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In this paper we present a scalable approach based on the latency-based linear multistep compound method to use graphic processing unit (GPU) to accelerate the power system simulations with electromagnetic transients.To balance between the computational load and accuracy, we modeled the power system using shifted frequency analysis. Then, to efficiently exploit the hardware, our computational approach is designed to utilize both data-parallel and task-parallel execution. In addition, a graph-based thread safety design is introduced to achieve high scalability in the paralleled component computations. Furthermore, our implementation introduces a translation layer for different heterogeneous computing frameworks during compile time, so that a wide range of GPU devices can be supported without losing performance. Finally, benchmark results show that our approach achieves faster-than-real-time capability for systems with hundreds to thousands of nodes.

In this paper we present a scalable approach based on the latency-based linear multistep compound method to use graphic processing unit (GPU) to accelerate the power system simulations with electromagnetic transients. To balance between the computational load and accuracy, we modeled the power system using shifted frequency analysis. Then, to efficiently exploit the hardware, our computational approach is designed to utilize both data-parallel and task-parallel execution. In addition, a graph-based thread safety design is introduced to achieve high scalability in the paralleled component computations. Furthermore, our implementation introduces a translation layer for different heterogeneous computing frameworks during compile time, so that a wide range of GPU devices can be supported without losing performance. Finally, benchmark results show that our approach achieves faster-than-real-time capability for systems with hundreds to thousands of nodes. [Display omitted] • Exploits data- and task-parallelism together in an automated way. • A graph-based approach to ensure thread safety to increase scalability. • A compile-time translation layer to allow execution on various platforms. • Faster-than-real-time for system with more than 10,000 dynamic components. • 82 × faster compared to an optimized sequential simulation. [ABSTRACT FROM AUTHOR]

This paper presents an accurate and efficient initialization strategy for modular multilevel converters (MMCs) based on the shooting method, a numerical technique aimed at deriving the periodic steady-state operating condition of any circuit. This technique is compatible with MMC models of different levels of detail and whose control scheme may include modulation strategies and capacitor voltage balancing algorithms. Electromagnetic transient simulations of the NORDIC32 power system modified by adding a high-voltage direct current link with 128-level MMCs prove that the proposed initialization strategy allows starting simulations close to steady-state, thereby significantly limiting initialization transients and their corresponding extra CPU time. • We present a technique to initialize grids with modular multilevel converters (MMCs). • The proposed technique is based on the shooting method (SHM) and is purely numerical. • Initialization transients (and, thus, CPU time) are minimized by the SHM. • The approach is compatible with different MMC models and control schemes. • A benchmark grid is simulated to validate the accuracy and efficiency of the method. [ABSTRACT FROM AUTHOR]

• Battery modeling allows accurate prediction of the parameters in long-term processes improving decision-making. • The generic modeling algorithm combines three methods in one model: the experimental database, the equivalent circuit, and the analytical equations. • The model input signals are power demand and environment temperature corresponding to power system simulations such as sizing procedures. • The generic model could easily be utilized for any ESS (with similar technology) by a few experimental procedures. The lengthy process of sizing and optimizing hybrid energy sources requires an accurate battery model. This paper presents a generic new energy storage system model premeditated to solve the optimization problem of the sizing procedure. The model comprises several methods, a lookup table, an equivalent battery circuit, and analytical equations. The database is created offline based on experimental results achieved under various conditions. In the first step, the model receives an external vector of signals comprising load power demand, instantaneous generated energy, and ambient temperature. Then, the algorithm predicts the impact of the load on the battery parameters by either interpolation or extrapolation. The results are utilized at an equivalent circuit that supplies the basic parameters and the battery constraints. Next, analytical methods reveal the more advanced parameters such as charge, supplied and remaining energy, etc. The results show that the proposed dynamic battery model can predict the battery states through all operating zones and under different battery conditions. The benchmark results present higher accuracy than other available models. The proposed model was employed in a sizing procedure to verify the model's accuracy. It was shown that the new model estimates the required source rating more precisely than standard models. Since the suggested algorithm is based on actual battery curves, it can be utilized for all types of batteries by reentering the data of any other battery. [ABSTRACT FROM AUTHOR]

This paper proposes a simplified yet accurate enough thermal model of Voltage Source Converters (VSC), aimed at circumventing the high computational cost of existing models, which prevents their use in electromechanical simulations. The proposed model reduces to a simple first-order system for thermal dynamics plus two quadratic equations separately modeling the IGBT and diode power losses. In addition, a methodology is provided to derive the proposed VSC thermal model parameters from manufacturer data. The proposed model is tested for two types of devices, both in steady and transient states. The results show that the reduced-order thermal model produces accurate results at a low computational cost, making it especially suitable for the co-simulation of thermal and electrical dynamic phenomena. • New methodology for embedding VSC thermal behaviour in electromechanical simulations. • Fast and slow thermal dynamics modelled by respective algebraic and differential equations. • VSC thermal model parameters computed from manufacturer datasheet. • Methodology validated for three VSC applications in steady-state and dynamic conditions. [ABSTRACT FROM AUTHOR]

• Proposing an new integration method that considers the relationship between simulation time-step and time constants of elementary transfer function blocks (ETFBs), including three integration modes: single-step integration, multiple-step integration, and static approximation. • Giving the implementation of static approximation for ETFBs with small time constants. • Discussing the determination of the threshold values of internal time-step for ETFBs. • Applying the proposed method to an open-source Simulation Toolkit for Electrical Power Systems (STEPS). With the development of renewable energy sources, the scale and complexity of power systems are continuously increasing, resulting in a high requirement for the efficiency of dynamic simulation. Increasing the simulation time-step is a possible measure for the fixed time-step (FTS) method to accelerate the simulation, yet also a potential cause for deteriorating the simulation accuracy. To improve the overall power system dynamic simulation speed without jeopardizing the expected accuracy, this paper proposes a novel Uneven Internal Time-Step Adjustment method based on Trapezoidal integration of elementary transfer function blocks (ETFBs). For ETFBs with different time constants, three different integration modes are defined, including single-step integration, multiple-step integration, and static approximation. Each ETFB can select an appropriate integration mode and adjust its internal time-step, automatically expanding the size of the simulation time-step. Implementation of static approximation for ETFBs with small time constants is given. Discussion on the determination of threshold values of internal time-step is provided, which mainly affect the accuracy of the system. The proposed method is applied to the open-source Simulation Toolkit for Electrical Power Systems (STEPS). Different cases are tested to obtain the maximum simulation time-step that can maintain numerical stability and validate the efficiency and accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

Highlights • An improved average value model (AVM) of modular multilevel converter (MMC) for large-scale system simulation. • Accurate performance in all types of faults and blocked state of MMC. • Easy modelling in commonly used software packages. Abstract Detailed model (DM) of modular multilevel converter (MMC) brings about a high computational burden for electromagnetic transient (EMT) simulation. Therefore averaged value model (AVM) of MMC is proposed for fast simulation of large-scale multi-terminal HVDC system. No direct electrical contact exists between AC and DC system in conventional AVM and therefore the coupling relationship among electric quantities in fault analysis could not be accurately modelled. In order to solve the aforementioned problem, an improved AVM (IAVM) of half-bridge (SB) MMC topology is proposed. All capacitor voltages of AVM are constant and an arm is directly equivalent to a controlled voltage source. The proposed AVM can be applied for the DC faults and blocking conditions by introducing a group of switches connecting AC and DC sides. Two extra controlled voltage sources are introduced for correct DC voltage offset in AC voltages under DC line-to-ground (LTG) faults. Simulation results verify the accuracy and efficiency of the IAVM. IAVM could be implemented in commonly used software packages and is suitable for power system fault analysis. [ABSTRACT FROM AUTHOR]

Highlights • A general framework for model validation from frequency perspective is proposed. • New parameters, Frequency Ramp Rate (FRR) and Activity Range (AR), are introduced. • A quantitative assessment method is proposed for the model validation process. • Proposed framework is implemented successfully for a large and real power grid. • The steps of implementation are clarified through detailed results and discussion. Abstract This paper proposes a quantitative model validation framework from the frequency perspective in which some of the technical issues of the process are solved. Two influential parameters of the process, namely the frequency ramp rate and activity range are introduced. A new quantitative assessment method including indices development and threshold calculation method is proposed. In order to reduce the complexities and efforts, all the capabilities of the existing models are initially tried (as approach 1) and upon its failure, more complex models are developed and employed (as approach 2). After discussing the theoretical aspects, the implementation steps and effectiveness of the process are demonstrated by applying the framework to a large and real power system. Some solutions for the practical issues are proposed and implemented. Since the simulation results of the first approach exceed some specified thresholds, the second approach is followed. Quantitative assessment of the second approach proves that the simulation results satisfy the specified thresholds for all incidents. The prominent and vital effect of different influential parameters and improving actions of the process are also demonstrated on the validated model. [ABSTRACT FROM AUTHOR]

Highlights • Identifying events from PMU data is a difficult recognition exercise. • Time series may be transformed into 2D images. • Convolutional neural networks can accurately recognize images and identify events. • A GPU accelerates training down to seconds, compatible with operation environment. • 100% positive recognition achieved for 4 types of events in the Brazilian system. Abstract This paper presents a new method to identify classes of events, by processing phasor measurement units (PMU) frequency data through deep neural networks. Deep tapered Multi-layer Perceptrons of the half-autoencoder type, Deep Belief Networks and Convolutional Neural Networks (CNN) are compared, using real data from Brazil. A sound success is obtained by a transformation of time-domain signals, from dynamic events recorded, into 2D images; these images wee processed with a CNN, taking advantage of the strong dependency existing among neighboring pixels in images. The training, computing and processing was achieved with a GPU (Graphics Processing Unit), allowing speeding-up of the process up to 30 times and rendering the process suitable to increase the online situational awareness of network operators. [ABSTRACT FROM AUTHOR]

Highlights • A non-linear fitting-based phasor measurement method for PMU calibrator is proposed. • Parameters setting methods are proposed to ensure uniqueness of the solution. • White noise restraining methods are proposed to further improve accuracy. • A PMU calibrator is developed based on the proposed method. • Testing results show that he PMU calibrator can provide valid test references. Abstract With the increasing penetration of renewable energies, phasor measurement units (PMUs) play increasingly important roles in security control and mechanism studies for power systems. The testing and calibration of PMUs are key to their effectiveness in a power system; therefore, providing valid test reference values with sufficient precision under steady-state and dynamic conditions is critical. This paper proposes a non-linear fitting-based phasor measurement method for a PMU calibrator to provide reference measurements. Two universal phasor-fitting models are built to represent different signals in PMU steady and dynamic testing. An objective function is presented, which obtains the minimum value of the sum of squares of a non-linear real-valued function based on phasor-fitting models. The methods to set the initial points and bound constraints of the parameters to be fitted are stated to make the objective function convex. An iterative technique, finding the local minimizer of the built objective function in the restricted region, is proposed to calculate the phasor, frequency, and rate of change of frequency (ROCOF). A white noise restraining method is proposed to further improve measurement accuracy. Then, the proposed method is implemented into hardware to develop a real PMU calibrator. To verify the accuracy of the PMU calibrator, simulations and experimental testing are carried out. Results show that the effectiveness of the PMU calibrator can meet calibration requirements under typical static and dynamic conditions of power systems with high penetration of renewable energies. The developed PMU calibrator can thus be used to calibrate PMUs. [ABSTRACT FROM AUTHOR]

Highlights • Investigation of RoCoF-driven tripping of distributed generators in the GB grid. • Thermostatic loads contribute to system inertial response by preventing DG tripping. • Analysis of frequency dynamics and activation settings of loss of mains protections. Abstract Integration of large amounts of asynchronous renewable energy sources (RES) would reduce the effective inertia of the future Great Britain (GB) network. As a result, after a large infeed loss, containing the grid frequency and limiting its rate of change (RoCoF) above certain thresholds would be a challenge for the system operator. In particular, large RoCoFs could activate RoCoF-sensitive loss-of-mains (LoM) protections of distributed generators (DGs) and trigger cascading disconnections. In this context, thermostatic loads (TCLs) can be controlled to collectively provide support and contribute to the overall system inertial and frequency response. This paper focuses on the transient response period after a frequency disturbance and the fast protection events occurring in this time frame. In particular, this works evaluates the interplay between the local activation settings of LoM protection of DGs and those used to enable the TCL support. This interaction is analysed through a case study on a 36-bus dynamic equivalent of the GB network which shows how local post-fault frequency dynamics drive the overall system response. Results show that TCLs are able to prevent RoCoF-driven DG tripping and reduce the need to adopt high LoM settings, decreasing the risks of maloperation associated with desensitised protections. [ABSTRACT FROM AUTHOR]

This paper proposes a simple approach to design fractional-order (FO) controller via internal model control (IMC) technique for load frequency control (LFC) problem in power systems. The proposed scheme utilizes the concept of CRONE principle, model-order reduction and FO filter in IMC framework to derive a robust controller. Initially, the scheme is applied to single-area power system and then extended to two-area interconnected system. The turbines considered are non-reheated, reheated and hydro type; and physical constraints of turbine and governor are also taken into account to validate the applicability in more realistic environment. Simulation results show that it can bring improved disturbance rejection performance in nominal condition as well as in presence of uncertainties and constraints in plant parameters. [ABSTRACT FROM AUTHOR]

During recent years power systems are operated near the nominal capacity of system equipment with low stability margin. Operation of power systems in this condition is extremely risky and power systems lose their stability with any intense failure of system equipment. In bulk power system, it is more critical and may cause a partial or overall blackout. The capability of black start to bring back system to a normal condition in the case of partial or overall shut down is very important in each power system. When a shutdown occurs, power plants with black start capability supply cranking power for non-black start power plants, pick up critical loads and energize required transmission lines. These actions should be done in minimum time interval to maximize system provided energy during the restoration process. Most important decision making during restoration process is the determination of start-up sequence of generation units. During the restoration process, units with black start capability (BS units) start at the beginning of the process to provide cranking power for non-black start units (NBS units). Hence the determination of NBS units is decision variable in the restoration problem. In this paper, this problem has been described as a bi-level optimization problem which in upper level determines the optimal start-up sequence of NBS units by using a Teaching-Learning Based Optimization algorithm and in lower level determines the optimal transmission path with minimum number of switching and maximum reliability between any two necessary buses using the searching path graph-based algorithm. The proposed approach has been implemented successfully on IEEE 24-bus RTS and IEEE 118-bus test systems. [ABSTRACT FROM AUTHOR]

A new technique is presented for solving the problem of enforcing control limits in power flow studies. As an added benefit, it greatly increases the achievable precision at nose points. The method is exemplified for the case of Mvar limits in generators regulating voltage on both local and remote buses. Based on the framework of the Holomorphic Embedding Loadflow Method (HELM), it provides a rigorous solution to this fundamental problem by framing it in terms of optimization . A novel Lagrangian formulation of power-flow, which is exact for lossless networks, leads to a natural physics-based minimization criterion that yields what is plausibly the best solution. For networks with small losses, as is the case in transmission, the ac power flow problem cannot be framed exactly in terms of optimization, but the method still retains its ability to select a solution. This foundation then provides a way to design a HELM scheme to solve for the minimizing solution. Although the use of barrier functions evokes interior point optimization, this method, like HELM, is based on the analytic continuation of a germ (of a particular branch) of the algebraic curve representing the solutions of the system. In this case, since the inequality constraints result in an unavoidable singularity at s = 1 , direct analytic continuation by means of standard Padé approximation exhibits numerical instabilities. This has been overcome by means of a new analytic continuation procedure, denominated Padé-Weierstrass, that exploits the covariant nature of the power flow equations under certain changes of variables. A side benefit of this procedure is that it can also be used when limits are not being enforced, in order to increase the achievable numerical precision in highly stressed cases. [ABSTRACT FROM AUTHOR]

In this paper, a fast load shedding remedial action scheme (RAS) is developed considering generation pattern of local wind farms using wide area monitoring framework. In the proposed RAS, the shedding candidates are selected and prioritized based on load types and their impacts on the voltage profile and transient performance of the system. The dynamics of wind farms are also included in the shedding requirements and formulas by defining effectiveness indices which are calculated based on the contribution of each generator to the dynamic performance of the system. This allows secure operation of the system after major contingencies while impacted customers are minimized. The proposed methodology, shedding formulas, and corresponding requirements are verified for the BC Hydro system using the PSS/E dynamic simulation package. [ABSTRACT FROM AUTHOR]

This paper presents a new dynamic model and control approach for static synchronous series compensator (SSSC) to participate effectively in automatic generation control (AGC) of an interconnected deregulated power system. In doing so, a new mathematical formulation is extracted to present the participation of the SSSC in the tie-line power flow exchange. Besides, fractional order controllers (FOCs) are employed to design an effective SSSC damping controller. The effectiveness of the proposed SSSC-based damping controller in preparing an efficient AGC ancillary service is compared with its earlier model. Two heuristic algorithms of improved particle swarm optimization (IPSO) and modified group search optimization (MGSO) are compared to optimize the controller parameters. To achieve realistic results under a competitive scenario, a diverse-GENCOs multi-DISCOs power system with the physical nonlinear constraints, bilateral contracts, and pool-co transactions are taken into consideration, simultaneously. Dynamic simulation results reveal that the proposed FOC-based SSSC damping controller is superior to the earlier one to improve the restructured AGC performance. Comprehensive examinations are carried out under the un-contracted step, higher degree step, and random load demands which act as contract violation scenarios to validate the damping performance of the proposed controller. To demonstrate the robustness of the proposed control approach, sensitivity analysis is accomplished in a wide range of loading condition and system parameters. [ABSTRACT FROM AUTHOR]

In this paper stochastic collocation method is proposed to solve probabilistic power flow (PPF) model of South Australia (SA). And this model is based upon historical acquisition of power system data of SA. In SA, numbers of wind farms are installed and the variability of wind speed brings more uncertainties into the power system. The traditional deterministic power flow (DPF) computation does not take into account the probabilistic nature of power system uncertainties, so PPF computation is imperative. However, as a commonly used PPF simulation method, Monte Carlo simulation (MCS) has a very high computation cost. Hence, in this paper sparse grid interpolation (SGI) is presented to accomplish PPF analysis with striking high computation efficiency. Meanwhile, instead of using theoretical wind power generation model, probabilistic collocation method (PCM) is used to construct realistic relationship between wind speed and wind power. In addition, fuzzy logic optimization is applied to PCM to improve the accuracy of the model output. The paper concludes with presentation of an aggregated DC power flow model of SA to compare the computation efficiency of the SGI and MC. [ABSTRACT FROM AUTHOR]

With wide applications of power electronic devices in modern power systems, simulation using traditional electromechanical and electromagnetic tools suffers low speed and imprecision. Multi-rate methods can enhance efficiency of simulation by decreasing the scale of systems in small time-steps. However, the existing traditional methods for multi-rate simulation suffer the problems of instability and simulation errors. These have hindered the application of multi-rate simulation in power industry. Therefore theoretical evaluation on different multi-rate simulation methods is crucial to understand the feasibility and limitation of the methods, and to contribute to overcome the drawbacks of the traditional methods. In this paper, the multi-rate simulation performance based on two traditional technologies and a Modified Thevenin Interface are evaluated to provide an overall feasibility of multi-rate algorithms in the power simulation. The Modified Thevenin Interface is proposed to overcome the drawbacks in synchronization. Three theorems are proposed and proved for theoretically analyzing the stability of the simulation methods. Error analyses of the multi-rate methods are performed to identify the relationships between errors and simulation conditions. Besides, the accuracy and efficiency performance in a practical project of VSC-MTDC shows the feasibility and necessity by using multi-rate simulation. Through the theoretical analysis, the issues of stability and accuracy of multi-rate simulation for the DC grids have been better understood, based on which an improved simulation algorithm has been proposed to overcome these issues. Long-term system dynamics of large-scale systems containing DC grids and fast transients of HVDC converters can be investigated simultaneously with high speed and sufficient accuracy. [ABSTRACT FROM AUTHOR]

A concept of sensitive line set is presented in this paper, aiming to enhance the ability of resilient power system to prevent and resist the external extreme disturbances. Furthermore, a new fault chain model is established, in order to obtain the above sensitive line set. The fault chain, calculated by this fault chain model, is consisted of the initial segment and the middle segment. The index of bus load rate for the initial and the middle segments is presented firstly to reflect the load condition of a system in the fault chain model. Besides, other indices, such as historical fault statistics, line load degree, and correlation coefficient in the initial segment and power flow transfer, sequent overload of lines, and damage of transmission sections in the middle segment, are concerned and normalized to predict all the fault chains. Then, the sensitive line set can be obtained after the risk calculation and level assessment for the fault chains. The set can become the basis for controlling process of resilient power system during the accident preventing and resisting stages. Finally, the rationality of the proposed sensitive line set is demonstrated via 39 bus system. [ABSTRACT FROM AUTHOR]

In this paper, we investigate optimal locations and capacity for integrating storage systems in the electric transmission grid to improve wind power production. The impacts on wind power production and conventional thermal generation due to operation of utility-scale storage systems are simulated. A compressed air energy storage (CAES) is chosen as an utility-scale storage technology, which can provide several hundred MWs of electric power. A mixed integer programming (MIP) is implemented for the mathematical formulation. The Electric Reliability Council of Texas (ERCOT) wind, load data and its simplified transmission system are used for a case study. To mandate wind power production, we apply 20% goal for renewable portfolio standard (RPS). Operation of 1350 MW CAESs improves wind power production and RPS target achievements, however, thermal generation does not significantly decrease under the given simulation condition. [ABSTRACT FROM AUTHOR]

Electromechanical oscillation is an inherent property of ac power systems which can occur in the forms of local and inter-area oscillations. The inter-area oscillations may impose a serious threat on the system if they are not controlled properly. Over the past two decades, many methods have been introduced to control and suppress electromechanical oscillations. This paper proposes a new supplementary emergency damping control (SEDC) to suppress inter-area oscillations. In the proposed approach, a system brittleness index (SBI) is introduced which can show system risk for splitting into uncontrolled islands. Following a sever fault, the value and sign of SBI is used as an indicator for activation of SEDC. By using sensitivity analysis of the inter-area mode with respect to line switching, the most effective transmission line switching (TLS) is utilized as an emergency damping control for suppressing inter-area oscillations. For this purpose, by offline studies, a priority list of the effective lines switching is prepared. Then, in the real time operational environment, by using an optimization algorithm, the most effective line switching is implemented as SEDC activation. The optimization algorithm guarantees system operation against any potential violation due to line switching. The proposed SEDC has been demonstrated on IEEE 39-buses system with promising results. [ABSTRACT FROM AUTHOR]

Real-time (RT) simulator is a powerful tool for analyzing operational and control algorithms in electric power systems engineering. For understanding the dynamic and transient behavior of a power systems, significant RT computation capabilities are essential. A single unit of RT simulator has limited simulation capabilities. The most common way of augmenting simulation capability is using a bank of locally connected RT simulators. However, creating a large-sized bank of RT simulators involves significant financial investments and hence may not be feasible at all research facilities. Power and energy systems research facilities that use RT simulators are at diverse physical locations. In addition to RT simulators, research facilities around the world house an array of facilities with unique power, energy, and control systems for innovative research. To leverage these unique research facilities, geographically distributed RT simulation based on Wide Area Network (WAN) is required. Typical RT simulators perform simulations with time-steps in the order of milliseconds to microseconds, whereas data latency for communication on WAN may be as high as a few hundred milliseconds. Such communication latency between RT simulators may lead to inaccuracies and instabilities in geographically distributed RT simulations. In this paper, the effect of communication latency on geographically distributed RT simulation is discussed and analyzed. In order to reduce the effect of the communication latency, a Real-Time Predictor (RTP), based on linear curve fitting is developed and integrated into the distributed RT simulation environment. Two geographically distributed digital RT simulators are used to perform dynamic simulations of an electric power system with a fixed communication latency and the predictor. Empirical results demonstrate the effects of communication latency on the simulation and the performance of the RTP to improve the accuracy of simulations. [ABSTRACT FROM AUTHOR]

We propose a novel hierarchical frequency and voltage control design for multi-area power system integrated with inverter-based resources (IBRs). The design is based on the idea of prioritizing the use of IBRs over conventional generator-based control in compensating for sudden and unpredicted changes in loads and generations, and thereby mitigate any undesired dynamics in the frequency or the voltage by exploiting their fast actuation time constants. A new sequential optimization problem, referred to as Area Prioritized Power Flow (APPF), is formulated to model this prioritization. It is shown that compared to conventional power flow APPF not only leads to a fairer balance between the dispatch of active and reactive power from the IBRs and the synchronous generators, but also limits the impact of any contingency from spreading out beyond its respective control area, thereby guaranteeing a better collective dynamic performance of the grid. This improvement, however, comes at the cost of adding an extra layer of communication needed for executing APPF in a hierarchical way. Results are validated using simulations of a 9-machine, 6-IBR, 33-bus, 3-area power system model, illustrating how APPF can mitigate a disturbance faster and more efficiently by prioritizing the use of local area-resources. • A new concept of "area-prioritization"-based power flow (APPF) dispatch is proposed to maximize the participation of inverter-based resources (IBRs) in frequency and voltage control. • A hierarchical computation architecture is developed to implement this prioritization. • Implementation steps are showcased via simulation of a 33-bus power system with 9 generators and 6 IBRs. [ABSTRACT FROM AUTHOR]

The power system protection against different threats has become a key and growing concern. A materialized threat provokes a sequence of chained events and counteractions in the grid. The simulation and analysis of the cascades leading to blackouts are extremely intricate due to various time scales, multiple interacting automatic and human-driving actions, and the large set of possible countermeasures. The possibility to simulate the cascading events, considering both behaviors of the system and human/automatic actions, is crucial for designing protective strategies, guiding investments and supporting policy decision making on reinforcing the system. In this paper, we present a simulation framework which, with a steady-state approach, provides system snapshots during cascading failures, taking into account the actions for minimizing the load-shedding or maximizing the restoration of the unserved loads. The conceptual framework is implemented as a software tool to simulate system behaviors and actions like automatic countermeasures, human interventions and optimal operational strategies to defend and restore the system. Combined with a suitable economic assessment method, it can be used to evaluate investments in countermeasures and the potential costs of different threats. It has been applied to study the countermeasures to enhance the security of the EU power transmission network. [ABSTRACT FROM AUTHOR]

The twelve-phase synchronous machines are widely used for the power supply of integrated power systems on board. This paper formulates two phase-domain (PD)-type models of twelve-phase synchronous machines for the simulation of nodal analysis-based electromagnetic transients programs (i.e., EMTP-type simulation). The PD model for the twelve-phase machine is first formulated, which avoids the interface error in the qd0 model. It is well-suitable for the implementation in EMTP-type simulators. To further improve the simulation efficiency of a power system with twelve-phase machines, a constant conductance PD (CC-PD) model is proposed, avoiding the re-factorization of the network conductance matrix at every time-step. Test results demonstrate the accuracy and efficiency of the two proposed PD-type models for the EMTP-type solution. • The PD and CC-PD models for the twelve-phase machine are formulated. • It fills the gap in EMT simulation for power systems with 12-phase machines. • The CC-PD model can be adopted in real-time EMT simulations for power systems. [ABSTRACT FROM AUTHOR]

• The paper has derived the correlations between the current of the neutral point reactor and the phase current of shunt reactors. After opening of the transmission line, due to the occurrence of permanent SPG or DPG faults, the current of the neutral point reactor is negatively correlated with the faulted-phase current of shunt-reactors. While these correlations would become invalid after the transient faults are cleared. • The paper proposed an adaptive three-phase reclosure method, which used Pearson correlation coefficient (PCC) to evaluate correlations between the currents of compensation reactors and construct a criterion for detecting when faults were cleared. • The proposed ATPAR scheme is easy implemented with low computational complexity and a fixed threshold. Simulation results showed that the ATPAR scheme proposed could reliably identify the fault nature and was unaffected by fault conditions and measurement errors. This study proposes a novel adaptive three-phase auto-reclosing (ATPAR) scheme for shunt-compensated transmission lines when a single- or double-phase-to-ground fault occurred, which is conducted on the correlations between the currents of shunt-reactors after the line opened. In this paper, the currents characteristics of compensation reactors are analyzed firstly through fault boundary condition theoretical, then, Pearson correlation coefficient (PCC) is used to construct criterions for identifying fault nature and fault cleared time. The proposed ATPAR scheme is implemented on a 230 kV-60 Hz IEEE 9-BUS power simulation system by using ATPDraw, and various faults which considered different fault conditions are simulated. The extensive simulation results verify the efficiency and reliability of the proposed ATPAR scheme. [ABSTRACT FROM AUTHOR]

• Modelling framework for automatic load frequency control studies of AC/DC grids. • It is aimed to slow transients caused by load/generation imbalances. • It is based on a suitable linear modelling of the VSC-based transmission grid. • Results are validated versus PSCAD with errors inferior to 3% This paper introduces an efficient simulation framework for automatic load frequency control (ALFC) studies of VSC-based AC/DC power grids. It is aimed at slow transients caused by large megawatt imbalances occurring either in the AC systems or DC grid. These studies involve the coordinated action of the primary and secondary control loops of power plants, ones requiring long simulation times ranging from various tens of seconds to minutes. To address these overly challenging AC/DC power system simulations, the developed modelling framework resorts to suitable linear models, i.e., VSC dynamic controls are devised to conform to the slow dynamics featuring the ALFC. The most fundamental dynamics of AC systems, DC grid and VSC stations are compiled with reasonable precision. This is demonstrated using a three-terminal, multilevel VSC-based HVDC system implemented in the PSCAD simulation package for comparative purposes; both solutions are shown to concur very well because root mean squared errors inferior to 3% are obtained. The practicality of this effective simulation framework is also demonstrated by studying a five-terminal VSC-based transmission grid facing large power imbalances imposed by load disconnections and VSC outages. [ABSTRACT FROM AUTHOR]

This paper presents a method to select the load buses for the placement of Distributed generation (DG) based on loss reduction and voltage improvement sensitivity of the system. The strategic placement of DGs can help in reducing power losses and improving voltage profile. The proposed work discusses some new sensitivity factors that can be useful for selecting the locations. The method has the potential to be used for integrating the available DGs by identifying the best locations in a power system. The proposed method has been demonstrated on IEEE 24-bus Reliability Test System (RTS). [ABSTRACT FROM AUTHOR]

Reactive power source planning problem has significant role for secure and economic operation of power system. Reactive power planning problem is nothing but the proper coordination of existing Var sources which lead to loss minimization and cost economic operation of the system. In the proposed approach several bio-inspired algorithms like Particle Swarm Optimization (PSO), Evolutionary Particle Swarm Optimization (EPSO), Adaptive Particle Swarm Optimization (APSO), Hybrid Particle Swarm Optimization (HPSO) and Bacterial Foraging Algorithm (BFA) are used for the reactive power planning problem. Finally a comparison of all these techniques are made on the basis of the results obtained when applied to different standard test system. [ABSTRACT FROM AUTHOR]

Traditionally, power system balancing operations consist of three consecutive control techniques, namely security-constrained unit commitment (SCUC), security-constrained economic dispatch (SCED), and automatic generation control (AGC). Each of these have their corresponding type of operating reserves. Similarly, energy storage resources (ESRs) may be integrated as energy, load following, or regulation resources. A review of the existing literature shows that most ESR integration studies are focused on a single control function. In contrast, recent work on renewable energy integration has employed the concept of enterprise control where the multiple layers of balancing operations have been integrated into a single model. This paper now uses such an enterprise control model to demonstrate the relative merits of load following reserves and energy storage integrated into the resource scheduling and balancing action layers. The results show that load following reserves and energy storage resources mitigate imbalances in fundamentally different ways. The latter becomes an increasingly effective balancing resource for high net-load variability and small day-ahead market time step. [ABSTRACT FROM AUTHOR]

Simulating a power system with both transmission and distribution networks modeled in detail is a huge computational challenge. In this paper, a Schur-complement-based domain decomposition algorithm is proposed to provide accurate, detailed dynamic simulations of such systems. The simulation procedure is accelerated with the use of parallel programming techniques, taking advantage of the parallelization opportunities inherent to domain decomposition algorithms. The proposed algorithm is general, portable and scalable on inexpensive, shared-memory, multi-core machines. A large-scale test system is used for its performance evaluation. [ABSTRACT FROM AUTHOR]

• Implementation of a distributed computational platform for collaborative work in the calculation of electromagnetic transients. • Performing simulations for large systems integrating smaller subsystems. • Distributed computing using separate computers (inside - or not - a LAN – Local Area Network) connected using internet protocols. • Performing electromagnetic transients calculation using geographically dispersed computers. • Conducting simulations within a subsystem with complete privacy, caring for intellectual property issues. This work presents a computational architecture tool aimed to provide a distributed and collaborative environment for electromagnetic transients calculations. Through this tool, different systems, running on different computers in distributed locations, can connect using internet protocols to form large systems. Innovatively, it allows the integration between the subsystems to occur on-demand, which differentiates it from the existing proposals in the literature. Also, it allows user interaction with the power system during the simulation. Such features are demonstrated by means of case studies running on the tool on-demand mode of operation. The opportunities arisen from the tool are further presented using a case study for large systems, 3200 buses, 28 wind farms and 7 solar farms, and also using smaller subsystems, 39 Bus. The results comprise the simulations total running time, a brief discussion about the computers communication latency and the benefits through collaborative work the tool adds to the field of electromagnetic transients calculation. [ABSTRACT FROM AUTHOR]

We report on the development of a comprehensive, stochastic simulation methodology that provides the capability to quantify the impacts of integrated renewable resources on the power system economics, emissions and reliability variable effects over longer periods with the various sources of uncertainty explicitly represented. We model the uncertainty in the demands, the available capacity of conventional generation resources and the time-varying, intermittent renewable resources, with their temporal and spatial correlations, as discrete-time random processes. We deploy Monte Carlo simulation techniques to systematically sample these random processes and emulate the side-by-side power system and transmission-constrained day-ahead market operations. We construct the market outcome sample paths for use in the approximation of the expected values of the various metrics of interest. Our efforts to address the implementational aspects of the methodology so as to ensure computational tractability for large-scale systems over longer periods include the use of representative simulation periods, parallelization and variance reduction techniques. Applications of the approach include planning and investment studies and the formulation and analysis of policy. We illustrate the capabilities and effectiveness of the simulation approach on representative study cases on a modified WECC 240-bus system. The results provide valuable insights into the impacts of deepening penetration of wind resources. [ABSTRACT FROM AUTHOR]

Growing utilization of distributed generations in the power system may lead to protection problems. Therefore, in the conventional methods, DGs should be disconnected from the grid in the fault condition. In the case of high penetration of DGs, this strategy leads to voltage sag problem. In this paper, the inverter based DGs are properly controlled in the fault condition instead of disconnecting from the grid. This approach is called fault ride through strategy. The simulation results show that the fault current is kept in the desired range by using the proposed algorithm and the protection coordination before connection of DG remains intact even after the connection of DG. In addition, the voltage sag is improved due to DGs reactive power injection during the fault condition. Moreover, this method has not any additional cost because the proposed control strategy is carried out on the interfaced inverter and there is no need to use additional elements. [ABSTRACT FROM AUTHOR]

This paper presents a new load frequency control (LFC) design, using the Coefficient Diagram Method (CDM) in a multi-area power system. The CDM controller has been designed to reduce the effect of uncertainties owing to variations in the parameters of governors and turbines as well as load disturbance. Each local area controller is designed independently, such that, stability of the overall closed-loop system is guaranteed. The CDM structure is built on the frequency response model of multi-area power system, and physical constraints of the governors and turbines are considered. Digital simulations for both two and three-area power systems are provided to validate the effectiveness of the proposed scheme. From the simulation results it is shown that, considering the overall closed-loop system performance with the proposed CDM technique, robustness is demonstrated in the face of uncertainties due to governors and turbines parameters variation and loads disturbances. A performance comparison between the proposed controller, model predictive controllers (MPC), and a classical integral control (I) scheme is carried out, confirming the superiority of the proposed CDM technique. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to design excitation controller for power systems to enhance small-signal stability. Partial feedback linearization scheme is used to design the controller for a linearized power system model which transforms a part of this model into a new system through linear coordinate transformation. In this paper, the excitation control law as a function of state variables is determined from the dynamics of the partly transformed new system provided that the controller stabilizes the remaining dynamics of the system which are not transformed through feedback linearization. The stability of the remaining dynamics is also discussed in this paper. Since the proposed control scheme uses state variables as feedback, it is analogous to a linear quadratic regulator (LQR) based excitation controller. Therefore, the performance of the proposed scheme is evaluated on a single machine infinite bus (SMIB) system and compared to that of an LQR controller. [ABSTRACT FROM AUTHOR]