当前迫切需要研究实现可再生能源与电网统一协调发展的能源互联网系统提供技术支撑.通过提出扩展的能源枢纽模型,基于考虑了太阳能光伏发电和可再生能源发电储能技术的参与.分析日常负载需求(例如电、热和冷却)和使用时间能源价格来设置优化问题.为了优化总能源成本,构建了一个数学模型,其中包括一些约束,例如能源枢纽的输入输出能量平衡,电价,系统的容量限制以及可再生能源发电技术的储能效率.比较了基于不同能源枢纽结构的运营案例,以评估太阳能应用和电池储能系统、可再生能源发电技术对运营效率的影响.结果表明,所提出的模型预测了电力和天然气的所需量的重大变化,从而导致总成本降低.

This paper comprehensively analyzes the defects and deficiencies of the existing fault location methods and proposes an accurate fault location method for distribution network, which includes three steps: scanning, screening and detailed analysis. Firstly, the distribution network is divided into main lines and branch lines, using node feature matrix for scanning processing. This step makes full use of the measurement capability of PMU and SCADA system. Next, the fault information feature matrix and the phase relationship of zero-sequence voltage and current are used to obtain the fault line. Finally, the fault line is analyzed in detail, and the principle of double-end fault location is used to calculate the fault distance. Experimental and simulation results show that this method is not affected by fault resistance and fault distance, and effectively improves the power supply reliability of distribution network.

The reactive power absorption of conventional line commutated converter–high-voltage direct current transmission systems challenges on the voltage stability of AC/DC power systems. Many online dynamic voltage stability assessment approaches have been put forward to AC power systems, but the impact of DC transmissions is seldom taken into account for AC/DC power systems. In this study, an online dynamic voltage stability assessment method of AC/DC power systems is proposed. The proposed method models the converter as an equivalent AC voltage source in series with the internal impedance by utilising the control mode model of DC transmission systems and the measured data of the converter bus. The equivalent AC voltage source can identify the dynamic of DC transmissions. Then the AC/DC power system can be modelled by the equivalent AC power system. Based on the nodal equivalent method, the proposed method establishes a voltage stability index of the equivalent AC power systems for the dynamic voltage stability assessment of AC/DC power systems. The simulation demonstrated the effectiveness of the proposed method.

To solve the problem of submarine cable route tracking, a multi way-points tracking control approach was designed based on Single Neuron Adaptive Proportional-Integral-Derivative controller (SNA-PID). Dynamic model of Remotely Operated Vehicle (ROV) was set up and simplified according to its kinetic characteristics and the actual needs of oceanic engineering application. Three SNA-PID controllers were used to control ROV's heading, surge velocity and sway velocity. And the LOS (line of sight) was utilized to guide ROV motion to track predefined way-points.

基于含风电接入的VSC-HVDC输电系统网侧换流站的基本结构,提出了接入交流电网发生三相短路时风电送出系统的低电压穿越综合控制策略.通过切换网侧换流站控制策略,并与chopper电路配合,实现网侧故障换流站向交流电网提供无功支撑,同时网侧非故障换流站和直流chopper电路协同泄放系统冗余功率,而风电场侧换流站始终维持风电场侧电压稳定.仿真分析表明,该策略可以保障系统送电端的风电场在故障期间正常运行并维持直流母线电压的稳定.在电压跌落幅度较小时可维持系统的有功输出以及无功支撑,而在电压跌落幅度较大时可最大程度地提高系统向电网输送无功的能力.

In this paper, the heat generation of 110kV cable GIS terminal discovered by infrared thermal imager is briefly described. The causes of heat generation are discussed by means of sheath current detection and circulation calculation, and further analysed by high frequency partial discharge monitoring system, timely handling of equipment hidden dangers, to avoid the occurrence of vicious accidents. Through the analysis and judgment of this accident, the significance of infrared temperature measurement, sheath current detection technology and high frequency partial discharge detection technology for the discovery of cable defects is proved, which provides a basis and reference for future work.

Line commutate converter-modular multilevel converter (LCC-MMC) hybrid high voltage direct current (HVDC) system combines the advantages of both LCC-HVDC and MMC-HVDC, and will be wildly used in the future. The sub-module will withstand a very high voltage if a fault occurs in MMC converter station. In order to reduce this voltage, the LCC converter must operate in inversion state through gate-shift (GS) control strategy as quickly as possible. Normally, the fault signal was sent to LCC station through communication and GS control strategy was triggered due to this signal. At the condition of communication fault, LCC converter station cannot receive a fault signal, thus the control strategy will not change. In this way, the SM voltage will be as high as 4100V which is beyond the maximum withstanding voltage of insulated gate bipolar transistor (IGBT). It will endanger the safety of devices. To solve the over voltage problem of IGBT, a new solution that designs a leakage thyristor valve between DC line and ground is proposed as well as the coordination control strategy. A simulation based on power systems computer aided design (PSCAD) is conducted to verify this method. The simulation results show that the proposed solution is valid.

Based on the demand for deep-sea submarine cable salvage in Northeast Asia, a mathematical model of Sub Marine Tracked Vehicle-Cable Salvage (SMT-CS) was designed in this study. Considering the slip characteristics of the submarine track, the mechanical model of the SMT-CS during steady-state steering was simplified to obtain the kinetic equation of the vehicle body during steady-state steering. According to the steering geometrical relationship, the arbitrary shear rate and shear displacement of the ground plane during the steering process were solved. Combined with the empirical shear model of bottom sediments, the longitudinal driving force, lateral resistance and resistance moment of the larboard and starboard were derived during steady-state steering. The functional relationship between the lateral shift of instantaneous center of the conventional steering rate and the turning radius and angular velocity of the vehicle body as well as that between the slipping rate and the turning radius and angular velocity of the vehicle body was derived according to the geometrical relationship of steering motion. These are of great reference value to the design, performance prediction and maritime application of SMT-CS in the future.

分布式能源接入电网后,会对交流电网的故障特性产生巨大影响,从而影响到原有保护之间的配合.对dq控制下的逆变器控制特性进行分析,得到了直流侧100 Hz分量与逆变器的故障特性之间的关系.在交流系统发生故障时,逆变器在电网故障下可等值成受出口母线电压控制的压控电流源;逆变器侧直流100 Hz分量由交流侧负序分量所决定.基于这2个重要关系,提出了基于直流100 Hz分量的交直流保护配合方法,实现了直流侧与交流侧过电流保护与距离保护III段之间的配合,并通过仿真验证了交直流保护配合的可行性与有效性.

In combination with the requirements of the Tracked Vehicle-Cable Salvage project, which is aiming at the characteristics of the submarine crawler slip, the impact of the slip rate on the tangential drive to steering radius and steering angular velocity of the submarine crawler chassis. it is analyzed from the theoretical and experimental levels. Simplify the force model of the working submersible during steady-state steering, and it can obtain the steady-state steering body dynamics equation; in order to solve the arbitrary shear rate and shear displacement of the grounding surface in the steering process. According to the steering geometry relationship, it can combined with the empirical experience of seafloor sediments. The model derives the longitudinal driving. lateral resistance and drag torque of the left and right side of the track when it is during steady-state steering; when we analyzes the instantaneous lateral shift of the track shear rate during steady-state steering; it derives the instantaneous rate of the instantaneous steering rate, which based on the geometric relationship of the steering motion The relationship between the offset and the steering radius of the body, the steering angular velocity, and the sliding rate as a function of the steering radius and steering angular velocity of the body; when the steering model test is carried out to verify the influence of the slip rate on the steering radius and the steering angular velocity; The slip rate has an effect on both the steering radius and the steering angular velocity. It was measured steering radius becomes larger, the steering angular velocity becomes smaller, and the theoretical prediction curve is basically consistent with the measured data.

The grounding current increases and the outer sheath heats up seriously, which will greatly reduce the operating heat capacity of the cable and affect the stable operation of the cable. Therefore, detecting the grounding current of the cable accessory is of great significance for monitoring the operation of the cable. In order to improve the operational monitoring level, the ground loop online monitoring system began to be gradually applied in the power system. In this paper, based on the operating environment of XLPE high-voltage cable, the structure design of the on-line monitoring system of grounding circulation is analysed. The examples of online monitoring system are given. The advantages and disadvantages of the monitoring system are discussed in combination with the operating experience.

研究了定功率控制（PQ控制）策略下的逆变型分布式电源的多电源故障等值方法,通过分析单个逆变型电源、多个等容量逆变型电源、多个不等容量逆变型电源以及多个逆变型电源异地接入的输出特性,进而得到多个逆变型电源的故障等值方法,该方法简化了含多个逆变型电源的复杂网络故障分析时的计算复杂度。同时,提出了逆变型电源的故障等值分区方法,并利用迭代法对区域内的多个逆变型电源进行迭代计算得到等值模型。最后利用PSCAD搭建了含多个逆变型电源的配电网络仿真模型。在配电网络不同线路发生故障时,对配电网进行区域划分,并利用文中提出的等值方法计算等值后的逆变型电源输出特性,通过将计算得到的结果与仿真得到的结果相比较,验证了故障等值方法的正确性和有效性。

Mathematical models of dynamic processes are often required for assessment, diagnosis and improvement of control loop performances in process industries. Data samples collected in daily operations of feedback control loops may enclose data segments suitable for process identification to obtain the mathematical models. This paper proposes a new method to search such data segments. The searching criterion is that the reference and process output in a feedback control loop should experience significant magnitude changes. Hypothesis tests are exploited to find changing positions of data segments with different probability distributions and to verify whether the reference and process output make significant magnitude changes inside one data segment or between two adjacent segments. Simulation and industrial examples are provided to illustrate the effectiveness of the proposed method. (c) 2018 Elsevier Ltd. All rights reserved.

The paper proposes a method to analyze root causes of occurring alarms, for a special type of alarm variables in thermal power plants, where alarms are arisen from binary-valued root-cause variables. A Bayesian network with one child node and multiple parent nodes is used to describe the relationship between an alarm variable and root-cause variables. Probability parameters in the network are updated recursively. Root causes of occurring alarms are determined from the parent node set with the largest posterior conditional probability. The proposed method can remove negative effects of false and missing alarms in the nodes, handle the co-existence of multiple root causes, and detect the incompleteness of known root causes. Industrial examples are provided to illustrate the effectiveness of the proposed method.

An emergency load shedding optimization model is proposed in this paper to solve the DC blocking fault of the multi DC receiving- end power grid. The model takes the load shedding of each node as the optimization variable and the minimum total load shedding as the optimization objective. It takes a variety of transient indicators as constraints and adopts Particle Swarm Optimization (PSO) combined with electromechanical transient simulation. The PSO algorithm is improved by adaptive parameter adjustment to improve its optimization ability. This paper improves the efficiency of the algorithm by parallel computing and verifies the feasibility of the algorithm by the provincial power grid model in China.

As typical loads with thermal energy storage property, thermostatically controlled loads possess potential to actively participate in emergency load shedding control without causing obvious adverse effect on end-use performance. Taking air conditioning load as an example, this paper proposed a strategy and a probability model for thermostatically controlled loads in emergency load shedding system. Single and aggregation model of air conditioning loads and emergency load shedding architecture were presented respectively. A decentralized load control strategy was designed to avoid aggregated power oscillations during load recovery process. Then, a solving method for coupled Fokker-Planck equation (CFPE) probability model of the load control strategy was proposed to describe thermostatically controlled load groups' control characteristics. Simulation results verify effectiveness of the proposed active power control strategy and the solving method of the probability model.

Optimal design is critical to the efficient operation of the combined cooling heating and power (CCHP) system, different design combinations will definitely lead to different characteristics. However, the problem of balancing different system performance by regulating the capacity of facilities and key parameters still remain unclear. This paper designs a CCHP system with the storage unit and the electric chiller. A multi-objective model considering the energetic, economic and environmental benefits has been built, aiming to optimize the rated power of the power generation unit (PGU), the capacity of storage unit, the electric chilling ratio and the on-off coefficient of the PGU. Moreover, the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is adopted to solve the optimal model, thus obtaining multiple optimal designing combinations focusing on different performance. The energy saving rate is chosen as an example, which is used for revealing the inherent effects of all designing parameters on the system performance. Furthermore, the coupling relationships between these objectives are quantified, thereby providing the reliable method of balancing the benefits of all participants for the decision-makers in the designing process.

Air conditioning is a load with thermal inertia, and short time control will not cause an obvious negative impact on user power consumption. Compared with the traditional mini-split-type air conditioner, it has the advantages of flexible control method, strong controllability, large power of the monomer, and so on. This paper studies the application potential of emergency control of central air conditioning in safe and stable operation of large power grid. Firstly, the working principle of central air conditioner and the model of central air conditioning are introduced. On this basis, the emergency control strategy of central air conditioning is put forward. Furthermore, the control strategy of central air conditioning response control signal of safety and stability control or frequency deviation signal is put forward. Finally, a practical engineering case is given to illustrate the feasibility of the proposed strategy and its application in a large power grid.

Alarm systems play an important role in industry to notify operators of abnormal and fault situations. In real industrial plants, however, a majority of abnormal alarm phenomena, including false alarms and missed alarms, always interfere with operators' judgment. Mathematical analysis of traditional univariate alarm techniques indicates that the alarm setpoint, the dynamic alarm order, and the alarm algorithm are the three main elements of alarm annunciation and alarm clearance. Based on this, we proposed a multi-setpoint delay-timer alarming strategy which optimizes the false alarm rate (FAR), the missed alarm rate (MAR), and the averaged alarm delay (AAD) by increasing the number of univariate alarm setpoints. The proposed alarming strategy is able to achieve a balance between alarming accuracy and alarming sensitivity. Its effectiveness is demonstrated with both simulation and industrial case studies.

Primary frequency control (PFC) responses for thermal power generation units are concerned about whether changes of turbine rotating speeds lead to proper responses of generator active powers. A new method is proposed to estimate performance metrics for PFC responses via system identification techniques. Dynamic models are identified from data samples of the turbine rotating speed and the main steam pressure as two inputs, and the generator active power as the output. Hypothesis tests are formulated to evaluate the qualities of identified models. If model qualities are satisfactory and the contribution from the turbine rotating speed to the generator active power is significant, then performance metrics are estimated from a noise-free unit step response of the identified model. The proposed method removes three major limitations of the most widely-used method in contemporary industrial practices, namely, (i) performance metrics are obtained from all data samples of PFC responses, instead of some specific data samples being sensitive to noises; (ii) the proposed method is applicable to arbitrary-type PFC responses, not limited to step changes of the turbine rotating speed; (iii) noticeable effects of the main steam pressure are separated to avoid erroneous performance assessment results. Examples from thermal power generation units are provided to illustrate the effectiveness of the proposed method.