Power System Oscillation Stability Research Articles

An Extreme Learning Machine Based Adaptive VISMA for Stability Enhancement of Renewable Rich Power Systems

Maintaining power system stability in renewable-rich power systems can be a challenging task. Generally, the renewable-rich power systems suffer from low and no inertia due to the integration of power electronics devices in renewable-based power plants. Power system oscillatory stability can also be affected due to the low and no inertia. To overcome this problem, additional devices that can emulate inertia without adding synchronous machines can be used. These devices are referred to as virtual synchronous machines (VISMA). In this paper, the enhancement of oscillatory stability of a realistic representative power system using VISMA is proposed. A battery energy storage system (BESS) is used as the VISMA by adding an additional controller to emulate the inertia. The VISMA is designed by using Fruit Fly Optimization. Moreover, to handle the uncertainty of renewable-based power plants, the VISMA parameters are designed to be adaptive using the extreme learning machine method. Java Indonesian Power Grid has been used as the test system to investigate the efficacy of the proposed method against the conventional POD method and VISMA tuning using other methods. The simulation results show that the proposed method can enhance the oscillatory stability of the power system under various operating conditions.

Power System Oscillation Damping and Stability Enhancement using Static Synchronous Series Compensator (SSSC)

Power System Oscillation Damping and Stability Enhancement using Static Synchronous Series Compensator (SSSC)

Characterization of Subsynchronous Oscillation with Wind Farms Using Describing Function and Generalized Nyquist Criterion

Eigen-analysis is widely used in the studies of power system oscillation and small-signal stability. However, it may give inaccurate analyses on subsynchronous oscillation (SSO) when nonlinearity is not negligible. In this paper, a nonlinear analytical approach based on the describing function and generalized Nyquist criterion is proposed to analyze the characteristics of SSO with wind farms. The paper first presents describing function-based model reduction considering key nonlinear elements involved in SSO, and then uses a generalized Nyquist criterion for accurate estimation of SSO amplitude and frequency. The results are verified by time-domain simulations on a detailed model with different scenarios considering variations of the system condition and controller parameters.

Security region-based small signal stability analysis of power systems with FSIG based wind farm

Based on the Security Region approach, the impact of fixed-speed induction generator based wind farm on the small signal stability of power systems is analyzed. Firstly, the key factors of wind farm on the small signal stability of power systems are analyzed and the parameter space for small signal stability region is formed. Secondly, the small signal stability region of power systems with wind power is established. Thirdly, the corresponding relation between the boundary of SSSR and the dominant oscillation mode is further studied. Results show that the integration of fixed-speed induction generator based wind farm will cause the low frequency oscillation stability of the power system deteriorate. When the output of wind power is high, the oscillation stability of the power system is mainly concerned with the inter-area oscillation mode caused by the integration of the wind farm. Both the active power output and the capacity of reactive power compensation of the wind farm have a significant influence on the SSSR. To improve the oscillation stability of power systems with wind power, it is suggested to reasonably set the reactive power compensation capacity for the wind farm through SSSR.

Impact of RE's Anti‐Islanding on Power System Oscillatory Stability

SUMMARYAlthough computer simulation is certainly a powerful tool for power system stability assessment, manual analysis is more helpful for understanding mechanism of unstable phenomena. Among unstable phenomena, oscillatory stability must be the most complex one. The paper analyzes the impact of recently developed Japanese RE's standard active anti‐islanding function named “frequency feedback with step injection” on power system oscillatory stability. Since active anti‐islanding makes islanded system unstable, it also makes stability of large interconnection worse. The question is how serious is the impact and how the impact can be mitigated. The paper presents a method for oscillatory stability analysis considering induction motor load, RE, and anti‐islanding function on RE so minutely as readers can reproduce. Analyses are performed as case studies on aggregated power sending and receiving systems in existing interconnection of Japan. The analyses results are verified by simulation results on the same case studies.

Model validation of DFIGs for power system oscillation stability analysis

The suitability assessment of system modelling is critical to a resource-limited computational environment, which aims to strike a balance between the modelling accuracy and efficiency. In this study, a novel approach to evaluate the damping torque contributions from different dynamic components of doubly fed induction generator (DFIG) to system oscillation stability is first proposed. Then, this approach is employed to investigate the change of DFIG parameters (i.e. parameters of induction generator and converter controllers, and connection status), with the aim of identifying impact mechanism of these parameters on the damping torque contribution of each dynamic component. On this basis, the dynamic model of DFIGs with least orders but acceptable accuracy for oscillation stability analysis can be determined under certain parameter conditions, which undoubtedly brings significant benefits to system planner and operator to mitigate computational burden and save planning time when dealing with large-scale power systems. In this study, the model validation of grid-connected DFIGs is demonstrated in the New York power system - New England test system (NYPS-NETS) example system with 16 machines and 68 buses. Time-domain simulation is used to verify the calculation results of the proposed approach.

REの単独運転検出が電力系統の動態安定度に及ぼす影響

Although computer simulation is certainly a powerful tool for power system stability assessment, manual analysis is more helpful for understanding mechanism of unstable phenomena. Among unstable phenomena, oscillatory stability must be the most complex one. The paper analyzes the impact of recently developed Japanese RE's standard active anti-islanding function named “frequency feedback with step injection” on power system oscillatory stability. Since active anti-islanding makes islanded system unstable, it also makes stability of large interconnection worse. The question is how serious is the impact and how the impact can be mitigated. The paper presents a method for oscillatory stability analysis considering induction motor load, RE, and anti-islanding function on RE so minutely as readers can reproduce. Analyses are performed as case studies on aggregated power sending and receiving systems in existing interconnection of Japan. The analyses results are verified by simulation results on the same case studies.

Gravitational Search Algorithm (GSA) Optimized SSSC Based Facts Controller to Improve Power System Oscillation Stability

Gravitational Search Algorithm (GSA) Optimized SSSC Based Facts Controller to Improve Power System Oscillation Stability

Probabilistic assessment of oscillatory stability margin of power systems incorporating wind farms

With the increase in penetration of wind power which is essentially intermittent and random, the dynamic performance of the power system will change significantly, and so will the characteristics of the oscillations and their stability margins. This paper provides an attempt to include probabilistic character of wind power into the power system oscillatory stability margin (OSM) analysis. Nataf transformation approach is applied to generate the wind speed samples, which models the correlation between the various wind farms. The mathematical model of OSM for wind farm integrated power system is formulated and is calculated by the integration-based eigenvalue tracing approach. Considering the uncertainties of the wind power, several statistical indices are presented to evaluate OSM. Monte Carlo simulation (MCS) is used to calculate these statistics. The impact of wind power uncertainty on OSM restricted by inter-area mode is investigated in four-machine two-area test system and 16-machine five-area test system, respectively, for different wind farm locations, wind power penetration levels and wind speed correlation (WSC) degrees. Appropriate conclusions are finally drawn.

Design of FACTS Device For The Improvement of Power System Stability using Mathematical Matching Controller

The power system installed with a FACTS device demonstrates the application of the model in analyzing the damping effect of the FACTS device stabilizer to improve power system oscillation stability. In case of single-machine infinite bus power systems to be studied and an example power system is presented which show the negative damping influence of STATCOM DC voltage regulator on power system oscillation and the effectiveness of STATCOM stabilizer superimposed on a STATCOM AC voltage regulator to counter attack the negative damping effect. The principle and working of STATCOM, how the STATCOM control the reactive power flow in transmission line can be explained. Philips-Heffrons model of a power system installed with a static synchronous compensator (STATCOM) and demonstrates the application of the model in analyzing the damping effect of the STATCOM and designing a STATCOM stabilizer to improve power system oscillation stability.

Power System Oscillations Damping Using Unified Power Flow Controller-Based Stabilizer

Problem statement: The Phillips-Heffron model of a power system with UPFC published by AJAS, demonstrates the effect of the UPFC in improving power system oscillation stability. Unfortunately, some of the equations have not been correctly derived and so working with this model in its existing form is misleading. Approach: In this study, the model is revisited and the equations are re-derived obtaining correct results. Three-machine power system installed with a UPFC is used to investigate the validity of these equations. Results: The simulation results demonstrated that the corrected model with an effective controller is active on damping of the low-frequency oscillations under different operating conditions. Conclusion: The corrected model works properly with power system networks for enhancing power system stability.

Effect of embedded voltage source converter on power system oscillation damping

This paper presents the damping torque analysis of power system oscillation stability as affected by the dynamic and control functions of an embedded voltage source converter (VSC). The objective of the study is to explain why and how the dynamic and basic control functions of the embedded VSC, ac and dc voltage regulation, provide damping to power system oscillations. The most important conclusion obtained in the paper is that both the dynamics and the dc voltage control of the VSC contribute a variable damping torque, which can be positive or negative, at different levels of system load conditions. More positive damping torque can be provided by the VSC at a heavier load condition. There exists a point of system load condition where the VSC provides no damping torque to power system oscillation hence dose not impose any influence on power system oscillation stability. The VSC studied in the paper can be the power-electronics-based interface of various FACTS (flexible ac transmission systems) devices, energy storage systems and renewable power generation units, although the focus of the discussion presented in this paper is the effect of the dynamics and basic control functions of the VSC themselves on power system oscillation damping. To demonstrate the analytical conclusions obtained in the paper, results of eigenvalue computation and nonlinear simulation of an example power system with STATCOM (static synchronous compensator) are given.

Comparison of UPFC-Based Stabilizer and PSS Performances on Damping of Power System Oscillations

This paper establises the linearized Philips-Heffron model of a power system equipped with UPFC and demonstrates the application of the model in analyzing the damping effect of the UPFC, and designing UPFC based stabilizer to improve power system oscillation stability. A comprehensive approach to the design of UPFC based stabilizer (power flow control, DC-voltage regulator and damping controller) is presented. In this case, the multi-machine power system with UPFC is studied and an example of power system is presented. It is shown that the DC voltage contributes negative damping to power system oscillations, which is confirmed by both eigenvalue computation and nonlinear simulation. To counterattack the negative damping effect due to the DC voltage regulator, UPFC based stabilizer is designed and its effectiveness is demonstrated by both eigenvalue computation and nonlinear simulation. Then the effects of UPFC and PSS on power systems are compared. Simulation results show that the performance of UPFC based stabilizer on damping of power system is better than PSS.

Comparison of UPFC-Based Stabilizer and PSS Performances on Damping of Power System Oscillations

This paper establishes the linearized Phillips-Heffron model of a power system equipped with UPFC and demonstrates the application of the model in analyzing the damping effect of the UPFC and designing UPFC based stabilizer to improve power system oscillation stability. A comprehensive approach to the design of UPFC based stabilizer (power flow control, DC-voltage regulator and damping controller) is presented. In this case, the multi-machine power system with UPFC is studied and an example of power system is presented. It is shown that the DC voltage contributes negative damping to power system oscillations, which is confirmed by both eigenvalue computation and nonlinear simulation. To counterattack the negative damping effect due to the DC voltage regulator, UPFC based stabilizer is designed and its effectiveness is demonstrated by both eigenvalue computation and nonlinear simulation. Then the effects of UPFC and PSS on power systems are compared. Simulation results show that the performance of UPFC based stabilizer on damping of power system is better than PSS.

Modelling and performance of fixed-speed induction generators in power system oscillation stability studies

This paper describes the modelling and performance effects of induction generator-based wind farms on the oscillation stability of power systems. For groups of 5, 10 and 20 induction generators, it is established that the basic dynamic properties of each group of generators are similar to those of a third-order equivalent machine model whether the generators are evenly loaded or unevenly loaded. The paper analyses the impact of induction-based wind generation on oscillation stability for multi-machine systems as applied to the standard IEEE 30 bus system. The effects of load model representation, system loading, generator output and transmission line network parameters are considered. In general, the multi-machine system is shown to be well damped under all normal operating conditions.

The Effective Role of AVR and PSS in Power Systems: Frequency Response Analysis

Two tradeoffs in the effectiveness of automatic voltage regulators (AVRs) and power system stabilizers (PSSs) are investigated together for the first time. The first is the effect of a high-gain fast response AVR on decreasing power system oscillation stability as well as increasing transient stability, and vice versa. The second is that a PSS can reduce transient stability by overriding the voltage signal to the exciter as well as increasing oscillation stability, and vice versa. In essence, the actions of the AVR and PSS devices are dynamically interlinked. A novel Bode frequency response framework for dynamic analysis of AVR and PSS performance and tradeoffs is presented. Bode frequency response also assists with the determination of suitable generator locations for PSSs and the assessment of robustness under changing power system operating conditions.

A unified model for the analysis of FACTS devices in damping power system oscillations. III. Unified power flow controller

For pt.II see ibid., vol.13, no.4, p.1355-62 (1998). This paper presents the establishment of the linearized Phillips-Heffron model of a power system installed with a unified power flow controller (UPFC). Two applications based on the Phillips-Heffron model are demonstrated: (1) study on the effect of UPFC DC voltage regulator on power system oscillation stability; and (2) selection of damping control signal for the design of UPFC damping controller.

Applications of modelling UPFC into multi-machine power systems

The paper establishes a non-linear dynamic model of a multi-machine power system with a unified power flow controller (UPFC) installed. The linearised Phillips-Heffron model of the system is then derived and used to study oscillation stability. To demonstrate the applications of the models developed in the paper, a case study of a three-machine power system to be installed with a UPFC is presented. The impact of various UPFC control functions upon the power system oscillation stability is investigated based on the linearised model with confirmation by simulation from the non-linear dynamic model. It is found that the basic control function within the UPFC, the voltage control of the DC link capacitor, interacts negatively with PSS. Results of counteracting the negative interaction by the readjustment of PSS or the introduction of a damping function into the UPFC itself to regain a satisfactory damping of power system oscillations are given in the paper.

Phillips–Heffron model of power systems installed with STATCOM and applications

The paper establishes the linearised Phillips-Heffron model of a power system installed with a static synchronous compensator (STATCOM) and demonstrates the application of the model in analysing the damping effect of the STATCOM and designing a STATCOM stabiliser to improve power system oscillation stability. Both cases of single-machine infinite-bus and multimachine power systems are studied and example power systems are presented. These show the negative damping influence of a STATCOM DC voltage regulator on power system oscillations and the effectiveness of the STATCOM stabiliser superimposed on a STATCOM AC voltage regulator to counterattack the negative damping effect.

98/01305 The connection between modal analysis and electric torque analysis in studying the oscillation stability of multimachine power systems: Swift, F. J. and Wang, H. F. Electrical Power & Energy Systems, 1997, 19, (5), 321–330

98/01305 The connection between modal analysis and electric torque analysis in studying the oscillation stability of multimachine power systems: Swift, F. J. and Wang, H. F. Electrical Power & Energy Systems, 1997, 19, (5), 321–330