COM and SSSC within the power system is performed in the MATLAB/Simulink environment using the power system blockset (PSB). The STATCOM scheme and the electric grid network are modelled by specific electric blocks from the power system blockset while the control system is modelled using Simulink. Two novel controllers for the STATCOM and SSSC are presented in this paper based on a decoupled current control strategy to ensure stable operation of the STATCOM under various load excursions. A novel control scheme for the static synchronous series compensator (SSSC) is also implemented to provide a full controllable series compensating (buck/boost) injected voltage over a specified capacitive and inductive range, independently of the magnitude of the transmission line current. The series reactive compensation scheme with an external dc power supply can also compensate for any voltage drops across resistive component of the transmission line impedance. The novel decoupled controller uses a phase locked loop (PLL) with a novel reduced inherent time delay to improve the transient performance of the SSSC. The performance of both STATCOM and SSSC schemes connected to the 230 kV grid are evaluated. The proposed novel control schemes for the STATCOM and SSSC are fully validated by digital simulation.
06102148 Optimum transient security constrained dispatch in competitive deregulated power systems Lin, X. J. et al. Electric Power Systems Researeh, 2006, 76, (4I, 209-216. The ongoing deregulation of the energy market needs to consider commercial implications when generators are re-dispatched to eliminate potential transient instability after a contingency to ensure transient security. A further complication is that different candidate contingencies may motivate different re-dispatch strategies because the advanced (critical) generator group is different in each case, or the sensitivity of the stability margin to power exchanges between generators is different. This paper develops a generalized approach that attempts to address all of these important issues in competitive deregulated power systems.
06/02149 Time stepping finite element analysis of a variable speed synchronous generator with rectifier Thorburn, K. et al. Applied Energy, 2006, 83, (4), 371 386. Several applications for renewable energy conversion make use of variable speed generators. A conversion from variable frequency to grid frequency is therefore essential. One part of the converter is a rectifier. A rectifier model is presented, which is integrated in a time stepping finite element simulation environment where the generator and circuit equations are solved simultaneously. The model handles bidirectional alternator speeds as the application is a linear generator for ocean wave energy conversion. The rectifier model is extended with a load model, consisting of R, L and E, and simulations show what impact the rectifier has on the generator's behaviour.
Economics, policy, supplies, forecasts 06•02150 A law enforcement perspective of electricity deregulation Horowitz, I. Energy, 2006, 31, (6-7), 905 907. In April 2004, the California Attorney General's (AG) office issued a white paper that provided a 'law enforcement perspective of the California energy crisis'. Three aspects of that paper are summarized: notably, the deficiencies in market oversight and enforcement that left the deregulated market prone to potential abuse, the principal modus operandi that some market agents used to exploit those deficiencies without fear of retribution, and the AG's 'recommendations for improving enforcement and protecting consumers in deregulated energy markets'.
06/02151 A novel method for fast computation of saddle node bifurcation in power systems using an optimization technique Karbalaei, F. et al. Energy Conversion and Management, 2006, 47, (5), 582 589. In this paper, a new method for computation of saddle node bifurcation is presented. In this method, initially, the problem is converted to an optimization problem, then solving the optimization problem, the obtained optimum point is the saddle node bifurcation. Here, instead of calculating several power flows, with very few iterative solutions of the optimization equations, which are similar to power flow equations, the saddle node bifurcation is obtained. The number of iterations in which the optimization problem is solved depends directly on the number of reactive power resources reaching their limits before saddle node bifurcation occurs. In the proposed method, for the increase of active power at PV buses, the loss function has been
Fuel and Energy Abstracts September 2006 331