Inter-area Oscillation Modes Research Articles

Estimation of interarea electromechanical modes during ambient operation of the power systems using the RDT–ITD method

Abstract An accurate awareness of the properties of the interarea electromechanical oscillation modes is essential for the secure operation of the power systems. Previously, the Ibrahim time domain (ITD) method has been applied to estimate the interarea oscillation modes using ring-down signals caused by major disturbances (such as three phase faults). In this paper, through the combination of the random decrement technique (RDT) and the ITD method, the RDT–ITD method is proposed to estimate the interarea modes during ambient operation of the power systems, using random responses caused by random changes of the loads. The estimated parameters include the frequencies, damping ratios and mode shapes. Considering the fact that both the ambient excitations and the measurement noise are stochastic in nature, Monte Carlo simulations were conducted to evaluate the performances of the RDT–ITD method in a statistical way. Simulation results in the 16 machine nonlinear power system model, as well as comparison results with the RDT-Prony method, the NExT-ERA method and the Subspace method realized by N4SID (Numerical algorithm for Subspace State Space System Identification) show that the RDT–ITD method is promising in estimating the interarea modes during ambient operation conditions. The RDT–ITD method was also validated using real PMU measurements from Sichuan power grid of China.

Hybrid adaptive neuro-fuzzy B-spline--based SSSC damping control paradigm using online system identification

B-spline membership functions have produced promising results in the field of signal processing and control due to their local control property. This work explores the potential of B-spline--based adaptive neuro-fuzzy wavelet control to damp low frequency power system oscillations using a static synchronous series compensator (SSSC). A comparison of direct and indirect adaptive control based on hybrid adaptive B-spline wavelet control (ABSWC) is presented by introducing the online identification block. ABSWC with identification (ABSWCI) provides the sensitivity information of the plant needed to control the system. The parameters of the control and identification block are updated online using a gradient descent-based backpropagation algorithm. The stability and convergence of the proposed control system is discussed based on Lyapunov stability criteria. The robustness of the proposed control algorithm has been evaluated for local and interarea modes of oscillations using different faults. The nonlinear time-domain simulations have been analyzed on the basis of different performance indices and time-frequency representation, showing that ABSWC effectively damps low-frequency oscillations and incorporation of online identification optimizes the control system performance in terms of control effort, which reduces the switching losses of the converter.

Effect of Large-Scale Wind Power Integration on Inter-Area Oscillation of Power System

With the fast development of the wind power, security constraints of power systems have become the bottleneck of the acceptable capacity for wind power. The underdamping oscillation modes of the inter-area is an important aspect of the constraints. In this paper, an equivalent model of a power system with wind plants has been established, and the impact of the integration of the large-scale wind power on the inter-area oscillation modes has been studied based on the frequency-domain and time-domain simulations. The results indicate that the damping of inter-area oscillation mode can be enhanced by the replacement of synchronous generators (SGs) with the wind generators. The enhancing degree is up to the participation value of the SGs replaced. The conclusion has been verified by the actual system example of Xinjiang-Northwest grid. It can provide a reference for system programming and operation.

Modal Research on the Low-Frequency Oscillation of AC/DC System with DFIG-Based Wind Farms

Low-frequency oscillation characteristics of AC / DC system with DFIG-based wind farms were studied. Detailed mathematical pure AC and AC / DC system model were established by considering the effects of doubly-fed wind turbine model and DC transmission dynamic model to do small signal stability analysis. The computed results of small signal stability of DFIG-based wind farms integrating pure AC CEPRI36 nodes system or with DC transmission that operated in four connection modes including bipolar neutral grounding at both ends mode, monopole ground return mode, monopole metallic return mode , monopole and two parallel conductor mode with earth return were investigated by using modal analysis method. Then, the characteristics of local oscillation modes and inter-area oscillation modes were respectively analyzed under the two operation modes of the wind farm participating active power dispatching and reactive power dispatching and consequently some new conclusions were drawn.

English

This paper describes a design procedure for a Grey ANFIS based power system stabilizer (GrANFISPSS) and investigates their robustness for a multi-machine power system. Speed deviation of a machine and its derivative are chosen as the input signals to the GrANFIS-PSS. A four-machine and a two-area power system is used as the case study. Computer simulations for the test system subjected to transient disturbances i.e. a three phase fault, were carried out and the results showed that the proposed controller is able to prove its effectiveness and improve the system damping when compared to a conventional lead-lag based power system stabilizer controller. The simulation result shows that the GrANFIS-PSS can be designed to achieve good performance merely using the combination of Grey prediction and Adaptive Neuro-Fuzzy Inference System (ANFIS). GrANFIS-PSS is designed to damp out the low frequency local and inter-area oscillations of the Multi-machine power system. By applying this GrANFIS-PSS to the power system the damping of inter-area modes of oscillations in a multi-machine power system is handled properly. The effectiveness of the proposed GrANFIS-PSS is demonstrated on two area four machine power system (Kundur system), which has provided a comprehensive evaluation of the learning control performance. Finally, several fault and load disturbance simulation results are presented to stress the effectiveness of the proposed GrANFIS-PSS in a multimachine power system and show that the proposed intelligent controls improve the dynamic performance of the GrANFIS-PSS and the associated power network

A Coordinated Design of PSSs and UPFC-based Stabilizer Using Genetic Algorithm

This paper details a new coordinated design between power system stabilizers (PSSs) and a unified power flow controller (UPFC) using genetic algorithms (GAs). A GA scheme determines the optimal location for a UPFC while tuning its control parameters, resulting in the optimization of the quantity, parameters, and locations of PSSs under different operating conditions. The problem is formulated as a multiobjective optimization problem in order to maximize the damping ratio(s) of electromechanical modes, matching different numbers of PSSs with a UPFC. The approach is successfully tested on the New England-New York interconnected system (a 16-machine and 68-bus system), proving its effectiveness in damping local and interarea modes of oscillations.

Influence of Wind Farm with PMSG Type on Small Signal Stability of Power System

In order to study the small signal stability of power grid after grid-connection of large-scale Permanent Magnet Synchronous Generator (PMSG) wind farms, the mathematical model of PMSG was established. By means of simulation on a simple power system, the damping characteristics of grid under different wind power penetration and different access location of wind farms were studied in detail. Simulation results show that along with the increase of wind power, the inter-area oscillation mode damping would reduce. When wind farm was attached the receiving area, the inter-area oscillation mode damping was lower than it when wind farm was attached the supplying area.

Coordinated Adaptive Control of Multiple Flexible AC Transmission Systems using Multiple-input—Multiple-output Neuro-fuzzy Damping Control Paradigms

This article presents a novel online adaptive non-linear multiple-input–multiple-output neuro-fuzzy control scheme for flexible AC transmission systems. The proposed control system synergistically integrates the time-frequency localization property of wavelets with locally controllable membership functions in the structure of neuro-fuzzy Takagi–Sugeno–Kang control. The proposed control scheme is checked for both multiple-input–single-output and multiple-input–multiple-output topologies. The performance of the proposed control system is validated against different contingencies and operating conditions using non-linear time-domain simulations and different performance indices. The results reveal that the proposed control scheme effectively damps the local and inter-area modes of oscillations.

Impact of Increasing Wind Power Generation on the North-South Inter-Area Oscillation Mode in the European ENTSO-E System

After the enlargement of the European ENTSO-E power system towards Turkey at the end of 2010, the East-West Inter-Area Oscillation mode in the enlarged the European ENTSO-E power system has been identified in the frequency range of 0.15 Hz (TP = 7s) accompanied by insufficient damping. By the end of 2012, more than 107 GW of wind generation capacity had been installed across Europe, representing about 25% of the peak demand of ENTSO-E power system. In this paper, the impact of large scale wind power generation in the European ENTSO-E system on the North-South Inter-Area Oscillation mode using a detailed dynamic model of the European ENTSO-E system is investigated by gradually replacing the power generated by the synchronous generators in the system either Full Size Converter or Doubly Fed Induction Generator (DFIG) wind turbines. Because the whole system is extremely nonlinear, the analysis method in state space is senseless; therefore the damping behavior of Inter-Area-Oscillations of the whole system was analyzed in detail using the analysis method in time domain. The model was created using DIgSILENT software.

A Coherency-Based Approach for Signal Selection for Wide Area Stabilizing Control in Power Systems

In this paper, a systematic procedure to select wide-area input/output control signals based on a signal coherency approach to damp out inter-area mode of oscillations is proposed. The coherent signal groups are chosen based on a data clustering approach. The input/output signal selection is carried out in two steps. First, the data is transformed into orthogonal space to make correlated variables uncorrelated, by applying principal component analysis. Then, the principal component vectors are given as input to a self-organizing map for final data clustering. From each clustered signal group, a signal out of those with common features is selected. For clustering, the data are collected from the system dynamic simulation considering few critical line contingency. The efficacy of the proposed feature selection based method is verified by comparing the results with a geometric-based approach and a pole vector direction based signal selection approach on 39-bus New England and 68-bus New England New York power systems.

Optimization of power system stabilizers using participation factor and genetic algorithm

This paper describes a method to determine the optimal location and the number of multi-machine power system stabilizers (PSSs) using participation factor (PF) and genetic algorithm (GA). The PF method is primarily used for number estimation and to identify the location of the PSSs, while the GA is applied to further reduce the number of PSSs, resulting in the optimization of their parameters and locations under different operating conditions. The problem is presented as a multi-objective optimization problem; maximizing the damping ratio of the electromechanical modes using different numbers of PSSs. The approach is successfully tested on the New England–New York interconnected system (16-machine and 68-bus), and its effectiveness in damping of local and inter-area modes of oscillations was proven. It is also compared to two other methods, which use only GA, in terms of damping ratio and computation time. In addition, the proposed approach demonstrates better performance compared to a fuzzy-based PSS when applied to the Iraqi National Super Grid System (INSGS).

Application of Coherency Property of Generator to Analysis of Low-Frequency Oscillation in Power System

Coherency is used to characterize the degree of confusion between generators which oscillate against each other, so it can judge the process which generators oscillate from local mode to inter-area mode. The coherency is the value of the direction cosine by using angle of the generators. when the direction cosines of two generator is 1 that indicates the oscillation direction between the two generators is inter-area oscillation mode; when the direction cosines of two generator is-1 that indicates the oscillation direction between the two generators is local oscillation mode. Coherency is affected by speed governing system and excitation system of generator.Using two area systems verifies the theoretical analysis is correct.

Design of wide-area robust damping controller based on the non-convex stable region for inter-area oscillations

In view of the low frequency, low damping ratio and long duration characteristics of the inter-area oscillation mode, the stable region is firstly extended by the eigenvalue shifted factor in this paper. Furthermore, a non-convex stable region is designed which can stabilize the system rapidly. Then a mixed H2/H∞ multi-objective robust control strategy based on the non-convex stable region is proposed considering the perturbation and system uncertainty. Finally, time-domain and frequency-domain simulations are carried out in the 4-machine and 16-machine test systems respectively, and simulation results verify that the proposed strategy is more effective and robust than the traditional H2/H∞ control strategy.

Wide Area Inter-Area Oscillation Monitoring Using Fast Nonlinear Estimation Algorithm

This paper presents the results of the development of Smart Grid transmission network applications in the Great Britain (GB) power system. A new Wide Area Monitoring System (WAMS) application for monitoring inter-area oscillations is developed. The core of this novel application is a fast nonlinear algorithm for the real-time estimation of the dominant inter-area oscillation mode, which processes GPS synchronized information obtained from Phasor Measurement Units (PMUs) installed in the power system. It is based on the Newton-Type Algorithm (NTA), an efficient parameter estimator. The paper focuses on the practical application of the new WAMS application: two data sets were tested, one based on computer simulations and the other based on real-life data records. The computer simulated oscillatory signals were obtained through dynamic simulations of the full GB power system model consisting of over 200 generators. The real-life data records used information collected by the FlexNet Wide Area Monitoring System (FlexNET-WAMS) installed in the GB network. Based on these data records, the features of inter-area oscillations in the GB network are drawn.

Enhanced design of an indirect adaptive fuzzy sliding mode power system stabilizer for multi-machine power systems

This paper presents an enhanced indirect adaptive fuzzy sliding mode based power system stabilizer for damping local and inter-area modes of oscillations for multi-machine power systems. The proposed controller design is based on an adaptive fuzzy control combining a proportional integral controller with a sliding mode controller. Generator speed deviation and its derivative are selected as input signals to a fuzzy logic system that approximates unknown power system functions and a proportional integral regulator is used to eliminate the undesirable sliding mode chattering. Using Lyapunov synthesis, adaptation laws are developed in an enhanced indirect adaptive fuzzy scheme which closely tracks changes in power system operating conditions. Performance of the proposed stabilizer is evaluated for a two-area four-machine power system subjected to different types of disturbances. Simulation results are compared to those obtained with a conventional PSS, with a fuzzy logic based stabilizer and with an adaptive fuzzy PSS clearly showing the effectiveness and robustness of the proposed approach.

Hybrid Neuro-fuzzy Legendre-based Adaptive Control Algorithm for Static Synchronous Series Compensator

This article presents a novel adaptive non-linear control scheme for a static synchronous series compensator to improve power system stability. The proposed control system synergistically integrates the Legendre polynomial functional neural network, a member of the orthogonal polynomials family, with adaptive neuro-fuzzy Takagi–Sugeno control. The control scheme exploits the online, model-free direct control structure, which reduces the computational complexity, latency, and memory requirements, to make the proposed control strategy highly suitable for real-time implementation. The performance of the proposed control system is validated against different contingencies and operating conditions using non-linear time-domain simulations and different performance indices. The performance of the proposed control system is compared with the adaptive neuro-fuzzy Takagi–Sugeno. The results reveal that the proposed control scheme effectively damps the local and inter-area mode of oscillations.

Wide-area Automatic Voltage Regulators Controller for Damping Oscillations Based on Inter-area Modes

This article presents a wide-area controller for automatic voltage regulators. The controller is designed for damping the power system inter-area oscillations. A centralized wide-area controller is designed considering the time delay of both the remote measurements and control signals. The controller design is based on the disturbed state-space model with reduction of the disturbances to a vector that excites the inter-area modes of oscillation. The controller design is achieved using the H∞ linear matrix inequality control method, which guarantees the robustness of the controller to system disturbances. The wide-area controller is designed and tested for the 16-machine 5-area study system.

Performance Assessment of Fuzzy Logic Power System Stabilizer on North Benghazi Power Plant

Fuzzy logic design has been implemented online to tune the power system stabilizer gain (KPSS). To assess the performance of the proposed technique, Benghazi North Power Plant (BNPP), at eastern Libyan network, has been utilized as a power system stabilizer (PSS) benchmark. The design considers different operating conditions and large disturbance. A selection of fuzzy rules is derived by means of system output power to tune KPSS, whereas Particle Swarm Optimization technique (PSO) is exploited to calculate the PSS parameters offline according to real-time measurements of the considered plant. Several simulation scenarios have been conducted to show the effectiveness of the proposed PSS in damping of local and interarea modes of oscillation of one-machine infinite-bus system. The study also contains comparison between the proposed technique and conventional PSS (CPSS).

Four-Area Load Frequency Control of an Interconnected Power System Using Neuro-Fuzzy Hybrid Intelligent Proportional and Integral Control Approach

AbstractThis article presents a novel control approach, hybrid neuro-fuzzy (HNF), for the load frequency control (LFC) of a four-area interconnected power system. The advantage of this controller is that it can handle nonlinearities, and at the same time, it is faster than other existing controllers. The effectiveness of the proposed controller in increasing the damping of local and inter-area modes of oscillation is demonstrated in a four-area interconnected power system. Areas 1 and 2 consist of a thermal reheat power plant, whereas Areas 3 and 4 consist of a hydropower plant. Performance evaluation is carried out by using fuzzy, artificial neural network (ANN), adaptive neuro-fuzzy inference system, and conventional proportional and integral (PI) control approaches. Four different models with different controllers are developed and simulated, and performance evaluations are carried out with said controllers. The result shows that the intelligent HNF controller has improved dynamic response and is at the same time faster than ANN, fuzzy, and conventional PI controllers.

Adaptive Damping Control of Inter-Area Oscillations Based on Federated Kalman Filter Using Wide Area Signals

The application of phasor measurement unit (PMU) measurements and adaptive wide-area damping control based on federated Kalman filters are investigated. The Kalman filters used for estimating the operating conditions are federated using chi-square variables and a confidence interval. When the power system is operating precisely at a preselected operating point, only the corresponding controller is active. When the power system is not exactly at the operating point, a combined controller is formed. A 68-bus, 16-generator system is used as a test system. Three DC lines, three ESDs, and remote PMU frequencies as added inputs are used as the example control. The simulation results demonstrated the good performances for adaptive damping the inter-area oscillation modes.