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The energy transition is aimed to take advantage of the operational flexibility of hydropower to extend the integration of intermittent renewable sources. Consequently, the hydrogenerators will have to operate in regimes far away from their designed best-point operation. In order to accurately assess the impact, this paper presents a useful approach to determine the overall operating efficiency of synchronous generators under intermittent operation. An accumulated average efficiency (AAE) model is proposed and compared against an alternative approach; the weighted average efficiency (WAE) model. It is found that the WAE approach produces unrealistic low efficiencies when the generator operates in synchronous condenser mode (SCM) for long periods. In general, the AAE supersedes the WAE for all the different load distributions that were investigated. This was further illustrated by a worked example and by constructing more complex load distributions. A load distribution dominated by SCM yields a difference as high as $33.18 \,\%$ , while an even distribution deviates $1.43 \,\%$ in their respective efficiencies. Finally, a yearly on-site measurement of our studied $103 \,\mathrm{MVA}$ generator’s concentrated load distribution revealed a discrepancy of $0.67 \,\%$ , which is a significant deviation considering what the operating regime would mean in terms of economic implications. [ABSTRACT FROM AUTHOR]

A novel brushless self-excited air-core compensated pulsed alternator (BSACPA) is presented in this paper. It consists of two submachines in cascade, among which one serves as an exciter and the other works as a generator. The rotor windings of the two submachines are connected by a reverse phase sequence to realize reversal of the magnetic field. The stator windings are connected by a rectifier to realize the brushless self-excited structure. As an air-core compensated pulsed alternator (CPA) of new topology, it is necessary to derive its mathematical model and carry out a comparative design. Thus, this paper focuses on the detailed design and analysis of a BSACPA prototype, which includes dimensional design and equivalent circuit establishment. In addition, the critical speed is also acquired. Accordingly, the numbers of winding coil turns are designed to increase the discharge current and power based on the theoretical analysis. Finally, the analysis and design are verified by finite-element analysis (FEA). [ABSTRACT FROM AUTHOR]

Unified power flow controller (UPFC) gains growing application in power systems due to its power flow regulation ability. However, there is still a dilemma in the incorporation of UPFC into security-constrained economic dispatch (SCED). The modeling of UPFC involves nonlinear and nonconvex operational constraints, which is difficult to solve efficiently and accurately. Conventional methods adopted Taylor expansion or sensitivity analysis to realize the convexification of UPFC models, which leads to a loop structure and is subject to initial point choice. In this paper, a novel three-terminal injected UPFC model is proposed. In the proposed model, the voltage source variables are eliminated completely. Instead, only power injection variables are introduced to equivalently describe physical characteristics and constraints of UPFC. The nonlinear and nonconvex operational constraints of UPFC are transformed into mixed integer second-order cone form. Moreover, compared with conventional UPFC models, the control characteristic of UPFC is considered in a more accurate and practical manner in the proposed SCED, which helps to prevent potential risks of power flow over-limit under N-1 contingencies. Simulation results show the effectiveness and efficiency of the established solution. [ABSTRACT FROM AUTHOR]

This paper focuses on the issue of network connectedness (NC) in security-constrained optimal transmission switching problems, which is complicated by branch contingencies and corrective line switching. Two criteria are firstly proposed with the principle of preserving NC as much as possible within reasonable limits. By extending the electrical flow based NC constraints, a proposition is derived to associate different cases of NC with the optimum of a linear program, yielding the mathematical formulation of the NC criteria. By Karush-Kuhn-Tucker conditions, this formulation is further transformed into a tractable version which can be incorporated with existing SCOTS models without affecting the applicability of original solution approaches. Finally, case studies on various networks and SCOTS models demonstrate the efficacy of the proposed approach. [ABSTRACT FROM AUTHOR]

The reduced inertia levels in low-carbon power grids necessitate explicit constraints to limit frequency’s nadir and rate of change during scheduling. This can result in significant curtailment of renewable energy due to the minimum generation of thermal plants that are needed to provide frequency response (FR) and inertia. Additional consideration of fast FR, a dynamically reduced largest loss and under frequency load shedding (UFLS) allows frequency security to be achieved more cost effectively. This paper derives a novel constraint from the swing equation to contain the frequency nadir using all of these services. The expected cost of UFLS is found probabilistically to facilitate its comparison to the other frequency services. We demonstrate that this constraint can be accurately and conservatively approximated for moderate UFLS levels with a second order cone (SOC), resulting in highly tractable convex problems. Case studies performed on a Great Britain 2030 system demonstrate that UFLS as an option to contain single plant outages can reduce annual operational costs by up to $\pounds $ 559 m, 52% of frequency security costs. The sensitivity of this value to wind penetration, abundance of alternative frequency services, UFLS amount and cost is explored. [ABSTRACT FROM AUTHOR]

In this paper, the mathematical model of an electricity generator with four static magnets and four dynamic magnets is suggested for the electricity generation. The introduced electricity generator is based on the electricity generator with two static magnets and two dynamic magnets, but it has three main advantages: it has more interactions between the static and dynamic magnets, it generates more electricity, and it generates smoother signals. Electricity generators are compared for the electricity generation. [ABSTRACT FROM AUTHOR]

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]

The increasing complexity of modern AC/DC power systems poses a significant challenge to a fast solution of large-scale transient stability simulation problems. This paper proposes the hybrid parallel-in-time-and-space (PiT+PiS) transient simulation on the CPU-GPU platform to thoroughly exploit the parallelism from time and spatial perspectives, thereby fully utilizing parallel processing hardware. The respective electromechanical and electromagnetic aspects of the AC and DC grids demand a combination of transient stability (TS) simulation and electromagnetic transient (EMT) simulation to reflect both system-level and equipment-level transients. The TS simulation is performed on GPUs in the co-simulation, while the Parareal parallel-in-time (PiT) scheduling and EMT simulation are conducted on CPUs. Therefore, the heterogeneous CPU-GPU scheme can utilize asynchronous computing features to offset the data transfer latency between different processors. Higher scalability and extensibility than GPU-only dynamic parallelism design is achieved by utilizing concurrent GPU streams for coarse-grid and fine-grid computation. A synthetic AC/DC grid based on IEEE-118 Bus and CIGRÉ DCS2 systems showed a good accuracy compared to commercial TSAT software, and a speedup of 165 is achieved with 48 IEEE-118 Bus systems and 192 201-Level detail-modeled MMCs. Furthermore, the proposed method is also applicable to multi-GPU implementation where it demonstrates decent efficacy. [ABSTRACT FROM AUTHOR]

Despite cascading failures being the central cause of blackouts in power transmission systems, existing operational and planning decisions are made largely by ignoring their underlying cascade potential. This paper posits a reliability-aware AC Optimal Power Flow formulation that seeks to design a dispatch point which has a low operator-specified likelihood of triggering a cascade starting from any single component outage. By exploiting a recently developed analytical model of the probability of component failure, our Failure Probability-constrained ACOPF (FP-ACOPF) utilizes the system’s expected first failure time as a smoothly tunable and interpretable signature of cascade risk. We use techniques from bilevel optimization and numerical linear algebra to efficiently formulate and solve the FP-ACOPF using off-the-shelf solvers. Extensive simulations on the IEEE 118-bus case show that, when compared to the unconstrained and N-1 security-constrained ACOPF, our probability-constrained dispatch points can significantly lower the probabilities of long severe cascades and of large demand losses, while incurring only minor increases in total generation costs. [ABSTRACT FROM AUTHOR]

In view of the uncertainty and intermittency of wind power, this paper proposes an optimal economical dispatch (ED) model and develops a method to estimate risk and manage hybrid power systems (traditional + wind~power~systems) for the short-term (24 h) operations. The model and the method have taken into account the large wind power penetration and the wind variability. The particle swarm optimization (PSO) refid="ref1"/ algorithm with constraints is applied to solve the ED problem. Value at risk (VaR) refid="ref2"/ and integrated risk management (IRM) refid="ref3"/ are used separately to assess the risk, so that an optimal tradeoff between the profit and risk is made for the system operations. The model and the method are tested on the standard IEEE 30-bus power system and network in Shanghai. The validity of the model and the method has been approved. [ABSTRACT FROM PUBLISHER]

Simultaneous vibration control and energy harvesting of vehicle suspensions have attracted significant research attention over the past decades. However, existing energy harvesting shock absorbers (EHSAs) compromise suspension performance for high-efficiency energy harvesting and being only responsive to narrow-bandwidth vibrations. In this paper, we propose a new ball-screw-based EHSA design – inerter pendulum vibration absorber (IPVA) – that integrates an electromagnetic rotary EHSA with a nonlinear pendulum vibration absorber.We show that this design simultaneously improves ride comfort and energy harvesting efficiency by exploiting the nonlinear effects of pendulum inertia. To further improve the performance, we develop a novel stochastic linearization model predictive control (SL-MPC) approach in which we employ stochastic linearization to approximate the nonlinear dynamics of EHSA that has superior accuracy compared to standard linearization. In particular, we develop a new stochastic linearization method with guaranteed stabilizability, which is a prerequisite for control designs. This leads to an MPC problem that is much more computationally efficient than the nonlinear MPC counterpart with no major performance degradation. Also, the effect of different road preview configurations on control performance is investigated, which is shown to have a significant impact on the control performance. Extensive simulations are performed to show the superiority of the proposed new nonlinear EHSA and to demonstrate the efficacy of the proposed SL-MPC. [ABSTRACT FROM AUTHOR]

This paper proposes a mathematical model for transmission planning in an environment where there is imperfect competition in electricity supply industry. The model is developed based on the concept of the leader-followers game in applied mathematics. The leader of the game is the transmission planner and the followers are the strategic electricity producing firms. The reaction of the strategic electricity producing firms to the transmission planning decision is modeled using the introduced concept of the worst-Cournot-Nash equilibrium. The worst-Cournot-Nash equilibrium can handle the multiple Nash equilibria problem. The whole mathematical formulation is a bilevel mixed-integer linear programming problem. This formulation is achieved using the Karush-Kuhn-Tucker optimality conditions and a binary mapping approach. The application of the proposed approach to the three-node example system and the modified six-node Garver's example system are studied. The transmission planning with perfect competition is formulated and used as the benchmark. The numerical results show that the proposed approach in this paper can efficiently allocate the additional transmission capacity to the transmission grid such that it reduces the market power cost in the electricity supply industry. However, further studies should be carried out to scale up the proposed approach to the larger case studies. [ABSTRACT FROM PUBLISHER]

In a recent paper, we proposed a system identification method for constructing reduced-order models for the electro-mechanical dynamics of large power systems, divided into multiple coherent clusters, using Synchrophasors. Every cluster in the actual model was represented as an aggregate generator in the reduced-order model. An aggregate network graph connected one aggregate generator to another. In this paper, we extend this identification approach to differential-algebraic (DAE) models. First, every cluster is associated with a unique terminal bus, referred to as the pilot bus, that couples its internal network to the rest of the system. The proposed algorithm uses Synchrophasor measurements from the pilot buses to identify the dynamic model of the aggregate generator for each cluster using nonlinear least squares while retaining the identity of all the pilot buses. The resulting reduced-order model is in the form of a nonlinear electric circuit described by aggregate differential and algebraic equations. We illustrate our results using two case studies, one for the IEEE 9-bus power system and another for the IEEE 39-bus power system. We also discuss how these reduced-order DAE models may be useful for designing shunt controllers at the pilot buses by using Synchrophasor feedback. [ABSTRACT FROM AUTHOR]

This paper proposes a new approach for power system transient stability simulation, which is based on a semi-analytical solution (SAS) of power system differential-algebraic equations. In this paper, an SAS is derived using the Adomian decomposition method as a closed-form explicit function of symbolic variables such as time, the initial state, and other variables on system conditions and; hence, it can directly give a power system's dynamic trajectory being accurate for a certain time window. Unlike a traditional numerical integration based simulation approach, the proposed new approach offline derives an SAS and online evaluates the SAS by plugging in values of symbolic variables for a series of time windows making up the desired simulation period. This paper further studies the maximum length of the time window for an SAS being accurate and proposes a divergence indicator for simulation using adaptive time windows. Implementation of this new approach on parallel computers is also studied. The new approach is validated through contingency simulation of the IEEE 10-generator 39-bus system with detailed generator models. [ABSTRACT FROM AUTHOR]

In the power control process of the range extender, both the engine and the generator are at risk of reaching the torque output limit. The limitation not only comes from the restriction of their own torque output capacity, but also comes from the additional constraints that are established to avoid power reverse undershoot. In order to improve the system performance under time-varying torque constraints, a real-time model predictive controller (MPC) that manipulates the torque commands of the engine and the generator to track the reference power is designed. Different from the traditional penalty function method, the quadratic function is taken as the penalty function in this paper, which greatly improves the efficiency of solving the optimal solution. Meanwhile, the steady-state torque command in the feasible region is taken as the extreme point of the quadratic penalty function, which avoids the penalty coefficient tending to infinity. By adjusting the penalty coefficients of different constraints, the overall optimal solution approaches the boundary of the active inequality constraints. And according to the Karush-Kuhn-Tucker (KKT) condition, it is proved that the optimal solution of the original problem can be obtained through iteration. The effectiveness and practicability of the proposed strategy are evaluated through numerical simulations on Simulink and experiments on a range extender. [ABSTRACT FROM AUTHOR]

The end-of-life (EOL) disassembly sequencing problem (DSP) has become increasingly important in the process of handling EOL products. This paper proposes a solution procedure for the “EOL DSP”; the procedure is based on a novel soft-computing algorithm that utilizes modified “simplified swarm optimization,” and the procedure combines the precedence preservative operator, feasible solution generator, self-adaptive parameter control, and repetitive pairwise exchange procedures. By taking into consideration the non-deterministic polynomial time (NP)-complete nature of the problem, the proposed algorithm efficiently seeks the optimal disassembly sequence with a novel approach; this approach involves reducing the initial solution space and using a combination of soft-computing algorithms for achieving higher computational efficiency and solution quality. The results presented in this paper show that the proposed algorithm outperforms the existing algorithms in terms of solution quality achieved in a limited computation time. [ABSTRACT FROM PUBLISHER]

Demand response (DR) has been recognized as a powerful tool to help mitigate power imbalances in a future smart energy system. This paper takes the point of view of a grid operator (GO) to establish an intraday resource trading framework, over which DR resources from different sectors (large industrial consumers and small- or middle-sized customers) are brought to the system level and are assessed by the GO along with the generators, with the aim of procuring the required system resources at minimal cost. Considering the distinct behaviors of the involved entities, Stackelberg game theory was adopted to analyze the coordination among the various decision makers. A unique Stackelberg equilibrium was identified that yields the optimal outcome for the resource trading game between the GO and demand-side participators. Simulation results demonstrated that the total procurement cost was minimized by applying the proposed approach. [ABSTRACT FROM AUTHOR]

This paper evaluates the effectiveness of different commercial relay functions in a local passive anti-islanding process for a permanent-magnet synchronous generator (PMSG)-based wind farm which is interfaced with a radial distribution network. The results are obtained through a comprehensive set of real-time simulation studies, conducted on a detailed topological model of a single-machine equivalent of the PMSG-based wind farm and the network, using three different commercial relays. The paper introduces the study set-up and methodology and, additionally, details of the mathematical and simulation models of the PMSG-based wind farm. The models and the methodology presented in this paper can be used, directly or with minor modifications, for many other impact-assessment studies. [ABSTRACT FROM AUTHOR]

This paper discusses the conceptual design and operation of an isolated power system, recognizing the reality that generator or turbine trips will occur. The level of reserve generating capacity must be set with proper balancing of capital expenditures and operating costs against revenue lost in a production shutdown. The way that reserve capacity is provided is as important as the amount of reserve; seemingly adequate reserve can turn out to be badly insufficient if it is not well distributed across the available reserve sources. The dynamic behavior of reserve capacity, as much as the amount of capacity that is ultimately available, is critical in determining how an isolated facility will behave in the wake of a unit trip or the loss of a grid connection. In this paper, experiences with detailed dynamic simulations of a range of isolated systems are described. These are related to test work and operational incidents that have provided practical calibrations. Based on simulation and experience, some guidelines are offered for configuring generation and selecting strategies for maintaining stability in large, isolated continuous-process facilities. [ABSTRACT FROM PUBLISHER]

This paper discusses the implementation of the inverse Jiles–Atherton vector hysteresis model with the 2-D Finite Element Method (FEM) for the analysis of an induction machine operating as self-excited generator. A differential reluctivity tensor couples the hysteresis model with the magnetic vector potential-based finite-element model. Experimental and simulated results (transient and steady state) are presented. [ABSTRACT FROM AUTHOR]

The small-signal stability analysis of power systems concerns the critical modes as well as the modes associated with a physical meaning, e.g., the interarea oscillation modes for weakly connected systems and the modes sensitive to a particular parameter. As the order of the power-system state matrix increases, it becomes more difficult to determine these modes. In this paper, a method is proposed to compute the interarea oscillation modes of large-scale power systems. The deviation in the active power of the transmission section is selected to identify the interarea oscillation modes. Then, the two-sided Jacobi-Davidson method combined with this selection is employed to compute these modes. Participation factors are used to separate the electromechanical oscillation modes. Numerical tests show that the proposed method is valid and efficient. [ABSTRACT FROM PUBLISHER]

In recent years, there has been a growing interest in incorporating microgrids in electrical power networks. This is due to various advantages they present, particularly the possibility of working in either autonomous mode or grid connected, which makes them highly versatile structures for incorporating intermittent generation and energy storage. However, they pose safety issues in being able to support a local island in case of utility disconnection. Thus, in the event of an unintentional island situation, they should be able to detect the loss of mains and disconnect for self-protection and safety reasons. Most of the anti-islanding schemes are implemented within control of single generation devices, such as dc-ac inverters used with solar electric systems being incompatible with the concept of microgrids due to the variety and multiplicity of sources within the microgrid. In this paper, a passive islanding detection method based on the change of the 5th harmonic voltage magnitude at the point of common coupling between grid-connected and islanded modes of operation is presented. Hardware test results from the application of this approach to a laboratory scale microgrid are shown. The experimental results demonstrate the validity of the proposed method, in meeting the requirements of IEEE 1547 standards. [ABSTRACT FROM PUBLISHER]

This paper presents a fast and robust wide-area backup protection scheme to detect the faulty condition and to identify the faulted line in a large power network. The proposed methodology uses positive-sequence synchrophasor data captured by either digital relays with synchronization capability or phasor measurement units dispersed over the network. The basic idea behind the new protection scheme is the comparison of bus voltage values calculated through dissimilar paths. Upon occurrence of a fault, the faulty condition is first detected and the bus(es) connected to the faulted line is(are) determined. Among transmission lines connected to the suspected bus(es), the faulted one is thereafter identified. In addition to two-terminal transmission lines, multiterminal lines are also incorporated. The performance of the proposed method is validated on the IEEE 57-bus test system in different fault conditions (fault type, fault location, and fault resistance). Discrimination of faulty and normal conditions is simulated by examining various stressed conditions, for example, load encroachment, generator outage, and power swing. The data requirement of the proposed technique is analyzed as well. To do so, a mathematical model for the optimal placement of measurement devices is developed and applied to different IEEE standard test systems. [ABSTRACT FROM AUTHOR]

Part one of this two-part paper presents new models for evaluating flexible resources in two-settlement electricity markets (day-ahead and real-time) with uncertain net loads (demand minus wind). Physical resources include wind together with fast- and slow-start demand response and thermal generators. We also model financial participants (virtual bidders). Wind is stochastic, represented by a set of scenarios. The two-settlement system is modeled as a two-stage process in which the first stage involves unit commitment and tentative scheduling, while the second stage adjusts flexible resources to resolve imbalances. The value of various flexible resources is evaluated through four two-settlement models: 1) an equilibrium model in which each player independently schedules its generation or purchases to maximize expected profit; 2) a benchmark (expected system cost minimization); 3) a sequential equilibrium model in which the independent system operator first optimizes against a deterministic wind power forecast; and 4) an extended sequential equilibrium model with self-scheduling by profit-maximizing slow-start generators. A tight convexified unit commitment allows for demonstration of certain equivalencies of the four models. We show how virtual bidding enhances market performance, since, together with self-scheduling by slow-start generators, it can help a deterministic day-ahead market to choose the most efficient unit commitment. [ABSTRACT FROM PUBLISHER]

Regenerating codes for distributed storage have attracted much research interest in the past decade. Such codes trade the bandwidth needed to repair a failed node with the overall amount of data stored in the network. Minimum storage regenerating (MSR) codes are an important class of optimal regenerating codes that minimize (first) the amount of data stored per node and (then) the repair bandwidth. Specifically, an [n,k,d] - (\alpha ) MSR code \mathbb C over \smash \mathbb F\!q stores a file \mathcal F consisting of \alpha k symbols over \smash {\mathbb {F}_{\!q}} among n$ nodes, each storing \alpha $ symbols, in such a way that: 1) the file k$ of the n$ nodes and 2) the content of any failed node can be reconstructed by accessing any d$ of the remaining symbols from each of these nodes. In practice, the file \mathcal F is typically available in uncoded form on some $k$ of the $n$ nodes, known as systematic nodes, and the defining node-repair condition above can be relaxed to requiring the optimal repair bandwidth for systematic nodes only. Such codes are called systematic–repair MSR codes. Unfortunately, finite– $\alpha $ constructions of $[n,k,d]$ MSR codes are known only for certain special cases: either low rate, namely $k/n \leqslant 0.5$ , or high repair connectivity, namely $d = n-1$ . Our main result in this paper is a finite– $\alpha $ construction of systematic-repair $[n,k,d]$ MSR codes for all possible values of parameters $n,k,d$ . We also introduce a generalized construction for $[n,k]$ MSR codes to achieve the optimal repair bandwidth for all values of $d$ simultaneously. [ABSTRACT FROM PUBLISHER]

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]

This paper proposes an investment cost recovery based efficient and reliable optimization approach to optimal allocation of thyristor controlled series compensator (TCSC) in double auction power market. The optimization technique has been used with an objective to maximizing the social welfare and minimizing the device investment cost by suitable location and rating of single TCSC in the system. The effectiveness of proposed approach for location of TCSC has been compared with some existing methods of single TCSC placement, in terms of its impact on social welfare, TCSC investment recovery and optimal generation as well as load patterns. The results have been obtained on 5-bus system, modified IEEE 14-bus system and 246-bus Indian practical Northern Regional Power Grid (NRPG) system. [ABSTRACT FROM PUBLISHER]

Neutral of large unit-connected generators is normally grounded through a large impedance; therefore, a small current passes from a stator phase to ground (PG) fault location. Consequently, locating the fault position cannot usually be performed based on a visual inspection. There are different methods for detecting the stator slot with a PG fault, which have practically been used for many years. These methods have some drawbacks such as further damages to the faulty generator, low accuracy, requiring expensive equipment, and taking long time for detection. This paper introduces a novel strategy for realizing a stator slot with the PG fault which can be used in large generators. This strategy can be easily implemented, and it is able to detect the fault location precisely. Based on this strategy, three different methods are proposed and their performances are investigated using a simulation based on the finite elements method. The simulation results are also verified using comprehensive experimental tests. [ABSTRACT FROM PUBLISHER]

With the development of power grid interconnection, disturbance propagation phenomena are more and more apparent in the form of electromechanical waves. Once a disturbance occurs, its propagation might cause cascading events and even large blackouts. With the help of advanced communications networks in smart grids, new event-based protection systems can be devised by the reveal of disturbance propagation mechanisms. In this paper, a widely used measurement-based protection system is analyzed and the idea of event-based protection is proposed. By introducing the inverse process of lumped mass method, the impact scope of generator inertia is proposed. Then, the structural frame model of power networks for disturbance propagation is built, which is sectionalized homogeneously. The spatial heterogeneity of propagation velocity of the electromechanical waves is depicted. According to the constant velocity characteristic of the segments in the structural frame model, a weighted undirected graph is formulated. Then, the Dijkstra algorithm based shortest path searching method for arrival time of electromechanical wave is proposed. The simulations are carried out to demonstrate the effectiveness of the proposed electromechanical wave propagation model and disturbance arrival time estimation algorithm. The research work is one of the essential steps for realizing event-based protection strategies. [ABSTRACT FROM AUTHOR]

Both Maximum Distance Separable and Euclidean self-dual codes have theoretical and practical importance and the study of MDS self-dual codes has attracted lots of attention in recent years. In particular, determining the existence of q -ary MDS self-dual codes for various lengths has been investigated extensively. The problem is completely solved for the case where q is even. This paper focuses on the case where q is odd. We construct a few classes of new MDS self-dual codes through generalized Reed–Solomon codes. More precisely, we show that for any given even length n , we have a q and q is sufficiently large (say q\ge 4^{n}\times n^{2}) . Furthermore, we prove that there exists a q -ary MDS self-dual code of length n if q=r^{2} and n$ satisfies one of the three conditions: 1) n\le r$ and n$ is even; 2) q$ is odd and n-1$ is an odd divisor of and $n=2tr$ for any $t\le (r-1)/2$ . [ABSTRACT FROM PUBLISHER]

This paper presents the numerical analysis of the bilevel programming approach for revenue- and network-constrained market clearing developed in its companion paper. The impact of minimum revenue conditions and minimum declared profits on generation and consumption levels as well as on locational marginal prices for energy is examined in detail through three case studies. First, the results from an illustrative example including minimum revenue conditions are comprehensively analyzed. The second case study is based on the IEEE Reliability Test System and considers minimum declared profits. In the third case study, a modified version of the IEEE 118-bus system is tested while accounting for minimum revenue conditions. In addition, the computational behavior of the proposed approach is illustrated with several case studies including the IEEE 300-bus system. Numerical results show the effectiveness of the proposed approach to handle revenue constraints as well as its superiority over the heuristic currently implemented in the Iberian electricity market. Moreover, simulations reveal that, unlike previous works in the literature, generation revenue constraints can be precisely incorporated in day-ahead market clearing while explicitly considering the standard economic-dispatch-based marginal pricing scheme and without requiring price uplifts. [ABSTRACT FROM AUTHOR]

This paper considers a linear quasi-cyclic product code of two given quasi-cyclic codes of relatively prime lengths over finite fields. We give the spectral analysis of a quasi-cyclic product code in terms of the spectral analysis of the row and column codes. Moreover, we provide a new lower bound on the minimum Hamming distance of a given quasi-cyclic code and present a new algebraic decoding algorithm. More specifically, we prove an explicit (unreduced) basis of an \ell A {\ell B} -quasi-cyclic product code in terms of the generator matrix in reduced Gröbner basis with respect to the position-over-term (RGB/POT) order form of the \ell A -quasi-cyclic row code and the \ell B -quasi-cyclic column code, respectively. This generalizes the work of Burton and Weldon for the generator polynomial of a cyclic product code (where \ell A= {\ell B}=1 ). Furthermore, we derive the generator matrix in Pre-RGB/POT form of an \ell A {\ell B} -quasi-cyclic product code for two special cases: i) for \ell A=2 and \ell B=1 and ii) if the row code is a one-level \ell A -quasi-cyclic code (for arbitrary \ell A ) and \ell B=1 . For arbitrary \ell A and \ell B , the Pre-RGB/POT form of the generator matrix of an \ell A {\ell B} -quasi-cyclic product code is conjectured. The spectral analysis is applied to the generator matrix of the product of an \ell -quasi-cyclic and a cyclic code, and we propose a new lower bound on the minimum Hamming distance of a given \ell -quasi-cyclic code. In addition, we develop an efficient syndrome-based decoding algorithm for \ell -phased burst errors with guaranteed decoding radius. [ABSTRACT FROM AUTHOR]

This paper proposes a new mathematical structure for evaluating the economic efficiency of transmission investment in a liberalized electricity market. The problem faced by a transmission planner is modeled using the concept of social welfare from economics. The behavior of generators is modeled as the Nash equilibrium of a strategic game. The Nash solution concept is reformulated as an optimization problem and a new concept—the Stackelberg-Worst Nash equilibrium—is introduced to resolve the problem of multiple equilibria. The proposed structure can take into account the effects of a transmission augmentation on both market power and strategic generation investment. Accordingly, the optimal solution to the transmission planner's problem may allow additional transmission capacity both to reduce market power and to defer investment in the generation sector. A methodology is proposed to decompose the benefits of a transmission augmentation policy into the efficiency benefit, competition benefit, and the deferral benefit. The outcomes of the proposed approach to transmission augmentation are compared with the outcomes of two other approaches to transmission augmentation using a simple three-bus network example. [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]

With the increasing use of renewable energy resources and energy storage devices, inverter-based distributed energy resources (DERs) become the important components in microgrids. As diesel generators with direct ac connections are the current most cost effective and reliable power sources, the stability investigation of microgrids should include both types of DERs. In this paper, dynamics of diesel generation will be included and the interaction of the diesel generators and the inverter-based DERs will be investigated using eigenvalue analysis and time-domain simulations. The significant contributions of this paper include: 1) identification of the stability problem in microgrids with inverter-based DERs and conventional generators and 2) investigation of the interaction problem of inverter-based DERs and conventional generators in islanded microgrids. [ABSTRACT FROM AUTHOR]

This paper presents modeling guidelines and a benchmark system for power system simulation studies of grid-connected, three-phase, single-stage Photovoltaic (PV) systems that employ a voltage-sourced converter (VSC) as the power processor. The objective of this work is to introduce the main components, operation/protection modes, and control layers/schemes of medium- and high-power PV systems, to assist power engineers in developing circuit-based simulation models for impact assessment studies, analysis, and identification of potential issues with respect to the grid integration of PV systems. Parameter selection, control tuning, and design guidelines are also briefly discussed. The usefulness of the benchmark system is demonstrated through a fairly comprehensive set of test cases, conducted in the PSCAD/EMTDC software environment. However, the models and techniques presented in this paper are independent of any specific circuit simulation software package. Also, they may not fully conform to the methods exercised by all manufacturers, due to the proprietary nature of the industry. [ABSTRACT FROM AUTHOR]

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]

There is currently a national push to create a smarter grid. Currently, the full control of transmission assets is not built in network optimization models. With more sophisticated modeling of transmission assets, it is possible to better utilize the current infrastructure to improve the social welfare. Co-optimizing the generation with the network topology has been shown to reduce the total dispatch cost. In this paper, we propose the concept of just-in-time transmission. This concept is predicated on the fact that transmission that is a detriment to network efficiency can be kept offline when not needed and, with the proper smart grid/advanced technology, can be switched back into service once there is a disturbance. We determine which lines to have offline based on the optimal transmission switching model previously proposed. A secondary topic of this paper focuses on flowgate bidding. Approved by the Federal Energy Regulatory Commission and implemented within the SPP and NYISO networks, flowgate bidding is defined as allowing a line's flow to exceed its rated capacity for a short period of time for a set penalty, i.e., price. We demonstrate the effectiveness of these models by testing them on large-scale ISO network models. [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]

The air-cooled turbo-generator often works in the more frequent start-up and shut-down operation. Either the misoperation or the failure of synchronizing controllers can cause the out of phase synchronization fault. The fault can disturb the power angle and cause a strong impact electromagnetic force for the generator. With the traditional numerical calculation method, it is difficult to calculate the variations of key physical parameters and the electromagnetic field in the end region of the generator under complex working conditions, especially the out of phase synchronization fault. In order to solve the problem, a calculation method of the nonlinear transient electromagnetic field with multi-domain field-circuit-grid coupled is proposed. The correctness of the model and method is validated by comparing the calculated and test values of the magnetic density flux at the key points of the generator under the no-load condition. Based on this method, the power angle variation, the magnetic flux leakage distribution in the end region, and the electromagnetic force on the end winding in the transient process of the fault are calculated and analyzed. [ABSTRACT FROM AUTHOR]

Constacyclic codes which generalize the classical cyclic codes have played important roles in recent constructions of many new quantum maximum distance separable (MDS) codes. However, the mathematical mechanism may not have been fully understood. In this paper, we use pseudo-cyclic codes, which is a further generalization of constacyclic codes, to construct the quantum MDS codes. We can not only provide a unified explanation of many previous constructions, but also produce some new quantum MDS codes. [ABSTRACT FROM AUTHOR]

Isolated microgrid power systems are prone to large frequency and voltage deviations, since they have limited generation and finite inertia and may include pulse power loads and large proportion of dynamic loads. Thus, they require effective power management methods to operate optimally, while satisfying operating and security constraints. In this paper, a novel integrated security-constrained model-based power management approach is proposed for isolated microgrids in all-electric ships during the normal/alert operating state. The new power management method was formulated as a multi-objective optimal control problem. A method based on the Nondominated Sorting Genetic Algorithm II was developed to solve the problem. The developed integrated security-constrained power management approach was applied to a notional all-electric ship computer model. The simulation results, conducted in PSCAD, showed the effectiveness of the new power management method. [ABSTRACT FROM PUBLISHER]

In traditional power system, economic dispatch and generation control are separately applied. Online generation adjustment is necessary to regulate generation reference for real-time control to realize economic operation of power systems. Since most economic dispatch solutions are centralized, they are usually expensive to implement, susceptible to single-point-failures, and inflexible. To address the above-mentioned problems, this paper proposed a multi-agent system based distributed control solution that can realize optimal generation control. The solution is designed based upon an improved distributed gradient algorithm, which can address both equality and inequality constraints. To improve the reliability of multi-agent system, the N-1 rule is introduced to design the communication network topology. Compared with centralized solutions, the distributed control solution not only can achieve comparable solutions but also can respond timely when the system experiences change of operating conditions. MAS based real-time simulation results demonstrate the effectiveness of the proposed solution. [ABSTRACT FROM PUBLISHER]

In order to simplify and increase the reliability of wind generators, a new type of a direct-drive directly grid-connected wind generator known as a slip–synchronous permanent-magnet generator (SS-PMG) is proposed. It consists of two integrated generating units, i.e., a directly turbine-connected slip PMG unit and a directly grid-connected PM synchronous generator unit. The main aim of this paper is to determine if this generator is stable under transient wind turbine and grid conditions. A transfer function model is developed to evaluate the dynamic performance of the wind generator system. The transient response of a single 15-kW grid-connected system is evaluated. It is shown that the generator is very stable under transient turbine torque conditions. Furthermore, it acts as a filter to prevent voltage flickering due to oscillatory turbine pulsations. A very important design aspect to take into account is the torque ripple characteristics of the slip PM generator as torque ripple can be transferred to the grid current under certain conditions. Simulated and dynamically measured results are shown for a series of 15-kW SS-PMG prototypes. [ABSTRACT FROM PUBLISHER]

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 objective of this paper was to investigate how the frequency of an electromagnetic pulse generated by an inward-emitting coaxial vircator is dependent upon the anode to cathode gap distance (AK-gap) in the vircator. Experimental tests of three different AK-gaps 29.5, 32, and 34.5 mm, were conducted with the high power microwave (HPM) system Bofors HPM Blackout. The system is working within the L- to S-band and the vircator is powered by a 1.8-kJ Marx generator at a maximum voltage of 600 kV. In addition, the experimental models of the coaxial vircators were also simulated in ATK MAGIC2D particle-in-cell code and the experimental frequency was compared with the theoretical frequency. The experimental frequency increased with decreasing AK-gap. [ABSTRACT FROM AUTHOR]

This paper proposes a day-ahead scheduling model in which the hourly demand response (DR) is considered to reduce the system operation cost and incremental changes in generation dispatch when the ramping cost of thermal generating units is considered as penalty in day-ahead scheduling problem. The power output trajectory of a thermal generating unit is modeled as a piecewise linear function. The day-ahead scheduling is formulated as a mixed-integer quadratically constrained programming (MIQCP) problem with quadratic energy balance constraint, ramping cost, and DR constraints. A Lagrangian relaxation (LR) based method is applied to solve this problem. Numerical tests are conducted on a 6-bus system and the modified IEEE 118-bus system. The results demonstrate the merits of the proposed scheduling model as well as the impact of introducing ramping costs as penalty and DR as incentives in the day-ahead scheduling of power systems. [ABSTRACT FROM PUBLISHER]