Power System Transient Stability Simulation Research Articles

Fast Power System Transient Stability Simulation

Power system transient stability simulation is of critical importance for utilities to assess dynamic security. Most of the commercially available tools use the traditional numerical integration method to simulate power system transient stability, which is computationally intensive and has low simulation speed. This makes it difficult to identify any insecure contingency before it happens. It is already proven that power system transient stability simulation achieved using the differential transformation method (DTM) requires less computational effort and has improved simulation speed, but it still requires further improvement regarding its accuracy and performance efficiency. This paper introduces a novel power system transient stability simulation method based on the adaptive step-size differential transformation method. Using the proposed method, the step size is varied based on the estimated local solution error at each time step. The accuracy and speed of the proposed simulation approach are investigated in comparison with the classical differential transformation method and the traditional numerical integration method using the IEEE 9 bus and 39 bus test systems. The simulation results reveal that the proposed method increases the simulation speed by 20–44.57% and 83–92% when compared with the classical DTM and traditional numerical-integration-based simulation methods, respectively. It is also proved that compared with the DTM-based simulation, the proposed method provides 45.27% to 58.85% and more than 90% accurate simulation results for IEEE 9 and IEEE 39 test systems, respectively. Therefore the proposed power system transient stability simulation method is faster and relatively more accurate and can be applied for online transient stability monitoring of power system networks.

Robustly Cooperative Control of Transient Stability for Power System Considering Wind Power and Load Uncertainty by Distribution Preserving Graph Representation Learning (DPG)

Aiming at the influence of wind power and load uncertainty on the transient stability of a power system under low carbon mode, this paper first proposes a collaborative preventive and emergency control model of transient stability by distribution preserving graph representation learning (DPG). Second, the uncertainty set of wind power output and load demand is studied, and the mathematical form of the two-stage robust transient stability collaborative control model is proposed. Then, the latest artificial intelligence technology is embedded into the global optimization algorithm of the model so as to further improve the solving efficiency of the algorithm. Finally, based on the developed improved two-stage robust optimization framework, an effective collaborative control method for transient stability is developed. The transient stability prediction and control system developed in this project is not only conducive to large-scale wind power grid connection but also expected to make academic contributions to development of power system transient stability and practical simulation verification.

Study on Reducing the Parallel Overhead of the BBDF Method for Power System Transient Stability Simulations

In the power system parallel transient stability simulation (TSS), the parallel overhead will rise significantly with the increase in concurrency, which will seriously affect the efficiency of parallel computing. However, there are relatively few studies on the parallel overhead in the power system research field at present. In this paper, the geneses of the parallel overhead are introduced from the point of view of computer technology. The composition of the parallel overhead of the bordered block diagonal form (BBDF) method and the nested BBDF (NBBDF) method of the power system parallel TSS is analyzed. The time consumption of computing tasks and the parallel overhead of the BBDF method and the NBBDF method implemented by message passing interface (MPI) and OpenMP under different thread scheduling patterns are tested in detail in the 2383wp system and two practical power systems (13 490 node and 24 886 node). On this basis, an efficient implementation of the NBBDF method based on subnet-core mapping and mixed programming of MPI and OpenMP is suggested, which can further reduce the parallel overhead and increase the speedup ratio to more than 17x with 64 cores in the 24 886-node system. At last, some rules are summarized based on the test results.

Parallel Algorithm for Transient Stability Simulation Based on Sherman-Morrison Formula

Parallel computing is an effective approach to transient stability real-time simulation of large-scale power system. In this paper, a new parallel algorithm for power system transient stability simulation is proposed by combining Gauss method and the Sherman-Morrison formula. The algorithm adopts the Gauss method to convert the differential-algebraic equations into a set of nonlinear algebraic equations by multi-stages discretization, while the algebraic system is solved using rigorous Newton method. On this basis, the whole Jacobian matrix involved in Newton method is split to a block diagonal matrix and a block constant coefficients matrix according to s time points, and then based on the block diagonal matrix, the computing tasks at s time points are fully decoupled through the extended Sherman-Morrison matrix inverse formula. The proposed algorithm preserves the good convergence of rigorous Newton method and meanwhile has a high degree of parallelism both in time and in space.

Improved Sparsity Techniques for Solving Network Equations in Transient Stability Simulations

When solving network algebraic equations during power system transient stability simulations, the nonzero elements in the independent vector and the elements needed in the solution vector are determined by the location of source nodes. Different kinds of source nodes will have a different influence on the solution process of the network equations. According to these features of source nodes, sparsity techniques, more specifically, the node ordering algorithm and sparse vector method, are improved in this paper. A new heuristic ordering algorithm is proposed to enhance the efficiency of the sparse vector method by reducing the number of nodes in the factorization path set of source nodes while maintaining the sparsity of the factorized matrix. A multipath sparse vector method is proposed to avoid the unnecessary computation in the iterative solution process of the network equations, whereby the idea of the method is to form different paths for different types of source nodes. Different paths are used to solve different elements in the solution vector. The correctness and effectiveness of these improvements is proven by the simulation results of three practical power systems (up to 13 490 nodes) and six IEEE examples (up to 162 nodes).

Power System Transient Stability Analysis Using Hybrid Model Based on the Finite Element Method

This paper presents a simple, but very powerful, numerical algorithm for the power system transient stability simulation. The aim of this paper is to fill the gap between the Transient Stability Programs (TSP) and the Electromagnetic Transient Programs (EMTP) by developing a new simulation tool based on the finite element (FE) representation of the power system element. The proposed hybrid model based on the Finite Element Method (FEM) allows us to avoid disadvantages of TSP comparing to EMTP that leads to the simulation of the electromechanical transients in a more accurate and efficient way. In order to show the principles of the proposed method in details, the proposed numerical method has been tested and compared to the solutions obtained by the well known and established EMTP simulation tool where a very good correlation has been demonstrated.

Power System Simulation Using the Multistage Adomian Decomposition Method

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.

Condition‐based exciter model complexity reduction for improved transient stability simulation

A reduced model approach to decrease computational complexity in power system transient stability simulation is presented. This study investigates conditions that make fast modes active or inactive using practical power system examples. Modes in the original system where fast dynamics do not appear can be neglected, allowing simulation steps to be increased without numerical stability issues. During a transient simulation, the proposed method switches dynamically between the original exciter model and the reduced one, depending on the switching criterion presented. A high level of accuracy is achieved and computational efficiency is increased. Case studies with the Western Electricity Coordinating Council system are provided to validate the performance of the proposed method.

A Practical Exciter Model Reduction Approach For Power System Transient Stability Simulation

Explicit numerical integration methods for power system transient stability simulation require very small time steps to avoid numerical instability. The EXST1 exciter model is a primary source of fast dynamics in power system transients. In case of the EXST1, the required small integration time step for entire system simulation increases the computational demands in terms of running time and storage. This paper presents a practical exciter model reduction approach which allows the increase of the required step size and thus the method can decrease the computational demands. The fast dynamics in the original EXST1 are eliminated in the reduced exciter model. The use of a larger time step improves the computational efficiency. This paper describes the way to eliminate the fast dynamics from the original exciter model based on linear system theory. In order to validate the performance of the proposed method, case studies with the GSO-37 bus system are provided. Comparisons between the original and reduced models are made in simulation accuracy and critical clearing time.

High-Speed Power System Transient Stability Simulation Using Highly Dedicated Hardware

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 10 000 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.

Transient Stability Simulation by Explicit and Symplectic Runge-Kutta-Nyström Method

The symplectic algorithm is a kind of new numerical integration methods. This paper proposes the application of the explicit and symplectic Runge-Kutta-Nyström method to solve the differential equations encountered in the power system transient stability simulation. The proposed method achieves significant improvement both in speed and in calculation precision as compared to the conventional Runge-Kutta method which is widely used for power system transient stability simulation. The proposed method is applied to the IEEE 145-bus system and the results are reported.

Speed-up the computing efficiency of power system simulator for engineering-based power system transient stability simulations

Power system simulator for engineering (PSS/E) has gained great success in power energy industry for its powerful simulation and analysis functions. Along with market deregulation, power system planning and stability analysis warrants more effective and faster techniques owing to the ever-expanding large-scale interconnection of power networks. Running large-scale system multiple case studies on PSS/E can be computationally very expensive and in some cases, simplifications have to be made in order to obtain some results. PSS/E dynamic simulations are accelerated with EnFuzion-based distributed computing method in this study. This approach is proved to be effective by testing with 39-bus New England power system under ‘N-1’, ‘N-2’ and ‘N-1-1’ contingencies analysis, and re-dispatch after disturbance with optimal power flow. The results show that the simulation process can be speeded up dramatically and the total elapsed time can be reduced proportionally with the increase of computer nodes.

Power system transient stability simulation under uncertainty based on Taylor model arithmetic

Abstract The Taylor model arithmetic is introduced to deal with uncertainty. The uncertainty of model parameters is described by Taylor models and each variable in functions is replaced with the Taylor model (TM). Thus, time domain simulation under uncertainty is transformed to the integration of TM-based differential equations. In this paper, the Taylor series method is employed to compute differential equations; moreover, power system time domain simulation under uncertainty based on Taylor model method is presented. This method allows a rigorous estimation of the influence of either form of uncertainty and only needs one simulation. It is computationally fast compared with the Monte Carlo method, which is another technique for uncertainty analysis. The proposed method has been tested on the 39-bus New England system. The test results illustrate the effectiveness and practical value of the approach by comparing with the results of Monte Carlo simulation and traditional time domain simulation.

Power System Transient Stability Simulation Based on OOP and TEF

In this paper, power system transient stability is simulated by using the new method of power system transient stability simulation. It combines the desirable features of both the time domain technique based on OOP (Object-oriented Programming) and the TEF (Transient Energy function) of detailed generator model. OOP is an alternative to overcome the problems associated with the development, maintenance and update of large software by electrical utilities. Several papers have already evaluated this approach for power system applications in areas such as load flow, security assessment and graphical interface. This paper applied the object-oriented approach to the problem of power system transient stability simulation. The modeling method is that each block of dynamic system block diagram is implemented as an object and connected each other. In the transient energy method, the detailed synchronous generator model is so-called two-axis model. For the excitation model, IEEE type1 model is used. The developed mothed was successfully applied to New England Test System.

Power system transient stability simulation based on module bi-directional iteration

A new simultaneous solution method using module bi-directional iteration is proposed for power system transient stability simulation. In this method, power network is partitioned into a tree hierarchy; computation modules are established for decomposed power networks and various power system components respectively. Through representing every computation module by a computation node, a computation tree is constructed by connecting the nodes together according to their electrical relations in power systems. A tree-traversing procedure called forward reduction and backward evaluation is performed to calculate correction factors of the variables in Newton iterations. This high-efficiency simulation method is feasible to be applied in parallel computation for large interconnected systems. Simulation tests are conducted on the New England 10-generator test power system and the North China-Northeast interconnected system, and the results are compared with those of the commercial software BPA to validate the effectiveness and correctness of this method.

A synchronous machine model for unbalanced analyses

This paper presents a new asymmetrical model of synchronous generators for power system transient stability simulations. The symmetrical component method has been used traditionally in the analysis of unbalanced faults in power systems. This is mainly because the synchronous generators, which play an important role in the power system, can be easily treated by the method. However, when analyzing a system that has elements with asymmetrical impedance, it may not be easy to use the symmetrical component method. In such cases, the simulations can be easily executed by using the phase coordinate method. However, there are few papers that derive a phase coordinate model of synchronous machines. This paper analyzes synchronous generators under asymmetrical conditions in detail by using the symmetrical component method, then derives a model of synchronous generators for the phase coordinate method. © 1997 Scripta Technica, Inc. Electr Eng Jpn 119(2): 46–59, 1997

A new method to approximate stator transients of synchronous machines in power system simulation

This paper presents a new method to approximate the effects of stator transients of synchronous machines in power system transient stability simulations during unsymmetrical faults. This method can approximate the DC offset currents which arise from the stator and network transients during faults. However, the method is based on the traditional model with stator and network transients neglected.

A Synchronous Machine Model for Unbalanced Analyses.

This paper presents a new unsymmetrical model of synchronous generators for power system transient stability simulations. The symmetrical component method has been used traditionally in the analysis of unbalanced faults in power system. This is mainly because the synchronous generators, which play an important role in the power system, can be easily treated by the method. However, when analyzing a system that has elements with unsymmetrical impedance, it may not be easy to use symmetrical component method. In such cases, the simulations can be easily executed by using the phase coordinate method. However, there are few papers that derive a phase coordinate model of synchronous machines. This paper analyzes synchronous generators under unsymmetrical condition in detail by using the symmetrical component method, and then it derives a model of synchronous generators for the phase coordinate method.

A NEW METHOD IN POWER SYSTEM SIMULATION TO APPROXIMATE TRANSIENTS OF THE SYNCHRONOUS MACHINES STATOR

Abstract This paper presents a new method to approximate the effects of synchronous machines stator transients in power system transient stability simulations. The method can approximate the DC offset currents which arise from the stator and network transients during three phase short circuit faults. However, the method is based on the traditional model with stator and network transients neglected.

A new model of saturated synchronous machines for power system transient stability simulations

This paper presents a new method to express the main flux saturation in synchronous machines. In the new method, the saturation is expressed by auxiliary currents and unsaturated magnetizing inductances instead of the saturated inductances. The new model using the currents contains only constant coefficients defined in terms of the unsaturated magnetizing inductances. >