Feasibility study of transient stability analysis for operator training simulators

Pipeline operating companies require skilled employees to operate their pipeline network with safety and meeting the customer’s nominations, seeking to reduce costs and preserve the environment. A useful pipeline operational functionality designed to train, qualify and certificate operators to perform those tasks successfully is the Operator Training Simulator (OTS). OTS reproduces operational scenarios without the necessity of being inside the control room, allowing the trainee to simulate daily operational routines such as pumps startup/shutdown, valves opening/closing, slack line prevention, leak identification and others. This work presents a detailed description of an Operator Training Simulator to be employed in a South African pipeline network, comprising around 2500km of pipes handling multi-products and crude oils. The designed OTS shall allow the trainee to have exactly the same environment the operator has at the control room, including machines, screens and functionalities like Leak Detection as well as Batch/Pig Tracking. Two modes of OTS operation are cited: an offline and an online one. The offline mode performs any simulation from a configured offline scenario. On the other hand, online mode allows the trainee to see actual real time data on a passive mode (without interfering with real operation). Besides, it can get a desirable real time scenario and continue from that point in an offline way, i.e. loading a start state scenario. Finally, it shall be presented and discussed the interaction between the OTS and the ability to reproduce local station operational sequences. The gain obtained with such interaction, as well as the consequent introduced complexity, is also commented.

The need to increase situational awareness in power systems is more evident than before. Increased power system complexity and integration of intermittent resources have contributed to the emerging need to monitor power systems in real time. Real time contingency analysis can increase situational awareness by monitoring the power system in real time and alarming the operators of the impending problems. Monitoring all multiple contingencies in real time is impossible and therefore, there is a need to reduce the number of monitored contingencies. This paper introduces a method for identifying most critical contingencies in power system for real-time monitoring.

This paper presents an overview of the research project “High-Performance Hybrid Simulation/Measurement-Based Tools for Proactive Operator Decision-Support”, performed under the auspices of the U.S. Department of Energy grant DE-OE0000628. The objective of this project is to develop software tools to provide enhanced real-time situational awareness to support the decision making and system control actions of transmission operators. The integrated tool will combine high-performance dynamic simulation with synchrophasor measurement data to assess in real time system dynamic performance and operation security risk. The project includes: (i) The development of high-performance dynamic simulation software; (ii) the development of new computationally effective measurement-based tools to estimate operating margins of a power system in real time using measurement data from synchrophasors and SCADA; (iii) the development a hybrid framework integrating measurement-based and simulation-based approaches, and (iv) the use of cutting-edge visualization technology to display various system quantities and to visually process the results of the hybrid measurement-base/simulation-based security-assessment tool. Parallelization and high performance computing are utilized to enable ultrafast transient stability analysis that can be used in a real-time environment to quickly perform “what-if” simulations involving system dynamics phenomena. EPRI's Extended Transient Midterm Simulation Program (ETMSP) is modified and enhanced for this work. The contingency analysis is scaled for large-scale contingency analysis using MPI-based parallelization. Simulations of thousands of contingencies on a high performance computing machine are performed, and results show that parallelization over contingencies with MPI provides good scalability and computational gains. Different ways to reduce the I/O bottleneck have been also exprored. Thread-parallelization of the sparse linear solve is explored also through use of the SuperLU_MT library. Based on performance profiling results for the implicit method, the majority of CPU time is spent on the integration steps. Hence, in order to further improve the ETMSP performance, a variable time step control scheme for the original trapezoidal integration method has been developed and implemented. The Adams-Bashforth-Moulton predictor-corrector method was introduced and designed for ETMSP. Test results show superior performance with this method.

With the development of science and technology, the cost of offshore wind power development and transmission has gradually decreased, making offshore wind power technology a research hotspot. The installed capacity has been increasing year by year. China has abundant offshore wind energy resources, which are much richer than those on land and are available for exploitation. Offshore wind speeds are stable and do not produce harmful substances. Therefore, studying the transient voltage stability of offshore wind power grid-connected systems to improve the utilization efficiency of offshore wind power and protect the ecological environment is critical. After large-scale wind power is connected to the grid, ensuring the stability of the system's transient voltage becomes crucial. This paper aims to deeply study the transient voltage stability of offshore wind farm grid-connected systems, providing theoretical support for the subsequent design and operation of offshore wind farms. A simulation model of a typical power system integrated with offshore wind farms was established using PSAT. Relevant transient voltage stability indices were calculated, and the impact of varying wind speeds on the transient voltage stability of the grid-connected system was investigated. Static Var Compensators (SVC) and Static Synchronous Compensators (STATCOM) were installed for comparative analysis. The results demonstrate that excessively low wind speeds degrade the system's transient stability, and the installation of SVC provides superior improvement in transient voltage stability compared to STATCOM.

Parallel time domain simulation is one of the reliable and potential methods that might realize the real-time online transient stability analysis of power system. In the paper, a new parallel calculation method, based on waveform relaxation method, is proposed for power system transient stability analysis. In the method, the entire transmission network is first divided into several subsystems by the geographical location; for each subsystem, its neighboring systems are represented as equivalent voltage sources at the boundary buses; the tie line flows are considered as the communication waveform among the subsystems; then, time domain simulation for each subsystem is performed in parallel. The test result of the practical system indicates that the new parallel algorithm completely achieves the on-line real-time or even over-real-time calculation speed and could be applied to the on-line transient stability analysis of practical system.

This paper describes a method of developing wideband multi-port system equivalents for use with real-time digital power system simulators. The proposed equivalent combines a frequency dependent network equivalent (FDNE) for the high frequency electromagnetic transients and a transient stability analysis (TSA) type simulation block for the electromechanical transients. The frequency dependent characteristic for FDNE is obtained by curve-fitting frequency domain admittance characteristics using the vector fitting method. The paper also introduces an approach for approximating the frequency dependent characteristic of large power networks from readily available typical power-flow data. The paper shows how the TSA algorithm can be adapted to a realtime platform. The validity of this method is confirmed with examples, including the study of a multi in-feed HVDC system based network.

\nThe improvement of transient stability of power system was one of the most challenging research areas in power engineer.The main aim of this paper was transient stability analysis and improvement of IEEE 9 bus system. These studies were computed using POWER WORLD SIMULATOR. The IEEE 9 bus system was modelled in power world simulator and load flow studies were performed to determine pre-fault conditions in the system using Newton-Raphson method. The transient stability analysis was carried out using Runga method during three-phase balanced fault. For the improvement transient stability, the general methods adopted were fast acting exciters, FACT devices and addition of parallel transmission line. These techniques play an important role in improving the transient stability, increasing transmission capacity and damping low frequency oscillations.\n

The wide application of WAMS (Wide Area Measurement System) provided a new thinking for transient stability analysis of power system. Based on real-time measurement information from WAMS, a method to quickly analysis power system transient stability that does not depend on network structure, model and parameters of power system is proposed in this paper. Firstly, the parameters of system are identified online by improved least squares method on basis of that the multi-machine power system is equivalently reduction to one machine infinity bus system. The equilibrium point and stability margin of equivalent system are rapidly computed, and then the stability of system is quickly judged. The simulation results show that the algorithm can accurately judge transient stability of system and has better antidisturbance ability and robustness. The issue of dependence of transient stability analysis on system model and parameter is solved. The adverse influences of data lose and measurement errors in actual measurement of the WAMS on analysis results are avoided effectively. Keywords-power system; wide-area measurement system; parameter identification; energy function; transient stability analysis

The operator training simulator (OTS) of Northeast China Power System is the first OTS in China, developed by Tsinghua University and installed in the Electric Power Dispatching and Communication Bureau of Northeast China. This paper describes the research works on the dynamic stability program in OTS of Northeast China Power System (DSPOTSNC),which covers: the hardware configuration; mathematical model and calculation method; and parallel transient stability method using five transputers. The relationship between dynamic stability program and other programs in the OTS, the difference between DSPOTSNC and ordinary dynamical program are also discussed in the paper.

The power transient stability analysis is one of the basis for determining the control strategy of power system security and stability. Considering the influence of power grid topology on the transient stability of power system, the transient stability evaluation model is constructed based on the graph attention neural network. The electrical components and their transient operation data are mapped to the graph data with the spatial topology characteristics of power system for model training, so as to improve the topological generalization performance of the model. The marginal contribution of input characteristics to the output of transient power angle stability evaluation model is quantitatively calculated based on Shapley additive explanation (SHAP), so as to improve the interpretability of data-driven method for transient power angle stability evaluation. The effectiveness of the proposed method is verified by the IEEE 39-bus system.

Hydropower is the largest renewable energy source in China. Transient stability is of great significance to the hydropower system. The extended equal area criterion (EEAC) theory is an effective method to analyze the system transient stability. The accuracy of the transient stability analysis is affected by the generator models. However, there is little research on the EEAC-based transient stability analysis of hydropower system considering different practical hydroelectric generator models. To fill this gap, this paper firstly introduces the characteristic of the second-order and fifth-order model of hydroelectric generators. Subsequently, the transient stability of the hydropower system considering generator models with different orders is analyzed based on EEAC theory and validated by time-domain simulation. Finally, the applicability of the second-order and fifth-order model is compared under different parameters of super-transient/ transient reactance, different fault locations and different super-transient time constants.

Affected by the current limitation, grid-forming inverters (GFMs) will transition to a current source under grid faults, which makes the inverter-based microgrid lose the voltage support and then be switched to a current source interconnection microgrid (CSIM). It may deteriorate the system's transient synchronization stability (TSS). This issue has not been studied previously. To this end, this article proposes an analysis and enhancement method of TSS of CSIM. First, a large signal synchronization model of CSIM is derived, which takes into account the effect of the current limitation strategy of GFMs and the dynamic interactions between GFMs and grid-following inverters (GFLs). Second, by constructing the Lyapunov energy function, the criterion of TSS is obtained and the impacts of parameters on stability are investigated. Based on the stability criterion, the feasible region of current references of GFLs is clearly described. Therefore, a dynamic current control method of GFLs is proposed. It can well address the absence of equilibrium points (EPs) and strengthen the transient stability. Meanwhile, a novel antiwindup strategy of GFMs considering synchronization stability constraint is proposed, which can contribute to the fault recovery of GFMs. Finally, simulation and experimental results verify the effectiveness of the proposed methods.

An approach has been proposed in this paper for processing unbalanced operating conditions in transient stability calculations. The suggested method combined positive sequence network usually used for traditionally balanced transient stability program with zero and negative sequence network which are available for traditional unsymmetrical fault routines. The zero and negative bus matrixes are usually available in sparse nature within any commercial software to handle large scale power system analysis. Therefore, they can be easily used in unbalanced transient stability routines, as described in this paper. Besides, a method is presented to evaluate DC offset currents in system branches during the phasor-based transient stability run. The DC offset arise from the stator and network transients during switching (including faults). Conventional phasor-based transient stability programs ignore the occurrences of such a DC offset in their simulation process. Approximating of DC and negative sequence current braking effects in AC machines and modeling negative, ground and overcurrent instantaneous protective equipments behavior in transient stability simulation are the main benefits of the proposed method. Computer test results in comparison with results carried out by detailed three-phase time-domain simulations using power system blockset (PSB) of MATLAB, show clearly the effectiveness of the method.

An optimized algorithm for optimal power flow based on deep learning

Several major blackouts in the past have shown the need for advanced wide‐area monitoring and control (WAMC) techniques. Advanced synchrophasor visualization and monitoring can be realized with time‐referenced power system data that are collected by phasor measurement units (PMUs) using synchronized clocks. Presently, PMUs are being deployed around the world at a rapid rate for various power system applications. When a necessary number of PMUs are installed at optimal locations throughout the network, the complete state of the system can be observed. PMUs take real‐time measurements to determine the state of the power system and can be used to enhance state estimation efficiency. With PMUs in place, there are many control and protection schemes that can be implemented successfully to take preventive and corrective actions. These remedial action schemes (RASs) are classified by the IEEE Power System Relaying Committee (PSRC) as system integrity protection schemes (SIPSs). This work involved the development of a real‐time hardware test bed in order to analyze the transient stability of a simulated power system by using synchrophasors to visualize system stress across a transmission line with and without load‐shedding schemes. The real time digital simulator (RTDS®) was used to model the power system in real time. PMUs, a satellite‐synchronized clock, and a synchrophasor vector processor (SVP) were used to test the synchrophasor application. Copyright © 2010 John Wiley & Sons, Ltd.