Wide Area Measurement System Data Research Articles

Battery energy storage-based system damping controller for alleviating sub-synchronous oscillations in a DFIG-based wind power plant

This paper presents the issue of the Sub-synchronous resonance (SSR) phenomenon in a series compensated DFIG-based wind power plant and its alleviation using a Battery Energy Storage-based Damping Controller (BESSDCL). A supplementary damping signal is developed considering the angular speed deviation and is incorporated into the BESS control system. Wide-area Measurement System data is used to determine the angular speed deviation. A linearized system model is developed to perform eigenvalue analysis, and to detect and examine unstable SSR modes. The variation of wind speed and three-phase fault are also taken into consideration to validate the robustness of the controller. To further verify the efficacy of the proposed damping controller, time-domain simulations are performed using MATLAB/Simulink. The application of the proposed BESSDCL stabilizes all the unstable system modes effectively at wind speeds of 7 m/s, 9 m/s, and 11 m/s, and at 40%, 50%, and 60% series compensation levels, as well three-phase fault conditions.

Power system event detection and localization—A new approach

Time-synchronized estimates acquired using the Wide Area Measurement System (WAMS) have substantially helped enhance the health of the modern power grid. WAMS data when used in conjunction with appropriate tools can aid in the timely detection of power system events. With the continuous expansion of the WAMS network, identification of events and narrowing down on their location is emerging as a serious challenge for power system operators. Therefore, in this paper an event detection and localization tool is developed which analyzes data obtained from multiple Phasor Measurement Units (PMUs) installed throughout the WAMS network in order to identify the occurrence of an event. The effectiveness of this tool is demonstrated using practical signals from the ISO-NE power system and simulation based signals obtained from a 4-machine 10-bus system. Occurrence of an event is flagged by comparing the wavelet energy and standard deviation values of a PMU signal against a threshold. An event localization algorithm based on the number of PMUs involved in the event detection stage is proposed. Based on the presented algorithm, disturbances are classified as local or wide-spread events. Finally, a method to identify a loss-of-synchronism condition using phase angle difference (PAD) signals obtained across transmission lines is also proposed.

Evaluation of Wavelet Transform Based Feature Extraction Techniques for Detection and Classification of Faults on Transmission Lines Using WAMS Data

The smart grid is an intelligent power system network that should be reliable and resilient for sustainable operation. Wide-Area Measurement Systems (WAMS) are deployed in the power grid to provide real-time situational awareness to the power grid operators. An excellent strategy for exploiting the WAMS data effectively is to extract relevant insights from the increasing volume of data collected. Feature extraction techniques are pivotal in developing data-driven models for power systems. This paper proposes an ensemble feature extraction method for developing intelligent data-driven models for transmission line fault detection and classification. A comparative efficacy analysis of the proposed ensemble feature extraction method is carried out with state-of-the-art feature extraction methods. The models developed and evaluated with the feature data derived with the proposed method give an accuracy of 100% for fault detection and 99.78% for fault classification. This method also has the advantage of significantly reducing training and testing time. Features are extracted from the WAMS data collected by simulating an IEEE39 bus test system in the PowerWorld simulator.

Development of methods for visual representation of low-frequency oscillation parameters in power systems

The development of wide area measurement system (WAMS) expands the analysis capabilities of the Unified power system based on computational processing of synchronized phasor measurements (SPM). The analysis of low-frequency oscillations (LFO) in the power system is one of the most relevant applications of WAMS data. The task of locating the source of forced LFO in real-time is highlighted. Due to the increasing complexity and heterogeneity of real power systems, a definitive solution to this problem does not currently exist. However, there are SPM data analysis methods that provide a high probability of identifying the source of oscillations. Informative representation of measurement signals, intermediate, and final LFO analysis results can serve as the basis for decision support tools for operational dispatch personnel. Direct visualization of raw data and computed parameters, such as a set of time function graphs, is inefficient due to the large volume. Therefore, compact high-level representations are in demand. This paper proposes some approaches to visualizing SPM data, computed LFO parameters, and the results of applying various oscillation source detection methods. The presented data visualization methods have been implemented by the authors in a LFO analysis software system.

Adaptive WADC scheme for damping inter‐area oscillation based on Jaya optimization algorithm in the presence of variable time latencies from WAMS data

The continual increase in the power network topological structure and long distances between load-generation sources lead to modern powers systems are operated near theirs stability margins. For this issue, reliable and secure operations of electric devices through inter-area oscillations remain an essential issue in the system dynamic stability. In the case of improper actions of controlling devices, the severe inter-area interactions may lead to wide-area instabilities and large blackouts. Using wide-area measurement system (WAMS), remote signals are transferred through communications links with different inherent time latencies. In the case of large time delays, the main controllers cannot work appropriately which leads to improper performance of damping controllers through severe inter-area fault event scenarios. For this issue, this paper presents an adaptive wide-area damping controller (AWADC) for damping inter-area oscillations in large power systems equipped with WAMS technology consisting of various time latencies. In this case, based on the IEEE C37.118.1 protocol, the generator buses are equipped with phasor measurement unit devices. Also, owing to the different communication links, the measured global signals (GSs) are involved within different time latencies. In this case, at each time window, considering time delay compensator (TDC) technology provided through Simevents discrete event tool, the overall time delay is evaluated and compensated. For identifying the best controlling GSs, considering two observability and controllability concepts, the system dynamic signals are evaluated which the best input decisioning signals and corresponding output controlling signals are provided. The proposed AWADC scheme consists of different compensating blocks which are adjusted through simple and well-known Jaya optimization algorithm (JOA) through online evaluations. The structure of the proposed AWADC controlling scheme is carried out on a modified 39-bus New England test system consisting of large synchronous generators whose damping performances are evaluated through severe fault events with the potential of unstable inter-area oscillations. Simulation results indicate the effectiveness of developed TDC and JOA techniques to provide proper controlling signals through the AWADC controller in the presence of different time latencies.

Application of standard ZET-algorithm for gaps filling in wide area measurement system data assets

This article explores the application of Standard ZET-algorithm for gaps filling in Synchronized Phasor Measurement data assets received from Wide Area Measurement Systems. In spite of Synchronized Phasor Measurement data assets apparent advantages, they have gaps affecting the accuracy of solving power engineering tasks. Authors analysed the reasons of gap occurrence in data assets, provided experiments with voltage and current data assets and collected the key points about application of Standard ZET-algorithm.

GIC Influence on UHV Power Grids Based on Kalman Filter and WAMS Data

Geomagnetically induced currents (GICs) flowing through transformers affect their normal operation and can lead to accidents in power grids. The reactive power loss caused by GICs is called GIC-Q. At present, geomagnetic data are usually used to calculate GICs in research. These methods do not have real-time characteristics and cannot be used for real-time research on GICs. Response mechanisms for GICs in 1000 kV ultra-high voltage (UHV) transformers and for the effect of GIC-Q on large power grids are urgently required to prevent damage. Based on the principle of Kalman filter, this paper presents a model and method of calculating and analyzing GIC disturbance using the reactive power measured by wide area measurement systems (WAMS). The proposed method exhibits superior characteristics for real-time analysis and solves the problem of real-time shortage in GIC research. The model provides a theoretical calculation of GIC-Q disturbance in a 1000 kV autotransformer. Further, this method was verified according to the measured reactive power in three 1000 kV substations in Shandong Province and the measured geoelectric field at the Anqiu geomagnetic observatory station on September 8, 2017. The calculation results show that the reactive power measured by phasor measurement units (PMUs) can be effectively used to calculate and analyze GIC-Q in the transformers, which is significant to prevent disasters in the power grid caused by magnetic storms through dispatch and operation.

MPTCP-H: A DDoS attack resilient transport protocol to secure wide area measurement systems

The penetration of distributed generators into the power distribution grid requires real-time control of the grid by monitoring the state of the power distribution grid. Such a large-scale monitoring cannot be performed by using traditional Supervisory Control and Data Acquisition (SCADA) systems due to its lack of the scalability. To address this issue, contemporary Wide Area Measurement Systems (WAMS) are deployed, which provide the dynamic snapshots of the power system. However, WAMS’s more open structure versus SCADA poses a risk of WAMS being vulnerable to cyberattacks. In particular, due to high responsiveness and availability requirements of WAMS applications, attacks i.e., Denial-of-Service (DoS) and Distributed DoS (DDoS) are of primary concern for WAMS.In this paper, we focus on internal DoS/DDoS attacks launched against the WAMS devices by exploiting the vulnerabilities. To counter such attacks, we propose a proactive and robust extension of the Multipath-TCP (MPTCP) transportation protocol, termed as MPTCP-H. The proposed extension mitigates the internal attacks by using a novel stream hopping mechanism, which periodically renews the subflows to hide the open port numbers of the connection. By doing so, MPTCP-H significantly increases the attacker’s cost for a successful attack without perturbing the WAMS data traffic. The experimental results show that the proposed MPTCP-H provides a significant DoS/DDoS attack mitigation for WAMS at the expense of reasonable overheads, i.e., additional latency and message.

Frequency stability control method considering limited EDCPS

Aiming at the problem of frequency stability of the asynchronous AC/DC hybrid power grid, a prediction model of post-disturbance steady frequency is proposed, which considers the emergency DC power support (EDCPS) and the frequency response of AC grids on both sides of the high-voltage DC (HVDC) link. This post-disturbance steady frequency of both AC grids can be predicted quickly by utilising the wide area measurement system data, and the desired amount of EDCPS can be calculated directly by using the setting value of the steady frequency for the disturbed AC grid. Then this study considers the fact that the voltage level of the AC buses at both ends of the HVDC system will affect the operation modes of the HVDC system, resulting in the limited EDCPS. Therefore, a calculation method of the actual EDCPS command for steady frequency control is proposed. It can automatically identify the actual operation mode of the post-disturbance HVDC system and calculate the actual EDCPS command corresponding to the desired EDCPS value. Simulations of a typical two-area AC/DC hybrid power grid are carried out to validate the effectiveness of the proposed method.

Power Network Protection Using Wide-Area Measurements Considering Uncertainty in Data Availability

The wide-area measurement system (WAMS) is being incorporated in power systems for improved performance of monitoring, control, and protection schemes. During unavailability of synchrophasor data from critical buses, schemes utilizing the WAMS may become inactive or susceptible to malfunction. WAMS data may not be available due to failure of communication or measuring instruments. This paper proposes a WAMS-data-based method to identify transmission line faults for data unavailability from critical buses. For this purpose, three indices based on network power flow are proposed. The first index selects buses in the disturbance area in a network by observing the variation in current injections. A subsystem is formed thereafter using the selected buses. The second index calculates the input and output power difference for the subsystem to detect a fault in the network. Finally, a voltage-based index is used to identify the faulted line. The proposed method was tested for the New England 39 bus system with/using PSSE simulations and real-time simulations in OPAL-RT. Results show the ability of the algorithm to detect faulted line(s) in the network even with data loss from selected buses and simultaneous faults. The method is also capable of distinguishing faults from power swing and load encroachment conditions.

Eigen-Analysis Considering Time-Delay and Data-Loss of WAMS and ITS Application to WADC Design Based on Damping Torque Analysis

Data-loss from wide-area measurement systems (WAMS) is a stochastic event and eigenvalues of power systems containing data-loss cannot be calculated directly. This paper proposes a unified model of WAMS data containing time-delay and data-loss according to its mathematical expectation. Based on Pade approximation, the model is incorporated into a system linearized model with WAMS. Thus, an eigen-analysis can be conducted to analyze the impacts of data corruption and to calculate the system stability time-delay margin. Then, the unified model is applied to damping torque analysis (DTA) to derive the damping torque index (DTI) with WAMS. The DTI can be used to select feedback signals and conduct the parameter design of a wide-area damping controller (WADC). Finally, the 2-area 4-machine (2A4M) Kundur system and Eastern China power grid (ECPG) are simulated to validate the feasibility of the model and its application. The results demonstrate the impacts of data corruption on system dynamic performance and the ability of the method to improve the small-signal stability of interconnected power grids.

Delay-Scheduled Controllers for Inter-Area Oscillations Considering Time Delays

Unlike the existing views that was introduced the existence of delay caused by the transmission of wide area measurement system data (WAMS) into the controllers input of the power oscilation damping (POD) by communication networks as a reason for poor performance of the POD controllers. This paper shows that the presence of time delay in the feedback loop may improve the performance of a POD controller in reducing inter-area oscilations. In fact, in a situation where the design and implementation of a POD controller for an FACT device is not easy without delays, in order to compensate for the delay effectively. In this work, a delayed scheduling method to design POD controllers is proposed. At first modeling of power system with delay as a design parameter was established. Then, the power oscillation damping delay scheduling (PODDS) based on objective function of the spectral abscissa was designed and the sufficient condition about stability of the closed-loop system is given. To evaluate the accuracy of the proposed control function and feasibility study, a four-machine power system for numerical simulation was used. The simulation results show that the controller designed in a wide range of delay changes decreases the power system oscilations without restricting SVC performance.

Applying Non-Nested Generalized Exemplars Classification for Cyber-Power Event and Intrusion Detection

Non-nested generalized exemplars (NNGEs) is a state of the art data mining algorithm which uses distance between a new example and a set of exemplars for classification. The state extraction method (STEM) preprocesses power system wide area measurement system data to reduce data size while maintaining critical patterns. Together NNGE+STEM make an effective event and intrusion detection system which can effectively classify power system events and cyber-attacks in real time. This paper documents the results of two experiments in which NNGE+STEM was used to classify cyber power contingency, control action, and cyber-attack events. Experimental results show that NNGE+STEM achieved greater than 94 and 97% accuracy for multiclass and binary class classification. Additionally, the NNGE+STEM false positive rate was below 0.5%, the average classification time was 0.2 ms, and the classifier had low memory requirements.

Adaptive concept of controlled islanding in power systems for wide‐area out‐of‐step prediction of synchronous generators based on adaptive tripping index

Here, based on wide-area measurement systems (WAMS), an adaptive tripping index (TI) is proposed for online prediction of tripping signals with respect to wide-area out-of-step (WAOOS) protection of synchronous generators. The proposed TI included two different equations consisting of a straight line for unstable inter-area oscillations and a sinusoidal line for WAOOS transient instability. For online identification of coherent generators with respect to inter-area oscillations, based on evaluating the correlation coefficients between generator behaviours, an index is proposed from which the global tripping signals (GTS) are calculated. The GTS consist of the rate of change of inter-area rotor angle oscillation between two oscillating areas in the centre of inertia frame. Actually, the proposed scheme is an adaptive and online index from which the critical inter-area angle is adjusted individually by evaluating GTS at each sampling time gathered from the WAMS data. The proposed strategy is implemented on an IEEE 39-bus test system and its performance is investigated by simulating typical scenarios during time-domain simulations. The results show the effectiveness of the proposed scheme for fast prediction of WAOOS protection in real-time environment.

Wavelet Ridge Technique Based Analysis of Power System Dynamics Using Measurement Data

In this paper, a wavelet ridge technique based approach is applied to analyze wide area measurement systems data representing power system dynamic behavior. When used to extract the oscillating trend from the measured network frequency signal, it efficiently tracks the oscillations in the presence of significant noise. Using multivariate signal analysis, a novel disturbance contribution index for individual generator is proposed to estimate how much a generator's contribution is in a severely disturbed power system, as recorded by various phasor measurement units. In other words, this index helps in quantifying how severely affected a particular machine is following a system-wide disturbance. It is shown that any control action applied on the most disturbed generator as identified by the disturbance contribution index, stabilizes the overall system more quickly, compared to the cases where control action is applied on other generators. When the analytic wavelet is used to extract the dynamic pattern from the signal, the recovered signal is also analytic. A new coherency index is also proposed, based on the properties of analytic signal, to indicate how similar two measured signals are. The proposed technique is demonstrated using synthetic signals, signals obtained from time-domain simulation of various power systems and actual phasor measurement units data.

Wide‐area measurement system‐based model‐free approach of post‐fault rotor angle trajectory prediction for on‐line transient instability detection

In order to achieve adequate time for emergency control against transient instability, a scheme to predict the post-fault rotor angle trajectory based on the grey Verhulst self-memory model is provided. The proposed scheme is model free and only uses wide-area measurement system data to provide timely, reliable information about the transient rotor angle stability. Moreover, the scheme is model-parameter-adaptive and takes full consideration of the non-linearity as well as uncertainty of power systems. Firstly, the grey Verhulst self-memory prediction model is presented to cope with the strong non-linear and non-autonomous nature of the power system. Secondly, the equal dimension and new information data model as well as the rolling prediction method are adopted to improve adaptability and robustness of prediction. Investigations with the IEEE-39 bus system and NCE China power system indicate that the proposed prediction scheme gives better prediction performance compared with the other two prediction methods, i.e. grey Verhulst prediction and auto-regressive prediction. Furthermore, combined with equal area criterion based on the severely disturbed generator pair, the proposed prediction scheme is conducted to detect transient instability. Simulation results indicate that the proposed prediction scheme is effective for prediction of transient stability.

Wide-Area Measurement—Based Model-Free Approach for Online Power System Transient Stability Assessment

Online assessment of transient stability of power systems is critical for avoiding blackout. The increasing installation of phasor measurement units in power systems and the advancement of the wide-area measurement systems make it possible to develop methods for online assessment of power systems by using a large amount of real-time synchronous data. In this paper, we propose an approach based on the largest Lyapunov exponent (LLE) for online transient rotor angle stability assessment, using only wide-area measurement systems data. Through establishing a mathematical model that accounts for the LLE value and the rotor speed, as well as analyzing the post-fault phase-plane trajectory, we present a fast stability criterion to determine whether transient instability occurs. The proposed approach is model-free and does not need long-time LLE data to identify the final sign of the LLE. Furthermore, to reduce computational cost and realize online assessment for large-scale power systems, the critical generator pair (CGP) is recognized as the observation for the rotor angle stability assessment, and an effective algorithm for identifying the CGP is presented. Several case studies on the IEEE-39 bus test system and East China power grid are reported to demonstrate the accuracy and effectiveness of the proposed approach.

Analysis of low frequency oscillation and source location in power systems

The major problem in current online diagnosis and analysis for power system oscillation is mainly concerned with finding the oscillation source in a fast and correct way using the data collected by the Wide Area Measurement System (WAMS). This paper for the first time proposes a scheme of cut set energy based on WAMS. Independent of accurate parameters, the scheme can make full use of WAMS data based on cut set energy construction and fast calculation to locate the source during oscillation. Afterwards, a scheme of torque decomposition is proposed, based on which the controller's torque can be divided into damping torque and synchronous torque by calculation through WAMS data, and this paper puts forward the abnormal response and simulation models calibration of influential controllers. Analysis of an oscillation case shows how the cut set energy scheme and the torque decomposition scheme are applied in a real-world power system, and the schemes are proven to be reliable and practical in identifying and locating oscillation sources.

Effective method to determine time‐delay stability margin and its application to power systems

In an interconnected bulk power system, wide-area measurement system (WAMS) can provide abundant remote measurement for the coordinated control system. However, WAMS data have obvious time delays, which affect the performance of the control system and should be properly considered. Time-delay stability margin (TDSM) is an index to reflect the maximum delay that a time-delay system can sustain without losing its stability. To construct a coordinated control system based on WAMS data, it is crucial to accurately and rapidly determine the TDSM value. In this paper, a novel Jordan-Taylor-Schur (JTS) approach to determine the TDSM value of power system is proposed. It consists of three, Jordan standardization, Taylor separation and Schur simplification. With the three procedures of this method, the model dimension of time-delay system can be reduced, and the stability criterion derivation can be rebuilt to omit some unnecessary variables so that both the computational efficiency and accuracy can be boosted. Further, it is worth highlighting that the proposed method can be applied to various Lyapunov-based stability criteria to improve their efficiency with small errors. Finally, three power systems with time delays have been used to demonstrate the effectiveness of the proposed method.

LEs based framework for transient instability prediction and mitigation using PMU data

This study presents a Lyapunov exponent (LE)-based framework for transient instability prediction and mitigation using wide area measurement systems data. For transient instability prediction, maximum LEs calculated using post-fault voltage magnitudes are used as input features to support vector machines to predict the transient stability status. To ensure that the proposed transient instability prediction approach does not rely on full network observability and is effective even if limited numbers of phasor measurement units (PMUs) are installed across large power grids, an optimal PMU placement from the transient stability point of view is also proposed. The robustness of the proposed instability prediction scheme is verified with respect to network topology change and measurement errors. For transient instability mitigation, an LE-based controlled islanding scheme is proposed. The proposed controlled islanding scheme determines the coherent generators, identifies proper load buses that should remain inside each group of coherent generators, specifies the boundary circuits and finally partitions the system into different islands while placing the coherent generators in the same island, maintaining connectivity inside islands and minimising the generation–load imbalance of islands.