Method For Transient Stability Analysis Research Articles

Research Methods for Transient Stability Analysis of Power Systems under Large Disturbances

Transient stability analysis is critical for maintaining the reliability and security of power systems. This paper provides a comprehensive review of research methods for transient stability analysis under large disturbances, detailing the modeling concepts and implementation approaches. The research methods for large disturbance transient stability analysis are categorized into five main types: simulation methods, direct methods, data-driven methods, analytical methods, and other methods. Within the analytical method category, several common analytical strategies are introduced, including the asymptotic expansion method, intrusive approximation method, and other analytical methods. The fundamental principles, characteristics, and recent research advancements of these methods are detailed, with particular attention to their performance in various aspects such as computational efficiency, accuracy, applicability to different system models, and stability region estimation. The advantages and disadvantages of each method are compared, offering insights to support further research into transient stability analysis for hybrid power grids under large disturbances.

A transient stability analysis method for wind power system with thyristor controlled phase shifting transformer based on branch potential energy index

With the growing usage of renewable energy technologies like wind power and photovoltaics, and the increased integration of FACTS (Flexible Alternating Current Transmission System) devices into the power system, the transient characteristics of the evolving power system undergo changes that require appropriate analysis methods. As a new type of FACTS device, TCPST (Thyristor Controlled Phase Shifting Transformer) is introduced to facilitate the superior operation of renewable energy sources by controlling the power flow of access branches. From the perspective of branches, the dynamic characteristics of renewable energy sources and TCPST might be uniformly studied and simply calculated in the transient stability analysis. Therefore, the paper proposes a transient stability analysis method for wind power systems with TCPST based on the branch potential energy index. First, considering the variation characteristics of branch potential energy, this paper employed the stability index to analyze the transient stability of branches and the system by finding vulnerable lines. Then, based on the stability index, the paper investigates the influence of wind turbine removal, the installation and control parameter adjustment of TCPST on the transient stability of wind power systems. The simulation results in PSAT demonstrate that the removal of a proper amount of wind turbine post-fault and the installation of TCPST can improve the transient stability of the wind power system. Furthermore, it can also be improved by reasonably adjusting the TCPST control parameters. All simulation results are verified by the time domain simulation method.

Power Feasible Region Ensuring Transient Stability of Droop-Based Multiconverters DC System

This article systematically focuses on the transient stability problem of droop-based multiconverters dc (MCdc) system caused by large power disturbances. Therefore, a new and effective transient stability analysis method is proposed. In the present method, it starts with reduced-order nonlinear mathematical modeling, followed by Lyapunov energy function building, and then the inscription of the largest estimated domain of attraction (LEDA) and the power feasible region (PFR). First, a state-variable equivalent transformation method is proposed. With this method, the droop-based MCdc system can be modeled as an equivalent single-converter (ESC) model without ignoring any coupling effects between the control state-variables. Second, a Takagi–Sugeno fuzzy model of the ESC is developed, which is able to construct the LEDA. Third, to ensure the transient stability of the MCdc system under large power disturbance, the concept of PFR is proposed. Furthermore, a PFR inscription algorithm is given based on the LEDA. In addition, the influence of control parameters on the PFR is analyzed, which will provide guidelines for the optimization of the PFR. Finally, the time domain experiments are carried out on the RT-BOX hardware-in-the-loop experimental platform to verify the effectiveness of the above theoretical analysis.

Calculation of the transient stability boundary of AC/DC inter‐connected system based on the stability margin of dynamic energy

Concerning the transient power angle stability problem in AC/DC inter-connected system caused by DC line grounding fault, a transient stability analysis method based on the stability margin of dynamic energy is proposed. First, the analytical expressions of the dynamic energy function before alpha retard, during alpha retard and after alpha retard are derived. According to the topologies of system and the integration intervals of energy function in different stages, the expressions of the acceleration energy, position energy and margin energy are obtained, which, respectively, reflect the rotating speed of system, the swing range of power angle and the system's ability of resisting in stability. Then, the surplus energy in the system is calculated by subtracting the sum of the acceleration energy and position energy from the margin energy, and the stability margin of the system is obtained. And then, the stability boundary of the system is derived. It is revealed that, if the stability margin is exactly right 0 at the end moment of alpha retard, the system is critical stable. Finally, hardware-in-the-loop tests are conducted in RT-LAB platform. The simulation results verify that, the stability margin reaches the minimal value at the end moment of alpha retard, and this value can clearly reflect the stability of system. Besides, the earlier the alpha retard starts or the longer the distance between the fault point and the rectifier outlet is, the better it is for the stability of system.

Research on the transient stability of HVDC rectifier-side AC system during the whole process of DC restart failure

HVDC restart failure can cause the DC power interruption, which may further result in the transient power angle of the rectifier-side AC system to go unstable. Concerning this problem, a transient stability analysis method considering dynamic changes of converter topologies during the whole process of the DC restart failure is proposed. First, dynamic energy models of the DC terminal and the AC filter in the whole process of the DC line restart failure are built, including the ‘restart at fault’, phase-shifted triggering and deionization stage. On this basis, according to the Lyapunov’s second theorem, the variation rate of the aperiodic component of generator dynamic energy is defined as the dissipation rate of dynamic energy, which characterizes the accumulation or the consumption trend of total system energy. Thus the stability of the system is assessed according to the dissipation rate of dynamic energy. Then, effects of the dynamic energy of the DC terminal and the AC filter on the dissipation rate of dynamic energy in the whole process of DC restart failure are illustrated, and the cause of the transient instability of the rectifier-side AC system is revealed. Finally, hardware-in-the-loop tests in RT-LAB verify that, when the amplitude of the generator outlet bus voltage rises during the ‘restart at fault’ and phase-shifted triggering stages, the dynamic energy of the DC terminal has a positive effect on the dissipation rate of dynamic energy, induces the total system energy to keep accumulating, which is not conducive for the stability of the system. In the deionization stage, the dynamic energy of the AC filter has a positive effect on the dissipation rate of dynamic energy, which is not conducive for the stability of system.

Transient stability analysis method and sensitivity study of unsaturated soil slopes under consideration of rainfall conditions

Transient stability analysis method and sensitivity study of unsaturated soil slopes under consideration of rainfall conditions

Transient stability domain estimation of AC/DC systems considering HVDC switching characteristics based on the polynomial Lyapunov function method

Transient stability analysis is a traditional yet significant topic in power systems. The switching control schemes of the HVDC converter station after fault bring new challenges to the direct method of transient stability analysis in AC/DC power systems. To apply the direct method to investigate the transient stability of power systems accommodating the switching characteristics of the line commutated converter (LCC) HVDC, continuous piecewise Lyapunov functions are constructed for a whole AC/DC system model including several classical LCC-HVDC control modes, and the continuity of Lyapunov functions is studied and guaranteed in transitions between control modes. Then, the Sum-of-Squares optimization is employed to find the optimal continuous piecewise Lyapunov functions. Finally, the transient stability domain is estimated for a sample system including the main control loops of LCC-HVDC, a three-order generator model, and a one-order exciter model. Tests in MATLAB environment are conducted to demonstrate the feasibility of this method.

A transient stability analysis method based on second‐order nonuniform Kuramoto model

A transient stability analysis method based on second‐order nonuniform Kuramoto model

Transient stability analysis of one special type of AC microgrids with a gas reciprocating generator unit

More and more gas reciprocating generator units are integrated into offshore platforms, due to their compact structure and high efficiency. This paper concentrates on the transient stability analysis of one special type of AC microgrids containing a gas reciprocating generator unit. Firstly, the operation principle for the gas reciprocating generator unit is presented, which mainly consists of a reciprocating internal combustion engine and a linear synchronous alternator (LSA). Afterwards, the mathematical model for the core part of the gas reciprocating generator unit LSA is proposed, based on the principle of armature reaction in traditional synchronous and asynchronous machines. Finally, the simplified model of the independent offshore power system with a gas reciprocating generator unit is derived, and numerical simulations on the transient stability of this typical AC microgrid are performed, from which the effectiveness and correctness of the LSA model are validated. The transient stability analysis method of the independent offshore power system and the mathematical model of LSA can provide beneficial guidance for the stable operation of other types of stand-alone AC microgrids.

A practical method of transient stability analysis of stochastic power systems based on EEAC

With the diversification of power systems and the application of power electronic technology, the uncertainty of power systems is becoming more and more serious, and the traditional deterministic transient stability analysis methods encounter severe challenges. In this paper, a practical method is proposed for transient stability analysis of stochastic multi-machine systems based on EEAC. Firstly, the stochastic differential equation model of multi-machine systems is established. Secondly, the stochastic multi-machine system is equivalent to a stochastic single-machine infinite bus system according to coherency. Finally, the acceleration and deceleration area is constructed, and Heun’s method is used to seek the critical clearing time of the system. The method is applied to analyse transient stability of four machine system. Compared with the numerical simulation based on Monte Carlo method, the simplicity and effectiveness of the method are verified. The impact of stochastic disturbance intensity on stability is also presented.

Effects of cascading failure intervals on synchronous stability

Cascading failure analyses are mainly based on simultaneous or quasi-steady-state (QSS) assumptions, which are inappropriate in cases of rapid cascading failure analysis and control. Fault interval is considered in the stability analysis of cascading failure for the first time in this article. Based on the extended equal area criterion (EEAC), a transient stability analysis method is proposed for cascading failure in consideration of intervals. The results show the periodicity of stable margin variations with intervals. The conclusions are validated in a Hamiltonian system, and the effects of time-varying factors are analyzed. The OMIB case shows that it may be over-optimistic to assess stability levels under simultaneous or QSS assumptions. The validity of all conclusions in this paper is verified with the New England system and with an actual power system.

Improved transient stability analysis method of power system with VSG inverter based on SMR

In order to reduce the effect of total inertia reduction on system stability after high penetration distributed power access, virtual synchronous generator technology(VSG) has become a research hotspot. In transient process, the inverter with VSG technology has similar dynamic behavior as synchronous machine. And traditional direct method has a certain conservatism in the analysis of transient stability. In this paper, an improved direct method based on SMR technology is proposed to analyze the transient stability of the power system with VSG inverter. By analyzing the virtual power angle transient characteristics of inverter with VSG strategy, a virtual power angle dynamic model is constructed, and the traditional direct method is improved by using SMR technology. Finally, the method is simulated by using the SMIB and IEEE three-machine nine-node systems. The results show that the improved direct method can correctly acquire the transient stability index and reduce the conservation of traditional method.

Numerical polynomial homotopy continuation method to locate all the power flow solutions

The manuscript addresses the problem of finding all solutions of power flow equations or other similar non-linear system of algebraic equations. This problem arises naturally in a number of power systems contexts, most importantly the direct methods for transient stability analysis and voltage stability assessment. Here, the authors introduce a novel form of homotopy continuation method called the numerical polynomial homotopy continuation method that is mathematically guaranteed to find all the solutions without ever encountering a bifurcation. Since finding real solutions is much more challenging, first the authors embed the real form of power flow equation in complex space, and then track the generally unphysical solutions with complex values of real and imaginary parts of the voltages. The solutions converge to physical real form in the end of the homotopy. The so-called gamma-trick mathematically rigorously ensures that all the paths are well-behaved along the paths, so unlike other continuation approaches, no special handling of bifurcations is necessary. The method is embarrassingly parallelisable. The authors demonstrate the technique performance by solving several test cases up to the 14 buses. Finally, they discuss possible strategies for scaling the method to large size systems, and propose several applications for security assessments.

Power system transient stability analysis through a homotopy analysis method

As an important function of energy management systems, online contingency analysis plays an important role in providing power system security warnings of instability. At present, N-1 contingency analysis still relies on time-consuming numerical integration to assess transient stability. To reduce computational cost, this paper proposes a transient stability analysis method based on homotopy analysis. The proposed method analyzes power system transient stability by computing bifurcation points of nonlinear differential equations. These bifurcation points constitute transient stability region boundaries. The method judges if the post-fault system can survive a disturbance by analyzing whether the initial values following fault clearance locate within the boundaries. The proposed method provides an alternative approach to assessing power system transient stability instead of traditional numerical integration. A simple case is presented to demonstrate application of the proposed method; the analysis results of the proposed method are consistent with the results of numerical integration.

Estimating Basin of Attraction for Multi-Basin Processes Using Support Vector Machine

A novel method of transient stability analysis is presented in this paper. The proposed method extracts data points near the basin-of-attraction boundary and then builds a support vector machine (SVM) model learned from the generated data. The constructed SVM classifier has been shown to reduce dramatically the conservativeness of the estimated basin of attraction.

A direct method for obtaining critical clearing time for transient stability using critical generator conditions

SUMMARYThis paper proposes a new method for transient stability analysis for electric power systems by extending our previous studies. A special feature different from the ordinary existing methods is that a minimization problem is formulated for obtaining critical clearing time for transient stability. The critical trajectory is defined as the trajectory that starts from a point on a fault‐on trajectory at critical clearing time and reaches a critical point of losing synchronism. This paper studies the treatment of the critical condition and then proposes a new formulation for the transient stability problem. It will be demonstrated that the solution of the minimization problem successfully provides the exact critical clearing time that agrees with the conventional numerical simulation method. Copyright © 2011 John Wiley & Sons, Ltd.

하이브리드 방법을 이용한 전력계통 안정도 해석

This paper explains hybrid method that combines Time domain simulation technique with the direct method of Transient stability analysis. First, it calculate trajectory of real system by Time domain Simulation using OOP(Object Oriented Programming method) and evaluate Transient Energy Function to induce stability index to calculate Transient stability margin. Once the status of system(stable or unstable) has been identified, proper criteria are proposed to stop time-domain simulation to reduce CPU time.

A new method for transient stability analysis

AbstractThis paper proposes a brand‐new method for transient stability analysis in power systems. The proposed method directly computes the critical trajectory for a given contingency to obtain the critical condition of the studied system. Although the method may be useful for general nonlinear dynamic systems, it is applied to the problem of obtaining a controlling UEP, unstable equilibrium point, which provides inevitable information for the energy function methods to assess transient stability. Namely, the proposed method effectively yields a critical trajectory on PEBS together with the controlling UEP, thus improving the conventional BCU method. The effectiveness of the proposed method is demonstrated in 3‐machine 9‐bus and 6‐machine 30‐bus systems. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 26–33, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20245

FAD-ATC: A new method for computing dynamic ATC

This paper presents a Fast and Accurate Dynamic method for ATC (FAD-ATC) calculations with considering transient stability analysis (TSA) and voltage stability analysis (VSA) termination criteria. This method can be used for contingency screening and ranking. Estimation of the determinant of Jacobian matrix is used for assessment of voltage stability. This method is compared with the following methods: energy difference between SEP (Stable Equilibrium Point) and UEP (Unstable Equilibrium Point), t s index of Chiang, and continuation power flow. TSA method use Athay's PEBS (Potential Energy Boundary Surface) and a new method named POMP. The POMP method follows the Point Of Maximum Potential (POMP) energy on post-fault system trajectory. This point is approximated by Taylor's expansion of second order. Since this method does not use any convergent algorithm, it is more reliable than all existing methods that use UEP. The goals of this method are assessment of ATC with considering VSA and TSA and assessment of dangerous contingencies. The ideas are demonstrated on 2, 3, 7 (Cigre), 10, 30 (IEEE) and 145 (Iowa State) bus networks.

CTV, COMPLEX TRANSIENT AND VOLTAGE STABILITY: A NEW METHOD FOR COMPUTING DYNAMIC ATC

This paper presents a fast and accurate dynamic method for ATC calculations considering transient stability analysis (TSA) and voltage stability analysis (VSA) termination criteria (CTV method). This method can be used for contingency screening and ranking. Estimation of the determinant of Jacobian matrix is used for assessment of voltage stability. This method is compared with the following methods: energy difference between SEP (stable equilibrium point) and UEP (unstable equilibrium point), t s index of Chiang, and continuation power flow. The TSA method uses Athay's PEBS (potential energy boundary surface) and a new method named POMP. The POMP method follows the Point Of Maximum Potential energy on post-fault system trajectory. This point is approximated by Taylor's expansion of second order. Because this method does not use any convergent algorithm, it is more reliable than all existing methods that use UEP. The goals of this method are assessment of ATC considering VSA and TSA and assessment of dangerous contingencies. The ideas are demonstrated on 2, 3, 7 (Cigre), 10, 30 (IEEE) and 145 (Iowa State) bus networks.