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This paper proposes an advanced emergency control strategy for embedded VSC-HVDC links after AC disturbances, such as line tripping and generation loss. The control goals are to minimize the impact of the disturbance on the AC-network, which includes improving the long-term voltage stability with utilizing possible unloading capacity of parallel AC elements. The proposed algorithm is evaluated against other control strategies for embedded VSC-HVDC links by applying it to a simple demonstration network. The test system includes all necessary VSC converter dynamics, the VSC-HVDC link current and voltage limits and simple load recovery characteristics for an evaluation of the long term voltage stability. The simulation results are explained and the advantages of the proposed emergency control strategy are discussed.

In a centralized emergency control system (CECS) with a third-generation algorithm, emergency control actions (CA) are selected under conditions of preventing disruption of dynamic stability, providing the required margin of stability in post-emergency condition, as well as preventing overcurrent and restricting voltage in network nodes to admissible limits. A methodology for selecting CAs for these last two conditions is described.

The conditions of power control of the hydraulic generating units of pumped-storage hydroelectric power stations with the use of the capabilities of asynchronized synchronous motor generators are considered. Characteristics that relate the size of the permissible surge in load in emergency control with limitations on the permissible deviation of the rotational speed of the hydroelectric generating units are obtained.

In recent years, Beijing has experienced severe air pollution which has caused widespread public concern. Compared to the same period in 2014, the first three quarters of 2015 exhibited significantly improved air quality. However, the air quality sharply declined in the fourth quarter of 2015, especially in November and December. During that time, Beijing issued the first red alert for severe air pollution in history. In total, 2 red alerts, 3 orange alerts, 3 yellow alerts, and 3 blue alerts were issued based on the adoption of relatively temporary emergency control measures to mitigate air pollution. This study explored the reasons for these variations in air quality and assessed the effectiveness of emergency alerts in addressing severe air pollution. A synthetic analysis of emission variations and meteorological conditions was performed to better understand these extreme air pollution episodes in the fourth quarter of 2015. The results showed that compared to those in the same period in 2014, the daily average emissions of air pollutants decreased in the fourth quarter of 2015. However, the emission levels of primary pollutants were still relatively high, which was the main intrinsic cause of haze episodes, and unfavorable meteorological conditions represented important external factors. Emergency control measures for heavy air pollution were implemented during this red alert period, decreasing the emissions of primary air pollutants by approximately 36% and the PM2.5 concentration by 11%‒21%.

This paper aims at reviewing and summarizing the vast variety of techniques to improve transient stability of power systems. A qualitative comparison of the techniques is presented and the future outlook is discussed. The techniques are categorized into conventional and renewable-based techniques. Conventional techniques are well established and have been employed in the past. Renewable techniques investigate how generators based on renewable energy sources (RES) can contribute to improving stability. Moreover, it is distinguished between techniques applying preventive and emergency controls. For preventive control, re-dispatch of generators and series compensation are extensively used in practice, whereas for emergency control, a great share of the techniques aim at voltage support during fault conditions. Regarding preventive control using RES-based generation, one approach which temporarily increases the voltage setpoint of the units in order to increase the synchronizing power, is reported. Regarding renewable energy source based emergency control, low voltage ride-through (LVRT) capability including voltage support is a well established method. Nevertheless, it is also highlighted that high voltage ride-through (HVRT) capability plays a critical role. The findings show that distributed generation must be included in existing control schemes for preventive control, and new improvement techniques taking full advantage of them need to be developed.

The integrated power system (IPS) is a foundation of all-electrical ships and vessels. The stability of IPS becomes a prerequisite of complicated cruise tasks. Thus, advanced stability analysis and regulation methods for IPS are of great importance. In this paper, a novel method is proposed for analyzing and enhancing transient stability of IPS, which is regarded as a cyber-physical system comprising of subsystems and connections. Criterions for determining input-output stability of such a system are firstly derived. Then, the stability analysis of IPS can be performed in the following two steps: 1) evaluating local input-output stability features of each subsystem independently through simulations. 2) Checking stability criterions with system topology and subsystem stability features. Moreover, synthetic approaches are proposed for stabilization and stability enhancement of IPS. To avoid system in-stability after major failures or topology changes, the optimal emergency control is performed to reconfigure subsystems. The other optimal regulation is used to strengthen system stability by adjusting subsystems’ control parameters during normal operation conditions. Case studies on a typical IPS validate the proposed stability analysis and enhancement approach.

In this paper, a novel direct yaw control method based on driver operation intention for stability control of a distributed drive electric vehicle is proposed. It was discovered that the vehicle loses its stability easily under an emergency steering alignment (EA) problem. An emergent control algorithm is proposed to improve vehicle stability under such a condition. A driver operation intention recognition module is developed to identify the driving conditions. When the vehicle enters into an EA condition, the module can quickly identify it and transfer the control method from normal direct yaw control to emergency control. Two control algorithms are designed. The emergency control algorithm is applied to an EA condition while the adaptive control algorithm is applied to other conditions except the EA condition. Both simulation results and real vehicle results show that: The driver module can accurately identify driving conditions based on driver operation intention. When the vehicle enters into EA condition, the emergent control algorithm can intervene quickly, and it has proven to outperform normal direct yaw control for better stabilization of vehicles.

The configuration of and algorithm for the centralized automatic emergency control system of the unified power system of Eastern Russia are described briefly.

In February 2014, the Beijing-Tianjin-Hebei (BTH) area experienced a weeklong episode of heavy haze pollution. Cities such as Beijing (BJ) and Shijiazhuang (SJZ) issued heavy pollution alerts for the first time and took emergency control measures. This study employed the Nested Air Quality Prediction Modeling System (NAQPMS) to simulate and analyze the three-dimensional structure of the source contributions of PM2.5 in the BTH area during this pollution episode and quantitatively assessed the effects of the emergency control measures. The results showed that during the polluted period (February 19–26), surface PM2.5 mainly originated from local sources (48%–72%). In the entire BTH area, southern Hebei (SHB) represented the largest internal contribution (33%), while the main external contributions came from Shandong (SD) (10%) and Henan (HN) (4%). Vertically, the local contribution was constrained below the near-ground layer, and rapidly decreased with altitude. The regional transport path from SHB and Shanxi (SX) to BJ appeared at 0.5–1.5 and 1.5–2.5 km, with contributions of 32%–42% and 13%–27%, respectively. The non-local source regions for the BTH area were SD below 1 km and mainly SX and HN above 1 km. Compared to the non-polluted period (February 27–28), the contribution from regional transport increased during the polluted period, indicating the key role of regional transport in the pollution formation. The emergency control measures had a relatively large effect on NO x and SO2 concentrations, but a limited effect on PM2.5. The stronger regional transport during the polluted period may have weakened the effects of the local emergency control measures. These results indicated that a coordinated emission control should be implemented not only over the BTH area but also over its surrounding provinces (e.g. SD, HN).

The purposes and tasks of emergency control in electrical supply grids with small power plants are analyzed. A method for controlling the dynamic stability of a synchronous generator based on synchronous vector measurements is introduced.

The possibility of using asynchronized machines, operating with a variable rotor rotation frequency, as counter- emergency control and high-speed regulation of the active power, is shown. The problems involved in using asynchronized machines to increase the active power and frequency regulation quality, and also to improve the dynamic characteristic of power systems, are considered.

Theoretical results of the development of the principles of scenario calculus are presented, which are obtained in the framework of the design of an emergency control system (ECS). Relying on the suggested system concept of the formation of a scenario system, consideration is given to the principles of the construction of operations in scenario spaces, which account for specific features of the scenario analysis and the process of the decision-making in the ECS. Principal problems of the development of scenario calculus on the basis of a system approach are treated, the classification of operations on scenarios is given, and a number of operations on elements of the basic metacollection are formalized.