Showing papers in "IEEE Transactions on Energy Conversion in 1995"
TL;DR: In this article, an analysis method is developed for modeling multi-phase cage induction motors with asymmetry in the stator, arising due to an interturn fault resulting in a disconnection of one or more coils making up a portion of a stator phase winding and any distribution and number of rotor bar and end-ring failures.
Abstract: An analysis method is developed for modeling of multi phase cage induction motors with asymmetry in the stator, arising due to an interturn fault resulting in a disconnection of one or more coils making up a portion of a stator phase winding and any distribution and number of rotor bar and end-ring failures. The approach, based on the winding functions, makes no assumption as to the necessity for sinusoidal MMF and therefore include all the space harmonics in the machine. Simulation and experimental results confirm the validity of the proposed method. >
497Â citations
TL;DR: The proposed neural network has a quite simple structure and provides a highly accurate identification of the optimal operating point and also ahighly accurate estimation of the maximum power from the PV modules.
Abstract: This paper presents an application of a neural network for the identification of the optimal operating point of PV modules for the real time maximum power tracking control. The output power from the modules depends on the environmental factors such as insolation, cell temperature, and so on. Therefore, accurate identification of optimal operating point and real time continuous control are required to achieve the maximum output efficiency. The proposed neural network has a quite simple structure and provides a highly accurate identification of the optimal operating point and also a highly accurate estimation of the maximum power from the PV modules. >
301Â citations
TL;DR: In this paper, a methodology for the selection of the optimum photovoltaic module for a specific power plant site is developed based on the capacity factors (CF) of the available PV modules.
Abstract: In this paper, a methodology for the selection of the optimum photovoltaic module for a specific power plant site is developed. The selection is based on the capacity factors (CF) of the available PV modules. Long term irradiance data recorded for every hour of the day for 30 years are used. These data are used to calculate the probability density function of the irradiance for different hours of a typical day in a month. The irradiance probability density function and the manufacturer's specifications on PV modules are used to calculate the capacity factors for the PV modules. The PV module with the highest average capacity factor for the specific site is the optimal and recommended PV module. In this paper, the price per installed maximum peak watt is approximately the same for different modules and hence the cost is not an issue. >
227Â citations
TL;DR: In this article, detailed dynamic equations for the power system and wind energy conversion system (WECS) components and their synthesis to a unified model are presented, which is the basis for creating simulation software able to perform the transient stability analysis of isolated diesel-wind turbine power systems for accurate assessment of their interaction.
Abstract: In the first part of this two-part paper, detailed dynamic equations for the power system and wind energy conversion system (WECS) components and their synthesis to a unified model are presented. This model is the basis for creating simulation software able to perform the transient stability analysis of isolated diesel-wind turbine power systems for accurate assessment of their interaction. Approximations in the various component models, when necessary, remain between limits that do not affect the accuracy of the analysis performed. A new general multimachine power system model is also developed which describes the topology and the complexity of wind-diesel power systems in a compact form which is easy to implement in the simulation software. >
212Â citations
TL;DR: The ability of the genetic algorithm to develop a proportional-integral (PI) controller and a state feedback controller for a nonlinear multi-input/multi-output (MIMO) plant model is studied.
Abstract: This paper discusses the application of a genetic algorithm to control system design for boiler-turbine plant. In particular we study the ability of the genetic algorithm to develop a proportional-integral (PI) controller and a state feedback controller for a nonlinear multi-input/multi-output (MIMO) plant model. The plant model is presented along with a discussion of the inherent difficulties in such controller development. A sketch of the genetic algorithm (GA) is presented and its strategy as a method of control system design is discussed. Results are presented for two different control systems that have been designed with the genetic algorithm.
199Â citations
TL;DR: In this paper, a neural network based maximum power tracking controller for interconnected PV power systems is presented, where the neural network is utilized to identify the optimal operating voltage of the PV power system.
Abstract: This paper presents a neural network based maximum power tracking controller for interconnected PV power systems The neural network is utilized to identify the optimal operating voltage of the PV power system The controller generates the control signal in real-time, and the control signal is fed back to the voltage control loop of the inverter to shift the terminal voltage of the PV power system to its identified optimum, which yields maximum power generation The controller is of the PI type The proportional and the integral gains are set to their optimal values to achieve fast response and also to prevent overshoot and also undershoot Continuous measurement is required for the open circuit voltage on the monitoring cell, and also for the terminal voltage of the PV power system Because of the accurate identification of the optimal operating voltage of the PV power system, more than 99% power is drawn from the actual maximum power >
176Â citations
TL;DR: In this article, a general method of saturation modelling for d-q-axis models of induction machines is presented, and a couple of models, obtainable with different selection of state-space variables, are presented.
Abstract: Main flux saturation is most frequently modelled by selecting either stator and rotor d-q axis currents or stator and rotor d-q axis flux linkages as state-space variables. This paper attempts to unify main flux saturation modelling in d-q axis models of induction machines by presenting a general method of saturation modelling. Selection of state-space variables in the saturated machine model is arbitrary and appropriate models in terms of different state-space variables result by application of the method. A couple of models, obtainable with different selection of state-space variables, are presented. The cross-saturation effect is explicitly present in all the models, except for the one with stator and rotor flux linkage d-q axis components as state-space variables. The models are verified by simulation and experimental investigation of induction generator self-excitation. >
157Â citations
TL;DR: In this paper, a new incremental model of a battery energy storage system (BES) is presented and merged into the load-frequency control of a power system, which is suitable for charging mode and discharging mode operations.
Abstract: Since a battery energy storage system (BES) can provide fast active power compensation, it also can be used to improve the performance of load-frequency control. In this paper a new incremental model of a BES is presented and merged into the load-frequency control of a power system. A comprehensive digital computer model of a two-area interconnected power system including governor deadband and generation rate constraint is employed for a realistic response. Computer simulations show that the BES is very effective in damping the oscillations caused by load disturbances. The BES model is suitable for charging mode and discharging mode operations. Optimization of controller gains is obtained by the second method of Lyapunov. >
148Â citations
TL;DR: In this article, the steady-state analysis of self-excited induction generators (SEIG) using an iterative method is described, which involves only simple algebraic calculations, but the accuracy and convergence is rapid.
Abstract: This paper describes the steady-state analysis of self-excited induction generators (SEIG) using an iterative method. By considering the conductances connected across the air gap nodes, an iteration procedure is developed for the determination of the self-excited per-unit frequency, which enables the equivalent circuit to be completely solved. The proposed method involves only simple algebraic calculations, but the accuracy is good and convergence is rapid. The method is subsequently extended to include core loss effects and the analysis of SEIG with series capacitance compensation. Very good agreement between experimental and computed results has been obtained on a 2 kW laboratory machine. >
130Â citations
TL;DR: In this article, a self regulating feature of a self-excited induction generator (SEIG) by connecting additional capacitors is examined, and a system consisting of both shunt and series capacitors has been analyzed.
Abstract: The self regulating feature of a self-excited induction generator (SEIG) by connecting additional capacitors is examined. A system consisting of both shunt and series capacitors has been analyzed. A methodology has been explained to choose an appropriate set of values of these capacitors for desired voltage regulation. Performance of short and long shunt configurations has been compared which shows the superiority of the short shunt connection. The results of a detailed investigation on a conventional 3.7 kW induction motor operated as a SEIG are presented to illustrate the effectiveness of the proposed method. Close agreement between predicted and test results has been observed, thereby establishing the validity of the analysis carried out and the criterion adopted. >
117Â citations
TL;DR: In this paper, the authors present and test a method to calculate the reduction in distribution system electrical line losses, and describe how to optimize plant size, plant location along a distribution feeder, and load transfer from an adjacent feeder.
Abstract: Strategically sited grid-support photovoltaic (PV) power applications have been proposed to provide value (cost savings) to electric utilities experiencing transmission and distribution system overloads. These applications can potentially defer transformer and transmission line upgrades, extend equipment maintenance intervals, reduce electrical line losses, and improve distribution system reliability. This research presents and tests a method to calculate the reduction in distribution system electrical line losses. It also describes how to optimize plant size, plant location along a distribution feeder, and load transfer from an adjacent feeder. Results at Pacific Gas and Electric Company indicate that a 0.50 MW PV power plant at Kerman, California, has $37,000 in energy loss savings value over the plant's life with additional value due to capacity loss savings. These results are site specific. >
TL;DR: In this article, a general model covering both the main-path magnetic saturation and frequency effects in the dynamic equations is proposed to predict the steady-state and transient performance of synchronous machines.
Abstract: It is generally felt that no major accuracy breakthrough in predicting the steady-state and transient performance of synchronous machines could be achieved without taking proper account of the iron saturation effects as well as eddy-current losses. Although the two issues were often treated separately in the past, this paper attempts to unite them by developing a general model covering both the main-path magnetic saturation and frequency effects in the dynamic equations. Mathematical analysis in the d-q space pinpoints cross-saturation coupling which, a priori, does not seem to be symmetrical for salient-pole machines. Yet the model is theoretically sound, since it fulfils at least the physical constraints using energy balance principles. Some test points from a 555-MVA turbine-generator are used for an initial assessment the model's capability to predict the field current and internal angle for various loading conditions.
TL;DR: In this paper, the authors set up a formulation to determine the optimal contract capacities and optimal sizes of battery energy storage systems for time-of-use rate customers and applied the advanced multi-pass dynamic programming and expert knowledge base rules to solve this problem.
Abstract: This paper sets up a formulation to determine the optimal contract capacities and optimal sizes of battery energy storage systems for time-of-use rate customers. The advanced multi-pass dynamic programming and expert knowledge base rules are then applied to solve this problem. Two industrial customers of the Taiwan Power Company System are used as examples to test this algorithm. Results show that the optimal sizes of battery energy storage systems and the optimal contract capacities of customers during the life cycle of battery energy storage systems can be achieved by this algorithm; therefore the maximum economic benefits of battery energy storage systems for time-of-use rate customers can be estimated. >
TL;DR: In this article, a general algorithm to simulate and assess the dynamic behavior of any isolated diesel-wind turbine power system is analyzed and implemented, which can be used to determine the wind energy penetration level at any disturbed operation conditions.
Abstract: In the second part of this two-part paper, a general algorithm to simulate and assess the dynamic behavior of any isolated diesel-wind turbine power system is analyzed and implemented. It is presented how the various power system and wind energy conversion system (WECS) component models described in detail in Part I of the paper can be implemented in order to create integrated simulation software. Case studies for the small size isolated power system on the French island of Desirade are given and analyzed. The algorithm is validated and its usefulness to determine the wind energy penetration level at any disturbed operation conditions is demonstrated. >
TL;DR: In this article, a detailed investigation on the transient behavior of the short shunt self-excited induction generator (SEIG) system subjected to different dynamic conditions is carried out, where an analytical model incorporating the cross-saturation effect has been used to predict the performance of the SEIG.
Abstract: A detailed investigation is carried out on the transient behaviour of the short shunt self-excited induction generator (SEIG) system subjected to different dynamic conditions. An analytical model incorporating the cross-saturation effect has been used to predict the performance of the SEIG. Experimental results are presented along with the simulated values. Response of the system to disturbances reveals excellent transient performance. The system has good overload capability and is free from operational problems related with short circuits and loss of excitation. By presenting typical results of a 3.7 kW, three-phase squirrel cage machine, the suitability of the short shunt SEIG for a simple, rugged and self regulated stand-alone generating system, is established. >
TL;DR: In this article, a flux-weakening control specifically designed for surface-mounted permanent magnet machines is presented. But the proposed method does not require knowledge of the machine or system parameters and is not suitable for high-speed machines.
Abstract: Permanent-magnet synchronous machines fed from current-regulated converters feature nearly ideal performance at low-to-moderate speeds. However, as rotor speed increases the back emf rises which results in loss of current regulation and decreased torque. In buried-magnet machine drives, flux weakening is often used to extend the speed range. This paper sets forth a flux-weakening control specifically designed for surface-mounted permanent-magnet machines which is simple and does not require knowledge of the machine or system parameters. The proposed method is demonstrated both experimentally and through the use of computer simulation. >
TL;DR: In this article, the authors discuss some typical design scenarios and the formulation of designs using the knowledge-based design tool IRES-KB with the aid of KAPPA-PC development tools.
Abstract: The wide variety of renewable energy resources and their highly site-specific and variable nature, coupled with different types and qualities of energy needs, pose a challenging problem to the designers of integrated renewable energy systems (IRES). This paper discusses some typical design scenarios and the formulation of designs using the knowledge-based design tool IRES-KB with the aid of KAPPA-PC development tools. A remote village with no electrical grid connection is chosen for this study since renewables are most likely to make their greatest impact in such locations. The versatility of IRES-KB is brought out in the discussion of the results.
TL;DR: This paper presents a step-by-step system identification approach to estimate the parameters of a three-phase salient-pole synchronous machine rated at 5 kVA from online small disturbance responses using the maximum likelihood algorithm.
Abstract: This paper presents a step-by-step system identification approach to estimate the parameters of a three-phase salient-pole synchronous machine rated at 5 kVA from online small disturbance responses. The machine equivalent circuit model linear parameters and the nonlinear saturated parameters are estimated. The estimation is performed using the maximum likelihood algorithm. Simulation studies based on the online measured small and large dynamic disturbances are performed to validate the accuracy of the identified machine model including the saturation. >
TL;DR: In this paper, a bispectrum analysis is introduced for three-phase induction machine faults identification and condition monitoring, which can be successfully applied to machine asymmetric faults, machine rotation speed and stator winding fault analysis and identification.
Abstract: Bispectrum analysis is introduced for three-phase induction machine faults identification and condition monitoring. Bispectrum analysis is capable of providing more information than power spectrum analysis. In the present investigation, machine vibration signals operating at different rotating speed and degree of unbalance are thoroughly analyzed. Very promising results were obtained and presented. The results and analysis indicate that bispectrum analysis can be successfully applied to machine asymmetric faults, machine rotation speed and stator winding fault analysis and identification.
TL;DR: In this article, the authors provide data and projections on emissions from electricity generation in selected countries around the world, makes some comparisons and suggests possible options, and make some comparisons between the two countries.
Abstract: Efforts are now underway in the industrialized countries to significantly reduce the emission of greenhouse and acid rain gases from power plants. However, indications are that rapid growth in the developing countries is quickly replacing what is being eliminated. This paper provides data and projections on these emissions from electricity generation in selected countries around the world, makes some comparisons and suggests possible options. >
TL;DR: In this article, a method for determining the thermal coefficients in electrical machines based upon a new linear lumped parameter model and accurate measurement of temperature and loss densities within the machine is presented.
Abstract: A method for determining the thermal coefficients in electrical machines based upon a new linear lumped parameter model and accurate measurement of temperature and loss densities within the machine is presented. The thermal network is reduced to a system of simultaneous equations. The equivalent thermal coefficients are determined by solving the equations using a singular value decomposition (SVD) method. Results obtained for a 4 kW totally enclosed fan cooled (TEFC) induction motor are presented and compared with established data. The technique is suitable for establishing more accurate thermal coefficients for composite materials and combinations of complex geometrical form. >
TL;DR: In this article, an ANN was used to memorize the reverse input/output mapping of the synchronous machine to provide good damping for both local and inter-area modes of oscillations.
Abstract: The effectiveness of an artificial neural network (ANN), functioning as a power system stabilizer (PSS), in damping multi-mode oscillations in a five-machine power system environment is investigated in this paper. Accelerating power of the generating unit is used as the input to the ANN PSS. The proposed ANN PSS using a multilayer neural network with error-backpropagation training method was trained over the full working range of the generating unit with a large variety of disturbances. The ANN was trained to memorize the reverse input/output mapping of the synchronous machine. Results show that the proposed ANN PSS can provide good damping for both local and inter-area modes of oscillations. >
TL;DR: In this paper, a robust controller for generator excitation systems is proposed to improve the steady-state and transient stabilities of generator generators by treating the nonlinear characteristics of the generator as model uncertainties, and taking into account such uncertainties at the controller design stage using a robust control methodology.
Abstract: This paper deals with the design and evaluation of a robust controller for generator excitation systems to improve the steady-state and transient stabilities. The unique approach used is to first treat the nonlinear characteristics of the system as model uncertainties, and then to take into account such uncertainties at the controller design stage using a robust control methodology. The performance of the controller has been evaluated extensively by nonlinear simulation. It is concluded that the robust controller provides better damping to the oscillatory modes of the system than the conventional PSS in all the cases studied. >
TL;DR: In this paper, the steady-state performance of single-phase induction generators based on the principles of harmonic balance is analyzed and experimental results are provided to justify the analytical approach and steady state calculations.
Abstract: The modeling and steady-state performance of single-phase induction generators based on the principles of harmonic balance is set forth in this paper. Magnetizing flux linkage saturation and flux dependent core loss resistances are included. Experimental results are provided to justify the analytical approach and steady-state calculations. >
TL;DR: An object-oriented power plant control system design tool is proposed in this paper which integrates modelling, analysis, design, simulation, and graphical user interface into one software suite and can be conveniently used to study power plant dynamic behaviour and develop modern control algorithms.
Abstract: An object-oriented power plant control system design tool is proposed in this paper which integrates modelling, analysis, design, simulation, and graphical user interface into one software suite. This facility can be conveniently used to study power plant dynamic behaviour and develop modern control algorithms. A design example of an adaptive governor shows the effectiveness of the design tool. >
TL;DR: In this article, a /spl mu/ synthesis based control design methodology is presented to deal with the parametric uncertainties in power system modeling and the design process involves a nominal power system model with uncertainty descriptions which represent the parameter perturbation of synchronous generator around its nominal operating point.
Abstract: Linear control design system stabilizers (PSSs) require the nominal power system model to be formulated as a linear time invariant system. Power system operating conditions vary with system configurations and loading conditions and coefficients in nominal system model change in a complex manner. A /spl mu/ synthesis based control design methodology is presented in this paper to deal with the parametric uncertainties in power system modeling. The design process involves a nominal power system model with uncertainty descriptions which represent the parameter perturbation of synchronous generator around its nominal operating point The proposed excitation controller enables the power system to be stable over a wide range of power system operating conditions. Simulation results both in the frequency domain and in time domain are presented. >
TL;DR: In this paper, the use of air-gap torque to measure efficiency and load changes of electric motors in the field is proposed. But, the method is applicable for induction motors as well as brushless-DC adjustable-speed and synchronous motors.
Abstract: Although air-gap torque equations have been known for several decades, this is the first known paper suggesting the use of air-gap torque to measure efficiency and load changes of electric motors in the field. Very few assumed values are required, and the method is applicable for induction motors as well as brushless-DC adjustable-speed and synchronous motors. Theoretical foundation for this proposed method is presented. Experiments conducted on an adjustable-speed motor show the validity and potential of this approach. >
TL;DR: In this paper, the nonlinear characteristics of the turbine are first modelled as multiplicative uncertainties and an optimal robust governor is designed by taking into account such uncertainties explicitly, which guarantees the stability and the performance of the speed control loop for the entire turbine operating range.
Abstract: Design and analysis of a hydraulic turbine generator governor using optimal robust control methodology are presented. The approach is unique in the sense that the nonlinear characteristics of the turbine are first modelled as multiplicative uncertainties; and an optimal robust governor is designed by taking into account such uncertainties explicitly. The advantage of this approach is that the designed governor will guarantee the stability and the performance of the speed control loop for the entire turbine operating range. The performance of the new governor is shown to be superior to that of the conventional PID controller during large load disturbances. The resulting governor is only a third order. Hence, it has the same level of complexity as any other electrical-hydraulic governor in use today. >
TL;DR: In this paper, a direct modeling method for analysis of a switched reluctance machine (SRM) system including the power electronic converter, control and the nonlinear magnetic field of the SRM is established.
Abstract: Transient analysis of a switched reluctance machine (SRM) system is complicated by its unconventional nonsinusoidal operation and highly nonlinear characteristics. The analysis, however, is essential not only for optimizing the SRM magnetic structure but also for proper control of the associated power electronic circuit. In this paper, a direct modeling method for analysis of a SRM system including the power electronic converter, control and the nonlinear magnetic field of the SRM is established. The finite element method is used to model the nonlinear magnetic field, and is coupled to the circuit model of the SRM overall system. Assumptions of current density in FEA and various types of flux-current characteristics in circuit analysis are eliminated. With simultaneous computation over the entire system, the computer model provides abundant information regarding the SRM system. Experimental results are presented to prove the accuracy of the model. >
TL;DR: In this paper, an on-line parameter identification and full-scale experimental verification for large synchronous machines (>50 MVA) is presented, where a step change of excitation is imposed to a generator when the machine is in normal operation.
Abstract: An on-line parameter identification and full-scale experimental verification for large synchronous machines (>50 MVA) is presented in this paper. A step change of excitation is imposed to a generator when the machine is in normal operation. The transient voltages, currents and the power angle are recorded. Based on the large disturbance equations and using the measured power angle as an observation argument in an identification algorithm, the synchronous machine electrical parameters (x/sub d/, x/sub d/', x/sub d/", T/sub do/', T/sub do/", x/sub q/, x/sub q/", T/sub qo/") and mechanical parameters (H,D) are obtained. In addition, the system parameters (equivalent infinite bus voltage V/sub bus/ and line reactance x/sub e/) are identified as well. The proposed method has been repetitively applied to turbogenerators and hydrogenerators with capacities up to 300 MVA. In particular, a field test has been conducted on a system with a capacity of 15000 MVA. The experimental results from all of the full-scale tests are consistent and the effectiveness of the proposed on-line identification method is verified. The plant experiences indicate that by adopting the identified parameters, the stability margin of the generator can be improved by up to 5%, resulting in 30-50 MVA more power generation. >