Remedial Action Schemes Research Articles

A Remedial Action Scheme to Prevent Mid/Long-Term Voltage Instabilities

The main objective of this article is to propose a special protection system (SPS) to execute efficient remedial actions to prevent mid-term and long-term voltage instabilities. In this method, when the operating point (OP) leaves the normal operation state, the proposed SPS is initiated to execute the required corrective remedial actions to bring the OP back to a normal state and maintain bus voltages above prespecified thresholds. Considering the local nature of Volt/Var control and in order to execute fast remedial actions, in this approach, the required generation rescheduling or load shedding procedures were selected based on the electrical distance concept. This allows for remedial actions with the highest impact on volt/var control. In addition, in generation rescheduling procedures, the proposed method uses the ability of utility-scale photovoltaic resources, which can change their generation quickly. This plays a major role in maintaining stability of power systems. Efficiency of the proposed algorithm was validated through several scenarios performed in IEEE 39-bus, Nordic32, and PST 16 test systems using DIgSILENT PowerFactory software. Results of these dynamic simulations and their comparison with some previously published methods show the effectiveness of this method in timely executing appropriate remedial actions to maintain system stability.

The impact of false data injection attacks against remedial action schemes

Deployment of energy management systems in electric utilities has resulted in improvement of situational awareness in power systems. However, additional cyber security issues are introduced in real-time operations. Substantial research has since been dedicated towards the feasibility and formulation of coordinated cyber-physical attacks against power systems. However, the full extent of their impacts contributing to cascading failures is not widely explored. This paper investigates to what extent such coordinated attacks against power system state estimation lead to large scale blackouts. To consider the worst case scenarios, false data injection attacks against parameter-based remedial action schemes are investigated on realistic power networks under large inter-area power transfers. Additionally, three indices are proposed to quantify the severity of the post-attack impacts: Loss of Observability after Cascading Failures, Loss of Observability after Controlled Islanding and Lines Recoverable after Controlled Islanding. The three indices will enable system operators to estimate the extent of recoverability of the grid after attacks have adversely impacted the power grid. All simulations are carried on synthetic Illinois 200-bus and South Carolina 500-bus systems.

Intelligent online catastrophe assessment and preventive control via a stacked denoising autoencoder

In all areas of engineering, catastrophe assessment is an essential prerequisite for remedial action schemes. Modelers constantly push for more accurate models, and often meet goals by using increasingly complex, data mining-based blackbox models. However, system operators tend to favor interpretable models for after-the-fact preventive control (PC). While switching from blackbox to interpretable solutions, a tradeoff occurs between accuracy and interpretability. To avoid this tradeoff, we develop an intelligent framework for online catastrophe assessment and PC via a blackbox stacked denoising autoencoder (SDAE) equipped with accuracy and the ability to derive a PC scheme. Specifically, we implement a transient stability cost-sensitive assessment (TSCA) and PC case in the context of a power grid. First, using only controllable variables, we build the TSCA model by adding a sigmoid unit on top of the SDAE. Considering power systems’ conservatism, we explore a novel TSCA model’s training criterion to determine the operation conditions’ degrees of stability and divide them into three classes: stable, unstable, and boundary. Second, given an operation condition identified as unstable or boundary by TSCA model and its desired degree of stability, the PC model (the reverse of a TSCA model’s mapping) consists of the top sigmoid’s backward mapping and the stack of denoising decoders from trained SDAE. The former is formalized as an optimization problem to push back the desired degree of stability to a desired SDAE’s highest-level abstraction. The latter decodes back the desired SDAE’s highest-level abstraction to a desired operation condition (essentially, a PC scheme nearest to the controlled operation condition in the coordinates along the underlying causes that generate the observed data). This approach actually resembles operators’ tendency to adjust and stabilize unstable conditions (in terms of underlying causes) with the fewest control actions. A simulation study on the IEEE New England 39-bus system shows that, as a blackbox technology, our framework not only provides superior online situational awareness, but also finds a viable PC scheme, thereby justifying its practicability in engineering.

Offshore Transmission Network Planning for Wind Integration Considering AC and DC Transmission Options

Along with development of remote wind farms, offshore transmission networks become an integral part of wider transmission system. In this paper, an offshore transmission network planning (TNP) model is proposed for large-scale wind integration. The proposed approach allows system planners to evaluate the economic and technical feasibility of a range of potential network and non-network options considering a variety of uncertainties. The framework can be divided into one high-level planning problem determining a suitable type of power transmission technology and network routine over given planning horizon, and several low-level problems that examine the feasibility and optimality of the solution from the high-level problem considering different remedial action schemes, which is expected to reduce the need for adding new lines considering a broad range of uncertainty during system operation. Numerical examples on an IEEE 14-bus test system and an Australian regional transmission grid illustrate the performance of the proposed TNP model.

New approach to transient stability prediction of power systems in wide area measurement systems based on multiple‐criteria decision making theory

To prevent power system blackouts following a large disturbance such as a fault, the speed and precision of the stability status prediction are two important factors for the remedial action schemes. A new approach for the transient stability prediction is presented employing the multi-criteria decision making (MCD) theory to consider both factors simultaneously in this study. It is shown that they depend on the prediction time, therefore solving the MCD problem results in finding the best time for the stability prediction. As the criteria quantifying is necessary in the MCD methods, in this study a new index is proposed to quantify the prediction speed. Furthermore, the support vector machine (SVM) classifier is employed as a transient stability predictor. In addition, the best features are selected and incorporated as the inputs of the SVM classifier according to the features selection methods. Finally, all proposed schemes are implemented on the IEEE 39-Bus test system. The obtained results show the prediction of stability at the optimum time causing the instability prevention with the less required remedial action.

Real-Time Secured Third Zone Relay Operation Under Dynamic Stressed Conditions

This paper proposes a new philosophy for detecting and predicting system conditions that are capable of endangering the integrity of the power system. Dynamic stressed conditions often lead to cascading outages. Distance relays are quite vulnerable to maloperations during these stressed conditions. Under such circumstances, the apparent impedance seen by the relays might encroach into the third zone and can cause maloperations. Moreover, under such conditions, generators experiencing stable power swings might also move to an out of step condition in subsequent stages. The objective of this paper is to develop a technique that not only differentiates the stressed conditions from faulted ones but further identifies if the system is approaching into an out of step condition. It suggests a Decision Tree-based logic that prevents the third zone of distance relay from maloperating and assists the system engineer to initiate remedial action schemes or restrain any unintentional islanding. Simulations were performed for two systems: WSCC 9 bus system and IEEE 39 bus system using the Power Factory-DIgSILENT simulation software tool. The performance of the proposed scheme has been further validated using real-time simulation tool ( Opal-RT 5600 ). The simulation and test results demonstrate the applicability of the scheme in maintaining the security of the system.

Stability of Wide-Area Power System Controls With Intermittent Information Transmission

This paper investigates the stability problem of wide-area damping controllers with intermittent information transmission. Due to the interruption in communication links between remote measurements and damping controller or from the damping controller to the damping actuators, the closed-loop system might become unstable. The instability is strongly related to the duration of interruption of information transmission. To estimate instability, this paper formulates the problem as continuous/discrete-time switched system and the stability conditions are derived using time-scale theory. This method allows us to handle continuous and discrete dynamics as two pieces of the same framework, such that the system will switch between a continuous-time subsystem (when the communication occurs without any interruption) and a discrete-time subsystem (when the communication fails). The contribution is to estimate the maximum allowable value of the time of interruption of information transmission that does not violate the exponential stability of the closed-loop system. The findings are useful in specifying the minimum requirements for communication infrastructure and the time to activate remedial action schemes. Simulations are performed based on both linear and nonlinear systems to validate the theoretical development.

Automated Corrective Actions by VSC-HVDC-Systems: A Novel Remedial Action Scheme

The introduction of high voltage direct current (HVdc)-systems based on voltage source converters (VSC) within the ac transmission system enables new operational strategies. Fast VSC set-point adaptations in post-contingency scenarios can re-establish a secure state of the overall system. However, these corrective actions require a reliable activation and global coordination, especially of the HVdc-system and its dc voltage control. A comprehensive approach addressing these requirements is presented in this work. The approach is divided into three main modules. During online operation, critical contingency events are identified based on local measurements. An expansion of the local converter control enables an activation of suitable corrective actions to be pre-determined by a corrective security constrained optimal power flow.

PMU Signals Responses-Based RAS for Instability Mitigation Through On-The Fly Identification and Shedding of the Run-Away Generators

This paper presents a new method of instability detection and subsequent stabilization of the power system network using a proposed multi-shot remedial action scheme (RAS) that can extemporaneously detect critical generators based on the dynamic states of generator computed from the terminal phasor measurement units. The instability detector is a moving window classifier that predicts impending instability using rate of change of individual generator transient energy indices evaluated from the d-q axis voltage as well as conventional severity indices based on generator angle and frequency. A comparative performance analysis of a spectral feature based ensemble decision tree classifier with a multivariate long short-term memory network is also presented. The proposed RAS identifies critical generators through individual machine transient energy formulation and recursive coherency matrix, evaluated solely from system-wide generator dynamic states, and maintains stability by tripping adaptively the run-away generators. Performance evaluation of the proposed scheme has been made on IEEE 39-bus network and it has been demonstrated that the proposed RAS is robust with regards to instability prediction and it can effectively identify critical generators and stabilize the network by tripping the same.

Ensemble-Based Algorithm for Synchrophasor Data Anomaly Detection

With the advent of phasor measurement units (PMUs), high resolution synchronized phasor measurements enables real time system monitoring and control. PMUs transmit data to local controllers in substations and phasor data concentrators for system wide monitoring and control application in the control center. They provide real-time phasor data for critical power system applications such as remedial action schemes, oscillation detection, and state estimation. The quality of phasor data from PMUs is critical for smart grid applications. Several methods are developed to detect anomalies in time series data, tailored for PMU data analysis. Nevertheless, applying stand alone methods (with fixed parameters) takes great tuning effort, and does not always achieve high accuracy. In this paper, we adopt an unsupervised ensemble learning approach to develop fast, scalable bad data/event detection for PMU data. The ensemble method invokes a set of base detectors to generate anomaly scores of the PMU data, and makes decisions by aggregating the scores from each detector. We develop two algorithms: 1) a learning algorithm that trains the ensemble model and 2) an online algorithm that infers the anomaly scores with the ensemble model over PMU data streams. The proposed method provides flag for data anomalies and triggers further analysis to differentiate between events and bad data. Using both simulated and real-world PMU data, we show that our ensemble model can be efficiently trained, can achieve high accuracy in detecting diversified errors/events, and outperforms its counterparts that use single standalone detection method.

Optimal Remedial Actions in Power Systems Considering Wind Farm Grid Codes and UPFC

This paper proposes a postcontingency remedial action scheme for power grids. A corrective action algorithm (CAA) is developed to eliminate postcontingency constraint violations so that further propagation of the contingency and possible blackouts is prevented. Since corrective actions should be determined quickly, a piecewise linear approximation for the nonlinear power flow equations considering unified power flow controller and wind farm grid codes is proposed. The proposed piecewise linear approximation-based method does not ignore the effect of reactive power flows in the network unlike classical dc approximation. The simulation results on various test systems demonstrate the effectiveness of the proposed CAA.

Designing centralised and distributed system integrity protection schemes for enhanced electric grid resiliency

System integrity protection schemes (SIPSs) are installed at substations to preserve power system stability by preventing bottlenecks in transmission and distribution networks and improving the overall reliability. SIPSs are also referred to as remedial action schemes, emergency control systems, special protection systems, and wide-area control schemes. Typical SIPSs have centralised computing architectures with applications to ensure reliable power system responses during transmission outages, remediate regional transmission bottlenecks caused by delays in the construction of new lines, prevent severe instability and blackouts due to faults and inadvertent disconnections, prevent line damage resulting from thermal limits, avoid voltage collapse, and protect against other critical events in the power system. This study proposes a distributed computing architecture for SIPSs, including algorithms that use DC and AC optimal power flow. The authors classify SIPS applications based on control types and propose novel algorithms for next-generation SIPSs using synchrophasors and real-time technology. The authors also propose testing requirements and architectures for validating SIPSs prior to field installation. Lastly, the authors share results obtained using the proposed SIPS for a transmission overload condition caused by excessive wind generation.

Resilient Cyber Infrastructure for the Minimum Wind Curtailment Remedial Control Scheme

Integration of distributed energy resources has been significantly increasing in the electric power grid. One of the predominant renewable energy sources, wind energy, possess a significant challenge for grid operations, due to its intermittency, uncertainity, and variability. In changing operating conditions with wind uncertainity, part of wind may need to be curtailed for the safe utilization of the transmission system. In order to minimize the wind power curtailment and to keep the power flow on a transmission line under limits, a cyber resilient distributed remedial action scheme (DRAS) is developed in this paper. The remedial action scheme (RAS) is formulated as an optimization problem, considering the real-power flow constraints of the transmission lines and given wind variability. In this paper, DRAS is developed to operate even with failures in the computing nodes to make it cyber-resilient. Distributed simplex algorithm is used for optimization in the distributed RAS. The DRAS is implemented in a decentralized platform called Resilient Information Architecture Platform for Smart Grid to enable cyber resiliency of DRAS. The effectiveness of the proposed approach is validated through offline simulations of the New England 39-bus system and online simulations of IEEE 14-bus test system. A cyber–physical testbed utilizing real time digital simulator, phasor measurement units, and BeagleBones has been used for the online simulation and validation of the developed cyber-resilient RAS.

A Control-Oriented Energy Function for Generation Shedding Determination for Transient Stability Control

This paper proposes a control-oriented energy function (COEF) based on passivity for transient stability control (TSC) of power systems and investigates the feasibility of an iterative process using the COEF for determining generation shedding (GS) requirements for real-time TSC, in particular, for severe cases when autoreclosing fails due to permanent faults. The COEF for TSC set up in this paper gives directly the GS requirement without calculations of stability region and Critical Clearing Time, and exempts all modeling assumptions except for nonnegative damping the generator models. The simulation with the full planning model of Western Electricity Coordinating Council system shows that the passivity-based COEF for TSC offers a concise, practical, and effective index for GS determination for transient stability control of power systems, which is particularly suitable for the Remedial Action Schemes that BC Hydro has been using.

A new mechanism for remedial action schemes design in a multi-area power system considering competitive participation of multiple electricity market players

Unlike to common protective devices that are used for protection of power system equipment, Special Protection System (SPS) means an automated protective system which detects abnormal and predetermined conditions of the power system and applies preplanned corrective actions in order to maintain system integrity. The SPS is widely used in a restructured environment because it is known as a rapid and low cost alternative for network expansion to increase the transfer capability. Although the economic motivations and technical aspects of SPS are proposed in some references, the economic design of an SPS in a restructured environment has received less attention. In this paper, an economic-based method is presented to design remedial action schemes in a Multi-Area Power System (MAPS) with presence of Multiple Electricity Markets (MEM). The innovations of the proposed method are twofold: on one hand, the protection schemes are updated after each electricity market clearing that increases its performance because of the proximity to real time conditions. On the other hand, these remedial actions are designed economically in an environment with several independent Market Operators (MOs) through the interaction with a central coordinator entity. The proposed method is applied on a three-area test system and its results are presented by further explanation of its technical and economic advantages.

Un enfoque sustentable al cultivo de tilapia

La acuicultura de tilapia (Oreochromis spp.) es a menudo desarrollada en sistemas extensivos o en sistemas controlados, los cuales presentan una diversidad de problemáticas; razón por lo que es necesario determinar las causas a estos problemas y ofrecer soluciones orientadas al desarrollo sostenible de la actividad. Los principales problemas en la mayoría de los cultivos son el reducido crecimiento y mortalidades elevadas, esto asociado al inadecuado manejo del cultivo. En este artículo se propone un modelo de cultivo de tilapia en recirculación, con bajo impacto ambiental y una alta productividad. Se propone el uso de plantas medicinales y probióticos, como una medida preventiva o correctiva contra patologías y sistemas de módulos de plantas flotantes y la biodigestión de lodos como una alternativa para evitar impactos al ambiente además de generar ganancias adicionales. En términos generales, el sistema de recirculación propuesto es un proyecto ambientalmente amigable con una alta productividad.

Decentralized State Estimation and Remedial Control Action for Minimum Wind Curtailment Using Distributed Computing Platform

Intermittency of wind energy poses a great challenge for power system operation and control. Wind curtailment might be necessary at the certain operating condition to keep the line flow within the limit. Remedial action scheme (RAS) offers quick control action mechanism to keep reliability and security of the power system operation with high wind energy integration. In this paper, a new RAS is developed to maximize the wind energy integration without compromising the security and reliability of the power system based on specific utility requirements. A new distributed linear state estimation (DLSE) is also developed to provide the fast and accurate input data for the proposed RAS. A distributed computational architecture is designed to guarantee the robustness of the cyber system to support RAS and DLSE implementation. The proposed RAS and DLSE is validated using the modified IEEE-118 Bus system. Simulation results demonstrate the satisfactory performance of the DLSE and the effectiveness of RAS. Real-time cyber-physical testbed has been utilized to validate the cyber resiliency of the developed RAS against computational node failure.

Analytic corrective control selection for online remedial action scheme design in a cyber adversarial environment

Cyber attacks and extreme events can cause severe consequences to the grid that require immediate response. Conventional remedial action schemes (RAS) use offline calculations to determine corrective control actions to deploy for a predetermined set of credible contingencies. Yet, cyber attacks cannot be sufficiently represented in a look-up table approach; such contingencies are highly dynamic and unpredictable. Online RAS with real-time calculation of corrective controls provides the most suitable and effective response. To achieve rapid computation and reduce the search space to only the most effective candidate control(s), the analytic corrective control selection method using clustering and factorisation techniques is developed based on controllability analysis. The resulting critical controls comprise a minimum set that is most effective in reducing the violations in the stressed areas of the system. While this study focuses on generators as the critical control mechanism, this methodology is broadly applicable to any corrective control for which a sensitivity matrix in relation to the violated components can be derived. The algorithm is evaluated with the IEEE 24-bus and IEEE 118-bus systems under compromised generator outage scenarios, and the identified critical control set is shown to be highly effective for reducing violations and improving RAS computation time.

An effective load shedding remedial action scheme considering wind farms generation

In this paper, a fast load shedding remedial action scheme (RAS) is developed considering generation pattern of local wind farms using wide area monitoring framework. In the proposed RAS, the shedding candidates are selected and prioritized based on load types and their impacts on the voltage profile and transient performance of the system. The dynamics of wind farms are also included in the shedding requirements and formulas by defining effectiveness indices which are calculated based on the contribution of each generator to the dynamic performance of the system. This allows secure operation of the system after major contingencies while impacted customers are minimized. The proposed methodology, shedding formulas, and corresponding requirements are verified for the BC Hydro system using the PSS/E dynamic simulation package.

Protection of Autonomous Microgrids Using Agent-Based Distributed Communication

This paper presents a real-time implementation of autonomous microgrid protection using agent-based distributed communication. Protection of an autonomous microgrid requires special considerations compared to large-scale distribution networks due to the presence of power converters and relatively low inertia. In this paper, we introduce a practical overcurrent and a frequency-selectivity method to overcome conventional limitations. The proposed overcurrent scheme defines a selectivity mechanism considering the remedial action scheme of the microgrid after a fault instant based on feeder characteristics and the location of the intelligent electronic devices (IEDs). A synchrophasor-based online frequency-selectivity approach is proposed to avoid pulse loading effects in low inertia microgrids. Experimental results are presented for verification of the proposed schemes using a laboratory-based microgrid. The setup was composed of actual generation units and IEDs using the IEC 61850 protocol. The experimental results were in excellent agreement with the proposed protection scheme.