Wide Area Control System Research Articles

Coordination of Controllers to Development of Wide-Area Control System for Damping Low-Frequency Oscillations Incorporating Large Renewable and Communication Delay

The modern power systems incorporate high penetration of renewable is a large, composite, interconnected network with dynamic behavior. The small disturbances occurring in the system may induce low-frequency oscillations (LFOs) in the system. If the (LFOs) are not suppressed within a stipulated time, it may cause system islanding or even blackouts. Hence, it is essential to investigate the behavior of the system under various levels of disturbances and control action must be taken to damp these oscillations. The established approach to damping the LFOs is by installing power system stabilizers (PSS). PSS uses the local signals from generators to control the oscillations. The dominant source of inter-area oscillations in power systems is due to overloaded weak interconnected lines, converter-interfaced generation, and the action of the high gain exciter present in the system. Consequently, wide area control is needed to control the inter-area oscillations existent in the system. This paper developed a coordinated design of conventional PSS, static compensator, renewable converters, and wide area controller for damping the local and inter-area oscillations in renewable incorporated power systems. The performance of the developed controller is evaluated through the time domain analysis and eigenvalue analysis. A comparison of the introduced controller has been done with other standard conventional methods. The choice of input signals for the wide area controller from the wide-area measurement system is done based on the controllability index. Additionally, the location of the controller must be identified to dampen the inter-area oscillations in the system. In this paper, the controllability index is calculated to find out the highly affected wide area signals for considering it as the feedback signal to a developed controller. The location of the controller is recognized by computing the participation factor. The developed controller has experimented on renewable incorporated large study power systems when time delay and noise are present in wide area signals.

Measurement Platform for Latency Characterization of Wide Area Monitoring, Protection and Control Systems

Measurement Platform for Latency Characterization of Wide Area Monitoring, Protection and Control Systems

Design of a decentralized wide-area control system to tolerate the loss of communication paths based on coherency analysis

The objective of this article is to design a wide-area control (WAC) system based on coherent groups of generators to overcome the loss of data and communication failures. In the conventional approach, the wide-area controller is designed by employing the state feedback control. It requires all the states on the controller input side and sending signals to all generators’ excitation systems on the output side. Therefore, good communication paths are necessary to get quality data every time. In addition, there should not be any data loss or false data due to phasor measurement units (PMUs) installed at every generator. However, it is not possible to get quality data without losing anything. Hence, it leads to the unstable condition of the entire power system. To address this problem, the area-wise coherency-based WAC system is proposed in this article to overcome the above-mentioned problems. The entire power system is divided into different areas based on coherency. Therefore, the centralized WAC system is divided into decentralized WAC systems based upon coherent groups of generators. This can be achieved by employing structurally constrained H2-norm optimization. Moreover, to validate the strength of the proposed controller, it is compared with different existing controllers reported in the literature by considering different case studies on IEEE-39 and IEEE-68 bus systems.

Wide area monitoring, protection, automation, and control systems for medium voltage networks

Distribution medium voltage networks have a branched structure, many power centers, longcable and overhead lines. This complicates the process of their automation, since significant capital costs for new equipment are required. New solutions based on modern technologies can help speed up this process and make it more efficient. The authors propose the use of synchronized phasor measurement technology for automating medium voltage networks. This paper considers approaches that describe the possibilities of implementing the WAMPAC principles in such networks, provides several examples where these principles apply.

Time Synchronization for Smart Grids Applications: Requirements and Uncertainty Issues

Smart grid implementation requires that multiple distributed systems are synchronized within and between substations. This is needed to coordinate the Intelligent Electronic Devices (IEDs) as well as to align in time the measurement data associated with the same event, but collected in different points of a broad geographical area. The time synchronization accuracy requirements in power systems are application-specific and are classified in the IEC Standard 61850-5:2013. Depending on such requirements, alternative solutions can be used. For instance, sub-microsecond time synchronization is essential for the implementation of Wide Area Monitoring, Protection, and Control (WAMPAC) systems. In fact, time synchronization directly and indirectly affects Phasor Measurement Units (PMUs) accuracy. The PMUs can measure the magnitude, the phase, the fundamental frequency and the Rate of Change of Frequency (ROCOF) of ac voltage and current waveforms at times synchronized to the Universal Coordinated Time (UTC). Among such quantities, the phase data are those most strongly affected by time synchronization. If time synchronization accuracy is within ±1 µs, its impact on synchrophasor phase measurement is in the order of a fraction of mrad, i.e., low enough to have a negligible impact on the state estimation uncertainty of most of transmission and distribution systems. However, the need to interpolate the missing phasor values when data from PMUs with a different reporting rate are collected and aligned in time may unexpectedly boost synchrophasor phase estimation uncertainty.

Application of IIA Method and Virtual Bus Theory for Backup Protection of a Zone Using PMU Data in a WAMPAC System

Many wide area monitoring, protection, and control (WAMPAC) systems are being deployed by grid operators to deal with critical operational conditions that may occur in power systems. Thanks to the real-time measurements provided by a set of distributed phasor measurement units (PMUs), different protection algorithms can be run in a central location. In this context, this article presents and validates a novel method that can be used as a backup protection for a selected area in a power system. It merges the integrated impedance angle (IIA) protection method with the theory of virtual buses in wide area electrical power systems. The backup protection works this way: once a fault is detected (pickup time), another delay (added to the pickup time) is defined in order to wait for the primary protection to act. If this does not happen, the algorithm generates its backup trip. The proposed method has been called the zone integrated impedance angle (Zone IIA). A real-time PMU laboratory has been used to test the proposed algorithm using a real-time digital simulator (RTDS). The algorithm has been programmed in a real-time automation controller (RTAC). It has been tested in two different simulated setups: first, a 400 kV transmission system, with and without the use of renewable energy sources (RES); second, a 150 kV submarine line between the Greece mainland and an island, which is currently the longest submarine alternating current connection in the world. The results obtained during the tests have yielded tripping times for area protection in the order of 48 ms, if no time delay is used between the fault detection and the trip order. According to the test results, the proposed method is stable, reliable, obedient, and secure, also with RES installed in the power system. Additionally, the method is selective, i.e., during the tests no trip was executed for external faults, no trip was executed in no-fault condition, and all the applied internal faults were detected and tripped correctly. Finally, the protection method is easy to implement. The method is also applicable to protection against short circuits in distribution systems. According to the trip times observed during the tests, it is clear that these algorithms are well suited to implement backup protections in transmission grids, even in scenarios with high penetration of renewable energies. Considering that backup trip times in transmission grids are usually set between 400 and 1000 ms, and that the actuation times obtained by the proposed algorithm are under 100 ms, the method is suitable for its use as a backup protection.

RBFNN assisted transient instability-based risk assessment of cyber-physical power system

Wide area monitoring and control of modern power system sprawling over large geographical area, has emerged as a viable technology employing phasor measurement units (PMUs) as its backbone. The PMUs are optimally placed to make the whole power system observable. Due to tripping of some generating units, or transmission lines the power balance gets disrupted. As a consequence, the power system becomes prone to risk of transient instability. Also, loss of observability becomes an additional risk due to tripping of transmission lines, which is instrumental for contributing to indirect observability. The purpose of this paper is to develop a predictive approach for identifying vulnerable generating units for proactive control actions to ensure transient stability. The methodology involves use of extended Kalman filter (EKF) for processing real-time PMU data for predicting the dynamic capability of generating unit so as to assess the power swings during transients arising due to contingencies. The radial basis feed-forward neural network (RBFNN) assisted algorithm categorizes generating units into marginal and risky categories based in their trend of swings with respect to dynamic capability curve of generating unit. The case-studies pertaining to IEEE-39 bus system under different contingencies, validate the efficacy of the proposed approach for real world applications. Since, the PMUs communicate synchronized data to PDCs the cyber system is an integral part of the wide area monitoring and control system. Therefore, a cyber physical approach takes into account the loss of observability as a risk from the cyber perspective. Both the risk associated with the physical as well as the cyber layers have been investigated.

Synchrophasor spoofing detection and remediation for wide-area damping control

Evolving cyber-attack threats put at risk automatic closed-loop systems to be incorporated in the smart grid. Wide-area control systems are particularly vulnerable to signal spoofing attacks due to sensor remoteness and dependence on satellite communication for time synchronization. A successful cyber-attack on a wide-area controller has the potential to reduce relative stability of the power system or worse, destabilize it. As such, detection algorithms must be deployed as defense against such attacks with the ability to autonomously correct for detected tampering or misoperation. The Spoof Catch and Restore Routine (SCR2), a combination of three real-time spoof detectors, each requiring limited information about the plant, is presented. Nonlinear simulations of a compromised wide-area control system deployed in the Western Interconnection show the effectiveness of SCR2 in detecting both delay-type and counterfeit-type spoofing attacks on wide-area sensors.

Time-frequency based cyber security defense of wide-area control system for fast frequency reserve

Global power systems are transiting from conventional fossil fuel energy to renewable energies due to their environmental benefits. The increasing penetration of renewable energies presents challenges for power system operation. The efficiency and sufficiency of responsive reserves have become increasingly important for power systems with a high proportion of renewable energies. The Fast Frequency Reserve (FFR), especially the Wide-area Monitoring System (WAMS)-based FFR, is a promising and effective solution to secure and enhance the stability of power systems. However, cyber security has become a new challenge for the WAMS-based FFR system. Cyber attacks on the FFR control system may threaten the safety of power system operation due to the rapid power controllability requirement of FFR. To address this problem, a time-frequency based cyber security defense framework is proposed to detect the cyber spoofing of synchrophasor data in WAMS-based FFR control systems. This paper first introduces the Continuous Wavelet Transforms (CWTs) to decompose spoofing signals. Then, the Dual-frequency Scale Convolutional Neural Networks (DSCNN) is proposed to identify the time-frequency domains matrix from two frequency scales. Integrating CWTs and DSCNN, an identification framework called CWTs-DSCNN is further proposed to detect the spoofing attacks in the WAMS-based FFR system. Multiple experiments using the actual data from FNET/GridEye are performed to verify the effectiveness of the framework in securing WAMS-based FFR systems.

A multi-objective optimization model for robust tuning of wide-area PSSs for enhancement and control of power system angular stability

A multi-objective optimization model for robust tuning of wide-area power system stabilizers (WAPSSs) aiming the improvement and control of angular stability of electric power system (EPS) is presented in this paper. In this work the WAPSSs are referred to power system stabilizers (PSSs) of fixed-structure with insertion of remote signals, from phasor measurement units (PMUs), in the control loops, that are used in a wide-area control system (WACS). The proposed model is composed of objective functions to maximize both the small-disturbance angular stability (SDAS) through the damping ratio and the large-disturbance angular stability (LDAS) using an index derived from transient energy function (TEF). Moreover, three objectives functions that contribute to the previous ones are taken into account: maximization of power system robustness for several operating conditions, minimization of eigenvalues sensitivity to small disturbances, and minimization of eigenvalues sensitivity with respect to time delay variations of remote signals. Swarm intelligence-based techniques are used to solve the multi-objective optimization model. Simulation results, with the benchmark interconnected system New England test system – New York power system (NETS-NYPS) of 16-generator and 68-bus, corroborate the applicability of the proposal.

Wide area monitoring, protection, and control application in islanding detection for grid integrated distributed generation: A review

The assimilation of Distributed Generation (DG) into the electric power system (EPS) has become more attractive as the world is following a trend to reduce greenhouse gas emissions by introducing more renewable energy forms resulting in high penetration scenarios. This high penetration of DGs brings several challenges to the protection philosophy of the EPS which compromises its reliability, availability, and efficiency. Under high DG penetration scenarios, conventional islanding detection methods (Idms) fail to detect an island as the grid loses its inertia to leverage a significant frequency and voltage mismatch necessary for Idms to effectively detect an islanding event. This has given rise to the birth of Artificial Intelligent (AI) methods that are found to perform better in islanding detection. AI Idms are computationally intensive and require a lot of data to operate accurately. Because the computational burden of these methods requires fast computing hardware, the current trend of AI Idms are integrated with Wide Area Monitoring, Protection, and Control (WAMPAC) system. This paper aims at reviewing all these Idms and the WAMPAC’s system latency when hosting AI Idms which are currently the best in islanding detection. This is done to determine if the WAMPAC system latency plus Idms computational time meet the islanding detection time specified by the IEEE Standard 1547 framework.

Cloud Simulation and Virtualization for Testing of Critical Energy Infrastructure Components

Cloud computing and cloud infrastructure are beginning to be applied in order to ensure effective functioning of management system of Critical Energy Infrastructure. This is improved informativeness of Supervisory Control and Data Acquisition system by the application of additional Wide-area Measurement and Control Systems (WAMCSs), since most of all processing and transition operations of data information streams of the WAMCSs may be performed by using on clouds. In light of these circumstances, it is importantly to get extensive modeling results considering wide area range of input data and latency time between critical energy infrastructure components and cloud infrastructure components. However, researchers were not, yet, had possibility to receive more adequate results based only mathematical modeling process. In this case, simulation models considering the cost time are more preferable than mathematical models. In the spirit development of this conception, authors are proposing to employ the simulation model based on virtual technology and Matlab Simulink toolkit in order to get modeling results for more important on-line mode of functioning of the WAMCSs.

Communication Network for Smart Microgrid

This paper conveys development, validation and performance analysis of a communication network for facilitating bi-directional communication in a microgrid adhering to smart grid communication standards. The work encompasses proposing a suitable topology for the communication network and communication technology selection from among technologies like IEEE 802.3, 802.11, 802.15.4 for data transfer by performing communication network simulation in Netsim, a network simulation software. The simulation in Netsim delivers the performance of communication network for various technologies through performance indices like throughput, packet delivery ratio, round trip delay, collisions, protocol overhead time, network setup time etc. Netsim simulation of the heterogeneous communication network, selected from analysis of communication network simulation using multiple technologies, enables its performance validation. This work renders better comprehension in realization of Wide Area Measurement System for real time data collection and status update, Wide Area Control Systems for real time control and Advanced Metering Infrastructure for user integration transforming a microgrid to a smart microgrid.

Reactive power control of photovoltaic power generation systems by a wide‐area control system for improving transient stability in power systems

AbstractAs the installed capacity of renewable energy sources is increasing, the role of inverters is becoming more important in the maintenance of power system stability. Therefore, in this study, we propose the use of a wide area control system (WACS) to control the inverters of photovoltaic (PV) systems in a coordinated manner to improve transient stability. In this method, we select PV systems whose reactive power injections are deemed to suppress the acceleration of the critical generator, based on a time‐domain simulation for each possible fault before the fault occurs. When a fault occurs, we trigger the reactive current injections with the selected PV systems that is, the WACS operates as an event‐based emergency control system. Numerical simulation results demonstrate that this method can further improve transient stability compared with an autonomous reactive current support function that is applied to existing PV inverters. The proposed WACS could be a promising approach to address the transient instability phenomena under unscheduled power flow conditions by periodically updating the control table based on real‐time information.

Reactive Power Control of Photovoltaic Power Generation Systems by a Wide-Area Control System for Improving Transient Stability in Power Systems

Reactive Power Control of Photovoltaic Power Generation Systems by a Wide-Area Control System for Improving Transient Stability in Power Systems

Cybersecurity of Wide Area Monitoring, Protection, and Control Systems for HVDC Applications

The flexibility provided by High Voltage Direct Current (HVDC) systems can be further extended by Wide Area Monitoring, Protection, and Control (WAMAPC) systems. WAMPAC systems enable many HVDC applications and, on the other hand, inevitably introduce cybersecurity concerns that need to be addressed. In this work, a security domain layer and decision framework is reported to detect and mitigate the impact of false data injection (FDI) attacks targeting HVDC stations. Specifically, a rule-based cyber-attack detection method is introduced and implemented on Raspberry Pi and tested on the real-time HVDC simulation facility on the real-time digital simulator (RTDS) platform at ABB U.S. Corporate Research Center.

Wide area controllers for excitation boosters for transient stability improvement

Excitation boosters (EBs) are one of the most cost-effective solutions to improve Fault Ride Through (FRT) capability of synchronous generators. However, they may lead to undesired behavior in multi-machine systems when governed by controllers that use local measurements. EB controllers based on a Wide Area Control System (WACS) have proved to be an effective solution to improve the overall transient stability of a multi-machine system. This paper compares two WACS-based EBs; one proposed in a previous work and a variant controller proposed here. In the comparison of WACS-based EBs, performance, design, implementation aspects and impact of communication latency are analyzed and discussed in detail.

Distributed Control of Networked Wide-Area Systems: A Power System Application

Newly, the advent of geographically distributed systems is lead to using communication networks for connecting the control system components to each other, which typically known as Networked Control Systems (NCSs). However, communication network-induced imperfections such as transmission delay and packet dropout will severely affect the wide area control system performance or even cause the instability of the system. Accordingly, this work proposes an efficient distributed networked-based sliding mode control framework for control of wide area systems inclusive of both random delay and random data packet dropout in their communication network connections where, the local sliding mode controllers are designed based on Linear Matrix Inequality (LMI) approach. The Lyapunov stability theory is used to derive efficient LMI-based delay-independent adequate conditions to design the asymptotic stable sliding surfaces for each interconnected subsystem, as well as the stabilizing of entire system. To verify the effectiveness and capability of the suggested method some simulation studies are provided over two power systems for better load frequency performance. Simulation results show performance improvement of the distributed networked wide area system despite of the existence of non-ideal communication network.

Design and Validation of a Wide Area Monitoring and Control System for Fast Frequency Response

This paper presents the design and validation of a Wide Area Monitoring and Control (WAMC) system for Fast Frequency Response (FFR) to address the challenges associated with reduced and non-uniformly distributed inertia in power systems. The WAMC system, designed for the power system in Great Britain, is termed “Enhanced Frequency Control Capability (EFCC).” It uses real time measurements from Phasor Measurement Units (PMUs) to monitor the system state in order to rapidly detect frequency disturbances and evaluate the magnitude of power imbalances. The impact of the disturbances on different parts of the network is considered to subsequently allocate the required response for different regions of the network, all within less than one second from the initiating event. The capabilities and characteristics of different resources (e.g., wind, energy storage, demand, etc.) are also evaluated and taken into account to achieve a suitable, optimized and coordinated response. Case studies using highly realistic hardware-in-the-loop setups are presented and these demonstrate that the proposed system is capable of detecting frequency events and deploying appropriate and coordinated responses in a timely fashion even with degraded communication conditions, thereby effectively enhancing the frequency control in future low-inertia systems and permitting higher penetrations of low-carbon and low-inertia energy sources.

Reliability components of the WAMS information network

Power system modes can be controlled by use of a wide-area monitoring and control system (WAMS). It is based on the phasor measurement units (PMUs), connected by an infor-mation network covering a significant territory. The functioning reliability of such a network deter-mines to a big extend the correct operation of the entire monitoring system. To assess its reliability, the one can be decomposed conveniently into four components: hardware or technical reliability, traffic reliability, software reliability, resistance to external negative impact on the transmitted in-formation, and to consider each m independently. In this paper, the main attention is paid to as-sessment of the reliability and availability of the first three components in the information network.