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The fast development of renewable energies leads to an increase in the power electronics penetration in transmission systems. This is particularly true if one considers a 100% renewable energies power system, where wind and solar photovoltaic energies, which make most of the renewable energies connections today, are connected to the grid through power electronics converters. Because power electronics-based generators and synchronous machines-based generators have very different dynamic behaviours, some approximations usually used to run transient simulations of transmission systems might not be optimal for future grids. The systematic use of the phasor approximation applied to the power lines, implemented in most of the Transient Simulation Programs, is indeed not relevant any more. To avoid the use of Electromagnetic Transient simulations, that are resource-demanding and time-consuming, this paper presents a novel Model Order Reduction technique for large grids with a high penetration of power electronic devices. Compared to the classical phasor approximation, this event-based state residualization approximation allows accurate transient simulations and at the same time an optimal reduction of the number of the system’s state variables depending on the observed variables, the considered events and the tolerated approximation error. [ABSTRACT FROM AUTHOR]

Power system planning is essential for ensuring development of a safe and stable power system. Articles on power system planning have been published in recent decades. In this paper, bibliometric analysis is applied to power system planning to identify its basic characteristics, and to summarize the research hotspots and trends. A total of 4562 publications were obtained from the Web of Science during 1971–2020. The 4562 publications cover 8136 keywords, 1526 journals, 107 countries/territories, and 2519 institutions. IEEE Transactions on Power Systems is the key journal in power system planning; USA, China, and England are the countries that dominate publication production. Research hotspots and trends were analyzed using author-keyword co-occurrence analysis and keyword burst detection. Four clusters were identified and topics from Cluster I (central nodes as power system stability and transient stability) and Cluster IV (central nodes as power system simulation and economics) are important for power system planning research. However, their relative popularities have declined over the past two decades. This indicates that Cluster II (central nodes as renewable energy, wind power, and energy storage) and Cluster III (central nodes as distributed generation and smart grids) will be the focus of future research. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to dynamic phasor-based transient stability simulation. The proposed method is based on the modified nodal analysis (MNA) approach to circuit simulation, which is used to construct continuous differential-algebraic equations (DAEs). The proposed method makes use of the stamp technique, which makes it possible to construct a general purpose MNA-based simulator. Stamp-based models for common power system components are derived in this work. A new MNA-based synchronous machine model is presented, which represents machines as nonlinear inductances instead of subtransient equivalents. The resultant continuous DAEs are numerically solved using the general purpose variable step and variable order library IDA. Simulation results from the IEEE 68 bus test system, a real 400 bus power system, and the IEEE 39 bus test system with an embedded HVdc transmission system demonstrate that the proposed method is suitable for large ac networks with power electronic devices. The results demonstrate good agreement between the proposed method and electromagnetic transient (EMT) simulation. The results also demonstrate that the proposed method is fast and scalable with CPU times that are up to 200 times faster than EMT simulation. [ABSTRACT FROM AUTHOR]

With continuing advances in high-performance parallel computing platforms, parallel algorithms have become powerful tools for development of faster than real-time power system dynamic simulations. In particular, it has been demonstrated in recent years that parallel-in-time (Parareal) algorithms have the potential to achieve such an ambitious goal. The selection of a fast and reasonably accurate coarse operator of the Parareal algorithm is crucial for its effective utilization and performance. This paper examines semi-analytical solution (SAS) methods as the coarse operators of the Parareal algorithm and explores performance of the SAS methods to the standard numerical time integration methods. Two promising time-power series-based SAS methods were considered; Adomian decomposition method and Homotopy analysis method with a windowing approach for improving the convergence. Numerical performance case studies on 10-generator 39-bus system and 327-generator 2383-bus system were performed for these coarse operators over different disturbances, evaluating the number of Parareal iterations, computational time, and stability of convergence. All the coarse operators tested with different scenarios have converged to the same corresponding true solution (if they are convergent) and the SAS methods provide comparable computational speed, while having more stable convergence to the true solution in many cases. [ABSTRACT FROM AUTHOR]

The paper presents accurate and simple dynamic model of a supercapacitor bank system for power system dynamics studies. The proposed model is derived from a detailed RC circuit representation. Furthermore, a complete control system of the supercapacitor bank is also presented. The proposed model is easy to integrate in any power system simulation software and consists of only up to four standard datasheet parameters. The performance of the proposed model in grid frequency control and low-voltage ride through is illustrated on IEEE 14-bus test system in DIgSILENT PowerFactory. It is shown that in case of transient stability simulations the ideal (simplified) model of the supercapacitor can be used while in case of frequency control the ideal representation may not always be appropriate. [ABSTRACT FROM AUTHOR]

In transient stability simulators such as PSS/E, the bus frequency is estimated using a window of (positive-sequence) phasor angle measurements. A digital filter is often used to account for the filtering effect in actual measurement devices and to eliminate sudden changes during frequency computations. Although transient stability simulators label the filtered angle derivative as the “frequency,” the frequency provided by such programs does not match actual measurements reported by phasor measurement units (PMUs), which makes it difficult to gauge the validity of studies (e.g., wide-area event detection and control applications) that are based on such simulations. In this paper, we implement a frequency computation method directly using positive phasor angles provided by simulators. The proposed method is tested on two systems extensively and validated against the measurements of an actual PMU. The improved frequency measurements closely match PMU responses. Cross-validation results also suggest the method may be used for other systems without conducting full time-domain simulations. [ABSTRACT FROM AUTHOR]

This paper analyses the frequency stability of ac grids in the presence of non-dispatchable generation and stochastic loads. Its main goal is to evaluate conditions in which the system is robust to large, persistent active power disturbances without recurring to time-domain simulations. Considering the ongoing energy transition to more renewable sources, defining robustness boundaries is a key topic for power system planning and operation. However, much of the research on long-term studies has not dealt with robust dynamic constraints, while short-term analyses usually depend on time-consuming simulations to evaluate nonlinearities. To bridge this gap, the authors derive an algebraic equation that provides sufficient conditions for robust frequency stability in ac power systems and a relationship among four key quantities: the maximum active power perturbation, the minimum system damping, the steady-state and the transient frequency limits. To achieve this goal, it uses a nonlinear average-model of the ac grid and Lyapunov's direct method extended by perturbation analysis requiring only limited knowledge of the system parameters. The algebraic calculations are validated using time-domain simulations of the IEEE 39-bus test system and results are compared to the traditional Swing Equation model. [ABSTRACT FROM AUTHOR]

The reliability of power systems with high penetration of renewables, a fast response mechanism, and precise decision-making scheme is more important than ever. This study presented a novel scheme that utilizes the predicted frequency nadir after a generation trip event to initiate necessary ancillary services such as fast spinning reserve units, energy storage units, and demand responses to restore the frequency back to the secure operating range. The proposed scheme coordinates Under-Frequency Load Shedding (UFLS) with ancillary services in the sense that the unnecessary load shedding can be avoided. By using the proposed scheme, the system becomes more resilient against disturbances, and the actions of load shedding are minimized. In this scheme, the frequency data is captured by phasor measurement units (PMUs), and a frequency nadir prediction algorithm is proposed. We demonstrate the effectiveness of the proposed scheme by using 1700-bus power system simulations and realistic frequency data from real generation trip events captured by a laboratory micro-phasor measurement unit (μPMU). [ABSTRACT FROM AUTHOR]

The article proposes a computationally efficient and robust method for estimating impulse or frequency response in the context of black-box multiple-input-multiple-output linear model identification of large power systems from simulations. The proposed approach is validated in conjunction with two realization algorithms – ERA method that is based on the established Ho-Kalman procedure for minimal realization, and the relatively new Loewner matrix based method. Practical aspects of identification in presence of numerical noise and nonlinearities are discussed. Study cases presented in the article include a linear model equivalent of a large-scale power system and the full-scale nonlinear transient model of the Eastern Interconnection. [ABSTRACT FROM AUTHOR]

Voltage stability assessment on a deterministic direction of loading variation may provide misleadingly high values of voltage stability margin due to uncertainties in load forecast. On the other hand, by disregarding loading forecast information and computing the worst case scenario, we may obtain unrealistic and very conservative margin values. This paper proposes a new voltage stability index that takes place between these two approaches. In this proposal, a set of credible loading variation directions is considered and the closest bifurcation point is determined within this set. A fast method for computation of this index is also proposed. The method is able to detect both saddle-node and limit-induced bifurcations. The efficiency of the proposed method is confirmed by means of numerical simulation on different power systems. [ABSTRACT FROM AUTHOR]

This paper emphasizes the importance of including unbalanced distribution systems for voltage stability studies in power systems. The paper aims to: discuss the various simulation methods for power system analysis; highlight the need for modeling unbalanced distribution system for accurate load margin assessment; demonstrate the influence of net-load unbalance (NLU) on voltage stability margin (VSM). We also share a T&D co-simulation interface with commercial power system solvers. The distribution system is evolving rapidly with high proliferation of distributed energy resources (DERs); these are not guaranteed to proliferate in a balanced manner and uncertainty resulting due to these DERs is well acknowledged. These uncertainties cannot be captured or visualized without representing the distribution system in detail along with the transmission system. We show the impact of proliferation of DERs in various 3-phase proportions on voltage stability margin through T&D co-simulation. We also study the impact of volt/VAR control on voltage stability margin. This analysis is only possible by representing the distribution system in detail through T&D co-simulation. Higher percentage of net-load unbalance (NLU) in distribution system aggravates the voltage stability margin of the distribution system, which can further negatively influence the overall voltage stability margin of the system. [ABSTRACT FROM AUTHOR]

Low frequency electromechanical oscillations can pose a threat to the stability of power systems if not properly addressed. This paper proposes a novel methodology to damp these inter-area oscillations using loads, the demand side of the system. In the proposed methodology, loads are assigned to an aggregated cluster whose demand is modulated for oscillation damping. The load cluster control action is obtained from an optimal output feedback control (OOFC) strategy. The paper presents an extension to the regular OOFC formulation by imposing a constraint on the sum of the rows in the optimal gain matrix. This constraint is useful when the feedback signals are generator speeds. In this case, the sum of the rows of the optimal gain matrix is the droop gain of each load actuator. Time-domain simulations of a large-scale power system are used to demonstrate the efficacy of the proposed control algorithm. Two different cases are considered: a power imbalance and a line fault. The simulation results show that the proposed controllers successfully damp inter-area oscillations under different operating conditions and with different clustering for the events considered. In addition, the simulations illustrate the benefit of the proposed extension to the OOFC that enable load to provide a combination of droop control and small signal stability augmentation. [ABSTRACT FROM AUTHOR]

This paper proposes a novel approach for power system dynamic simulation based on the differential transformation (DT). The DT is introduced to study power systems as high-dimensional nonlinear dynamical systems for the first time, and is able to avoid computations of high-order derivatives with nonlinear differential equations by its transform rules. This paper, first, proposes and proves several new transform rules for generic nonlinear functions that often appear in power system models, and then uses these rules to transform representative power system models such as the synchronous machine model with trigonometric functions and the exciter model with exponential and square root functions. This paper also designs a DT-based simulation scheme that allows significantly prolonged time steps to reduce simulation time compared to a traditional numerical approach. The numerical stability, accuracy, and time performance of the proposed new DT-based simulation approach are compared with widely used numerical methods on the IEEE 39-bus system and Polish 2383-bus system. [ABSTRACT FROM AUTHOR]

In this paper, we propose a data-driven load fluctuation model, based on high-resolution historical demand data from multi-regional systems, that can be used for research such as power system generation control studies and probabilistic load flow studies. As in previous studies, the random load fluctuations are modeled as independent Gaussian random variables; however, unlike in previous studies, we do not assume the relationship between the standard deviation and the base demand in each region is known a priori. Instead, we propose a framework for determining the relationship between the base demand level and short-term demand uncertainty. The developed framework has been tested using actual 5-minute demand data from the New York and New Zealand power systems. The results demonstrate that the proposed models outperform those used in previous work. Coefficients of the example cases are included, the parameters of which can be applied to similar multi-region systems. [ABSTRACT FROM AUTHOR]

Homotopy analysis method (HAM) is a popular semi-analytical method used widely in applied sciences. It stands out from the rest of the semi-analytical methods as it provides a family of solutions to nonlinear equations, including ordinary differential equations (ODEs), partial differential equations, etc. The convergence characteristics of the solutions can be varied by changing an auxiliary parameter ($\hbar$) in HAM. The convergence region of solution of ODEs using HAM can be improved by applying it over multiple intervals of time, which is referred to as multi-stage HAM (MHAM). In this paper, MHAM models for the IEEE Model 2.2 synchronous machine, IEEE Type-1 excitation system, first-order governor and first-order turbine models have been developed. The applicability of MHAM for power system dynamic simulations has been investigated in this paper using seven widely used test systems ranging from 10 generators 39 bus systems to 4092 generators 13 659 bus systems. The effect of number of terms, $\hbar$ and the time step on the accuracy and stability of the solution has been studied. The effectiveness of MHAM has been compared with the modified Euler (ME) and midpoint Trapezoidal (TrapZ) methods. The accuracy of MHAM has been found to be comparable with ME and TrapZ methods for the values of $\hbar$ between $-$ 1.05 and $-$ 0.95. The best accuracy is obtained for $\hbar$ = $-$ 1.0, which is a special case of MHAM called multi-stage homotopy perturbation method (MHPM). In this paper, it is also shown that MHPM is equivalent to multi-stage adomian decomposition method, which has been recently explored for large power system simulations. [ABSTRACT FROM AUTHOR]

A continuous Online Monitoring System (OMS) for power system stability based on Phasor Measurements (PMU measurements) at all the generator buses is proposed in this paper. Unlike the state-of-the-art methods, the proposed OMS does not require information about fault clearance. This paper proposes a convolutional neural network, whose input is the heatmap representation of the measurements, for instability prediction. Through extensive simulations on standard IEEE 118-bus and IEEE 145-bus systems, the effectiveness of the proposed OMS is demonstrated under varying loading conditions, fault scenarios, topology changes, and generator parameter variations. Two different methods are also proposed to identify the set of critical generators that are most impacted in the unstable cases. [ABSTRACT FROM AUTHOR]

This paper describes the use of large electric grids in university electric power system courses. Since much actual power system information is not publicly available, the application of public domain synthetic grids developed by the authors is presented including a 2000-bus grid. Discussion of the educational applications utilized in a senior level class are given for power flow analysis and sensitivity, economic dispatch, contingency analysis, optimal power flow (OPF), security-constrained OPF, transient stability, and real-time dynamic operations. In each of these, the application of the large synthetic grids give students insights and experience with cases closer to actual power systems in complexity and size. [ABSTRACT FROM AUTHOR]

The paper proposes a new adaptive approach to power system model reduction for fast and accurate time-domain simulation. This new approach is a compromise between linear model reduction for faster simulation and nonlinear model reduction for better accuracy. During the simulation period, the approach adaptively switches among detailed and linearly or nonlinearly reduced models based on variations of the system state: it employs unreduced models for the fault-on period, uses weighted column norms of the admittance matrix to decide which functions to be linearized in power system differential-algebraic equations for large changes of the state, and adopts a linearly reduced model for small changes of the state. Two versions of the adaptive model reduction approach are introduced. The first version uses traditional power system partitioning where the model reduction is applied to a defined large external area in a power system and the other area defined as the study area keeps full detailed models. The second version applies the adaptive model reduction to the whole system. The paper also conducts comprehensive case studies comparing simulation results using the proposed adaptively reduced models with the linearly reduced model and coherency-based reduced model on the Northeast Power Coordinating Council 140-bus 48-machine system. [ABSTRACT FROM AUTHOR]

Interarea power oscillation damping enhancement in large interconnected power systems is often accomplished using supplementary controls at the synchronous machines involved and with the use of flexible ac transmission system devices. The power system literature has demonstrated that wide area signals could be more effective than the local signals for these controllers. In some cases where phasor measurement units are used, all the required control signals may not be available. To alleviate these cases, control signals are obtained using estimated signals from a “dynamic state estimator,” and a robust supplementary controller is deployed. In this paper, the cited strategy is illustrated using a static var compensator. The feasibility of the proposed method has been demonstrated on the IEEE 50-generator test system. [ABSTRACT FROM AUTHOR]

The aim of this paper is to define and develop an optimal hierarchical demand-side power-system primary-frequency control structure in order to provide a reliable complement to generator inertia and governor response while improving inter-area oscillation damping. This resilient optimal load control strategy utilizes both wide-area and local signals to guarantee that the system remains stable in the case of communication failures. In the device layer, we deal with demand-response and frequency regulation by minimizing the total disutility of consumers subject to power balance and frequency regulation over the network. In the supervisory layer, we handle the power system's electromechanical oscillations using an linear-quadratic regulator (LQR)-based state feedback scheme with sparsity promotion to achieve the necessary tradeoff between complexity and performance. Since the wide-area feedback loops are built on top of an existing decentralized load control strategy, this design approach creates a decentralized/hierarchical demand-side load-control structure with significant advantages in terms of reliability and operational flexibility. Our study clearly shows by simulation that a demand-side hierarchical load-control strategy has a significant potential for improving the dynamic performance of power systems, even when implemented with a limited number of measurement units and controlling less than $1\%$ of the total base load. [ABSTRACT FROM AUTHOR]

The motivation and training of a proficient and diverse pool of power engineers, system operators, and policymakers is an important challenge for the electric industry. Power system experts are increasingly in demand globally to facilitate transitions to more environmentally friendly energy systems. More generally, citizens with a basic understanding of load balancing and renewable energy sources are more effective partners in increasingly complex power economies and political decisions. To address the need for an accessible general introduction to power systems, we are developing Griddle, an educational video game that introduces secondary school students to the basics of power system design, scheduling, and operation. We describe the design of Griddle's gameplay and underlying simulation, improvements made in response to user feedback, alignment with emerging teaching standards, and a high school classroom evaluation (n = 178) of Griddle's significant transformative impact, with the goal of validating the game-based learning approach and sharing “lessons learned” with designers of related tools. We find that Griddle is effective at engaging students and presents evidence that it helps students integrate key concepts, and we identify areas where further development and study are needed. [ABSTRACT FROM AUTHOR]

To mitigate forced oscillation and avoid confusion with modal oscillation, fundamentals of forced oscillation in multimachine power system are investigated. First, the explicit formulation of the oscillation is formulated in terms of forced disturbances and system mode shapes. Then, forced oscillation amplitude, components and envelope are intensively studied. Consequently, measures for mitigating the oscillation are obtained. Forced oscillation can also be effectively detected and discriminated from modal oscillation by utilizing its uniqueness of components properties and envelope shapes. Study results of the 10-machine 39-bus New England test system and a real-life power system demonstrate the correctness of theoretical analyses and effectiveness of detection methods for forced oscillation. [ABSTRACT FROM AUTHOR]

The presence of frequency sensitive loads such as motors has sustainable impact on power system frequency response (SFR). With increasing wind power penetration into the power system, guidelines for frequency regulation need to be revised to ensure system stability and reliability. Frequency regulation becomes more critical with the presence of frequency sensitive loads in wind integrated power system. This paper presents the impact of frequency sensitive loads on system frequency when wind farm is integrated with the conventional power system. A small-signal linearized model of variable speed wind turbine generator is derived. The typical SFR model is developed for wind farm integrated power (WFIP) system. Sensitivity and stability analysis is carried out for linearized model of WFIP system. The observations drawn from the analysis can be useful for the system operators for decision making of appropriate schemes for primary frequency control, demand response, and setting of relays, etc. for secure and stable power system operation. The proposed analysis is validated in IEEE 9-bus system using MATLAB simulation studies. [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]

Dynamic response of loads has a significant effect on system stability and directly determines the stability margin of the operating point. Inherent uncertainty and natural variability of load models make the stability assessment especially difficult and may compromise the security of the system. We propose a novel mathematical “robust stability” criterion for the assessment of small-signal stability of operating points. Whenever the criterion is satisfied for a given operating point, it provides mathematical guarantees that the operating point will be stable with respect to small disturbances for any dynamic response of the loads. The criterion can be naturally used for identification of operating regions secure from the occurrence of Hopf bifurcation. Several possible applications of the criterion are discussed, most importantly the concept of robust stability assessment (RSA), that could be integrated in dynamic security assessment packages and used in contingency screening and other planning and operational studies. [ABSTRACT FROM PUBLISHER]

Estimation of electromechanical modes of a power system has attracted attention in the past few decades because it can provide vital information about the stability of the system. In this paper, a new state-space model is proposed for online detection of parameters of a ringdown signal using an extended Kalman filter (EKF). The proposed model can estimate both constant and time-varying parameters. Furthermore, stability analysis of the proposed model is performed to demonstrate the convergence of the parameters. Simulation results confirm the desirable performance of the proposed method for ringdown parameter estimation. [ABSTRACT FROM PUBLISHER]

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]

This paper presents a method to determine suitable countermeasures against emerging aperiodic small disturbance rotor angle (ASD) instability. The method utilizes stability indicators, computed in real time, to define a criterion for ASD stability. Sensitivities of these stability indicators are then determined and used to identify the most influential nodes for countermeasures. To increase the computational speed, only nodes visited by a self-propagating graph, rooted at the vulnerable generator, will have their sensitivities calculated. The steady state voltages after a given countermeasure are then determined, using a grid transformation coefficient (GTC) and a numerical, iterative solution to an equation system. The stability criteria can then be assessed to evaluate the sufficiency of a suggested countermeasure. The method is demonstrated on a synthetic 8-bus network and a 464-bus model of the Western Denmark transmission grid. The method successfully demonstrates its ability to efficiently identify and evaluate countermeasures for a large, practical system. [ABSTRACT FROM PUBLISHER]

Short-term voltage stability is an increasing concern in today's power systems due to the growing penetration of induction motors. This paper proposes a systematic method for optimal placement of dynamic VAR support against short-term voltage instability. The problem is formulated as a multi-objective optimization model minimizing two conflicting objectives: 1) the total investment cost and 2) the expected unacceptable short-term voltage performance subject to a set of probable contingencies. STATCOM is employed for its stronger dynamic VAR support capability. Indices for quantifying the short-term voltage stability and the related risk level are proposed for problem modeling. Candidate buses are selected based on the concept of trajectory sensitivity. Load dynamics are fully considered using a composite load model containing induction motor and other typical components. A relatively new and superior multi-objective evolutionary algorithm called MOEA/D is introduced and employed to find the Pareto optimal solutions of the model. The proposed method is verified on the New England 39-bus system using industry-grade models and simulation tool. [ABSTRACT FROM AUTHOR]

Several studies have recently reported the capability of doubly-fed induction generator (DFIG) wind farms in improving the dynamic performance of power systems. Since wind farms are more often located far from the system conventional generation centers, local signals do not comprise enough content for damping inter-area oscillations. This paper presents a particle swarm optimization (PSO)-based wide-area damping controller (WADC) for the DFIG wind farms. The proposed controller is designed with a centralized nature on the basis of latest technological development of wide-area measurement system (WAMS). Damping both inter-area and local oscillatory modes are intended in the design process. The most challenging deficiency against WAMS real-time applications is the variable communication latency which can deteriorate the system stability if not properly accounted for in the controller design process. The proposed WADC hence incorporates effective means to compensate for the destructive characteristics of WAMS delayed signals. The PSO technique is applied to normalize and optimize the parameters of WADC. A set of comprehensive case studies are conducted on a 16-bus six-machine test system and the obtained numerical evidences are thoroughly discussed. [ABSTRACT FROM AUTHOR]

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]

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]

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]

This paper proposes a method for online identification of modes corresponding to low-frequency oscillations in a power system. The proposed method has considered the effect of colored Gaussian noise produced due to filters used for signal preprocessing. In order to mitigate the effect of colored Gaussian noise, the paper first proposes a modified total least square estimation of signal parameters via rotational invariance techniques (TLS-ESPRIT) that utilizes first and second rotational shift invariance properties of the signal. In the next step, the modified TLS-ESPRIT utilizes the signal transformed in an orthogonal basis. The proposed method has been compared with the improved Prony, the TLS-ESPRIT and the fourth-order cumulant-based TLS-ESPRIT (4CB-TLS-ESPRIT) using a test signal for identification of the modes at different noise levels. Robustness of the proposed method is established in the presence of colored Gaussian noise through Monte Carlo simulations. Estimation of modes for a two-area power system, using the proposed method, is carried out in the present work. Comparison of the proposed method with other methods is also performed on real-time probing test data obtained from the Western Electricity Coordinating Council (WECC) network. [ABSTRACT FROM PUBLISHER]

This paper studies real-time estimation of stability margin of a power system under disturbances by continuous measurement data. The paper presents a ball-on-concave-surface (BOCS) mechanics system as a power system's adaptive equivalent representing its real-time status and the stability region about a monitored variable. The parameters of the equivalent are adaptive to the operating condition and can online be identified from the phase-plane trajectories of the monitored variable. Accordingly, the stability margin and risk of instability can be estimated. Case studies on a two-generator system and a 179-bus system show that the BOCS system can be applied either locally or for wide-area stability monitoring in real-time calculation of stability margin. This paper proposes a new idea for using real-time measurements to develop and identify a power system's adaptive equivalent as a basis for online prediction of instability. [ABSTRACT FROM PUBLISHER]

It is possible to prevent collapse of the whole post-fault power system, which is in unstable condition, by determining the splitting boundary so as to calm down the system oscillation. A fast method of searching for the splitting boundary of power system controlled islanding is presented in this paper, the aim of which is to minimize the load-generation imbalance in each island. The method contains three phases, namely, defining the domain of each generator according to power flow tracing algorithm, determining an initial splitting boundary based on the grouping information of generators, and refining the initial one to get the final splitting boundary. A real-time searching program for power system splitting boundary was developed based on the method. Simulations on the IEEE 118-bus power system and a practical power system show that the proposed method is effective and fast. [ABSTRACT FROM PUBLISHER]

In this paper, a new class of preconditioners for iterative methods is proposed for the solution of linear equations that arise in the time-domain simulation of the power system. The system of linear equations results from an attempt to solve the differential algebraic equations (DAE) encountered in the power system dynamic simulation. The preconditioners are based on the multifrontal direct methods. The proposed method is compared to the incomplete LU factorization (ILU) based preconditioned iterative methods and other conventional direct linear sparse solvers. The comparison shows the proposed method achieves great computational efficiency relative to these other methods. [ABSTRACT FROM PUBLISHER]

In isolated power systems, frequency stability is traditionally considered to be assured by maintaining sufficient spinning reserve that is usually equal to the largest generation output of all the units in operation. However, the system security depends on the spinning reserve allocation to the units in operation and the provision of adequate emergency or fast reserve that need be available in the first crucial seconds after a loss of generation event. The system emergency reserve is usually much lower than that expected if only the unit droops are taken into account. Also, the generating units can be overloaded for a short time period and this capability can contribute to a faster frequency restoration. This paper presents an improved speed governor model that utilizes the short time overloading capability of the generating units. The efficient computational method described in the paper for the optimal spinning reserve allocation in isolated power systems was developed by taking into account a composite security criterion in the most economic way. Furthermore, a statistical analysis is presented in order to investigate the contribution of spinning reserve to the short-term system security. In the paper the developed method is applied to a typical isolated power system and it demonstrates its advantages. [ABSTRACT FROM AUTHOR]

Repeated simulations have been most widely applied in analyzing the sensitivities of the power system dynamics with respect to controller inputs. This approach is computationally intensive and it does not explicitly show the physical insights. A transfer function matrix based approach is proposed in this letter for control input sensitivity analysis. A bottom up method is also presented to build the respective transfer function matrix. The effectiveness of the method is demonstrated through case studies. [ABSTRACT FROM AUTHOR]