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Interfacing of ac electrical machine models in power system transient simulation programs is receiving increasing attention in the literature. Models based on the voltage-behind-reactance (VBR) formulation have been recently proposed to achieve a direct interface with external power networks. However, the rotor-position-dependent interfacing inductances due to dynamic saliency in synchronous machine models increase the computational cost of the overall system solution and limit the application of most VBR formulations. This paper presents new methods for elimination of dynamic saliency using continuous- and discrete-time approximation techniques to achieve explicit formulations. The proposed models have simple interfacing circuit consisting of decoupled constant-parameter RL branches. The new models are implemented in MATLAB/Simulink and the PLECS toolbox, and are shown to offer simple and easy-to-use interface, high accuracy, and numerical efficiency as compared to the existing models. The proposed models can find wide application in common state-variable-based transient simulation programs. [ABSTRACT FROM PUBLISHER]

Standby generation systems in low- and medium-voltage applications connect to the utility power system in a number of different ways. Typically, an automatic transfer switch is a part of most power system connections. Engineers can choose three- or four-pole transfer switches for the intertie point. The application's sensitivity to a power interruption during switching helps determine transfer-switch selection. The transfer switch can be contactor or circuit breaker based, or it can be a bypass design. At medium voltage, special requirements must be considered. Ultimately, the correct arrangement must be chosen depending upon grounding locations and neutral bonding. Incorrect power system bonding and grounding can cause unwanted transients or hazardous multiple grounds (improper ground-fault protection) depending upon the transfer-switch selection. Improper design can create unintentional current paths and defeat ground-fault protection. A transfer switch must be chosen for robust operation and maintenance at the beginning of the design process. [ABSTRACT FROM PUBLISHER]

Electrothermal coordination (ETC) is introduced for cable based transmission grids. ETC is the term covering operation and planning of transmission systems based on temperature, instead of current. ETC consists of one part covering the load conditions of the system and one covering the thermal behavior of the components. The dynamic temperature calculations of power cables are suggested to be based on thermoelectric equivalents (TEEs). It is shown that the thermal behavior can be built into widely used load flow software, creating a strong ETC tool. ETC is, through two case scenarios, proven to be beneficial for both operator and system planner. It is shown how the thermal behavior can be monitored in real-time during normal dynamic load and during emergencies. In that way, ETC enables cables to be loaded above their normal rating, while maintaining high reliability of the system, which potentially can result in large economic benefits. [ABSTRACT FROM PUBLISHER]

This paper presents a fully analog demonstrator based on power system emulation for high-speed power system stability analysis. A benchmark using a fixed two-machine topology has been implemented. The characteristics of the emulated components (i.e., generators and transmission lines) are reprogrammable and short circuits can be emulated at different distances from the generator. This first realization is limited to transient stability analysis, as the main focus during design was put on computation speed. Indeed, the emulated phenomena are 10\thinspace000 times faster than real time. Moreover the authors aim to emphasize that such highly dedicated computation architectures are not only competitive in terms of speed, but also in terms of modularity. [ABSTRACT FROM PUBLISHER]

This paper presents an ultra-high speed hardware platform dedicated to power system dynamic (small signal) and transient (large signal) stability. It is based on an intrinsic parallel architecture which contains hybrid mixed-signal (analog and digital) circuits. For a given model, this architecture overcomes the speed of the numerical simulators by means of the so-called emulation approach. Indeed, the emulation speed does not depend on the power system size. This approach is nevertheless not competing against high-performance numerical simulators in term of accuracy and model complexity. It targets to complement the numerical simulators with the advantage of speed, portability, low cost and autonomous functioning. The proof of concept is a flexible and modular 96-node hardware platform. It is based on a reconfigurable array of power system buses called Field Programmable Power Network System (FPPNS). Details on this hardware are given. Two benchmark topologies with, respectively, 17 nodes and 57 nodes are provided. Comparisons with a digital simulator are done in terms of speed and accuracy. The calibration of the system is explained and different applications are proposed and discussed. The promising results of this hardware platform show that the design of a fully integrated solution containing hundreds of power system buses can be achieved in order to provide a low cost solution. [ABSTRACT FROM PUBLISHER]

This paper proposes two methods to speed up the demanding time-domain simulations of large power system models. First, the sparse linear system to solve at each Newton iteration is decomposed according to its bordered block diagonal structure in order to solve only those parts that need to be solved and update only submatrices of the Jacobian that need to be updated. This brings computational savings without degradation of accuracy. Next, the Jacobian structure is further exploited to localize the system response, i.e., involve only the components identified as active, with an acceptable and controllable decrease in accuracy. The accuracy and computational savings are assessed on a large-scale test system. [ABSTRACT FROM PUBLISHER]

This paper presents a mixed-integer linear programming (MILP) reformulation of the thermal unit commitment (UC) problem. The proposed formulation is simultaneously tight and compact. The tighter characteristic reduces the search space and the more compact characteristic increases the searching speed with which solvers explore that reduced space. Therefore, as a natural consequence, the proposed formulation significantly reduces the computational burden in comparison with analogous MILP-based UC formulations. We provide computational results comparing the proposed formulation with two others which have been recognized as computationally efficient in the literature. The experiments were carried out on 40 different power system mixes and sizes, running from 28 to 1870 generating units. [ABSTRACT FROM PUBLISHER]

Numerical methods play an important role in improving efficiency for power system time-domain simulation. Motivated by the need to perform high-speed extended-term time-domain simulation (HSET-TDS) for online purposes, this paper presents design principles for numerical solvers of differential algebraic systems associated with power system time-domain simulation, focusing on DAE construction strategies, integration methods, nonlinear solvers, and linear solvers. We have implemented a design appropriate for HSET-TDS, and we have compared the proposed integration method, Hammer-Hollingsworth 4 (HH4), with Trapezoidal rule in terms of computational efficiency and accuracy, using the New England 39-bus system, an expanded 8775-bus system, and PJM 13 029-bus system. [ABSTRACT FROM PUBLISHER]

A method is proposed in this paper to determine the frequency-dependent loss of power transformer for very fast transient simulation. The attenuation factors and the corresponding natural frequencies of the transformer at measurable range were extracted using measured power transformer network functions and the vector-fitting method (VFM). The approximate frequency-dependent formula of attenuation factors was established by analyzing the theoretical transformer model. Then, the parameters in the formula were optimized by fitting the real part (attenuation factors) and imagine part (natural angular frequencies) of poles obtained by VFM. The time-domain simulation process can be divided into two steps. First, the lossless transformer transient response, which could be expressed as the sum of the natural frequency components, is obtained by solving the network differential equations. Second, the attenuation factors calculated by the approximate formula are added directly on the corresponding frequency components. By comparing with the measured results, it is shown that the proposed fitting formula for calculating the attenuation factors could improve the simulation accuracy in comparison with the existing methods. [ABSTRACT FROM AUTHOR]

This paper proposes the use of Sprott chaos synchronization (SCS)-based voltage relays for fault protection in microdistribution systems (MDSs). The Sprott chaos system is used as a voltage detector to track the dynamic errors between the normal signal and disturbance signals. The proposed voltage relay is used to detect disturbances, such as serious voltage sag and swell, and uses a critical trigger time to isolate the fault section. It is proposed that the restoration strategy then restores the unfaulted but blackout zones, and confirms security operations, including load-power balance, power generation limits, voltage limits, and power-flow limits. Computer simulations are conducted by using an IEEE 30-bus power system and MDSs, to show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents three algorithms for identification of dominant inter-area oscillation paths: a series of interconnected corridors in which the highest content of the inter-area modes propagates through. The algorithms are developed to treat different sets of data: 1) known system model; 2) transient; and 3) ambient measurements from phasor measurement units (PMUs). These algorithms take feasibility into consideration by associating the network variables made available by PMUs, i.e., voltage and current phasors. All algorithms are demonstrated and implemented on a conceptualized Nordic Grid model. The results and comparison among three algorithms are provided. The applications of the algorithms not only facilitate in revealing critical corridors which are mostly stressed but also help in indicating relevant feedback input signals and inputs to mode meters which can be determined from the properties of dominant paths. [ABSTRACT FROM PUBLISHER]

The scope of this paper is the investigation of the development of fault currents in a circuit breaker (CB) during a pole-to-ground fault in a generic multiterminal HVDC cable system based on voltage-source converters. It aims to contribute to the current discussion of which requirements on breaking time and peak current HVDC CBs need to fulfill in such networks. Therefore, the fault current is broken down into the individual contributions from the different network components, and the influence of the key parameters on the development of the fault current in the CB of the faulted cable is illustrated. [ABSTRACT FROM PUBLISHER]

The current transformer (CT) is prone to the magnetic core saturation during the power system faults. The CT saturation can prolong and/or miscoordinate operation of relays and thus may result in the system stability problems and equipment damage. This paper proposes a new hardware-based method to suppress or prevent the CT saturation. The proposed approach is based on adding a controllable resistor at the CT secondary circuit which dynamically generates a flux to oppose the time varying flux associated with the decaying dc component of the fault current. Part I of this two-part paper presents the concept, the controllable-switch operational strategy, the design steps, and the parameters of the controllable resistor. Part II provides a comprehensive evaluation of the controllable resistor based on offline digital time-domain simulation and control-hardware-in-the-loop studies. [ABSTRACT FROM PUBLISHER]

The facilitation of maintenance of hydrokinetic energy conversion systems is supported by minimizing the exposure of components located underwater. The described onshore converter station's design was motivated by this thought. The station includes the functions of power-electronic ac–dc–ac conversion and connection to the electric grid, thus leaving only turbine, variable-frequency ac generator, and connecting ac cable exposed underwater. A challenge in this configuration are potential electromagnetic traveling waves on the ac cable. They can be triggered through power-electronic pulses and cause significant overvoltages at the generator side. A key contribution is the modification of existing mathematical equations resulting in a novel methodology for expressing the overvoltages as a function of the traveling time and steepness of the pulses. This serves as the basis for an overvoltage reduction method involving the targeted selection of parameters of a suitable filter. It is applicable to distributed tidal energy and instream river conversion and electric drive systems involving long ac cables. The resulting overall design is validated through electromagnetic transients simulation. The results substantiate the proposed methodology of analysis and design. [ABSTRACT FROM PUBLISHER]

The power-flow (PF) solution is a fundamental tool in power system analysis. Standard PF formulations are based on the solution of a system of nonlinear equations which are computationally expensive due to the iterations needed. On the other hand, distribution-system (DS) automation algorithms should be fast enough to meet real-time performance. The conventional load representation, as constant P–Q, becomes less accurate as we get closer to the actual load's level. In this paper, a new load model is proposed which represents the loads' voltage dependency. A simple curve-fitting technique is used to derive a voltage-dependent load model which splits the load as a combination of an impedance and a current source. With this representation and some numerical approximations on the imaginary part of the nodal voltages, it is possible to formulate the load-flow problem as a linear power-flow (LPF) solution which does not require iterations. The approximation has been tested in systems up to 3000 nodes with excellent results. The LPF formulation is particularly important in the context of optimization algorithms for automated smart distribution systems. The extension of the technique to unbalanced distribution systems will be presented in future work. [ABSTRACT FROM PUBLISHER]

Power system model quality is key to safe and reliable electricity delivery. A novel method using disturbance data recorded by phasor measurement units (PMUs) is proposed to improve the integrity of dynamic models, which consists of both model validation and model parameter identification. In the model validation step, event playback is applied to simulate the model's response for a rigorous comparison with measured response captured by PMUs. A large mismatch indicates model deficiency. In the parameter identification step, an automatic calibration method using the extended Kalman filter (EKF) techniques and trajectory sensitivity analysis is formulated to save significant effort and time from manual tuning. Case studies are presented to demonstrate that the proposed method has adequate performance for model validation and parameter calibration in terms of accuracy, good convergence speed and robustness with respect to measurement noises. The proposed method is cost-effective and complements traditional equipment testing for improving dynamic model quality. [ABSTRACT FROM PUBLISHER]

A distance relaying scheme is susceptible to power swing. To avoid unintended trip operation during such conditions, a power swing blocking function is utilized in distance relays. However, if a fault occurs during power swing, the relay should detect the fault and trip as soon as possible. The detection of fault in a series-compensated line during the power swing is further complicated due to complex transients produced by series capacitor and the metal–oxide varistor (MOV) protecting it. This paper proposes a negative-sequence current-based technique for detecting all types of faults during the power swing in a series-compensated line. The technique is tested for different series-compensated systems including a 9-bus 3-machine power system. Different types of faults: symmetrical, asymmetrical, and high resistance occurring during the power swing are simulated through EMTDC/PSCAD to test the algorithm. The method is compared with available techniques and found to be accurate and fast. [ABSTRACT FROM PUBLISHER]

Resonant overvoltages caused by transformer energization in relatively weak systems, especially during power system restoration, are investigated in this paper. These transient overvoltages may result in failures, especially for surge arresters. A theoretical analysis is performed to obtain the transformer inrush current harmonics and the transmission-line lengths for which the harmonic resonance is likely to occur. The temperature rise of surge arresters is proposed as an index to diagnose a harmonic resonance case. An appropriate electrothermal model for metal–oxide surge arresters is developed using the thermal model and proposed combined electrical model. Comprehensive transient simulation studies are performed to find out the harmonic resonance cases using the proposed index. Obtained simulation results are in good agreement with the analytical results. To reduce such harmonic resonance cases, controlled closing of the transformer can be utilized. In this paper, the proper instants for transformer energization are proposed in such a way that the overvoltage is reduced to acceptable values. [ABSTRACT FROM PUBLISHER]

The reconfigurable-hardware real-time power system simulator (RH-RTS) is a field-programmable gate-array (FPGA)-based real-time simulator that is developed based on the concept of simulators hardware reconfigurability (i.e., to change the underlying hardware architecture of the simulator to accommodate various power system topologies). The uniqueness of the RH-RTS is the underlying hardware architecture. The RH-RTS has a massively parallel customized hardware architecture that is tailored to the solution of the mathematical model of the power system under consideration. The RH-RTS enables the simulation of large power systems with a computation-time per simulation time-step in the range of tens of nanoseconds. Not only does the RH-RTS provide a means for real-time operation (e.g., for closed-loop testing of physical control/protection platforms in hardware-in-the-loop (HIL) configuration), it also provides a means for faster-than-real-time operation (e.g., for statistical switching studies). This paper provides validation and evaluation of the performance of the RH-RTS. This paper presents a case study involving the simulation of a power system in both real time and faster than real time. The computation time per simulation time-step is as low as 24 ns, for realistic size systems, which is, by far, the lowest computation time reported in the technical literature. [ABSTRACT FROM PUBLISHER]

Real-time frequency estimation in three-phase power systems is revisited from the state space point of view, in order to provide a unified framework for frequency tracking in both balanced and unbalanced system conditions. This is achieved by using a novel class of widely linear complex valued Kalman filters, which provide unbiased frequency estimation and are faster converging and more robust to noise and harmonic artifacts than the existing methods. It is shown that the Clarke's transformed three-phase voltage is circular for balanced systems and noncircular for unbalanced ones, making the proposed widely linear estimation perfectly suited both to identify the fault and to provide accurate estimation in unbalanced conditions, critical issues where standard models typically fail. The analysis and simulations show that the proposed model outperforms the recently introduced widely linear stochastic gradient-based frequency estimators, based on the augmented complex least mean square. Comprehensive simulations on synthetic and real-world power system data, in both balanced and unbalanced conditions, support the approach. [ABSTRACT FROM PUBLISHER]

Recently, the subspace-least mean square (S-LMS) method has been proposed for power system measurement. The high accuracy and high resolution of the S-LMS method are achieved at the cost of being computationally expensive. In this paper, the S-LMS method is enhanced in two aspects: 1) speed and 2) accuracy. The computation burden of S-LMS is significantly reduced in three ways: 1) exploring the sparsity of power system signals; 2) using an iterative multisectional search scheme; and 3) the combination of these two techniques. Further, detection of the harmonic components based on the fact that they are multiples of the fundamental frequency has been effectively employed, resulting in a more accurate and robust algorithm for fundamental and harmonic estimation in the presence of noise. The enhanced S-LMS algorithm, which detects harmonics more accurately, is more than 150 times faster than the original S-LMS if the interharmonic level is negligibly low. The dynamic behavior of the method is discussed and the method is compared with Prony and DFT. Simulations show the methods are highly resilient to off-nominal conditions and noise. [ABSTRACT FROM AUTHOR]

This paper examines testing methods and devices for sending data to line protection devices using the synchronous digital hierarchical (SDH) protocol. The paper has arisen as a result of cooperation between the Institute of Power Engineering and the Polish Power Electrical Utility Operator (PSE). The main objective of the tests was to investigate the possibilities of using already installed or new SDH telecommunication devices in power system protection systems. A range of protection functionality tests was considered along with SDH devices tests that focused on certain conditions and possible problems that may occur during normal operating conditions. [ABSTRACT FROM AUTHOR]

Protective relay settings for wind turbine generators often depend on short-circuit calculations performed using sequence network circuits in rms-based protection software. Traditional assumptions made in deriving the sequence network representation of induction machines result in some error in short-circuit calculations, which could potentially cause incorrect relay settings. A more accurate sequence network model of induction machines is derived in this paper to aid in short-circuit calculations in induction-generator-based wind plants. A rigorous mathematical approach to defining the stator short-circuit current equations under general faults is described and validated with transient simulations. The sequence network model of the induction machine is derived from the closed-form mathematical solutions. An example short-circuit calculation is performed on a simple network in this paper, and found to have a marked improvement in accuracy from traditional sequence network calculation methods for unbalanced faults. Resonant effects of power factor correction capacitors are also described. [ABSTRACT FROM AUTHOR]

Electrical excitation doubly salient (EEDS) machines and electrical excitation flux-switching (EEFS) machines, both of which have simple and robust rotor structure and good flux regulation capability, are suitable for use as generators in dc power systems that need high reliability and good constant-power operating capability. In this paper, the basic design dimensions and electromagnetic performance of the EEFS machines are analyzed and those of the EEDS machines are also given for comparison. Compared with the EEDS machine, the EEFS machine exhibits bipolar stator flux-linkage and sinusoidal back-EMF waveforms as well as larger torque density. Then, control schemes of the two machines for voltage regulation of dc power systems are discussed, and in order to improve the steady state and dynamic performance of the EEFS generator dc power system, an improved direct torque control scheme is presented. It develops the strictly linear relationship between the torque and sinusoidal value of the torque angle, and can regulate the instantaneous torque directly and smoothly without current loop. Besides, the flux weakening control of the proposed scheme is also studied. The EEFS generator dc power system with excellent dynamic performance and lower flux and torque ripple has been achieved experimentally. [ABSTRACT FROM AUTHOR]

In the field of electricity markets, the development of training tools for engineers has been extremely useful. A novel experimental economics approach based on a computational Web platform of an electricity market is proposed here for the practical teaching of electrical engineering students. The approach is designed to diminish the gap that exists between theory and practice in this field, through a methodological strategy for teaching/ learning called “simulation.” In the proposed simulation exercise, groups of students operate as market agents and have the freedom to create their own strategies. Additionally, a theoretical model and a specific simulation tool are used for the evaluation of the proposed strategies. The test system is based on the market structure of the Chilean wholesale electricity market and was tested on student groups at two universities. Based on the students' performance, the strategic behavior of agents and their impact on market price evolution are described and analyzed. Student assessment supports the conclusion that the proposed experimental economics framework offers a useful mechanism in student practical work for understanding and explaining the observed phenomena. [ABSTRACT FROM AUTHOR]

Electromagnetic Transients Program (EMTP) is widely used in power system dynamics studies. However, in most cases EMTP is found inadequate for dealing with the realistic size power systems due to the small time step resulting in relatively slow simulation speeds. To accelerate the EMTP simulations of power system dynamics, a novel frequency-adaptive methodology is proposed. In this method, a new transformation is presented. The properties of the transformation and the numerical solutions based on the transformation are discussed. The component models obtained by discretizing the differential equations at the branch level are also given which are convenient for EMTP implementation. The proposed method allows using large time steps without sacrificing accuracy, which greatly improves the simulation speed. To validate the proposed methodology, a general program has been developed. Furthermore, various case studies substantiate the claims and demonstrate the application of the method. [ABSTRACT FROM PUBLISHER]

CG Global R&D is developing a resistive-type superconducting fault current limiter (SFCL) under the Ministry of Power, National Perspective Plan for R&D in Indian Power Sector. A resistive-type 440-V 800-A single-phase SFCL is developed using YBCO tape in stage I of the project, and an 11-kV 1250-A three-phase SFCL will be developed in stage II. The 440-V 800-A SFCL is assembled with seven parallel modules. Each module has series-connected YBCO tapes to accommodate the design length. The SFCL is tested at 77 K for continuous current of few hours, fault currents at low voltage, and fault currents at 440 V up to 100 ms (5 cycles). The evaluated data will be used to develop an 11-kV 1250-A three-phase SFCL in stage II. [ABSTRACT FROM PUBLISHER]

Growing concerns about petroleum supplies and air pollution have spurred increased interest and research into hybrid electric vehicles (HEVs). While standard driving cycles are commonly used for the purpose of propulsion chain optimization, the issue of how representative they actually are is questioned. This paper proposes a novel methodology for modeling real-world vehicle missions by considering the stochastic characteristics of the driving pattern and the dependence among the variables of the mission, i.e., vehicle speed, acceleration, and road gradient. The modeling procedure is based on a Markov matrix formulation, and a simulation algorithm is implemented to generate an unlimited number of stochastic mission profiles. Two kinds of mission natures have been modeled and discussed so as to stress the mission impact on the energy consumption according to the propulsion chain sizing. The approach is then validated using the architecture of a series HEV powered by a diesel generator and batteries. The results on fuel consumption are presented, and the benefit of the proposed method over conventional approaches is argued. [ABSTRACT FROM PUBLISHER]

The purpose of this paper is to present an improved model-based controller for power turbine generators (PTGs) on a shipboard grid system. Propulsion can be accomplished by means of main diesel engines. One arrangement for the onboard power requirements of merchant ships is the PTG extract part of the exhaust gas from the main diesel engines. The speed control, however, is difficult to keep in place because of fouling conditions and variations across time. The proposed controller is evaluated by comparing it with the conventional controller in a simulation. Furthermore, the proposed controller is evaluated in a prototype. In the simulation result using the proposed controller, the limit speed overshooting as a transient response is improved by more than 25 \%. In the prototype test, the limit frequency overshooting is 0.60\%, and the settling time is 3.8 s. Hence, the proposed controller is confirmed to have an excellent property. [ABSTRACT FROM AUTHOR]

This paper describes an apparatus for generating a signal representative of steady-state and transient disturbances in three-phase waveforms of an ac electrical system as described in IEEE Std 1159-09. It can be configured as a synthesizer of randomly distorted signals for different applications: for testing the effects of disturbed grid on equipment and to generate patterns of electrical disturbances for the training of artificial neural networks, which are used for measuring power quality tasks. For the first purpose, voltage and current amplifiers are added in the output stage, which allows the generation of disturbed signals at grid level. [ABSTRACT FROM PUBLISHER]

This paper is the first of a series of publications detailing the development of an AI-based adaptive autoreclosing (AA) algorithm. In part 1, a detailed model of the Scottish 132 kV network has been constructed on a real-time digital simulator. The system model is discussed, including the network topology, line and source modeling, and the doubly fed induction generator-based wind farm model. An initial investigation on the penetration of harmonics from local wind farms is conducted using short circuit faults on two transmission lines in the network. This is necessary to ascertain to what extent wind farms may interfere with the AA scheme. Along with validating the model, the results suggest that penetration of harmonics is only significant on lines adjacent to the wind farms. [ABSTRACT FROM AUTHOR]

Following part 1, this paper describes the development and real-time testing of an adaptive autoreclosing scheme for a 132-kV system with high penetration of wind generation. Having previously established the real-time system model, this second part concentrates on the hardware and software tools used to build the relay development platform, the algorithm itself, and the testing of this algorithm. A results section documents tests of the neural–network-based algorithm and is shown to be 100% reliable. Further successful tests on a 400-kV system suggest that the algorithm is robust to other system configurations. [ABSTRACT FROM AUTHOR]

This paper presents a dynamical model for simulating combined cycle power plants to be used for assessing the plant behavior during large transients and for restoration procedures. The 80th dynamic order model considers the complex structure of the heat recovery steam generator and calculates the main variables that are critical during these transients. The model has the double purpose of studying both the plant behavior under the usual control systems as well as innovative logics and control strategies for increasing its performances in terms of regulation and emergency services. The possible use of combined cycle power plants for supplying a restoration area is finally investigated adopting different control strategies that also involve the regulating capacity of the steam turbine. [ABSTRACT FROM PUBLISHER]

Synchronized phasor measurement units (PMUs) are becoming a key element of monitoring, protection, control, and state estimation applications in power systems and are the basis for the implementation of wide area monitoring systems. This paper investigates the possibility of using a software-only precision time protocol synchronization method to synchronize different PMUs inside the same substation and how this synchronization impacts the state estimation. In this context, as a case study, the output data of the PMUs have been used to estimate the state of a portion of real power system. A laboratory experimental setup has been built to evaluate the performance achievable with the proposed synchronization solution. The results thus obtained are discussed in terms of stochastic performance. [ABSTRACT FROM AUTHOR]

Superconducting fault current limiters (SCFCLs) represent a promising solution to the problem of increasing short-circuit currents in the grid. The SCFCL is based on the fast transition from the superconducting state to the normal state, causing a sudden increase in the impedance of the network. In this paper, we simulate the behavior of resistive-type SCFCL modules. The SCFCL modules are based on MCP-BSCCO 2212 coils. The superconductor acts as a nonlinear resistance that varies with the current and the temperature. The behavior of the simulated curves is consistent with the experimental results. Short-circuit currents as high as 37 \kApeak were limited to about 10% of their peak values in the first half cycle. [ABSTRACT FROM AUTHOR]

Rapid changes and developments are being witnessed in the transformer design technologies. The phenomenal growth of power systems has put tremendous responsibilities on the industry to supply reliable and cost-effective transformers. The advent of high-temperature superconductor (HTS) materials has increased interest in research and development of superconducting transformers with major projects being carried out worldwide. The major challenges in the design and development of HTS transformers are the modeling of short-circuit and inrush currents the transformer can withstand. Even though HTS technology is claimed to be more efficient, reliable, and eco-friendly, use of HTS transformers must be appropriately verified through the proper modeling of power system network. [ABSTRACT FROM AUTHOR]

We propose a high-temperature superconducting fault-current-limiting cable (SFCLC), which is a hightemperature superconducting cable with a fault-current-limiting function. The SFCLC is expected to achieve fault-current limitation by flux-flow resistance of a long cable length. Particularly, in this paper, we focus on E–I –T characteristics of a YBCO-coated conductor at the flux-flow region. Based on the obtained E– I–T characteristics, we develop a numerical model and investigate current-limiting characteristics of the SFCLC for different cable lengths and fault conditions into a model power system. [ABSTRACT FROM AUTHOR]

Liquid storage of gaseous fuel on board of vehicles as possible alternative to high-pressure storage is receiving an increasing attention because of the higher mileage, the lower cost of the tank, and the faster refill allowable. The research effort devoted to liquid storage is also boosting the advance of cryogenics on board of vehicles, thus opening the way to the synergic use of superconductors. In such a context, superconducting magnetic energy storage (SMES) for regenerative braking may represent a possible alternative to electrochemical batteries or to developing technologies such as supercapacitors or flywheels. In this paper, the feasibility of SMES for regenerative braking on board of hybrid vehicles with cryogenic fuel tank is investigated. Possible application scenarios are discussed. The design of the superconducting magnet based on commercially available superconducting tapes and the cooling are addressed. The performance of the power control system is also investigated by means of a MATLAB/Simulink simulation model. [ABSTRACT FROM AUTHOR]

The distribution static compensator (DSTATCOM) is used for load compensation in power distribution network. In this paper, a new topology for DSTATCOM applications with nonstiff source is proposed. The proposed topology enables DSTATCOM to have a reduced dc-link voltage without compromising the compensation capability. It uses a series capacitor along with the interfacing inductor and a shunt filter capacitor. With the reduction in dc-link voltage, the average switching frequency of the insulated gate bipolar transistor switches of the DSTATCOM is also reduced. Consequently, the switching losses in the inverter are reduced. Detailed design aspects of the series and shunt capacitors are discussed in this paper. A simulation study of the proposed topology has been carried out using power systems computer-aided design simulator and the results are presented. Experimental studies are carried out to verify the proposed topology. [ABSTRACT FROM AUTHOR]

In this paper, a new formulation for power system state estimation is proposed. The formulation is based on the regularized least squares method, which can deal with ill-posed problems. In this approach, the mathematical unfeasibility which results from the lack of measurements is eliminated. A test procedure based on the variance of estimated linearized active power flow is proposed to identify the observable islands. Some systems of the technical literature are used to show the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

Time-domain scheduling simulation is the most effective tool for predicting the operational costs in wind-integrated power systems, because it can represent the inter-temporal constraints that limit the balancing actions of the thermal plant, storage, and demand-side measures. High wind penetrations demand just-in-time commitment decisions that reflect the uncertainties in the wind infeed, so that it is desirable to generate the scheduling decisions using stochastic unit commitment (SUC) with rolling planning. However, the computational burden can make such methods impractical in long simulations. We present an efficient formulation of the SUC problem that is designed for use in scheduling simulations of single-bus power systems. Unlike traditional SUC techniques, the proposed formulation uses a quantile-based scenario tree structure that avoids the need for exogenous operating reserves. We compare the performance of various tree topologies in year-long simulations of a large system. Simple quantile-based trees give statistically significant cost improvements over fixed-quantile deterministic methods and compare favorably with trees based on Monte Carlo-generated scenarios. [ABSTRACT FROM PUBLISHER]

In power system reconfiguration, the status (ON/OFF) of switches are optimized such that maximum power is delivered to loads after the occurrence of a fault. The optimized reconfiguration is achieved by prioritizing power delivered to vital loads over semi-vital and nonvital loads. The formulation presented in this paper considers a new balanced hybrid (AC and DC) shipboard power system (SPS). Analysis of the nonconvex reconfiguration formulation is done by an appropriate nonconvex solver and by convex approximation. Unlike the nonconvex solution that is based on branch-and-bound methods, convex approximation significantly reduces complexity. It is shown that for the hybrid SPS reconfiguration problem, low complexity convex approximations are effective in finding optimal solutions. Cumulative distribution function (CDF) of the power delivered to loads is presented to showcase the system robustness against random fault scenarios. A combined objective of maximizing power delivery and minimizing the number of switching actions is included in the analysis. Tradeoff between power delivered and number of switching operations after reconfiguration has been discussed at steady state. A separate analysis is also included to observe the intermediate dynamic switch states while the reconfiguration is in progress to capture the trade-off more prominently. [ABSTRACT FROM PUBLISHER]

Power system security analysis is often strongly tied with contingency analysis. To improve Monte Carlo simulation, many different contingency selection techniques have been proposed in the literature. [ABSTRACT FROM PUBLISHER]

Real-time electromagnetic transient simulation plays an important role in the planning, design, and operation of power systems. Inclusion of accurate and complicated models, such as the universal machine (UM) model and the universal line model (ULM), requires significant computational resources. This paper proposes a digital hardware emulation of the UM and the ULM for real-time electromagnetic transient simulation. It features accurate floating-point data representation, paralleled implementation, and fully pipelined arithmetic processing. The hardware is based on advanced field-programmable gate array (FPGA) using VHDL. A power system transient case study is simulated in real time to validate the design. On a 130-MHz input clock frequency to the FPGA, the achieved execution times for UM and ULM models are 2.5 \mu\s and 1.42 \mu\s, respectively. The captured real-time oscilloscope results demonstrate high accuracy of the emulator in comparison to the offline simulation of the original system in the EMTP-RV software. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel single-phase Z-source inverter topology with input and output sharing the same ground. It is simple in structure and only utilizes two switches while keeping the voltage transfer ratio the same as for the full-bridge inverter. One-cycle control is adopted. Highly efficient constant-frequency control can be achieved without an accurate model of the converter. The unique feature of the proposed topology is verified by operating principle, simulation and experimental results. This topology can be used in distributed power systems where dual grounding is needed. [ABSTRACT FROM AUTHOR]

Classic linear models of fossil fired steam units have been used for decades in power system dynamic analyses. The effect of main steam pressure is often ignored or the more complex models of boiler and its control systems should be adopted in the simulations. Moreover, the variations of turbine enthalpy drop are not considered in those models, which may result in a great deviation of output power during a transient period after a disturbance. A new model with little increase in complexity is built in this paper to improve the accuracy of classic models, where the boiler effect and the enthalpy droop variations are considered by a simplified boiler model and replacements of three turbine model parameters. Test data of a 600-MW coal fired generation unit are adopted to compare the performance of the proposed model with that of a classic one. Higher accuracy of the new model are observed and it is proposed to replace the classic models in power system dynamic analyses. [ABSTRACT FROM PUBLISHER]

This paper proposes voltage-shift acceleration control for islanding detection of distributed-generation (DG) inverters. The proposed method is conceptually based on a traditional dq-based voltage positive feedback control. A main improvement of the proposed control is that the anti-islanding performance and its impact on inverter output control can be consistent regardless of inverter operation points. An analytical approach based on a small-signal model of an inverter controller is used to prove the proposed control. Also, an analytical design method is proposed to obtain proper control gain that satisfies two conflicting issues: successful anti-islanding and limited impact on inverter control. Simulation and experimental tests were conducted to validate the proposed detection algorithm and its design method. In addition, simulation results on a two DGs system are shown to investigate the performance in multiple DGs operation. [ABSTRACT FROM AUTHOR]

The unified power-quality conditioner (UPQC) is used to mitigate the current and voltage-related power-quality (PQ) problems simultaneously in power distribution systems. Among all of the PQ problems, voltage sag is a crucial problem in distribution systems. In this paper, a new methodology is proposed to mitigate the unbalanced voltage sag with phase jumps by UPQC with minimum real power injection. To obtain the minimum real power injection by UPQC, an objective function is derived along with practical constraints, such as the injected voltage limit on the series active filter, phase jump mitigation, and angle of voltage injection. Particle swarm optimization (PSO) has been used to find the solution of the objective function derived for minimizing real power injection of UPQC along with the constraints. Adaptive neuro-fuzzy inference systems have been used to make the proposed methodology online for minimum real power injection with UPQC by using the PSO-based data for different voltage sag conditions. The proposed method has been validated through detailed simulation and experimental studies. [ABSTRACT FROM AUTHOR]