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This paper describes a procedure for calculating generator circuit breaker duty. Currently, commercially available software products help in determining the duty for a general-purpose circuit breaker. However, further calculations are needed to determine the duty for a special-purpose generator circuit breaker. IEEE Std C37.010-1999 provides the calculation procedure for general-purpose circuit breakers. In order to evaluate a special-purpose generator circuit breaker, this paper will expand the steps and methodology used in IEEE C37.010-1999 by presenting a procedure and detailed calculations for finding a duty multiplication factor based on the test $X/R$ ratio of generator circuit breakers given in IEEE C37.013-1997 (Standard for AC High-Voltage Generator Circuit Breakers Rated on a Symmetrical Current Basis). This way, engineers can still make a generator circuit breaker assessment although generator circuit breaker evaluation module is not included in many commercial short-circuit programs. [ABSTRACT FROM AUTHOR]

In this paper, a flexible optimization-based framework for intentional islanding is presented. The decision is made of which transmission lines to switch in order to split the network while minimizing disruption, the amount of load shed, or grouping coherent generators. The approach uses a piecewise linear model of AC power flow, which allows the voltage and reactive power to be considered directly when designing the islands. Demonstrations on standard test networks show that solution of the problem provides islands that are balanced in real and reactive power, satisfy AC power flow laws, and have a healthy voltage profile. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel iterative approach to contingency filtering for corrective security-constrained optimal power flow (CSCOPF) problems that include conflicting contingencies. The rescheduling index (the minimum of the maximal controllable rescheduling value in the post-contingency state) becomes the filtering index in a modified CSCOPF (MCSCOPF) model designed to deal with conflicting contingencies. Moreover, a decomposed parallel interior point method (DPIPM) is developed to factorize the primal-dual system into blocks according to contingency scenarios and compute these blocks with a coarse-grained parallelism. The feasibility and effectiveness of the proposed approach is verified by solving for conflicting contingencies in a standard testing system and a real-world system. [ABSTRACT FROM PUBLISHER]

In a recent work, the authors computed generator parameters from a load-rejection test based on what they called hybrid state model of the synchronous machine. The state matrices were presented in compact numerical form and may prove tedious to implement. Such a model is a complicated function of the unknown machine parameter vector to be computed which is not always easy to comprehend in an identification process for engineering applications. In this paper, therefore, the decoupled property of the so-called hybrid model along with the application of the complete well-known solution of the linear control systems theory is used to derive time-variant analytical waveforms of the phase voltages and the field current following a generator tripping (load rejection) and an open stator field short-circuit tests in terms of the generator parameters. In the cross-identification approach, the field short-circuit test is used to compute the generator d-axis parameters while the q-axis parameters are obtained from the load-rejection test q-axis data. The proposed identification technique is successfully applied for the parameter identification of a 4-pole 1.5-kVA, 208-V, and 60-Hz saturated laboratory synchronous generator. [ABSTRACT FROM PUBLISHER]

This paper proposes a new framework in calculating the ex post prices for the spot electricity market. The proposed method finds a set of prices that are as consistent as possible with the actual outputs of resources correctly following their dispatch instructions. Two alternative consistency metrics are proposed in the paper. One measures the difference between the actual performance of an individual resource and its bid-based profit-maximizing response to the ex post prices in a perfectly competitive market. Another measures the difference between the ex post price and the price that supports the actual response of an individual resource. Compared to the existing approaches adopted in the real-time electricity markets in the U.S., the proposed method solves the ex post energy and ancillary service prices directly and simultaneously. It does not require heuristics that are hard to justify, and has a much clear definition for the pricing problem than the existing approaches do. Moreover, the proposed approach is flexible in the price control required by the market operators. Numerical examples are presented to further demonstrate the validity of this approach. [ABSTRACT FROM AUTHOR]

This paper presents an online procedure for the automatic search of the maximum-torque-per-ampere operating region for a synchronous reluctance motor. The algorithm is based on a signal-injection method with a random-based perturbation pattern applied to a common direct-torque-controlled drive. Among motor parameters, only the stator resistance is required to perform the automatic procedure. Simulations and experimental results are presented in the paper, demonstrating the benefits of the proposed algorithm. The solution is easily extended to any ac drive. [ABSTRACT FROM PUBLISHER]

A hybrid generator with a photovoltaic energy conversion system is proposed with supercapacitors and lead-acid batteries in a dc-coupled structure. The objective of this system is to supply the prescribed reactive and active power to the grid. This paper focuses on the strategy, which makes it possible to ensure a high battery state of charge and overcharge security by designing a dedicated local control system. A continuous dynamic model and a control design of the power system studied are proposed in this paper. Simulation and experimental results illustrate the performances obtained. [ABSTRACT FROM AUTHOR]

This paper considers the problem of selecting a set of residual generators for inclusion in a model-based diagnosis system, while fulfilling fault isolability requirements and minimizing the number of residual generators. Two novel algorithms for solving the selection problem are proposed. The first algorithm provides an exact solution fulfilling both requirements and is suitable for small problems. The second algorithm, which constitutes the main contribution, is suitable for large problems and provides an approximate solution by means of a greedy heuristic and by relaxing the minimal cardinality requirement. The foundation for the algorithms is a novel formulation of the selection problem which enables an efficient reduction of the search-space by taking into account realizability properties, with respect to the considered residual generation method. Both algorithms are general in the sense that they are aimed at supporting any computerized residual generation method. In a case study the greedy selection algorithm is successfully applied in an industrial sized automotive engine system. [ABSTRACT FROM AUTHOR]

The interturn short circuit of field windings in synchronous machines will cause the field current increasing, reactive power output decreasing as well as the aggravation of vibration. In this paper, by using the multiloop theory and analyzing the steady-state characteristics of stator and rotor fault currents, the steady-state expression of each loop current is obtained, and then differential equations in steady-state system are reduced into linear equations; according to the principal that components of the same frequency are equal, the steady-state solution of the ac and dc components of each loop current can be obtained and the steady-state calculation of the fault can be achieved rapidly. The field winding interturn short-circuit experiments have been carried out on a 12-kW synchronous machine with three pairs of poles, the results of which agree well with that of steady-state simulations. Based on the aforementioned characteristics analysis and simulation results, an online fault monitoring method in view of the unbalanced current effective value of stator branches is proposed, by which the fault characteristics can be extracted to the highest degree and short circuit with small turns in field winding can be sensitively reflected. [ABSTRACT FROM AUTHOR]

This paper proposes a hula-hoop energy-harvesting system that integrates a hula-hoop motion transformer with an electromagnetic generator. The hula-hoop motion transformer converts the linear motion from environment, machinery, or even human body into rotational one under specifically designed dynamic conditions. Then, the system can generate power through electromagnetism after combining the electromagnetic generator with the rotational motion. The equations prescribing the relation between induced voltage and power for the system are derived according to Faraday's theory. Meanwhile, the physical model of energy-harvesting system is established and the governing dynamic equations are derived as well via the Lagrange's equations. Good agreement of induced voltage and power between theoretical and experimental results is obtained. The maximum power that the system can generate is approximately 5 mW when the frequency and amplitude of the external excitation are 8 Hz and 11.2 N, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a receding-horizon multi-step optimization is proposed to correct nonviable transmission voltages and prevent long-term voltage instability. The proposed control scheme is based on real-time control, inspired by model predictive control, and steady state power-flow-based equations. In order to anticipate load behavior and avoid using dynamic equations in the control scheme, explicit formulations are used to model evolution of load with time. The simulation results of the proposed technique are presented on the Nordic32 test system. [ABSTRACT FROM PUBLISHER]

This paper presents the application of dynamic phasor analysis to understand the effect of passive phase imbalance schemes on the torsional modes of a turbine-generator system. These schemes have been proposed in the previous literature as subsynchronous resonance (SSR) countermeasures. Dynamic phasor analysis of the unbalanced system yields a linearized and time-invariant model which facilitates eigen-analysis. It is seen that large levels of phase imbalance can cause a significant movement in the subsynchronous network modal frequencies. Therefore, in specific cases, SSR can be avoided due to detuning of the torsional and network modes. However, the analysis also shows that damping torque in a series compensated network is negative at subsynchronous frequencies even with phase imbalance. Therefore, phase imbalance cannot be a general countermeasure to the problem of SSR. [ABSTRACT FROM AUTHOR]

Multirobot systems represent an enticing area of research with numerous real-world applications. Teams of multiple robots can achieve tasks that are more difficult or even impossible for a single robot, e.g., environment exploration, search and rescue, or surveillance operations. In a previous work, the authors developed a system for the single-operator manual control of a multirobot system. However, such teleoperation systems commonly suffer from inadequate perception of the remote environment. This paper extends the previously presented work by adding a fuzzy force-feedback (FFF) augmentation for the manual control of a multirobot system. The FFF augmentation delivers additional information to the operator. Moreover, it guides the operator toward the smooth control of the robotic group. The force feedback was generated by a system of fuzzy controllers monitoring the state of the multirobot group. The performance of the system was evaluated in a virtual environment, and the recorded forces were explored in various scenarios. The force-feedback augmentation demonstrated the following improvements: 1) operator's increased obstacle awareness and 2) improved maneuvering performance. [ABSTRACT FROM PUBLISHER]

This paper is focused on structural approaches to study diagnosability properties given a system model taking into account, both simultaneously or separately, integral and differential causal interpretations for differential constraints. We develop a model characterization and corresponding algorithms, for studying system diagnosability using a structural decomposition that avoids generating the full set of system analytical redundancy relations. Simultaneous application of integral and differential causal interpretations for differential constraints results in a mixed causality interpretation for the system. The added power of mixed causality is demonstrated using a Reverse Osmosis Subsystem from the Advanced Water Recovery System developed at the NASA Johnson Space Center. Finally, we summarize our work and provide a discussion of the advantages of mixed causality over just derivative or just integral causality. [ABSTRACT FROM PUBLISHER]

It is difficult to forecast renewable energy resources due to their variability. High uncertainty of the resources increases the concern about the reliable operation of the electric power system. Storage devices have been considered a candidate to control variable energy resources, and most studies on storage devices are performed in the economic dispatch. Therefore, electric power adequacy may be an issue. In this paper, a new approach in the optimal power flow framework is proposed for deploying storage devices, and the feasibility and economic impact analyses are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we present a new Matlab-based toolbox for power system analysis, called MatDyn. It is open-source software, and available for everyone to download. Its design philosophy is based on the well-known open-source Matlab toolbox MATPOWER , but its focus is transient stability analysis and time-domain simulation of power systems, instead of steady-state calculations. [ABSTRACT FROM AUTHOR]

The precise information of permanent-magnet synchronous generator (PMSG) rotor position and speed is essentially required to operate it on maximum power points. This paper presents an adaptive network-based fuzzy inference system (ANFIS) for speed and position estimation of PMSG, where an ANFIS-based model reference adaptive system is continuously tuned with actual PMSG to neutralize the effect of parameter variations such as stator resistance, inductance, and torque constant. This ANFIS-tuned estimator is able to estimate the rotor position and speed accurately over a wide speed range with a great immunity against parameter variation. The proposed system consists of two back-to-back connected inverters, where one controls the PMSG, while another is used for grid synchronization. Moreover, in the proposed study, the grid-side inverter is also utilized as harmonic, reactive power, and unbalanced load compensator for a three-phase, four-wire (3P4W) nonlinear load, if any, at point of common coupling (PCC). This enables the grid to always supply/absorb a balanced set of fundamental currents at unity power factor. The proposed system is developed and simulated using MATLAB/SimPowerSystem (SPS) toolbox. Besides this, a scaled laboratory hardware prototype is developed and extensive experimental study is carried out to validate the proposed control approach. [ABSTRACT FROM PUBLISHER]

Analysis of breakdown mechanism in gas-insulated trigatron switches is important for the engineering design and function prediction. Based on the gas discharge theory, a physical model was proposed to estimate the breakdown time for gas-insulated trigatron switches. And the model can explain the breakdown in the trigatron switches with two modes of the breakdown mechanism, i.e., fast breakdown mode (FBM) and slow-breakdown mode (SBM). Based on Raether breakdown criterion, this paper discussed the factors affecting on the E-field enhancement. The E-field is composed of the static E-field and the dynamic E-field, which leads to transformation of breakdown mechanism. Some coefficients could be determined by experiment and simulation, which are helpful to get the quantitative solution of breakdown time. [ABSTRACT FROM AUTHOR]

This paper presents accurate electromechanical analysis of piezoelectric beam-type transducers with interlayer slip, based on the Euler?Bernoulli beam theory. The closed solutions of two different kinds of piezoelectric beam-type transducers under external harmonic loads are derived. The effects of the interfacial slip parameter on the responses of the transducers are discussed. Comparisons with other related experimental and theoretical results are also given, and good agreement is found. [ABSTRACT FROM AUTHOR]

For the nonlinear power flow problem specified with standard PQ, PV, and slack bus equality constraints, we present a sufficient condition under which the specified set of nonlinear algebraic equations has no solution. This sufficient condition is constructed in a framework of an associated feasible, convex optimization problem. The objective employed in this optimization problem yields a measure of distance (in a parameter set) to the power flow solution boundary. In practical terms, this distance is closely related to quantities that previous authors have proposed as voltage stability margins. A typical margin is expressed in terms of the parameters of system loading (injected powers); here we additionally introduce a new margin in terms of the parameters of regulated bus voltages. [ABSTRACT FROM PUBLISHER]