Stability Of Large-scale Power Systems Research Articles

Physics-Informed Learning Based Wind Farm Two-Machine Aggregation Model for Large-Scale Power System Stability Studies

Physics-Informed Learning Based Wind Farm Two-Machine Aggregation Model for Large-Scale Power System Stability Studies

Control and Stability of Large-scale Power System with Highly Distributed Renewable Energy Generation: Viewpoints from Six Aspects

Control and Stability of Large-scale Power System with Highly Distributed Renewable Energy Generation: Viewpoints from Six Aspects

Coordination of PSS and FACTS damping controllers to improve small signal stability of large-scale power systems

This paper presents an approach for designing parameters of power system stabilizer (PSS) and FACTS damping controllers in a large scale practical power system. The objective is maximizing damping ratio of the target mode, and tracking technology (MTT) is used to avoid frequent alternations of target mode in optimization procedures. An improved planted growth simulation algorithm (IPGSA), which has high search efficiency and quick convergence speed, is proposed to optimize controller parameters coordinately. Based on case study of a large-scale power grid, and by using local and interregional low-frequency oscillation modes as target modes, simulation results verify proposed method in this paper. Furthermore, coordination optimization strategy adapted to multi-operating conditions demonstrates that the proposed approach is robust.

Wide-area damping state feedback and output feedback controller design strategy considering time delays and actuator saturation based on parametric Lyapunov theory

Remote signal transmission time delays are the major factors to affect the performance of wide-area damping controller (WADC) and even deteriorate stability of large-scale power system. If the physical structure and the mathematical model of the system are different, the method of mathematically dealing with time delay is not the same. From the perspective of mathematical application engineering, there are two main ways to deal with the communication time delay: linear matrix inequalities (LMI) theory and conventional time-delay predictive compensation theory. Traditional time delay damping controller based on linear matrix inequalities (LMI) suffers relatively large conservatism and complexity. Traditional time delay damping controller based on time delay compensation has no clear relation between the control parameter and the time delay. On the other hand, the saturation of actuator leads to the deterioration of control performance and even threat system stability. The existing methods for saturation are negative feedback anti-saturation after the actuator is saturated, which is an afterwards control and it is difficult to well eliminate the influence of saturation. In this paper, a novel design strategy for wide-area time-delay damping controller based on parametric Lyapunov theory is derived. The explicit expression of the controller parameter value associated with the time delay is determined. This strategy can deal with arbitrary large time-vary delay theoretically and have extremely low controller dimension, which makes it have potential capability to be applied in large-scale inter-connected power systems. The control strategy is determined according to the system stability original definition (The system energy function is finite and positive and its first derivative is negative), which avoids complex matrix inequalities cyclic solution and reduces the conservatism of the controller. Moreover, it can directly give simple and explicit control law and specific control parameters, which enable this method to adjust its parameters online according to the exact time delay obtained by GPS. In the design process, the saturation characteristics of the actuator are taken into account in the linearization model of the closed-loop system. This makes it very adaptable to actuator saturation, so that the proposed design strategy can ensure the small signal stability of the closed-loop system considering time delays and actuator saturation. Case study is undertaken based on a New England ten-machine 39-bus power system, which stands for a large scale power system to verify the feasibility and effectiveness of the proposed design strategy. Compared with the free weight matrix damping controller (FWMC), which is a kind of LMI-based design strategy with excellent performance, the advantages and superiority of the proposed control strategy are verified. The proposed design strategy based on state feedback and output feedback has better control performance than FWMC.

Improved Wind Farm Aggregated Modeling Method for Large-Scale Power System Stability Studies

Nowadays, with the highly penetrated wind generations, the accurate wind farm (WF) model is required for power system stability analysis. Due to the complexity on detailed WF model, the aggregated model, with a reasonable reduction of the detailed model meanwhile retaining the required level of accuracy is essential to be developed. In this paper, an improved WF aggregated modeling method for large-scale power system stability studies is proposed. To overcome the limitations of the traditional methods, a geometric template matching based time series wind turbines clustering method is developed. Moreover, a multiobjective optimization algorithm, which fully considered the wind speed disturbance and system fault together, is designed to identify both the generator and control parameters. Additionally, to shrink the size of the identified parameters and increase the modeling accuracy, a sensitivity and correlation analysis based key parameters selection scheme is also adopted. To verify the effectiveness of the proposed method, dynamic responses of the proposed aggregated model are compared against the responses of the traditional equivalent model for various wind scenarios through an actual case.

Coordinated design and application of robust damping controllers for shunt FACTS devices to enhance small-signal stability of large-scale power systems

This paper presents a robust and coordinated supplementary damping controller design of multiple reactive FACTS controllers and their application in a large-scale power system. Reactive FACTS devices, such as static synchronous compensators (STATCOM) and static VAR compensators (SVC), are considered and assessed for their damping controller design. Control objectives, including regional pole placement and norm bounded mix sensitivities, are used to solve the bilinear matrix inequality (BMI) problems in each linearized model via a two-step method. Multiple damping controllers are sequentially designed to avoid coupling effect among the input signals and increase the reliability of the proposed design. A 5-area 16-machine 68-bus power system is used for the implementation of the damping controllers. Numerical linear analysis and real-time simulations in a test platform based on Real-time digital simulators (RTDS) are adopted to test the feasibility and robustness of the coordinated damping controllers.

Hierarchical Decentralized Control for Enhanced Rotor Angle and Voltage Stability of Large-Scale Power Systems

Several hierarchical centralized control schemes for either rotor angle or voltage stability improvement have been proposed in the literature. They all rely on exchanging information between different subsystems of a large-scale power system. By contrast, in this paper, we propose a hierarchical decentralized control scheme to enhance a unified manner rotor angle and voltage stability while using metered values collected within each subsystem, without any exchange of information between subsystems. Specifically, weakly coupled coherent areas of a power system are first determined. Then, secondary control agents are implemented in each of them to detect and damp rotor angle and voltage instabilities using local synchrophasor measurements. Decentralized control laws based on Lyapunov theory are implemented on FACTS devices for achieving global rotor angle asymptotic stability. Finally, a tertiary voltage control agent provides reference settings to the secondary voltage agents and takes control actions in case the latter fail to damp voltage instabilities. We show that the proposed scheme minimizes the communication bandwidth requirement while exhibiting a system-wide situational awareness. Simulations carried out on the IEEE 118-bus system demonstrate the effectiveness of the proposed hierarchical decentralized control method.

Power hardware-in-the-loop setup for power system stability analyses

Most ongoing activities in the field of network stability support are made by pure simulation studies. In order to accelerate progresses and lower costs of design during development phases, new methods for verifying ideas and inventions have to be developed. The authors propose to utilise a power hardware-in-the-loop test bench for large-scale power system stability analysis. The advantage of this approach is that, e.g. new controls implemented for power electronic coupled generation can be directly studied concerning their impact on large-scale power system stability. This approach is shown for two different study cases; both featuring high penetration of power electronics interfaced distributed generation units in the electrical networks.

Simplified variable frequency induction-motor drive model for power system stability studies and control

Abstract: Powerful variable frequency drives (VFD) are becoming more widely used in power systems. However, there are only a few works addressed to VFD motor dynamics that are suitable for large-scale power system stability studies. The paper proposes a fundamental frequency simplified model of the VFD, which provides an adequate modeling for the study of electromechanical transients in large-scale power systems. Its implementation was carried out in Power System Toolbox (PST), an open source software available for both scientific and commercial purposes. The model was complemented by a number of protection and control strategies that allow to perform adequate modeling for severe disturbances.

Sequential design and global optimization of local power system stabilizer and wide-area HVDC stabilizing controller

A sequential design and global optimization method is proposed to coordinately design local and wide-area controllers to enhance the overall stability of large-scale power system. The sequential design is used to assign the distributed local power system stabilizer (LPSS) and high-voltage direct current (HVDC) wide-area stabilizing controller (HVDC-WASC) to the concerned damping modes. The global optimization is used to simultaneously optimize all the overall control gains of LPSSs and HVDC-WASC. Moreover, the optimization model, which has an adaptive ability of searching and updating dominant oscillation modes, is established. Both the linear analysis and nonlinear simulation results verify the effectiveness of the proposed design method in enhancing the stability of large-scale power systems.

Probabilistic Analysis of Small-Signal Stability of Large-Scale Power Systems as Affected by Penetration of Wind Generation

This paper proposes a method of probabilistic analysis to investigate the impact of stochastic uncertainty of grid-connected wind generation on power system small-signal stability. The proposed method is “analytical” in contrast to the numerical method of Monte Carlo simulation which relies on large number of random computations. It can directly calculate the probabilistic density function (PDF) of critical eigenvalues of a large-scale power system from the PDF of grid-connected multiple sources of wind power generation, thus to determine the probabilistic small-signal stability of the power system as affected by the wind generation. In the paper, an example of 16-machine power system with three grid-connected wind farms is used to demonstrate the application of the proposed method. The results of probabilistic stability analysis of the example power system are confirmed by the Monte Carlo simulation. It is shown that the stochastic variation of grid-connected wind generation can cause the system to lose stability even though the system is stable deterministically. The higher the level of wind penetration is, the more the probability that the system becomes unstable could be. Hence indeed penetration of stochastically variable wind generation threatens stable operation of power systems as far as system small-signal stability is concerned.

縮約系統調整器を用いたハイブリッド型系統縮約手法

In order to analyze transient stability of large-scale power systems, it is advantageous to apply system reduction method to external systems. Short-circuit current method is one of the typical engineering reduction techniques. However, the dominant eigenvalues are not necessarily conserved in the reduced system. Therefore, the hybrid reduction method in which controller parameters are adjusted to conserve the dominant eigenvalues was proposed. Automatic voltage regulator (AVR) and power system stabilizer (PSS) have been used for parameters adjustment so far. However, since there are many parameters in AVR and PSS, complicated procedures are required to adjust them. Therefore, in this paper, the reduced system regulator (RSR) is proposed for hybrid system reduction method. The RSR has only two parameters for adjustment. It is easier to adjust the RSR than AVR/PSS. In addition, the initial gains of the RSR are set zero so that dynamic behavior of the system is not influenced before the adjustment. The effect and the accuracy of the hybrid system reduction method with RSR are examined using a typical longitudinal power system, IEEJ WEST 10-machine system model.

Dynamic model of wind energy conversion systems with variable speed synchronous generator and full-size power converter for large-scale power system stability studies

This paper presents a dynamic model for variable speed wind energy conversion systems, equipped with a variable pitch wind turbine, a synchronous electrical generator, and a full power converter, specially developed for its use in power system stability studies involving large networks, with a high number of buses and a high level of wind generation penetration. The validity of the necessary simplifications has been contrasted against a detailed model that allows a thorough insight into the mechanical and electrical behavior of the system, and its interaction with the grid. The developed dynamic model has been implemented in a widely used power system dynamics simulation software, PSS/E, and its performance has been tested in a well-documented test power network.

Wind Turbine Modelling for Power System Stability Analysis—A System Operator Perspective

In recent years, computer models of wind turbines for power system stability studies have been developed and supplied to power system operators worldwide. The development of such models is of particular significance for stability studies on systems experiencing very large penetrations of wind energy such as the electricity system in the Republic of Ireland. There is a large variation in the complexity of models developed and no widespread agreement on the level of modelling detail required. The use of multiple wind turbine models for large-scale stability studies is also proving difficult. In addition, the majority of models have not been validated. This paper will examine model development and use from the perspective of the Irish grid operator. The validation of developed models will be discussed, and a generic modelling approach will be proposed for large-scale power system stability investigations.

Enhancement of power system transient stability using a nonlinear coordinated excitation and TCPS controller

A robust nonlinear coordinated generator excitation and thyristor-controlled phase shifter (TCPS) controller is proposed to enhance the transient stability of a multimachine power system. To eliminate the nonlinearities and interconnections of the multimachine power system, a direct feedback linearization (DFL) compensator through the excitation loop is designed. Considering the effects of plant parametric uncertainties and remaining nonlinear interconnections, a robust decentralized generator excitation controller is proposed to ensure the stability of the DFL compensated system. Only the bounds of the generator parameters are necessary to be known in the design of the proposed controller, while the transmission network parameters, system operating points or the fault locations need not be known. Since the proposed controller can ensure the stability of large-scale power system within the whole operating region for all admissible parameters, the transient stability of the overall system can be enhanced significantly. Digital simulation studies were conducted on a three-machine power system to show the effectiveness of the proposed control scheme in enhancing the transient stability of the system regardless of the network parameters, operating points and fault locations.

98/01300 Carbon dioxide capture in molten carbonate fuel cell power plants fueled with coal and natural gas: Reimer, P. et al. Proc. Intersoc. Energy Convers. Eng. Conf., 1997, 32, 805–810

A robust nonlinear coordinated generator excitation and thyristor-controlled phase shifter (TCPS) controller is proposed to enhance the transient stability of a multimachine power system. To eliminate the nonlinearities and interconnections of the multimachine power system, a direct feedback linearization (DFL) compensator through the excitation loop is designed. Considering the effects of plant parametric uncertainties and remaining nonlinear interconnections, a robust decentralized generator excitation controller is proposed to ensure the stability of the DFL compensated system. Only the bounds of the generator parameters are necessary to be known in the design of the proposed controller, while the transmission network parameters, system operating points or the fault locations need not be known. Since the proposed controller can ensure the stability of large-scale power system within the whole operating region for all admissible parameters, the transient stability of the overall system can be enhanced significantly. Digital simulation studies were conducted on a three-machine power system to show the effectiveness of the proposed control scheme in enhancing the transient stability of the system regardless of the network parameters, operating points and fault locations.

レイリー商による大規模電力系統の動態安定度評価

A method of assessing dynamic stability of large-scale power system by Rayleigh's quotient is proposed. One-machine infinite-bus systems show damping torque characteristics similar to diagonal components of operational transfer matrices for original multimachine systems, which means that design of PSS with one-machine systems controls those components. An expression for damping constants of oscillation modes is derived based on an energy function and its time derivative for a simplified system representation. This expression demonstrates that oscillations do not necessarily become unstable even if there are some generators with negative damping; and the effect of damping torque is determined by eigenvectors. The expression is generalized with Rayleigh's quotient, and a method of estimating eigenvalues of large-scale power systems is proposed. With this method, approximate eigenvalues are refined to accurate eigenvalues. Only a specified number of eigenvalue analyses are required irrespective of the number of generators, hence much calculation is saved. Finally, this method is applied to a 107-machine system to verify its effectiveness.

Underexcitation limiter models for power system stability studies

Underexcitation limiter models suitable for use in large scale power system stability studies are presented. These models are compatible with current IEEE recommended excitation system models. Using these models, it is expected that most underexcitation limiters in use on large system-connected synchronous machines can be represented.

Dynamic modelling of battery energy storage system and application to power system stability

A useful and systematic dynamic model of a battery energy storage system (BES) is developed for a large-scale power system stability study. The model takes into account converter equivalent circuits, battery characteristics and internal losses. Both charging mode and discharging mode are presented. The model is expressed in equivalent transfer function blocks, and it can be easily used in dynamic stability analysis of a power system. To examine the dynamic behaviour of the model, applications to the damping of turbogenerator torsional oscillations are performed. Active and reactive power modulation by the BES can be controlled according to system requirements. Eigenvalue analysis and dynamic simulations are performed to demonstrate the damping effect of the BES.

Sparse formulation of the transient energy function method for applications to large-scale power systems

The authors present a sparse-matrix formulation of the transient energy function method, to analyze the transient stability of large-scale power systems. The proposed formulation preserves the original network structure and avoids network reduction. Consequently, all matrices used in the calculations are very sparse, leading to a significant saving in computational time as compared to the reduced-network-formulation approach. The proposed solution can handle very-large-scale power systems which are beyond the scope of the current reduced-network techniques. The sparse formulation is applied to several practical utility systems of up to 300 generators and 1724 buses. It is concluded that the results obtained demonstrate the superiority and potential of the sparse formulation in the stability analysis of large-scale power systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>