Adaptive Emergency Control of Power Systems Based on Deep Belief Network

Emergency control is an essential means to help system maintain synchronism after fault clearance.Traditional“offline calculation,online matching”scheme faces significant challenges on adaptiveness and robustness problems.To address these challenges,this paper proposes a novel closed-loop framework of transient stability prediction(TSP)and emergency control based on Deep Belief Network(DBN).First,a hierarchical real-time anti-jitter TSP method using sliding time windows is adopted,which takes into account accuracy and rapidity at the same time.Next,a sensitivity regression model is established to mine the implicit relationship between power angles and sensitivity.When impending instability of the system is foreseen,optimal emergency control strategy can be determined in time.Lastly,responses after emergency control are fed back to the TSP model.If prediction result is still unstable,an additional control strategy will be implemented.Comprehensive numerical case studies are conducted on New England IEEE 39-bus system and Northeast Power Coordinated Council(NPCC)140-bus system.Results show the proposed method can detect instability of system as soon as possible and assist in maintaining reliable system synchronism.

Empirical Study on Emergency Broadcasting： Based on the US, UK and Japan’s Experience

Construction and use of national emergency broadcast system, related to the safety of lives and property. Broadcasting system has the simple construction, easy to set up, transmission distance, wide transmission range, transmission speed, etc., in the notice of emergency incidents, emergency command, emergency evacuation and emergency settle played a pivotal role. In the recent years, countries earthquakes, tsunamis and other natural disasters occur frequently, causing great loss of life and property, the establishment of the emergency broadcast system, more and more government attention. We introduced the emergency broadcast system in Japan, the United States, Britain and other countries, analyzes the problems our country to carry out emergency broadcast services need to pay attention, and made recommendations.

Research and Application of Safety Information and Control System of Nuclear Power Station

The thesis researches the safety infonnation and control system （SICS） design principle and introduces engineering application in CPR1000 nuclear power station in China. The SICS provides sufficient control and monitoring means to bring and maintain the plant in a safe state as a backup of main computerized control mean （MCM）, in any plant conditions that are probable during a planed or unplanned unavailability of the MCM. The successful engineering applications of SICS in different digital I＆C system platform are introduced in the paper. The thesis gives the research conclusion for new general SICS of digital I＆C system.

Modeling study of source contributions and emergency control effects during a severe haze episode over the Beijing-Tianjin-Hebei area

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 NOx 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).

Comparison of three flocculants for heavy cyanobacterial bloom mitigation and subsequent environmental impact

Cyanobacteria can accumulate as a heavy biomass on the leeward side of large eutrophic lakes,posing a potential threat to public health.The mitigating capacity of three flocculants and their potential impacts on the major environmental features of water and sediments was evaluated.Results indicate that polyaluminum chloride(PAC)and ferric chloride(FeCl)are efficient flocculants that can rapidly mitigate cyanobacterial blooms with chlorophyll-a concentrations higher tnan 1500 ug/L within 15 min.In comparison,cationic starch with chitosan could only treat cyanobacterial blooms in chlorophyll-a concentrations of less than 200μg/L.The addition of FeClcaused a decline in the pH value,while dissolved oxygen in the water column dropped to 2 mg/L during cationic starch with chitosan treatment for a high cyanobacterial biomass group.Thus,a combination of flocculants and oxygenators should be considered when treating high-concentration cyanobacterial blooms for emergency purposes.Additionally,the cell lysis of cyanobacteria caused by cationic starch with chitosan can result in an increase in total dissolved phosphorus and total dissolved nitrogen.Furthermore,the high accumlation of nutrients in sediments after the settling of cyanobacteria can cause high internal phosphorus pollution.The increase in the total organic carbon of the sediments can threaten lake restoration achieved by planting submerged macrophytes.

Emergency Control Strategy for Power Systems with Renewables Considering a 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.

Fast emergency control strategy calculation based on dynamic equivalence and integral sensitivity

To simplify the transient stability analysis of a large-scale power system and realize real-time emergency control,a fast transient stability simulation algorithm based on real-time dynamic equivalence is proposed.Generator models are grouped and aggregated according to a fast numerical integration.A fast calculation method of the admittance matrix is then proposed to calculate the parameters of an equivalent system,and numerical integration is performed using the obtained equivalent system.Then,based on integral sensitivity,a new fast emergency control strategy is proposed for the equivalent system.The final emergency control strategy is obtained by mapping the control strategy for the equivalent system back to the original system.The results of a simulation on an East China Power System that includes 496 generators and 5075 buses show that the suggested algorithm can output an accurate transient stability simulation result and form an effective emergency control strategy.The proposed algorithm is much faster than the existing solutions and has the potential to be used for online pre-decision.

Online Decision-Making and Control of Power System Stability Based on Super-Real-Time Simulation

During power grid cascading failure,the operating point changes frequently,resulting in a mismatch or inaccuracy of online pre-decision making emergency control strategy.To solve this problem,an online power system stability decisionmaking and control method based on super-real-time simulation is presented in this paper.A decision-making and control system is developed in which the three main operation modes,offline pre-decision-making,online pre-decision-making,and real-time control,are all coordinated.To verify the method,ADPSS(advanced digital power system simulator)is used to simulate a digital power grid with about 20,000 buses.The closed-loop operation of the digital power grid and the online decisionmaking and control system are implemented.Test results show that when online pre-decision making control strategies are mismatched,aided real-time control works well and can prevent power grid stability loss.

Decentralized Voltage Control of Power Systems Using Multi-agent Systems

systems.In our proposed smart self-healing method,two types of control agents are defined,namely master and local,which are applied in two steps.In the first step,the power system returns to the normal state after fault occurrence.Immediately after a fault detection in a power system,the system is divided into three subsystems using spectral graph partitioning.Partitioning is conducted based on reactive power flow in transmission lines.For each subsystem,a local control agent and a performance index(PI)are defined.Whenever the PI of a subsystem exceeds its threshold limit,the local control agent uses the Sugeno fuzzy system to intelligently select and apply control actions.In the second step as performed by the master control agent,the power system is transformed to an optimal state by solving the optimization problem.Simulations on a 39-bus New England reveal the effective performance of the proposed method.

Swarm controlled emergence for ant clustering

Purpose–Swarm controlled emergence is proposed as an approach to control emergent effects in(artificial)swarms.The method involves the introduction of specific control agents into the swarm systems.Control agents behave similar to the normal agents and do not directly influence the behavior of the normal agents.The specific design of the control agents depends on the particular swarm system considered.The aim of this paper is to apply the method to ant clustering.Ant clustering,as an emergent effect,can be observed in nature and has inspired the design of several technical systems,e.g.moving robots,and clustering algorithms.Design/methodology/approach–Different types of control agents for that ant clustering model are designed by introducing slight changes to the behavioural rules of the normal agents.The clustering behaviour of the resulting swarms is investigated by extensive simulation studies.Findings–It is shown that complex behavior can emerge in systems with two types of agents(normal agents and control agents).For a particular behavior of the control agents,an interesting swarm size dependent effect was found.The behaviour prevents clustering when the number of control agents is large,but leads to stronger clustering when the number of control agents is relatively small.Research limitations/implications–Although swarm controlled emergence is a general approach,in the experiments of this paper the authors concentrate mainly on ant clustering.It remains for future research to investigate the application of the method in other swarm systems.Swarm controlled emergence might be applied to control emergent effects in computing systems that consist of many autonomous components which make decentralized decisions based on local information.Practical implications–The particular finding,that certain behaviours of control agents can lead to stronger clustering,can help to design improved clustering algorithms by using heterogeneous swarms of agents.Originality/value–In general,the control of(unwanted)emergent effects in artificial systems is an important problem.However,to date not much research has been done on this topic.This paper proposes a new approach and opens a different research direction towards future control principles for self-organized systems that consist of a large number of autonomous components.

Probabilistic Energy and Reserve Co-dispatch for High-renewable Power Systems and Its Convex Reformulation

This paper proposes a probabilistic energy and reserve co-dispatch(PERD) model to address the strong uncertainties in high-renewable power systems. The expected costs of potential renewable energy curtailment/load shedding are fully considered in this model, which avoids insufficient or excessive emergency control capacity to produce more economical reserve decisions than conventional chance-constrained dispatch methods. Furthermore, an analytical reformulation approach of PERD is proposed to make it tractable. We firstly develop an approximation technique with high precision to convert the integral terms in objective functions into analytical ones. Then, the calculation of probabilistic constraints is equivalently transformed into an unconstrained optimization problem by introducing value-at-risk(Va R) representation. Specifically, the Va R formulas can be computed by a computationally-cheap dichotomy search algorithm. Finally, the PERD model is transformed into a convex problem, which can be solved reliably and efficiently using off-the-shelf solvers. Case studies are performed on IEEE test systems and real provincial power grids in China to illustrate the scalability and efficiency of the proposed method.

Security value based expansion planning of power system with integration of large-scale wind power

Concerning the integration of large-scale wind power,an integrated model of generation and transmission expansion planning is proposed based on the assessment of the value of steady state and dynamic security.In the assessment of security value,the unit commitment simulation based on the predicted hourly load and wind power output data in the planning horizon is used to evaluate the costs of preventive control,emergency control and social losses due to the uncertainty of load and wind power.The cost of preventive control consists of the fuel cost of power generation,the environmental cost and the load shedding cost.This not only provides a systematic method of security assessment of power system expansion planning schemes,but also broadens the perspective of power system planning from the technology and economic assessment to the measure of the whole social value.In the assessment process,the preventive control and emergency control of cascading failures are also presented,which provides a convincing tool for cascading failure analysis of planning schemes and makes the security assessment more comprehensive and reasonable.The proposed model and method have been demonstrated by the assessment of two power system planning schemes on the New England 10-genarator 39-bus System.The importance of considering the value of security and simulating hourly system operation for the planning horizon,in expansion planning of power system with integration of large-scale wind power,has been confirmed.

Frequency Stability of Power System with Large Share of Wind Power Under Storm Conditions

The operation of transmission systems with large share of wind power is specially challenging under storm conditions.Under the stormy wind speed conditions,wind turbine protection system is designed to shut down the turbine to avoid excessive mechanical load.The sudden loss of wind power from large offshore plants is difficult to forecast accurately,which results in a large amount of power imbalance.The severity of such a wind power imbalance towards frequency stability needs to be studied for the future power systems.In addition,the overhead transmission lines can also be affected during storms,thereby increasing their probability of failure in the operation of power system under the islanded conditions.This paper investigates how the stormy weather can threaten the frequency stability of future Danish power system with large share of wind power and how to avoid the frequency instability through proper control and defence strategies such as high-voltage direct current(HVDC)control and load shedding.Sensitivity studies are performed for ramp rates of HVDC control,load shedding strategies,inertia of the system with different volumes of disturbances to understand their impact on frequency stability.

An enhanced cascading failure model integrating data mining technique

An enhanced cascading failure model integrating data mining technique is proposed in this paper.In order to better simulate the process of cascading failure propagation and further analyze the relationship between failure chains,in view of a basic framework of cascading failure described in this paper,some significant improvements in emerging prevention and control measures,the subsequent failure search strategy as well as the statistical analysis for the failure chains are made elaborately.Especially,a sequential pattern mining model is employed to find out the association pertinent to the obtained failure chains.In addition,a cluster analysis model is applied to evaluate the relationship between the intermediate data and the consequence of obtained failure chain,which can provide the prediction in potential propagation path of cascading failure to reduce the risk of catastrophic events.Finally,the case studies are conducted on the IEEE 10-machine-39-bus test system as benchmark to demonstrate the validity and effectiveness of the proposed enhanced cascading failure model.Some preliminary concluding remarks and comments are drawn.

Traumatic Diaphragmatic Hernia Associated with Pelvic Ring Fracture

Traumatic diaphragmatic hernia （TDH） is an uncommon injury and a marker of severe trauma.This injury is rarely associated with pelvic ring fracture,although TDH is one of the most dangerous comorbidities of such fractures.Since this condition is easily misdiagnosed in emergency cases,we reported two cases and analyzed the clinical symptoms,diagnosis,treatment,and outcome of this comorbidity.Based on these results,we recommended an appropriate method for diagnosis and treatment and proposed a contraindication in treating TDH associated with pelvic fracture.