Wide Area Measurement System Research Articles

Leveraging MapReduce and Synchrophasors for Real-Time Anomaly Detection in the Smart Grid

The rapid detection of anomalous behavior in SCADA systems such as the U.S. power grid is critical for system resiliency and operator response in cases of power fluctuations due to hazardous weather conditions or other events. Phasor measurement units are time synchronized devices that provide accurate synchrophasor measurements in power grids. The rapid deployment of PMUs enable improved real-time situational awareness to grid operators through wide area measurement systems. However, the quantity and rate of measurements obtained from PMUs is significantly higher than traditional devices, and continues to grow as more are deployed. Efficient algorithms for processing large-scale PMU data and notifying operators of anomalies is critical for real-time system monitoring. In this paper, we propose a novel, two-step anomaly detection approach that processes raw PMU data using the MapReduce paradigm. We implement our approach on a multicore system to process a dataset derived from real PMUs containing 4,500 PMUs ($\sim 18$∼18 million measurements). Our experimental results indicate the proposed approach detects constraint and temporal anomalies in under three seconds on 8 cores. Our work demonstrates the applicability of MapReduce for designing anomaly detection algorithms for the smart grid, and motivates the creation of novel MapReduce approaches for other SCADA applications.

Wide‐area measurement system‐based online calculation method of PV systems de‐loaded margin for frequency regulation in isolated power systems

This study proposes a photovoltaic (PV) systems de-loaded margin online calculation method that allows PVs to participate in isolated power system frequency regulation with a proper de-loaded margin. The de-loaded margin determines PVs' frequency regulation capacity. The larger de-loaded margin of PVs provides more reserve capacity for frequency regulation, while more economic benefits are sacrificed correspondingly. Therefore, a tradeoff between PVs' economic benefit and their frequency regulation reserve capacity is necessary. Taking into account these two factors, a dynamic calculation method of PVs optimal de-loaded margin based on the systems real-time operation condition is proposed. Real-time monitoring of the systems operation condition is realised by wide-area measurement system. The calculated de-loaded margin can meet the system frequency regulation requirement with PVs' minimum economic loss. RTDS simulation is conducted in an actual industrial isolated system driven by thermal power and PVs to verify the effectiveness of the proposed method.

Optimal Design of a Wide Area Measurement System for Improvement of Power Network Monitoring Using a Dynamic Multiobjective Shortest Path Algorithm

Wide area measurement system (WAMS) usually contains three dependent infrastructures called management, measurement, and communication. For optimal operation of a power system, it is necessary to design these infrastructures suitably. In this paper, measurement and communication infrastructures in a wide area network are designed independently from a management viewpoint, considering an adequate level of system observability. In the first step, optimal placement of measurement devices is determined using an integer linear programming (ILP) solution methodology while taking into account zero-injection bus effects. In the next step, new dynamic multiobjective shortest path (MOSP) programming is presented for the optimal design of communication infrastructure. The best architecture design is introduced in terms of optical fiber power ground wire (OPGW) coverage for the suggested central control bus and the number of phasor measurement units (PMUs). The applicability of the proposed model is finally examined on several IEEE standard test systems. The simulation results show better performance of the proposed method compared with other conventional methods. The numerical results reveal that applying the proposed method could not only reduce the OPGW coverage cost, the number of PMUs, and the number of communication links but could also improve the system technical indexes such as latency as subsidiary results of the optimization process.

PMU Placement in Electric Transmission Networks for Reliable State Estimation Against False Data Injection Attacks

Currently the false data injection (FDI) attack bring direct challenges in synchronized phase measurement unit (PMU) based network state estimation in wide-area measurement system, resulting in degraded system reliability and power supply security. This paper assesses the performance of state estimation in electric cyber-physical system paradigm considering the presence of FDI attacks. The adverse impact on network state estimation is evaluated through simulations for a range of FDI attack scenarios using IEEE 14-bus network model. In addition, an algorithmic solution is proposed to address the issue of additional PMU installation and placement with cyber security consideration and evaluated for a set of standard electric transmission networks (IEEE 14-bus, 30-bus, and 57-bus network). The numerical result confirms that the FDI attack can significantly degrade the state estimation and the cyber security can be improved by an appropriate placement of a limited number of additional PMUs.

Situational Awareness Enhancement of Smart Grids Using Intelligent Maintenance Scheduling of Phasor Measurement Sensors

Phasor measurement units (PMUs) have emerged as the sensors for smart grids because of their inherent capability to provide with synchronized current and voltage phasors at buses sprawling over large geographical area. Thus, PMUs or phasor measurement sensors (PMSs) constitute the edifice for wide area measurement system to provide with situational awareness (SA) for a complex interconnected electric grid by providing with real-time data. They assist in predicting future disturbances and also for decision-making of control actions. The PMS outage has adverse impact on grid operation. Therefore, their periodic maintenance must be carried out to ensure healthy and reliable operation to enhance SA. In this paper, optimized routine and self-supervision test intervals for ensuring maximum observability of the grid have been proposed. Since PMSs are taken out of service during maintenance, an intelligent maintenance scheduling algorithm has been proposed such that SA is maximum. Case studies pertaining to an example nine-bus, IEEE 14, 24, 30 and new England 39-bus system validate the efficacy of proposed approach. To prove the efficacy of results, general confidence intervals are reported for observability.

WAMS Cyber-Physical Test Bed for Power System, Cybersecurity Study, and Data Mining

Researchers from various cross disciplinary fields such as power systems, data science, and cybersecurity face two distinct challenges. First, the lack of a comprehensive test bed that integrates industry standard hardware, software, and wide area measurement system (WAMS) components and protocols impedes the study of cybersecurity issues including vulnerabilities associated with WAMS components and the consequences of exploitation of vulnerabilities. Second, a lack of comprehensive labeled Synchrophasor data along with other system related information imposes challenges to the development and evaluation of data mining algorithms that can classify power system cyber-power events. In this paper, a WAMS cyber-physical test bed was developed using a real time digital simulator with hardware-in-the-loop simulation. Commercial control and monitoring devices, hardware, software, and industry standard communication networks and protocols were combined with custom MATLAB, Python, and AutoIt scripts to model realistic power system contingencies and cyber-attacks. An automated simulation and control engine was developed to randomize modeled cyber-power events including power system faults, contingencies, control actions, and cyber-attacks. Scripts were added to capture heterogenous sensor data and create ground truth labeled datasets. The WAMS cyber-physical test bed is capable of simulating various sized power systems and creating datasets without altering the hardware configuration. A WAMS architecture is presented to document the integration of various components. Finally, test bed applications, simulated cyber-power scenarios, the dataset development process, and selected results are presented.

Optimal PMU Placement Using Modified Greedy Algorithm

Phasor measurement units (PMUs) provide synchronized measurements of real-time phasors of voltages and currents. It is considered as an important element of the smart wide area measurement system used in advanced power system monitoring, protection, and control applications. This paper proposes a new approach based on a greedy algorithm to solve the optimal phasor measurement unit placement (OPP) problem in the power network. The main purpose of proposed approach is to find out a high-quality solution in a reasonable time that ensures the practicability when applying for a real power network. The OPP problem is solved under both normal operating and contingency conditions. Moreover, some other realistic aspects that may affect the OPP problem, such as PMU channel limitation, zero injection bus, the presence of conventional measurements, are also considered to solve simultaneously. The simulations on IEEE 14-bus, 30-bus, 57-bus, 118-bus test systems, and especially on a large-scale network—the Polish 2383-bus system, are presented for evaluating the feasibility of proposed approach. The results of this study showed that the proposed method is effective and feasible to solve the OPP problem for a real power network.

Toward a wide-area load shedding scheme: Adaptive determination of frequency threshold and shed load values

Conventional under frequency and under voltage load shedding (UFLS and UVLS) schemes are generally independent than each other. Besides, in these schemes, the operating thresholds, amounts, and location of shed loads are settled in constant values for different disturbances. Due to these technical flaws, the conventional load shedding schemes fail to retrieve power system stability which outlines the necessity of devising improved adaptive mechanisms. To this end, the ongoing study proposes an adaptive UFLS scheme based on wide area measurement systems (WAMS). In contradiction to the existing methods, the proposed approach is featured with an adaptive manner. In other words, the frequency threshold of load shedding relays is adaptively tuned at each disturbance. Furthermore, a wide-area index is proposed to select the amount of required shed loads. Extensive numerical studies conducted on a real-world case study are involved to evaluate performance of the proposed approach.

A method for the identification of low frequency oscillation modes in power systems subjected to noise

The high penetration of renewable energy sources and the consequent integration of such distributed energy generation systems into the grid have significantly increased the interaction between power sources, which can result in low frequency oscillations. Different control techniques are proposed in literature to suppress low frequency oscillations, but the first step to attenuate such oscillations is to characterize them in terms of their dominant modes. This paper combines different results from literature to propose a unified two-step methodology for the mode characterization of low frequency oscillations based on the signals acquired by wide area measurement systems. Since the measured signals typically contain noise, the first stage of the proposed method uses the basis pursuit denoising method combined with a Tunable Q-factor wavelet transform to increase the signal-to-noise ratio and improve the identification results. In a second stage, an improved version of the matrix pencil algorithm, as proposed in this paper, is used to identify the parameters of low frequency oscillation dominant modes. Both simulation and experimental results show that the proposed method has better characterization accuracy than traditional methods, especially when Gaussian noise is considered in the measurements. In addition, the processing time has proven to be reasonable for online identification and characterization of low frequency oscillations.

Micro-PMU for distribution power lines

Miniaturisation, low cost, and easy live installation are development directions of phasor measuring unit (PMU) in power distribution network lines. Here, a new distributed PMU device for wide area measurement system of distribution network was designed. It gained energy from the line by high-density inductive draw-out power module, measured current and voltage waveforms by PCB Rogowski coils and spatial capacitive voltage divider, respectively, and achieved voltage and current collection in the whole network by distributed synchronous sampling. It provided a new solution to the development of new PMU in the distribution network lines. At present, prototypes of PMU have been tested online in Shandong province and the monitored data have been returned. Each module could work normally and stably. Measurement results could reflect the line current and voltage accurately.

A unified framework for wide area measurement system planning

Wide area measurement system (WAMS) is one of the essential components in the future power system. To make WAMS construction plans, practical models of the power network observability, reliability, and underlying communication infrastructures need to be considered. To address this challenging problem, in this paper we propose a unified framework for WAMS planning to cover most realistic concerns in the construction process. The framework jointly optimizes the system construction cost, measurement reliability, and volume of synchrophasor data traffic resulting in a multi-objective optimization problem, which provides multiple Pareto optimal solutions to suit different requirements by the utilities. The framework is verified on two IEEE test systems. The simulation results demonstrate the trade-off relationships among the proposed objectives. Moreover, the proposed framework can develop optimal WAMS plans for full observability with minimal cost. This work develops a comprehensive framework for most practical WAMS construction designs.

Highlighting the Deficiencies in Some Existing Optimal PMU Placement Techniques

Synchrophasor technology is receiving a global acceptance for electric power grid Wide Area Measurement System, (WAMS), an important function in a smart power transmission grid. A critical challenge in the synchrophasor technology deployment is the optimal choice of Phasor Measurement Unit (PMU) locations on the power grid. Researchers have proposed several techniques and algorithms in this respect. This work evaluated some of the major techniques and established that the available techniques and the factors they considered are not sufficient for a real-life optimal PMU placement (OPP). It also pointed to a method that could be applied to achieve a practical and robust solution for effective PMU placement for synchrophasor applications in a real-life electric power grid. It, therefore, calls for a shift in paradigm in the studies for the optimal PMU placement locations.

Inter‐harmonics monitoring method based on PMUs

More and more inter-harmonics are brought to the power grid due to the integration of renewables and the wide-area deployments of the electronic devices. This may lead to the exacerbation power system stability problems such as the subsynchronous oscillation in western China. The synchronisation and high-reporting rates of phasor measurement units (PMUs) make them an effective tool to monitor the appearance, propagation and distribution of inter-harmonics for protection and control strategies. In this study, the instantaneous powers of the single phase and the three phase that contain inter-harmonics are analysed. The phasor value of the signal containing the inter-harmonics is computed. It is found that the analysis based on the instantaneous power, phasor magnitude or phasor angle cannot distinguish whether the harmonic is subsynchronous or supersynchronous. Then, an inter-harmonics monitoring method that is based on complex numbers of phasor measured by PMUs is proposed in this study. This proposed method has been implemented in the main station of the wide-area measurement system in western China. A number of field data events are used to verify the correctness of the theoretical derivations.

A New Power System Restoration Technique based on WAMS Partitioning

An important feature of a Wide-Area Measurement System (WAMS) is the ability to recover data during a communication failure. This paper presents a novel scheme of partitioning a PMU installed power network into a number of WAMS regions in order to make the power system restoration process simpler. This algorithm also proposes the optimal placement of Phasor Data Concentrators (PDCs) in each region to record the data from PMUs. This paper considers the restoration constraints like transformer equivalent bus, generation-load balance and the observability of region for the partitioning of power system. The proposed scheme is demonstrated with an IEEE-30 bus system. It is then applied on IEEE-39, IEEE-118 bus systems and on a Northern Regional Grid of the Indian Power Grid.

A new scheme of WADC for damping inter-area oscillation based on CART technique and Thevenine impedance

In this paper, based on the CART technique and wide area measurement system (WAMS), a new scheme of wide area damping controller (WADC) is presented for inter-area oscillation in which each generator is equipped with an individual WADC which works based on the global inter-area signals. The proposed WADC scheme is an individual controller which uses angle and speed deviation of the center of inertia of the oscillating areas as global inter-area signals (GIS) (ΔωCOI, ΔδCOI). Each individual WADC consists of two CART1 and CART2 which perform as optimal gain estimators for estimating optimal gains K1 and K2 of the individual WADC of each generator. In fact, the proposed WADC scheme is an online and non-model based controller consisting of two CARTs which estimate optimal gains (K1, K2) from which inter-area control signal (ICS) is produced for direct presentation to AVR of generators. In this scheme, for selecting the most effective generators for participating in damping control, a combination index (CI) is presented which is maximized by binary genetic algorithm (BGA) for achieving most damping. The proposed CI index consists of generation pattern and Thevenin impedance of generators. For this purpose, for online estimation of Thevenin impedance of generators, an online approach is presented in which by using three consecutive measurements Thevenin impedance of generators are evaluated. The proposed CARTs are trained off line and then in the real time working mode of the proposed approach by using online GIS signals estimate optimal gains K1 and K2 from which individual control signal is deveopled. The proposed control scheme is demonstrated on IEEE 39-bus test system with promising damping effect for inter-area oscillation.

Power System Event Ranking Using a New Linear Parameter-Varying Modeling with a Wide Area Measurement System-Based Approach

Detecting critical power system events for Dynamic Security Assessment (DSA) is required for reliability improvement. The approach proposed in this paper investigates the effects of events on dynamic behavior during nonlinear system response while common approaches use steady-state conditions after events. This paper presents some new and enhanced indices for event ranking based on time-domain simulation and polytopic linear parameter-varying (LPV) modeling of a power system. In the proposed approach, a polytopic LPV representation is generated via linearization about some points of the nonlinear dynamic behavior of power system using wide-area measurement system (WAMS) concepts and then event ranking is done based on the frequency response of the system models on the vertices. Therefore, the nonlinear behaviors of the system in the time of fault occurrence are considered for events ranking. The proposed algorithm is applied to a power system using nonlinear simulation. The comparison of the results especially in different fault conditions shows the advantages of the proposed approach and indices.

Design of LCC HVDC wide‐area emergency power support control based on adaptive dynamic surface control

In AC–DC parallel systems, line-commutated-converter (LCC)-based high-voltage direct-current (HVDC) emergency control strategy can improve the stability of the power system. This study proposes an LCC HVDC emergency control strategy that utilises the global information measured by wide-area measurement systems. The design of the proposed LCC HVDC emergency control strategy takes advantage of dynamic surface control and adaptive control. The Lyapunov stability analysis is used to prove that the AC–DC parallel system is uniformly ultimately bounded in the presence of the uncertainties. A two-area four-generator AC–DC parallel system is developed in PSCAD/EMTDC to verify the effectiveness and correctness of the proposed strategy. Simulation results show that the proposed LCC HVDC emergency control strategy can improve the stability of an AC–DC parallel system and is robust. Its superiority is demonstrated by comparing the proposed method with controllers designed using backstepping technique and pole placement technique.

Optimal cost wide area measurement system incorporating communication infrastructure

A wide area measurement system installation cost minimisation and observability maximisation using binary gravitational search algorithm have been reported. Various methods have been employed in the past to determine the optimal locations of devices to retain the observability of the system. However, the costs of communication infrastructure (CI) from phasor data concentrator to phasor measurement units (PMUs) have not been given proper attention. To address this issue, the PMU placement problem has been formulated incorporating the cost of CI also in this study. Contingency cases have also been included to improve the reliability of the system. Besides, the effects of the presence of preinstalled PMUs have been considered. The results obtained for IEEE 14-bus, 30-bus and 118-bus systems have been compared with other methods in the literature. The test results reveal that the proposed methodology produced the PMU locations with higher observability and lesser distance path of establishing communication link compared to an existing method.

Wide-area measurement system-based supervision of protection schemes with minimum number of phasor measurement units.

Cascade tripping of power lines triggered by maloperation of zone-3 relays during stressed system conditions, such as load encroachment, power swing and voltage instability, has led to many catastrophic power failures worldwide, including Indian blackouts in 2012. With the introduction of wide-area measurement systems (WAMS) into the grids, real-time monitoring of transmission network condition is possible. A phasor measurement unit (PMU) sends time-synchronized data to a phasor data concentrator, which can provide a control signal to substation devices. The latency associated with the communication system makes WAMS suitable for a slower form of protection. In this work, a method to identify the faulted line using synchronized data from strategic PMU locations is proposed. Subsequently, a supervisory signal is generated for specific relays in the system for any disturbance or stressed condition. For a given system, an approach to decide the strategic locations for PMU placement is developed, which can be used for determining the minimum number of PMUs required for application of the method. The accuracy of the scheme is tested for faults during normal and stressed conditions in a New England 39-bus system simulated using EMTDC/PSCAD software. With such a strategy, maloperation of relays can be averted in many situations and thereby blackouts/large-scale disturbances can be prevented.This article is part of the themed issue 'Energy management: flexibility, risk and optimization'.

Observation and Applications of Electromechanical Wave Propagation Based on Wide-Area Synchronous Measurement

Electromechanical wave propagation affects many aspects of power grids, including control and protection. FNET/GridEye, a wide-area distribution-level measurement system, is found to be able to provide unprecedented insight into power system electromechanical wave behavior. This paper discusses the power system electromechanical wave propagation observed in FNET/GridEye and the implementation of algorithms based on wave propagation, including disturbance detection and location, and the development of the propagation speed distribution map.