Power System State Estimation Research Articles

Dynamic state estimation of power system using hybrid whale-tunicate optimized unscented Kalman filter based on wide area measurement systems

The Energy Management Systems (EMS) utilizes Dynamic State Estimation to monitor the operating condition of the power grid. For a synchronous generator, the speed and angle of a rotor are the most important dynamic states. These states are responsible for producing uncertainty in the power system models. Extended Kalman Filter (EKF) and Unscented Kalman Filters (UKF) are utilized to estimate the dynamic states of the power system when it perceives significant disturbances or noise. The conventional Unscented Kalman Filter (UKF) has limitations in terms of slow convergence speed and its lack of positive semi-definiteness. This prohibits its ability to accurately track the transients of the system. The scaling parameters of UKF (alpha and beta) are optimally tuned to overcome these issues. In this paper, a novel Hybrid Whale-Tunicate-based UKF (HW-TO-UKF) is proposed for tuning the scaling parameters of UKF for reducing the mean difference between the real state and the measured state. During the validation of the proposed method, better robustness and statistical efficiency are achieved by defining the objective function as the minimization of the error difference between the actual and measured states. The simulation is carried out on the WSCC-3 and NPCC-48 machine systems to demonstrate the performance of the proposed HW-TO-UKF over the existing models.

Enhanced dynamic state estimation of regional new energy power system under different abnormal scenarios

AbstractThe high proportion of renewable energy sources in the power grid increases the failure probability of the system, which becomes a new challenge for the safe and stable operation of the regional power grid. To ensure stable control of the power network with substantial renewable energy integration, this article proposes a new method that combines the long short‐term memory (LSTM) neural networks and adaptive cubature Kalman filter (ACKF) to improve the prediction accuracy of mutation data inherited from the renewable generation. Four abnormal scenarios, including low voltage ride‐through (LVRT), high voltage ride‐through (HVRT), continuous fault ride‐through and bad data injection of the regional power grid are investigated through extensive case studies. The proposed method is implemented on the IEEE 30‐node system for performance verification. The simulation results demonstrate that the proposed method has considerably higher robustness than the traditional Kalman filter algorithm and can effectively improve the overall state estimation accuracy of the renewable energy power system under different scenarios.

Privacy-preserving federated learning for detecting false data injection attacks on power system

False data injection attacks (FDIA) against power system state estimation have been well studied due to its potential threat to real-time energy management. However, the existing works either focus on the case with a sufficiently large local data sets or the local data can be transmitted to a central node, or the case where the system parameters can be easily acquired through communication. This contradicts with real-world applications where the measurement data is geographically distributed and the system parameters are unknown, and also leads to data leakage issues. To solve the problem, a novel FDIA detection algorithm is proposed based on federated learning, through which a global detection model is generated. In the proposed algorithm, the state owners execute a federated learning algorithm using their own data, which avoids massive data transmission and protects the data privacy. Moreover, to prevent the model parameter from exposure to attackers, artificial noise is added into the model estimations to guarantee differential-privacy. Theoretical results show a trade-off in algorithm accuracy and its privacy preserving level. Simulations on the IEEE 30-bus system validate the effectiveness of the proposed mechanism on FDIA detection and its trade-off in accuracy and privacy preserving.

Forecasting-Aided State Estimation in Power Systems During Normal Load Variations Using Iterated Square-Root Cubature Kalman Filter

The main aim is to estimating the voltage profile at all the buses in the system before the arrival of next set of hybrid measurements from field. The effectiveness of the algorithm ISCKF during load variations is evaluated with respect to already implemented Kalman filter approaches for this application. This includes the sudden changes in loads which occurring in practical power systems. The utilization of an iterated square-root cubature Kalman filter (ISCKF) for power system forecasting-aided state estimation (FASE) is being studied during normal load variations. Its implementation involves "Newton-Gauss iterative method being embedded into the square-root cubature Kalman filter (SCKF)" at the measurement update step of Kalman filter. The square-root factor of error covariance matrices is calculated by utilizing QR decomposition to avoid losing of positive definiteness of the matrix. The estimation is carried out utilizing hybrid measurements from remote terminal units and phasor measurement units. The state vector is forecasted using the proposed method in the interval period between two measurement arrivals from the devices. Thereby, caters to state estimation of the voltages at buses in the system even when the measurements are unavailable. The efficacy of the proposed algorithm to FASE is evaluated for IEEE 30-bus system and Northern Region Power Grid (NRPG) 246-bus system. The simulation results show that the proposed ISCKF outperforms the CKF by significant improvement in accuracy of forecasting-aided state estimation. ISCKF will be able to give results before the next set of hybrid data arrives (expected from an estimation algorithm). Therefore, the proposed estimation algorithm is applicable for real-time practical application, with respect to large power systems as well.

Physics-informed graphical neural network for power system state estimation

State estimation is highly critical for accurately observing the dynamic behavior of the power grids and minimizing risks from cyber threats. However, existing state estimation methods encounter challenges in accurately capturing power system dynamics, primarily because of limitations in encoding the grid topology and sparse measurements. This paper proposes a physics-informed graphical learning state estimation method to address these limitations by leveraging both domain physical knowledge and a graph neural network (GNN). We employ a GNN architecture that can handle the graph-structured data of power systems more effectively than traditional data-driven methods. The physics-based knowledge is constructed from the branch current formulation, making the approach adaptable to both transmission and distribution systems. The validation results of three IEEE test systems show that the proposed method can achieve lower mean square error more than 20% than the conventional methods.

An online method for the accuracy level evaluation of the phasor measurement units

Online evaluation of the accuracy level of the phasor measurement unit (PMU) is very useful in assessing the accuracy ranges of PMU measurements. Such results can be applied to avoid the misoperation of power system protection and control and enhance the accuracy of power system state estimation. Because the theoretical values are unknown, the evaluation indices defined in the IEEE/IEC standard 60255-118-1, such as the total vector error, frequency error, and rate of change of frequency error, cannot be calculated online. To address this concern, a new index named the total waveform error (TWE) is proposed in this paper. It is defined as a ratio of fundamental root-mean-square (RMS) value to fundamental residual RMS, where harmonic components are excluded in the TWE calculation. For a specific window length, two TWE thresholds are set according to the IEEE standard C37.118.1 to divide the PMU measurement into 3 accuracy levels. Theoretical analysis and simulation tests show that the TWE is effective in accuracy-level evaluation. Two examples are given to illustrate the TWE applications of evaluating accuracy levels of PMU measurements.

Distributed Dynamic State Estimation of Power Systems Considering Dynamic State Constraints based on Phasor Measurements Units

Background: Dynamic state estimation can provide detailed information about power systems. However, there is no clear, dynamic equation for the state transition of bus voltages in power systems. Currently, smoothing methods based on historical data are commonly used, but they cannot ensure accurate state prediction in power systems with a large amount of renewable energy. Moreover, the fast sampling rate of phasor measurement units generates a vast amount of real-time data for the dispatch center, making it challenging for centralized state estimation to meet real-time demands. Objective: This paper proposes a distributed power system state estimation considering dynamic state constraints to address the above issues. Methods: By incorporating the constraints between the dynamic states of the system dynamic components and the bus voltage phasors, the state transition equations for bus voltage phasors are constructed based on the predicted dynamic states and the nodal injection power equations. This allows taking the dynamic model constraints into account when predicting bus voltage phasors. Then, based on the principle of hierarchical coordination and distributed state estimation, the method of estimation-coordination-correction is adopted to acquire system state information quickly and accurately. method: By incorporating the constraints between the dynamic states of the system dynamic components and the bus voltage phasors, the state transition equations for bus voltage phasors are constructed based on the predicted dynamic states and the nodal injection power equations. This allows taking the dynamic model constraints into account when predicting bus voltage phasors. Then, based on the principle of hierarchical coordination and distributed state estimation, the method of estimation-coordination-correction is adopted to acquire system state information quickly and accurately. Results: Furthermore, an IEEE 9-bus system and an IEEE 39-bus system are used to validate the proposed method. The proposed method is compared with other algorithms to prove its superiority. result: Furthermore, an IEEE 9-bus system and an IEEE 39-bus system are used to validate the proposed method. And the proposed method is compared with other algorithms to prove its superiority. Conclusion: The simulation results show that the proposed method can effectively improve the accuracy of the state estimation results of power systems under dynamic conditions. conclusion: The simulation results show that the proposed method can effectively improve the accuracy of the state estimation results of power systems under dynamic conditions. other: None

A Bad Data Resilient Multisensor Fusion Framework for Hybrid State Estimation

This paper proposes a novel estimation fusion approach for hybrid multi-stage power system state estimation. Hybrid estimation fusion architectures allow the incorporation of new classes of sensors without doing away with pre-existing estimators. The fusion module is responsible to produce final estimates based on the optimal merging of the individual estimators' outcomes. The proposed fusion formulation is based on the Maximum Correntropy Criterion (MCC), an optimization criterion borrowed from the information theoretic area that has been recently applied to conventional power system state estimation and enables the automatic suppression of bad data effects. In this paper, the correntropy-based formulation is used to replace the traditional minimum variance fusion methodology in the second stage of the hybrid estimation algorithm. To assess the applicability of the novel method, a three-sensor, MCC-based fusion architecture is evaluated through simulations conducted on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IEEE</i> 14-bus, 30-bus, 57-bus, and 118-bus test systems. In the absence of bad data, the results confirm the expected compatibility between the proposed MCC-based fusion and the conventional minimum variance formulation. In addition, extensive experiments considering distinct bad data scenarios under several operational conditions have been performed. They illustrate a novel functionality imparted by the proposed approach to the fusion module, namely, the ability to automatically reject discrepant data. Therefore, MCC fusion provides an extra layer of protection against the harming effects of individual estimates contaminated with gross errors.

Design of Linear Deception Attacks Against State Estimation in Multi-plant Power Systems

Design of Linear Deception Attacks Against State Estimation in Multi-plant Power Systems

Robust Particle Filter Design With an Application to Power System State Estimation

This paper develops statistically robust particle filters that exhibit high statistical efficiency and good robustness to outliers. Three types of outliers, namely, observation outliers, structural outliers and innovation outliers, are considered. Two robust particle filters are developed and their performance are assessed. Firstly, a weight reconstruction particle filter is proposed that makes use of the projection statistics to derive non-zero particle weights in response to observation outliers. Secondly, a fitting-based particle filter is developed that generalizes the former filter to the case of structural and innovation outliers. This filter approximates the next estimated values using both the projection statistics and the linear fitting technique. The designed filters are applied to the state estimation of decentralized machines' internal state estimation and local bus frequency estimation in power systems. Simulation results performed on a four-machine two-area power system and the 39-bus <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">New England</i> power system demonstrate the excellent performance of the proposed robust particle filters in dealing with various types of outliers.

High-Resolution Real-time Power Systems State Estimation: A Combined Physics-embedded and Data-driven Perspective

High-Resolution Real-time Power Systems State Estimation: A Combined Physics-embedded and Data-driven Perspective

A Distributed Robust System-Wide State Estimation Method for Power Systems Based on Maximum Correntropy

The distribution of measurement noise applied in practical power system state estimation (PSSE) can deviate from the assumed Gaussian model and the performance of an estimator becomes bad if the Gaussian model is still used. This paper proposes a new distributed robust PSSE method for multi-area power systems. The non-Gaussian model is utilized to fit the measurement noise distribution to reach high model accuracy. The proposed distributed method is derived based on the maximum correntropy criterion to further reduce the impact of non-Gaussian measurement noise and outliers. The influence function combined with the finite-time average consensus algorithm is used to implement the proposed distributed robust method in a fully distributed manner. Simulations conducted on the IEEE 30-bus, 118-bus and 300-bus systems and the Polish 2383-bus system demonstrate the robustness and effectiveness of the proposed distributed method. Each local area can get the system-wide robust state estimation solution by only using local information and small amounts of data from neighboring areas. Our proposed distributed robust method has at least twelve percent improvement in reducing the mean squared error under Gaussian-Uniform noise. It is verified the communication network applied for the proposed method is fairly flexible while the existing distributed approaches use a fixed communication network when the power systems are partitioned. The simulation results also verify the robustness of the proposed method to bad data and communication failure.

Intelligent anomaly detection method for power and electricity data based on cubic exponential smoothing model

During the operation of the power system, abnormal electricity data are inevitably generated. How to efficiently detect and identify these abnormal data is a crucial component of power system state estimation, and it is also the foundation for the safety and stability of power system operation. Traditional anomaly detection methods only focus on specific power system characteristics, and there are problems with high computational complexity and low accuracy. To address the shortcomings of traditional methods for anomaly detection in power and electricity data, a smart anomaly detection method for power and electricity data based on a cubic exponential smoothing model is proposed. The cubic exponential smoothing model uses historical data to predict the current regional electricity consumption and then subtracts the predicted value from the true value to obtain the residual term. Finally, the DBSCAN density clustering algorithm is used to cluster the residual term, achieving the recognition of abnormal electricity data. We conduct an experimental comparison of regional electricity consumption data of a certain power grid. The results indicate that the proposed method has achieved good results in both detection rate and false alarm rate indicators in the intelligent detection of abnormal data in power and electricity consumption.

Measurement protection to prevent cyber–physical attacks against power system State Estimation

Smart applications supporting modern power systems are susceptible to cyber–physical attacks, particularly False Data Injection attacks that manipulate the input measurements of State Estimation (SE) compromising its output states. This paper proposes an Integer Linear Programming formulation that protects an optimal number of measurement units to prevent cyber–physical attacks, enhancing the robustness of SE. Our approach exhibits low complexity, applies to both linear and nonlinear SE, and converges rapidly toward the optimal solution. The formulation requires information about the grid topology and measurement distribution but does not depend on the power flow equations. Also, the generalized formulation can be customized to consider distinct protection costs for all measurement types, various priorities for different measurements, and a range of measurements and pseudo-measurements. Simulations are performed on the widely used IEEE 14 and 118-bus systems to verify the approach for linear and nonlinear SE and illustrate its practicality.

Educational Tool for Power System State Estimation Teaching and Learning

Educational Tool for Power System State Estimation Teaching and Learning

State estimation for distribution power systems by applying an advanced optimization approach

New centralized automation functions in distribution system control centers are needed in order to ensure the control of both distribution network and connected DGs. Consequently, state estimators need to be developed for future distribution systems to assess the network’s state in real time, i.e., minutes typical time frame, based on real, and virtual measurements. This paper proposes a new method based on the particle community optimization algorithm to estimate the state of electricity distribution networks. To increase the efficiency, accuracy, and speed of convergence rate to the answer and prevent the main particle assembly algorithm from fluctuating, the second particle assembly loop is provided in addition to the mutation algorithm and the isolation function. To consider the uncertainty of loads in distribution networks, modeled as active and reactive, virtual measurements with realistic error have been modeled. Results are presented and discussed to prove the efficiency of the proposed method, including sensitivity analysis for parameters used by the algorithm. The simulation results on two 6-bus and 34-bus radial distribution networks of the IEEE test show that the estimation of the distribution state based on the proposed DLM-PSO algorithm has a lower estimation error and standard deviation than the original HBMO, GA, WLS, and PSO algorithms.

Artificial Intelligence-Based State Estimation in Power System and Phasor Measurement Units

In the dynamically varying modern power system, it is challenging to monitor and estimate state variables of the network. In this work, state variables such as voltage magnitude and phasor angle are estimated using artificial intelligence (AI) techniques such as machine learning (ML) and deep learning (DL) methods. Among various ML models available, the few models considered in the proposed work for the state estimation (SE) in power system are decision tree, support vector machine, Ensemble boost, Ensemble bag (Eboost/bag), and artificial neural network (ANN). Similarly, DL models such as gate recurrent unit (GRU), long short-term memory (LSTM), and bidirectional LSTM are proposed for the SE. Among all these AI techniques, ANN and GRU gives better results than other models. Among them, the performance of GRU, a DL tool is found as best when compared to ANN, the ML. The accuracy of AI techniques are measured using evaluation metrics. The obtained results from AI compared to conventional techniques, weighted least square, and regularized least square method. Phasor measurement units is contributing more to minimize the SE errors based on its maximum observability and proved by using IEEE 14 and 30 bus systems.

A robust crow search algorithm based power system state estimation

The State Estimation (SE) computational procedure plays a crucial role in modern electric power system security control by monitoring and analyzing operational conditions and predicting any emergency. In order to estimate state variables, Power System State Estimation (PSSE) takes into account the magnitudes and phases of voltage on each bus. To address the state estimation challenges in power systems, in this paper, we propose a novel application of the Crow Search Algorithm (CSA) specifically tailored for the state estimation problem. We have assessed the introduced algorithm using the frameworks of both the IEEE 14-bus and IEEE 30-bus test systems. The first formulation is the Weighted Least Square (WLS) method, and the second is the Weighted Least Absolute Value (WLAV) method, both of which are objective function formulations. By comparing the results, it is clear that CSA-based SE is superior to the other metaheuristic algorithms considered, namely Genetic Algorithm (GA), Particle Swarm Optimization (PSO), and Artificial Bee Swarm Optimization (ABSO). As a point of comparison, we use the Newton–Raphson method for calculating load flow. It has been shown that the proposed CSA-based SE technique has better accuracy than the other two algorithms in all different test systems. With this study, the power system is operated more accurately and reliably by the operators operating the system.

Anomaly Detection in Power System State Estimation: Review and New Directions

Foundational and state-of-the-art anomaly-detection methods through power system state estimation are reviewed. Traditional components for bad data detection, such as chi-square testing, residual-based methods, and hypothesis testing, are discussed to explain the motivations for recent anomaly-detection methods given the increasing complexity of power grids, energy management systems, and cyber-threats. In particular, state estimation anomaly detection based on data-driven quickest-change detection and artificial intelligence are discussed, and directions for research are suggested with particular emphasis on considerations of the future smart grid.

A comparative evaluation of Stacked Auto-Encoder neural network and Multi-Layer Extreme Learning Machine for detection and classification of faults in transmission lines using WAMS data

Smart grid is envisaged as a power grid that is extremely reliable and flexible. The electrical grid has wide-area measuring devices like Phasor measurement units (PMUs) deployed to provide real-time grid information and resolve issues effectively and speedily without compromising system availability. The development and application of machine learning approaches for power system protection and state estimation have been facilitated by the availability of measurement data. This research proposes a transmission line fault detection and classification (FD&C) system based on an auto-encoder neural network. A comparison between a Multi-Layer Extreme Learning Machine (ML-ELM) network model and a Stacked Auto-Encoder neural network (SAE) is made. Additionally, the performance of the models developed is compared to that of state-of-the-art classifier models employing feature datasets acquired by wavelet transform based feature extraction as well as other deep learning models. With substantially shorter testing time, the suggested auto-encoder models detect faults with 100% accuracy and classify faults with 99.92% and 99.79% accuracy. The computational efficiency of the ML-ELM model is demonstrated with high accuracy of classification with training time and testing time less than 50 ms. To emulate real system scenarios the models are developed with datasets with noise with signal-to-noise-ratio (SNR) ranging from 10 dB to 40 dB. The efficacy of the models is demonstrated with data from the IEEE 39 bus test system.