Emergency Control Research Articles

Incorporating demand response in two-stage frequency emergency control

A decline in power system inertia challenges the frequency control, especially in a regional receiving-end power system. Conventionally, load shedding (LS) is the principal measure to recover the reduction in frequency. This paper proposes a two-stage frequency emergency control (EC) strategy to coordinate the LS and demand response (DR) techniques for frequency regulation to effectively and economically restore stable operation. The framework is divided into first-stage control (EC-I), second-stage control (EC-II), and coordination between EC-I and EC-II. EC-I deals with the condition when the system frequency markedly falls due to severe contingencies, with the LS approach adopted to alleviate the power-demand imbalance. Such control is devised to restore the system frequency above the set frequency index (fnadir,x) with the lowest cost. EC-II is performed based on EC-I to help the system promptly recover to a stable state. The LS and DR techniques are combined in EC-II to further reduce the control expenditure, and a control method for TCLs is proposed with less communication and computational burden to realize the power reduction. To minimize the overall control expenditure, a coordination process is designed with the coordination between EC-I and EC-II, which is reflected in the determination of the value of fnadir,x, as this parameter considerably influences expenditures in both EC-I and EC-II. The proposed framework is implemented in an IEEE 39-bus system, with simulation results demonstrating the effectiveness and economy of the strategy.

A safety preserving control architecture for cyber‐physical systems

AbstractIn this article, we propose a networked control architecture to ensure the plant's safety in the presence of cyber‐attacks on the communication channels. In particular, we consider systems subject to both state and input constraints that must be preserved for safety reasons despite any admissible attack scenario. To this end, first, two different detectors are proposed to detect attacks on the setpoint signal as well as on the control inputs and sensor measurements. Then, an emergency controller (EC), local to the plant, is designed to replace the networked controller whenever an attack is detected. Finally, the concept of robust N‐step attack‐safe region is introduced to ensure that the EC is activated, regardless of the detector performance, at least one‐step before the safety constraints are violated. It is formally proved that the plant trajectory is uniformly ultimately bounded in an admissible region regardless of the attacker's actions and duration. Finally, by considering a continuous‐stirred tank reactor system, numerical simulations are presented to show the proposed solution's capabilities.

Multi‐objective coordinated dispatch of high wind‐penetrated power systems against transient instability

High-level wind power penetration has significantly changed the power system's static and dynamic characteristics, which tends to decrease the overall system transient instability. This study proposes a multi-objective preventive-emergency coordinated control method against transient instability in the presence of uncertain wind power generation. This method optimally coordinates preventive control (PC) and emergency control (EC) to simultaneously minimise the total control cost and the expected stability margin. PC includes synchronous generator dispatch and wind farm power curtailment to reduce the overall percentage of renewable power to a safe level. EC adopts an emergency demand response scheme, in which the demand is immediately reduced for stabilising post-contingency system and avoiding wide-spread blackout. Wind power uncertainty is modelled through Taguchi's testing scenarios. The proposed method was verified on both New England 39-bus system and Nordic-32 system using industry-grade dynamic models and simulation software. Simulation results verified that the proposed method can optimally balancing system control cost and system expected stability margin.

Emergency control strategy for renewable power systems considering utility-scale energy storage transient

Integration of renewable energy generators has greatly altered both static and dynamic characteristics of the system. Combined with the uncertainties it introduced, the risk of a system being transient instable is significantly alleviated. This paper proposes a multi-objective coordinated post-contingency control method. It aims to increase post-contingency system security with emergence control (EC) while minimizing the total control cost. Two ECs are adopted in this paper: energy storage systems (ESSs) and emergency load shedding (ELS). ESSs are immediately connected to the network after contingency occurrence to provide both active and reactive power support. ELS will be triggered when the support from ESSs is insufficient to stabilize the system to prevent further deterioration of system security. Performance of the proposed method was evaluated on a modified New England 39-bus benchmark system. The results indicate that the proposed method can find solutions to stabilize the system against credible contingencies and optimally balance between system stability and economy.

Analysis of cyber vulnerabilities of the emergency control and relay protection to assess the reliability and survivability of electrical power systems in the era of total digitalization

Cyber threats pose an increasing threat to energy objects. It is essential to ensure the cybersecurity of automatic control systems, such as relay protection devices (RP), devices of regime control (RC) and emergency control (EC), automated control systems. At the same time, the issues of cybersecurity include not only the problem of hacker attacks, but also the whole complex of problems relating to adequate functioning of cybernetic systems in the power industry. The authors consider two of the most acute aspects of cybersecurity in the energy systems of the future in the era of total digitalization: large-scale prepared cyber attacks on the electrical power systems (EPS) as a whole and large-scale cyber attacks on distribution networks with small-scale generation facilities and active consumers.

Analysis of the emergency control and relay protection structures approached from the point of view of EPS reliability and survivability by taking into account cybersecurity threats

Cyber threats pose an increasing threat to energy objects. It is essential to ensure the cybersecurity of automatic control systems, such as relay protection devices (RP), devices of regime control (RC) and emergency control (EC), automated control systems. At the same time, the issues of cybersecurity include not only the problem of hacker attacks, but also the whole complex of problems relating to adequate functioning of cybernetic systems in the power industry. The authors propose a methodical approach to the analysis of the structure of automatic means of regime and emergency control in terms of their impact on the reliability and survivability of power systems (EPS), taking into account the known threats to cybersecurity.

Lifestyle behaviours and perceived well-being in different fire service roles.

Aspects of the work environment influence employee well-being. However, it is unclear how employee lifestyle behaviours, health characteristics and well-being may differ within a broader occupational sector. To investigate the health characteristics, lifestyle behaviours and well-being of three Fire and Rescue Service (FRS) occupational groups that differ in shift work and occupational demands: operational firefighters (FF), emergency control (EC) and administrative support (AS) workers. Data were obtained via an online survey using previously validated questionnaires to assess health characteristics, lifestyle behaviours and perceived well-being. Differences between groups were explored, controlling for confounding variables, using analysis of covariance (ANCOVA) methods. Effect sizes are reported where appropriate to demonstrate clinical significance. Four thousand five hundred and sixty-four FRS personnel volunteered, with 3333 (73%) completing the survey out of a total workforce of 60000 (8%). FF reported the lowest prevalence of chronic medical conditions (10%), compared with AS (21%) and EC (19%) workers. Total physical activity (PA) was 66% higher among FF compared with EC and AS workers. Components of sleep and self-rated health were independent predictors of well-being irrespective of FRS role. FF reported the highest levels of PA and highest perceptions of well-being, and the lowest prevalence of obesity and chronic medical conditions, compared with other FRS occupational groups. These findings may be used to inform FRS workplace intervention strategies.

A real-time, rapid emergency control model for sudden water pollution accidents in long-distance water transfer projects

A real-time, rapid emergency control (EC) model is proposed to cope with sudden water pollution accidents in long-distance water transfer projects. The EC model outputs the method of EC based on pollutant properties. A generalized form of EC model is proposed and tested with a demonstrative project. The rapid prediction formulas of emergency control parameters (ECPs) are proposed under different states of water diversion. The closing times of check gates and the pollution range are calculated by the rapid prediction formulas of ECPs. A case study is examined under the scenario of a sucrose spill in a demonstrative project conducted in the Fangshui to Puyang channel of the Beijing–Shijiazhuang Emergency Water Supply Project in the middle route of the South-to-North Water Transfer Project. The relative errors of peak concentration and arrival time of peak concentration are less than 20%. However, we could not use an actual toxic soluble pollutant to validate the EC model, so we performed the experiment with sucrose to test the EC model based on its concentration variation. The final result shows that the model is able to play a fundamental role in the decisions involved in the Emergency Environmental Decision Support System.

High-speed algorithm for calculating the neutron field in a reactor when working in dialog mode with a computer

The large-scale construction of atomic power stations results in a need for trainers to instruct power-station personnel. The present work considers one problem of developing training computer software, associated with the development of a high-speed algorithm for calculating the neutron field after control-rod (CR) shift by the operator. The case considered here is that in which training units are developed on the basis of small computers of SM-2 type, which fall significantly short of the BESM-6 and EC-type computers used for the design calculations, in terms of speed and memory capacity. Depending on the apparatus for solving the criticality problem, in a two-dimensional single-group approximation, the physical-calculation programs require approx. 1 min of machine time on a BESM-6 computer, which translates to approx. 10 min on an SM-2 machine. In practice, this time is even longer, since ultimately it is necessary to determine not the effective multiplication factor K/sub ef/, but rather the local perturbations of the emergency-control (EC) system (to reach criticality) and change in the neutron field on shifting the CR and the EC rods. This long time means that it is very problematic to use physical-calculation programs to work in dialog mode with a computer. The algorithmmore » presented below allows the neutron field following shift of the CR and EC rods to be calculated in a few seconds on a BESM-6 computer (tens of second on an SM-2 machine. This high speed may be achieved as a result of the preliminary calculation of the influence function (IF) for each CR. The IF may be calculated at high speed on a computer. Then it is stored in the external memory (EM) and, where necessary, used as the initial information.« less