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Power system blackouts are usually triggered by the initial contingency and then deteriorate as the branch outage spreads quickly. Thus, it is crucial to eliminate the propagation of cascading outages in its infancy. In this paper, a model predictive approach is proposed to protect power grids against cascading blackout by timely shedding load on b...
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... 10 is severed as the initial disturbance of power systems, and Figure 4 shows the cascading process of the IEEE 57 Bus Systems without protection schemes. After 6 cascading steps, the system ends up with 43 connected branches (5 branches with the transmission power) and the total transmission power of 1.004pu. In contrast, Figure 5 presents the topology evolu- tion of the IEEE 57 Bus Systems with NPS at the 4th cascading step. It is observed that the power system is well protected by NPS since most branches in the network are in a good state of transmitting power among buses. Specifically, the cascading process stops after implementing the optimal load shedding at the 4th cascading step, and the system remains unchanged with the total transmission power of 9.156pu and 53 connected branches in operation and no idle branches. Moreover, the objective function is minimized with the value of 0.1068. The upper panel in Fig. 6 describes the evolution of Saddle Point Dynamic (6) within 10s, and the tra- jectories get stable after 4s. The lower panel shows the load shedding on each bus at the 4th cascading step. There are no negative amounts of load shedding, which implies the absence of generator tripping during power systems ...
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This paper proposes a methodology for enhancing power systems resiliency by proactively splitting an interconnected grid into small self-sustaining islands in preparation for extreme events. The idea is to posture the system so that cascading outages can be bound within affected areas, preventing the propagation of disturbances to the rest of the s...
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... Subsequently, adopting control methods based on deterministic safety criteria becomes crucial. This involves considering safety constraints during grid operation and employing sensitivity analysis [10], mathematical programming [11,12], and other methodologies to devise optimal control schemes. The objective is to eliminate abnormal operational states of the power grid and prevent cascading failures. ...
The increasing uncertainty of wind power brings greater challenges to the control for mitigation of cascading failures. In order to minimize the risk of cascading failures in large-scale wind power systems at a lower economic cost, a multi-stage blocking control model is proposed based on sensitivity analysis. Firstly, the propagation mechanism of cascading failures in power systems with wind power integration is analyzed, and the propagation path of such failures is predicted. Subsequently, sensitive lines that are prone to failure are identified using the power sensitivity matrix, taking into account the effects of blocking control on the propagation path. By constraining the power flow of these sensitive lines, a multi-stage blocking control model for the predicted cascading failure path is proposed with the objective of minimizing the control cost and cascading failure probability. Based on probabilistic optimal power flow calculations, the constraints related to wind power uncertainty are transformed into opportunity constraints. To validate the effectiveness of the proposed model, the IEEE 39-node system is used as an example, and the results show that the obtained control method is able to balance economy and safety. In addition, the control costs for the same initial failure are higher as the wind power penetration rates and confidence levels increase.
... The critical impact of voltage instability in the initiation of blackouts has prompted researchers to scrutinize on this phenomenon for the last two decades [3,4]. Protection against voltage instability and maintaining voltage within permissible limits is usually achieved either with preventive or corrective measures which influence the situation before and after the fault, respectively. ...
In this paper a novel under-voltage load shedding approach is presented for voltage stability of power systems. Given the significance of load model on load shedding plan, in addition to adoption of a voltage-dependent load model, the total grid load is divided into discrete levels corresponding to the discrete number of feeders connected to each bus. Through demand response and designation of critical loads, the load shedding plan and costs are optimized. Using the assumptions and network characteristics and their combination, which has not been previously carried out, the load shedding problem is handled in two offline and online forms. In the offline solution, the improved discrete particle swarm optimization (IDPSO) is used. Then, by combining the IDPSO algorithm with ANN as a novelty of the proposed approach, by assessing different faults, establishing a database and neural network training tools, the proposed method is applied in the online mode on the basis of data received from network PMUs leading to very fast solutions and therefore higher margin of voltage stability. The proposed approach is implemented on an IEEE 57-bus test network and the results of both offline and online methods are discussed for different fault scenarios.
... However, the risk control of cascading failures is still confined to the preventive control of cascading failures or the corrective control of a given cascading failure stage, especially for the initial outage. Zhai et al. (2019) compared two corrective control models of cascading failures: non-recurring corrective control and that of two consecutive cascading failure stages. The simulation results show that the two consecutive stages perform better than non-recurring corrective control. ...
The control research on cascading failures is critical to ensure the reliability of power supply. A path-driven multi-stage corrective control model for the whole process of cascading failures is established to eliminate the risk of cascading failure. For the cascading failure process caused by overloading, the selection criterion for subsequent outage is defined according to the mechanism of propagation of cascading failures. The path-driven constraints and power relaxation constraints are extracted based on the selection criterion for a subsequent outage. A model coupled with non-scheduled multi-stage decision-making is designed by considering the flexibility of control action implementation to optimize the sum of control cost and load-shedding risk for elimination of cascading failures. The verification results show that the proposed method can reduce the probability of outages of tripped branches and successfully eliminate cascading failure.
... e., triggering events) [22,28]. Considering that lots of blackouts are initiated because of the overload precondition [31], it is indispensable to alleviate the system stresses caused by overloads, which helps to avoid the catastrophic consequences and prevent cascading failures. ...
... The complexity (in the behaviour which results from the dynamics of the electricity grid) increases as moderation bring additional layers like the information network, renewable energy generation, making the electricity grid into a smart grid. Zhai et al. [19,20] , Zhang et al. [21] and Zhai et al. [22][23][24][25] formulated a systematic way of tracing the source of cascading failure in a direct current (DC) electricity network through DC power flow equation. The initial disturbances causing a failure in one of the elements in a network might cause problems to other elements in the electricity network in the optimal control theory, and the magnitude of impact can be solved by the system of DC power flow equations. ...
... For simplicity, a DC power flow model [19][20][21][22][23][24][25] is used to model Singapore power grid system. DC power flow model is a suitable substitute for alternating current (AC) power flow in high voltage transmission network as DC model can help in reducing computation effort without sacrificing the validity of the results as compared to AC power flow model [44,45] . ...
... DC power flow model is a suitable substitute for alternating current (AC) power flow in high voltage transmission network as DC model can help in reducing computation effort without sacrificing the validity of the results as compared to AC power flow model [44,45] . Zhai et al. [19,20] , Zhang et al. [21] and Zhai et al. [22][23][24][25] modelled the state of the transmission line in a power system while computing the DC power flow to handle overloading problem in a power network. The cascade model that characterizes the connection state of the transmission line Bus i and Bus j is given by: ( , ) 1, 2 ; ...
Critical infrastructure such as the transportation, power generation, water supply, telecommunications, security and health services/systems, etc. are essential for providing a reliable flow of goods and services, crucial to the functioning of the economy and society. These infrastructures are closely linked and dependent on one another, and these interdependencies need to be modelled in order to analyse the disruptions and vulnerabilities of critical infrastructure networks as a whole. With increased, investment and complexity in the coupling of gas and electricity network, limitations and vulnerabilities of the coupled networks are becoming increasingly relevant to the operational planning of the critical infrastructures. Current modelling of a coupled gas and electricity network will be used in conjunction with nation input-output interdependency model to model physical critical infrastructures and critical infrastructure interdependencies, respectively. This research work will tackle two possible scenarios that might happen in the gas network while evaluating the cascading impact both in the physical model perspective and input-output interdependency model perspective. The results will provide insights on how disruption in the gas network affects the electricity grid and its corresponding economic impact on all economic sectors in a nation.
... From the anatomy of the world's worst power system blackouts, it is noticed that failure in the protection system turns out to be the most significant factor for the occurrence of cascading events leading to a blackout. It was involved in about three-fourth of the reported grid disturbances [1][2][3]. To provide secured protection to the power system elements, relaying systems must isolate the faulty elements only during abnormal conditions. ...
For the stable operation of the smart grid, the development of a faster, reliable, and secure protective relay algorithm is essential. From the past blackout reports, it is revealed that during different system critical operating conditions distance relay meets dependability and selectivity challenges and operates unnecessarily. To restrict the operation of distance relay only to fault conditions, an intrinsic time-scale decomposition (ITD) based backup protection scheme is proposed. The ITD method decomposes current signals into baseline and residual components. A reliable index is defined as the energy of a significant baseline component that has the highest kurtosis value. The energy-based index effectively accomplishes symmetrical fault-system stress events discrimination task. For technical evaluation of the method, different power system models such as the IEEE-39 bus test system and the Indian Eastern Region Grid (IERG) were considered and simulated using EMTDC/PSCAD software. The response of the method is compared with other existing techniques. The method uses an adaptive threshold selection approach to detect a fault condition and thus the response is independent of system configuration and structure. With this advantage, unintentional tripping of the power system during different critical operating conditions can be avoided.
... Mathaios et al. [20] incorporated grid splitting in preventive control to isolate the propagation of cascading failures and boosted system resilience in times of inclement weather. Zhai et al. [21] designed two corrective control schemes, one of which eliminates cascading failure at a given cascading step, the other takes corrective actions in two consecutive steps. Subsequently, the corrective control was extended from a single cascading failure path to multiple possible cascading failure paths [22]. ...
... To demonstrate the merit of the proposed method, the MSCC model is compared to the non-recurring corrective control (NCC) model [21] under the same initial disturbance. The NCC model is designed to eliminates the cascading failure at a given cascading step. ...
Abstract Minimizing the risk of cascading failures in a power system is vital to balance the operational economy and security. A multi‐step corrective control (MSCC) method is proposed to mitigate cascading effects in terms of reducing risk of blackout by considering the multi‐step propagation characteristics of cascading failures caused by overload. Based on fault chain model and the DC power flow equation, the dynamic interaction between the process of cascading failures and control schemes is first discussed. The corrective control problem is then expressed as a multi‐step decision‐making optimisation problem based on the defined risk indices. The MSCC model with flexibility of control timing is designed by optimizing probability weighting expected cost and overload risk of cascading failure. In this control method, generation re‐scheduling and load shedding are selected as the main remedial actions, and a multi‐layer coding genetic algorithm is employed to obtain the optimal remedial control schemes. The numerical results indicate that control schemes generated by the proposed method could mitigate the cascading failures and result in better performance than non‐recurring corrective control (NCC) in terms of economy and operational risk.
... Protection and control techniques have been improving to factor in the complex nature of power systems [1]. Power blackouts have been a long persisting challenge to all power systems globally, directly affecting overall productivity in industries and other socio-economic environs [2], [3]. One of the main power outages recorded in history is the US-Canada blackout in 2003 that lasted 96 hours, affecting over 50 million people. ...
... Human error and overgrown vegetation along a major transmission line contributed to this outage. J o u r n a l P r e -p r o o f [2] The blackout report attributed the cascading collapse of the grid to the failure of control operators to detect the extent of the damage to the larger power system [4]. Since then, significant efforts have been made by researchers and utility companies to prevent voltage collapse caused by both natural and technical faults [5]. ...
... ] (2) where represents the penalty cost associated with each load bus and is the active power demand at each bus. The ℎ is obtained from equation (1) where the bus ( ) is an element of the selected buses ( ) for load shedding. ...
Voltage collapse tends to occur due to the voltage instability created during large faults. As a last resort, under-voltage load shedding (UVLS) is performed after all the available power operation and control mechanisms have been exhausted. Load shedding techniques have advanced from the conventional and adaptive methods that are less optimal compared to computational intelligence-based techniques. Recent works have identified hybrid algorithms to give more optimal solutions for UVLS problems with multi-objective functions. In this paper, a novel hybrid ABC-PSO algorithm, adapted from a software estimation project, is used to perform UVLS on a modified IEEE 14-bus system. Eight overload conditions are imposed on the system ranging from 105% to 140% loading, where FVSI ranking is used in identifying weak buses. The load shedding is then performed following decentralized relay settings of 3.5 seconds, 5 seconds and 8 seconds, which gives an overall 99.32% recovery of voltage profiles. The proposed hybrid ABC-PSO algorithm is able to shed optimal amounts of load, giving an 89.56% post-contingency load, compared to GA’s 77.04%, ABC-ANN at 84.03% and PSO-ANN at 80.96%. This study has been simulated on MATLAB software, using the Power System Analysis Toolbox (PSAT) graphical user and command-line interfaces.
... The introduction of phasor measurement units (PMUs) in power systems allows to develop the real-time protection scheme by estimating the system states for emergency control [10]. For example, [11] proposes a model predictive approach to prevent the cascading blackout of power systems by predicting the cascading failure path and taking the corresponding remedial actions in time. ...
... To avoid the vagueness, it is necessary to clarify the concept of cascading step. To be precise, a cascading step refers to one topological change (e.g. one or multiple simultaneous branch outages) of power networks due to branch overloads or stochastic factors such as hidden failures of relays, human errors and the weather [11]. ...
... P b,i and P b i , characterize the lower and upper bounds of the injected power on the ith bus, respectively. In theory, the minimum injected power on each bus is equal to the negative value of its total load, while the maximum injected power depends on the power generation from the generator connected to this bus [11]. represents the vector of power flow on branches, and σ j specifies the threshold of power flow on the jth branch. ...
Due to uncertainties and the complicated intrinsic dynamics of power systems, it is difficult to predict the cascading failure paths once the cascades occur. This makes it challenging to achieve the effective power system protection against cascading blackouts. By incorporating uncertainties and stochastic factors of the cascades, a Markov chain model is developed in this paper to predict the cascading failure paths of power systems. The transition matrix of Markov chain is dependent on the probability of branch outage caused by overloads or stochastic factors. Moreover, a robust optimization formulation is proposed to prevent the cascading blackouts by optimal load shedding and generation control for multiple cascading failure paths with relatively high probabilities. Since each state on the cascading failure paths can be described by one convex set, the proposed robust optimization problem is equivalent to the best approximation problem in Euclidean space. Thus, an efficient numerical solver based on Dykstra’s algorithm is employed to deal with the robust optimization problem. In theory, we provide a lower bound for the probability of preventing the cascading blackouts of power systems. Finally, the proposed approach for power system protection is verified by a case study of IEEE 118 bus system.
... tree contact [7], flashover [8], equipment faults [9], etc) play a crucial role in triggering the cascading outage of power systems. Thus, it is vital to identify the initial disruptive contingencies that cause the catastrophic cascading failure so that remedial actions can be taken in advance to prevent the blackout [10]. ...
... And the symbol dim(δ ) denotes the dimension of the variable δ . By selecting a different unit vector e i , Equation (10) can provide the gradient of objective function with respect to a different disturbance. ...
Due to the evolving nature and the complicated coupling relationship of power system components , it has been a great challenge to identify the disruptive contingencies that can trigger cascading blackouts. This paper aims to develop a generic approach for identifying the initial disruptive contingencies that can result in the catastrophic cascading failures of power systems. The problem of contingency identification is formulated in the mathematical framework of hybrid differential-algebraic system, and it can be solved by the Jacobian-Free Newton-Krylov method, which allows to circumvent the Jacobian matrix and relieve the computational burden. Moreover, an efficient numerical algorithm is developed to search for the disruptive contingencies that lead to catastrophic cascading failures with the guaranteed convergence accuracy in theory. Finally, case studies are presented to demonstrate the efficacy of the proposed identification approach on the IEEE test systems by using different cascade models.
