Structural emergency control for power grids (original) (raw)
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Distributed FACTS for Power System Transient Stability Control
Energies
The high penetration of renewable energy sources, combined with a limited possibility to expand the transmission infrastructure, stretches the system stability in the case of faults. For this reason, operators are calling for additional control flexibility in the grid. In this paper, we propose the deployment of switchable reactors and capacitors distributed on the grid as a control resource for securing operations during severe contingencies and avoiding potential blackouts. According to the operating principles, the line reactance varies by switching on or off a certain number of distributed series reactors and capacitors and, therefore, the stabilizing control rule is based on a stepwise time-discrete control action. A control strategy, based on dynamic optimization, is proposed and tested on a realistic-sized transmission system.
Emergency Control Concepts for Future Power Systems
Proceedings of the 18th IFAC World Congress, 2011
In this paper, three approaches to increasing power system security are presented which are particularly relevant with respect to emerging fundamental changes in the operation paradigms of electric grids. Special attention is given to the challenge of maintaining system stability and security of supply in the presence of distributed and fluctuating renewable power generation and the integration of electro-mobility into the distribution grid. The proposed remedies, tailored for integration into future "smart grid" communication and control structures, consist of introducing controlled islanding schemes for interconnected transmission grids, highly distributed under-frequency load shedding mechanisms on the customer level, and controlled disconnection of electric vehicles in case of a distribution grid overloading. The motivation and principles of operation of each measure are presented and illustrated by a simulation example.
IEEE Transactions on Power Systems, 2015
This paper proposes a decentralized adaptive emergency control scheme against power system voltage instability. Decentralized control architecture is proposed by segregating the system into several local areas or zones based on the concept of electrical distance. Intelligent agents are assigned in each area to monitor the bus voltages and generator reactive powers to detect any threat of voltage collapse and to actuate countermeasures. A novel performance index has been formulated based on the load voltage and generator reactive power violations to identify the severity of disturbance and the risk of system emergency in each area. The coordination of the timing of the countermeasures among the agents is achieved through the formulation of the integral of the performance index. The simplicity and the adaptive nature of the proposed control scheme to provide countermeasures against any disturbance make it useful for real-time application. The robustness of the proposed approach has been validated through several case studies using the New England 39-bus test system and a more realistic Nordic32 test system.
A model-predictive approach to emergency voltage control in electrical power systems
2004 43rd IEEE Conference on Decision and Control (CDC) (IEEE Cat. No.04CH37601), 2004
Recent blackouts have shown that traditional local protection against power system collapse is not always sufficient to arrest instabilities. This paper shows that centralized systems can perform better than traditional local protection, as well as outlining how the decision logic of such centralized systems can be implemented. We present a coordinated system protection scheme (SPS) against voltage collapse based on model predictive control and heuristic tree search. It coordinates dissimilar and discrete controls such as generator, tap changer and load shedding controls in presence of soft and hard constraints on controls as well as voltages and currents in the network. The response with the coordinated SPS is compared to an SPS based on local measurements using simulation of the Nordic 32 test system. In terms of the amount of load shedding required to restore voltage stability, the simulations indicate that load shedding based on local criteria is near optimal in the system studied. However, when also generator controls are considered as emergency controls, the coordinated scheme reduces the amount of required load shedding by 35% compared to the local scheme.
Advances in Science, Technology and Engineering Systems Journal, 2021
Modern power systems are topologically and structurally complicated due to their complex interconnections. Consequently, the complexity of the dynamic stability assessment becomes more tedious, most especially, when considering a power electronics-based power system operating under faulty conditions. This paper, therefore suggests an alternative approach of Network Structural-Based Technique (NSBT) for the analysis and enhancement of transient stability of a power system considering Flexible Alternating Current Transmission Systems (FACTS) devices integration. The mathematical formulations based on the NSBT as well as the dynamic swing equations, required for carrying out the stability analysis, are presented. The structural characteristics of the network are captured by considering the interconnections of the network elements and the impedances between them. The eigenvalue analysis is then explored to identify suitable and possibly weak load node locations where the influence of FACTS device placement within the network, could be most beneficial. The transient stability analysis before and after critical outage conditions is investigated. The transient stability of the network operating under critical outage condition is then enhanced considering the integration of a multi-UPFC controller, which is suitably located as identified by NSBT. The effectiveness of the suggested approach is tested using the modified standard IEEE 5-bus, 30-bus networks as well as the practical Nigerian 28-bus grid incorporating a multi-FACTs controller. The results obtained show that the FACTS device contributes significantly to improving the transient stability of a multi-FACTS-based power network. The information provided by this study is highly beneficial to the system operators, utilities investors and power engineers, most especially, for predicting system collapse during critical outage conditions.
Stochastic Optimization of Power System Dynamics for Grid Resilience
Proceedings of the Annual Hawaii International Conference on System Sciences
When faced with uncertainty regarding potential failure contingencies, prioritizing system resilience through optimal control of exciter reference voltage and mechanical torque can be arduous due to the scope of potential failure contingencies. Optimal control schemes can be generated through a two-stage stochastic optimization model by anticipating a set of contingencies with associated probabilities of occurrence, followed by the optimal recourse action once the contingency has been realized. The first stage, common across all contingency scenarios, co-optimally positions the grid for the set of possible contingencies. The second stage dynamically assesses the impact of each contingency and allows for emergency control response. By unifying the optimal control scheme prior and post the failure contingency, a singular policy can be constructed to maximize system resilience.
Fault Tolerant Control of Power Grids
International Journal of Robust and Nonlinear Control, 2014
This special issue contains article on fault detection and isolation and fault tolerant control methods applied to different aspects of modern power grids, both for accommodating faults in the power grid, and for accommodation of faults in power generating units.
Dynamic observer-based power system emergency control
International Journal of Electrical Power & Energy Systems, 1986
This paper considers the problem of centralized structural control of power systems in emergency states, when large generationfload disturbances provoke power mismatch in the system, causing a viability crisis. The proposed control strategy with the action on demand and/or generation is initiated by the fast detection and estimation of disturbance magnitudes, using a decentralized low-order observer, based on locally available frequency and tie-line power exchange measurements in control centres of all the areas operating in a large interconnected power system. The paper proposes a suitable control strategy for this type of emergency and presents a systematic procedure for decentralized observer design. Finally, it gives an illustrative example of the application of such a power mismatch estimator in a twoarea interconnected power system.
Application of Distributed Control to Mitigate Disturbance Propagations in Large Power Networks
During the past decades the electric power infrastructure has evolved into one of the largest and most complex systems due to its extreme dimension, geographic reach and high reliability requirements. Maintaining sufficient security margins requires major enhancement of the existing control. Particular emphasis should be placed on improving the ability of the system to survive extreme contingencies, triggered by very unlikely chains of events, but capable of propagating into widespread outages. In this paper, a distributed control scheme is proposed to mitigate disturbance propagations in large power networks. We find a linear state feedback that simultaneously optimizes a standard Linear Quadratic Regulator (LQR) cost criterion and induces a pre-defined communication structure. The proposed controller provides supplementary damping through the excitation of the generators. The main advantage of this approach lies in the limited communication and limited model information required for the design which makes it practically applicable for large scale systems. We use a large two-dimensional mesh structure test system with homogenous parameters, to demonstrate that the proposed controller performs almost as well as the optimal centralized control with far less amount of communication and computation. The choice of test system is due to the fact that electromechanical wave propagation behavior observed in actual power systems can be readily recognized in that structure.