The high proportion of new energy, the high degree of power electronics, and the high degree of load freedom in the new-type power system bring with complex and changeable topologies and dynamic characteristics. The power balance and stable operation of new-type power systems will face more severe challenges in the situations with weak grid strength and large source-load fluctuations. However, electrochemical energy storage having rapid response and flexible configuration can effectively improve the dynamics characteristics of new-type power systems as well as play a supporting role in multiple time scales. This paper has summarized the research status of conventional energy storage technologies and discussed the technical advantages and application prospects of electrochemical energy storage in new-type power systems. Moreover, the active support capacity and optimal configuration of electrochemical energy storage in new-type power systems have been studied with considering the dynamic characteristics of new power systems and the demand for power and energy balance. This paper will guide the use of electrochemical energy storage to maintain safe and stable operation of new-type power systems.

With the rapid development of modern communication and measurement technology, the era of " wind power big data" has followed. The effective characteristic quantities can be extracted from numerous data dimensions to improve the prediction accuracy of wind power. Shap value could explain the degree of influence of characteristic variables on prediction results. In this paper, the attribution analysis model based on Shap was used to sort out the 6-dimensional characteristic variables that have a great influence on wind power. The 6-dimensional data and wind power data were imported into the abnormal data identification model based on LOF-ARIMA, so that the data cleaning method could be applied in the history data used in wind power prediction. According to the VMD-PSO-BiLSTM decomposition model, the ultra-short-term prediction of wind power can be carried out. The result shows that the prediction accuracy of wind power can be effectively improved.

Substation unmanned aerial vehicle （UAV） inspection is one of the important directions for the development of smart grids. Compared with transmission lines, substation equipment is numerous and centralized, resulting in relatively small air gaps around them and complex electromagnetic field distribution.The UAV inspection has been put forward higher requirements. In this paper, a suspended conductor discharge test platform is constructed, and the initial discharge voltage of the UAV-wire gap is experimentally studied. The finite element method is used to calculate the maximum electric field on the UAV surface during gap discharge, and this value is used as the electric field threshold. For the electric field distribution of typical equipment in 220kV substations, the electric field safety distance for UAV inspections in substations is proposed；200μT is used as the magnetic field threshold of the main control part of UAVs to determine the magnetic field safety distance for UAV inspections. The research results show that for the current typical UAV structure,when the 220kV substation load current is less than 315A, the inspection safety distance is mainly restricted by the electric field, which can be set to 37cm； when the load current is large, the inspection safety distance can be determined by the magnetic field.

In order to obtain more accurate transient model parameters of the doubly-fed wind turbine converter, ensure the accuracy of the simulation analysis results of wind power grid operation, and meet the requirements of safe and stable operation of the new energy high proportion power system, this paper proposes a parameter identification method driven by output response error. The parameters to be identified are determined according to the electromechanical transient model of the double-fed fan, and the interface technology between MATLAB and PSASP is developed to realize the cyclic call between MATLAB and PSASP. The final identification value is determined according to the minimum error between the dynamic response curve under the real value and the dynamic response curve under the identification value, and the effectiveness and universality of the identification method are verified.

 In recent years, with the increasing popularity of low-power devices and devices, the Radio Frequency Energy Harvesting （RFEH） technology has received extensive attention. Based on the introduction of several structures of the RFEH system,this paper focuses on the principle of each part of system. Firstly, it introduces the basic structures of parts and analyzes the optimizing methods for each part.Then it focuses on the development status of the key and popular technologies of RFEH.Finally, based on the current research problems, some development trends are discussed. 

With high proportion of wind power connected to the system, converting large-scale new energy into clean gases such as hydrogen, and cooperating with gas equipment to solve the issue of renewable energy consumption and reduce carbon emissions. Firstly, this study introduce the energy flow structure and critical equipment operation strategies of the electricity-gas-hydrogen energy interconnection system model. Secondly, taking into account the uncertainty of wind power and load, constructed an optimization planning model including gas generating units, hydrogen storage devices, fuel cells and power-to-gas equipment, and transformed into a mixedinteger programming model by second-order cone relaxation and piece-wise linear method. Finally, the example is validated by the IEEE 9-bus power system and 7-node natural gas system. The results show that the use of hydrogen storage device and fuel cell can reduce the total planning cost while improving wind power consumption and reducing carbon emissions, and the planning scheme considering uncertainty can improve the flexibility of the system and ensure the reliable operation of the system.

Variable speed pumped storage units have the ability to deeply participate in frequency regulation in the power system with a high proportion of wind power connected to the grid. Aiming at the problem of frequency disturbance of power system caused by short-term wind power fluctuation, according to the different operating conditions of pumped storage units, a model predictive control strategy for pumped storage to participate in frequency regulation is proposed. When the power generation is running, the load shedding backup of the fan is used to improve the problem of poor frequency regulation effect caused by the water hammer effect of the pumping and storage unit； In electric operation, the rapid response of the pumping and storage unit is used to effectively smooth the fluctuation of wind power and improve the wind energy utilization rate of the wind turbine. Under the premise of considering the respective constraints of pumped storage units and wind turbines, this strategy solves the optimal control problem in the rolling time domain, coordinates the distribution of active output between each unit, and improves the frequency regulation performance of the power grid. Finally, the proposed strategy is simulated and verified on the MATLAB/ Simulink simulation platform, and the results show that the proposed strategy can improve the frequency regulation effect of pumped storage units when smoothing wind power fluctuations.

Under the demand of long-distance and large-capacity delivery of new energy, the flexible high voltage direct-current, HVDC） transmission technology with modular multilevel converter, MMC） as the core has been rapidly developed in China, and gradually deeply integrated with the traditional high voltage AC power grid to form a highly electronic AC-DC hybrid power system. However, compared with the traditional AC power grid, MMC and other power electronic devices significantly broaden the response bandwidth of the series-parallel system, aggravate the interaction between power grid devices, and frequently cause broadband oscillation from several Hz to several thousand Hz in HVDC projects that have been put into operation, which seriously affects the power supply safety. Modeling and stability analysis have become the key requirement in AC-DC hybrid power system. In this paper, the methods of mathematical modeling and model simplification of MMC are summarized, which provides reference value for future mathematical modeling technology of MMC.

In the HVDC transmission system, the DC differential protection of thyristor inverter is misactivated in case of out-of-area faults, and a new method for thyristor inverter protection based on Park transform and Teager energy operator is proposed with thyristor inverter as the research object. Firstly, the Park transform is used to analyze the AC side current of the inverter, establish the equilibrium relationship with the DC side current, and put forward the main criterion, and secondly, the zero-sequence current of the inverter AC side ground fault and the Teager energy operator of the inverter AC side current are used as auxiliary criteria. Finally, the protection and traditional DC differential protection are compared by PSCAD simulation, and the results show that the protection can effectively solve the problem of traditional DC differential protection misoperation in out-of-area faults, and the protection method can operate correctly for phase short circuit faults in the DC differential protection that cannot be operated.

 Based on the dispatching problem that the uncertainty of wind power and reasonable distribution of power flow in the network has an impact on unit output, a two-stage optimal dispatch model with wind power is established in this paper. According to the characteristic that the forecasting accuracy of wind power is gradually improved from the in-day time-scale, to the real-time time-scale, during in-day rolling dispatching the model predicts the wind power output data according to the time queue method, constructs the initial dispatch for optimizing the generation cost, and determines the basic output of the unit；In the real-time dispatching, in order to further reduce the error, the wind power output is predicted through Monte Carlo scene generation and reduction, taking into account the uncertainty of wind power； Through the dynamic power flow of active and reactive power joint regulaiton, each unit can share the active unbalanced power in proportion according to the frequency characteristic coefficient, adjust the reactive unbalanced power according to the node area control strategy, correct the basic output of the unit, realize the reasonable distribution of power flow,establish a dispatching model to optimize the network loss and voltage level, and solve the model through particle swarm optimization. Finally, take the improvement of IEEE14-node system as an example to carry out simulation verification.

 Due to the randomness of wind, the frequent variable pitch action of wind turbine leads to frequent failures of variable pitch system. The research on fault diagnosis and fault warning of variable pitch system of wind turbine is more and more important. In this paper, we first focus on the blade zero offset fault of wind turbine, use GH-Bladed fan simulation software to simulate blade zero offset under different working conditions, and study the effect of zero deviation on the impeller speed and blade root bending moment of the operating unit, and use the comparison of wind turbine axial acceleration 1P harmonic amplitude and 3P harmonic amplitude to determine the blade zero deviation curve. The blade zero deviation determination model is constructed. Then, based on the neural network technology, the historical data of SCADA （Supervisory Control And Data Acquisition） in the actual operation of the unit was analyzed, the feature extraction and data analysis and processing of variable pitch fault were completed, and the LSTM （Long short-term memory neural network） model with attention mechanism was trained to build the AT-LSTM （attention based LSTM） health state prediction model of variable pitch. By comparing AT-LSTM with recurrent neural network （RNN） and long short-term memory neural network （LSTM）， we prove that adding attention mechanism can improve neural network.

The frequent occurrence of extreme disasters seriously threatens the safe and reliable operation of the regional integrated electricity-natural gas system （RIENGS）。Coordinating fault recovery and maintenance strategies can effectively improve system resilience. For the deeply coupled RIENGS, this paper proposes a coordinated optimization strategy of two-stage fault recovery and maintenance scheduling during and post-disaster. Firstly, in the first stage of the disaster, a fast recovery model of the RIENGS is established, considering the load priority and network reconfiguration strategy to realize the rapid recovery of important loads in the emergency recovery stage. Then, in the second stage of post-disaster, the network reconfiguration and maintenance scheduling optimization model of the RIENGS is established with the objective function of minimizing the total cost of load loss and the maintenance time, and the model is transformed into a mixed integer second-order cone programming （MISOCP）problem. Finally, the effectiveness of the proposed method in reducing the load loss of the RIENGS is verified by numerical examples of a 13-node distribution network with a 7-node gas distribution network.

 Based on the mechanism of field ionization, a two-dimensional axisymmetric fluid model is established to simulate the development of needle plate electrode streamer discharge in water under positive nanosecond pulse voltage. The temporal and spatial distributions of streamer discharge morphology, electric field intensity and space charge density in water with different applied voltage amplitude and pulse rising time were obtained. The simulation results show that with the increase of applied voltage amplitude, the amount and velocity of charge in the discharge channel increase; When the rising edge of the pulse becomes steeper, the radius of the discharge channel increases and the corresponding maximum electric field intensity decreases. The simulation results show that the water temperature in the pulsed discharge increases, but there is no obvious vaporization phenomenon. The conclusions of this paper are helpful to understand the initiation and development of streamer discharge in water with nanosecond pulse and the mechanism of liquid dielectric discharge.

In order to promote the “double carbon" target, China will accelerate the development of distributed PV in counties.In this paper, we firstly obtain certain precision images of roofs of county buildings with the help of high resolution remote sensing information technology. Then we extract edge contours based on image processing techniques such as Sobel operator edge detection and threshold segmentation to eliminate non-building information in the images, and obtain the roof area of buildings, and immediately after estimate PV capacity. Secondly, with the objective of minimizing the comprehensive cost of distribution network including line renovation, transformer expansion, energy storage and distributed PV investment and operation cost, and taking into account the PV development potential constraint, a two-layer planning model of source-grid-load-storage is established, and the model is solved rapidly by quantum particle swarm algorithm. Finally, the practicality of the source-grid-load-storage planning technique, which takes into account the potential assessment of PV development in a county distribution network, is verified to improve the economy and rationality of the planning scheme.

Transformer oil is commonly used in electric power equipment and pulse power equipment, and the improvement of its insulation performance is of great significance to the safety of the equipment. Based on the two-dimensional axial symmetric fluid model, simulating the discharge phenomenon in the transformer structure of needle plate under nanosecond high voltage pulse, used the Poisson equation, fluid dynamic equation and convection thermal diffusion equation. The simulation results show that when the discharge field reaches 4.5×108V/ m and the spatial charge density reaches 103/ m3.Upon discharge to 30 ns, the temperature at the tip rises to 413 K, vaporizing the oil to produce the gas phase, and generating a new flow injection discharge in the gas phase region.

For the grid connected to large-scale wind power via voltage source converter based high voltage direct current （VSC-HVDC）， a large number of synchronous generators are replaced and frequency regulation capability is weakened in the grid. Therefore, this paper proposes a coordinated control strategy to improve the frequency response capability of the grid. The strategy uses DC capacitance and wind turbine power backup to adjust the frequency. A system frequency response model is used to analyse the grid frequency response characteristics and the key factors affecting frequency；A relationship between DC voltage and grid frequency is established to control the DC capacitor to absorb or release energy to achieve VSC-HVDC inertia support； Based on the over-speed load shedding control scheme, the deviation and differential of grid frequency is introduced into the wind turbine control system to achieve integrated frequency control. Finally, the effectiveness of the proposed control strategy is verified in grid connected with large-scale wind power via VSC-HVDC. The results show that the proposed strategy can significantly improve the inertia level and primary frequency response of the grid.

In the combined power generation of new energy and thermal power, the virtual power plant can adjust the demand side of the power grid to slow down the fluctuation of new energy power generation and play a role in absorbing it. Under the concept of virtual power plant, the thermal power plant and wind farm are taken as a whole, the load optimization distribution method of the unit is studied, and the multi-objective plant-level load optimization mathematical model that takes into account both the speed and economy is established. By adjusting each objective function The weights of to meet the target needs in different situations, the mathematical model is solved by the predator-predator genetic algorithm. This method improves the shortcomings of the slower convergence speed of the genetic algorithm, and finally conducts experimental analysis through simulation. The test simulation results verify the effectiveness of the model and improve the system's ability to absorb wind power.

In low-current grounding system of distribution network, the zero-sequence current signal is very weak when single-phase grounding fault occurs, especially when high-resistance grounding fault occurs, it is difficult to accurately select the line. In this paper, a new method of fault line selection for distribution network based on flexible grounding of new neutral points is proposed. When single-phase fault occurs, a high-speed power electronic switch is used to put in a small resistance grounding branch at the neutral point, which combines the advantages of power supply reliability of small current grounding system with obvious signal of large current grounding system. Using the amplitude of zero sequence current and the change of phase difference of zero sequence current before and after incorporating small resistance as the criterion, the unsatisfactory situation of line selection under the condition of high resistance grounding is effectively solved, and the accurate line selection of distribution network fault is realized. PSCAD/EMTDC simulation environment is used to simulate single-phase grounding fault of distributior network, and the simulation results show that the proposed scheme has good reliability and effectiveness under different fault conditions.

Load side flexibility resource synergy source side multimodal heating electrothermal comprehensive low carbon energy system and to alleviate the "three norths" region “wind hot conflict" phenomenon, improve the wind power given amount so as to reduce the carbon footprint of the system put forward a kind of meter and electric heating demand response - electric integrated energy system of field source of coordination of economic operation model. Source side through the solar-thermal power stations equipped with heat storage device and electrical heating device coordination unit cogeneration heating to a certain extent over decoupling the "thermal power" the work mode, side set up steady electric power flow, load meter and electric demand side response, the model of integrated optimization goal considers the system total operating costs, abandon the wind punishment cost and carbon trading costs. The model was simulated based on the improved IEEE30 power grid and 6-node heat grid system. The calculation results show that the coordinated operation of source and load can effectively reduce the carbon emission of the system, improve the grid-connected generation of new energy and reduce the total dispatching cost of the system.

Overhead lines are often used in transmission lines of Modular Multilevel Converter Multi-Terminal Direct Current （MMC-MTDC） system. When the DC transmission line of the converter station is struck by non-fault lightning stroke, the high frequency oscillation might occur in the DC voltage and the DC current of the converter station with gradual attenuation in a short time, which might lead to the subsequent low-frequency oscillation on the DC side. This paper firstly analyses the mechanism of low-frequency oscillations on the DC side by taking the most severe oscillation of the receiving DC voltage control station as the research object, and proposes a DC additional damping controller optimized method to improve the system inertia and suppresses the current oscillation in the DC line by adding a virtual inertia link to the voltage outer loop. Finally, based on RT-LAB5600real-time simulation platform, a four-terminal MMC-MTDC system simulation model is built to verify the correctness of the theoretical analysis of low frequency oscillation and the effectiveness of DC additional damping controller.

 To solve the problem of low voltage gain of traditional two-stage matrix converter, a Split Source Two-Stage Matrix Converter (SSTSMC) is proposed by combining split source network with two-stage matrix converter. Firstly, the topology and working principle of the proposed SSTSMC are introduced, and the rectifier stage of the SSTSMC is applied to the modulation strategy without zero vector, and the inverter stage is applied to the traditional SVPWM modulation strategy, which can effectively improve the voltage transmission ratio of the two-stage matrix converter; Secondly, in order to obtain better waveform quality and reduce the harmonics of the output voltage and current, the modulation strategy of the rectifier stage and the inverter stage of the converter is improved by analyzing the operating characteristics of the split source network and the two-stage matrix converter. Finally, the effectiveness of the proposed topology and the improved modulation strategy is verified by simulation experiments.

Abstract: The access of distributed power generation has caused a noticeable impact on the safe and stable operation of the distribution network. It is necessary to conduct in-depth analysis and select appropriate grid-connected operation scheme to improve the operation characteristics of the distribution network. Based on the radial structure of medium-voltage distribution network, using the constant power load model, this paper analyzes the mechanism of the impact of distributed power generation connected to medium-voltage distribution network, deduces the relationship between the system loss and voltage change after the connection of distributed power generation and the connection location, access capacity and power factor of distributed power generation, and obtains the calculation formula of the optimal configuration of distributed power generation through quantitative analysis. The simulation results show that the control of the network loss and node voltage of the distribution network system can be achieved by properly adjusting the various grid connection parameters of the distributed generation, so as to obtain the optimal operation scheme of the distributed generation connecting to the medium-voltage distribution network.

With the high proportion of new energy such as wind power integration into power system and the increasing of equipment condition-based maintenance scheduling, the contradiction and conflict between the transmission equipment and the power transmission system is more difficult to balance and the decision of power transmission system maintenance scheduling is challenged. To meet this challenge, A condition-based maintenance scheduling of power transmission system is proposed considering the uncertainty of wind power. Firstly, the model of equipment failure rate and its relationship to maintenance schedule is established based on the equipment condition monitoring and evaluation technologies. Secondly, the expressions of the power system failure risk and maintenance risk are given according to the risk theory, in which the power system operating cost is evaluated based on the security constrained unit commitment. Finally, the model and method for the condition - based maintenance scheduling of power transmission system considering wind power uncertainty is presented with the goal of minimizing the sum of power system failure and maintenance risks, and a modified IEEE-30 test system is used to exhibit the effectiveness of the proposed approach.

Energy storage has bidirectional fast power throughput and flexible layout, customized control strategy can be an effective means of power flow control in power system. Aiming at the short-term overload problem of local transmission and transformation equipment caused by source load fluctuation or component failure in a high proportion of new energy power system, a power flow decentralized coordinated optimal control strategy based on large-scale energy storage is proposed. Firstly, based on the impact energy of energy storage and the weight coefficient of each branch, the comprehensive control sensitivity is proposed, the controllable energy storage nodes with weak off-limit control effect on to be adjust branch were eliminated to realize the optimization of controllable energy storage nodes. Secondly, the dynamic optimization model is constructed with the goal of minimizing the total control cost, and the dynamic optimization model is transformed into a linear optimization model by using the big M method, the purpose is to consider the energy storage capacity adjustment and the minimum number of equipment involved in adjustment, and to develop an optimal control strategy.Finally, the effectiveness and rationality of the proposed strategy are verified based on the improved IEEE RTS24 bus system.

With the growth of the grid-connected capacity of wind farms, thermal power units, as the main source of reactive power, have been heavily replaced. The problem of reactive power and voltage in the power grid has become increasingly prominent. It has become a development trend for wind farms to provide reactive power auxiliary services for the power grid. The var-voltage adjustment coefficient is an important parameter for wind farms and thermal power units to respond to the changes of reactive power and voltage in the power grid, and its reasonable setting is of great significance to ensure the voltage level of the power grid. Based on considering the uncertainty of wind power output and load, this paper establishes an optimal model for the var-voltage adjustment coefficient of the power source, which aims to improve the grid voltage level and considers the grid operation constraints, and uses the WOA to solve the model. The simulation of the high wind power proportion system based on the IEEE-39 bus system shows that the probability of voltage out of limit and the level of voltage fluctuation are reduced by using the optimized var-voltage adjustment coefficient.

 Vienna rectifier is the most common front part of the charging module of automobile DC charging pile, and the stable operation of the front system directly affects the running state of the whole charging module, so the fault diagnosis of Vienna rectifier is very important. In view of the open-circuit fault characteristics of Vienna rectifier's power switch and electrolytic capacitor, in this paper, a Complementary ensemble empirical mode decomposition （CEEMD） and Particle swarm optimization are proposed. PSO optimizes the diagnostic method of Random forest （RF） algorithm. This method takes the input current as the original signal, analyzes the waveform characteristics of the open-circuit fault of the core device, and uses CEEMD method to decompose the fault current signal. On this basis, the fault feature vector is constructed, and the extracted feature vector is input into the particle swarm optimization random forest model to identify the fault state. The Vienna rectifier simulation model is built to verify the feasibility and superiority of the proposed method. The simulation results show that the method has a good diagnosis result, the diagnosis rate reaches 93.8% and the diagnosis time is shortened. It has practical significance for the fault diagnosis of automobile DC charging pile.

It has become one of the key tasks of constructing China's power market to ensure and promote the consumption of wind power by market mechanism. Aiming at the problems of the connection between medium and long-term trading and day-ahead spot trading in China's electricity market, as well as the unreasonable and imperfect trading mechanism of wind power in the market, a day-ahead market clearing model is designed which takes into account the decomposition of medium and long-term contract electricity of power producers. Based on the comprehensive consideration of wind power generation capacity, day-ahead predicted power and regulation capacity of conventional units, the daily time-sharing power contract curve of medium and long term contract power decomposition between wind power producers and conventional units is established to determine the bidding space of each power generation entity participating in day-ahead bidding. On this basis, by introducing the coordination factor which can reflect the influence of wind power forecast error and volatility on system operation cost, a day-ahead market secondary clearing model based on wind power coordination price is constructed. This model is helpful to realize the organic combination of medium and long term trading and day-ahead spot trading, and give full play to the advantages of centralized spot market mechanism to promote wind power consumption. An example is given to verify the effectiveness of the proposed market clearing model.

With the large-scale distributed generation connected to the distribution network, the timing mismatch between its output and load demand makes it difficult to absorb new energy in the power supply area. For this reason,an optimal allocation method of power supply regional source-load-storage is proposed to improve the capacity of new energy consumption. Taking the distributed power supply, energy storage and controllable load in the power supply area of the distribution network as the configuration object, the energy storage and controllable load transfer strategy is constructed, and the two-layer optimal allocation model of source, load and storage in the power supply area is established. The optimization goal of the upper model is to achieve the maximum absorption of distributed power. The optimization objective of the lower model is to minimize the peak-valley difference of the expected net load in the power supply area. In view of the difference between DG and load output time series, LHS technology is adopted to deal with it, and intelligent optimization algorithm is used to solve the model. Taking the power supply area topology of a city as an example, an example is given to prove the rationality and effectiveness of the method.

At present, due to the increase in the penetration rate of renewable energy generated by wind power and photovoltaic power generation in China, the problem of lack of flexible resources is becoming increasingly prominent, and the volatility and uncertainty of new energy power generation such as wind power and photovoltaic power generation lead to greater pressure on the peak regulation and supply security of the power grid, and the power market mechanism has not been fully constructed, the market-oriented mechanism of electricity price is not mature enough, and the demand-side response resources have not been actively mobilized. With the continuous increase of the number of electric vehicles in China, and the disorderly access of electric vehicles will cause the adverse impact of “peak on peak"， so it is reasonable to arrange electric vehicles to participate in demand response in an orderly manner. Secondly, the ways in which electric vehicles participate in demand are explored, and the participation in demand response in the form of aggregators is determined. Then, the orderly charging and discharging strategy of electric vehicle aggregators is designed, the idea of electric vehicle load aggregators participating in demand response is proposed, and the trading mechanism of demand response is constructed. Finally, with the goal of benefiting electric vehicle users, electric vehicle load aggregator platform and power grid, the upper and lower limits of electric vehicle charging and discharging are formulated, and numerical simulation is used to verify them.

In order to improve the heating capacity and peak regulation capacity of generation units, the low-pressure cylinder zero output technology has attracted more and more attention. Based on a 300 MW pure condensing unit, the thermal system model was built by Ebsilon software and the system modeling after heat supply transformation was carried out. The thermal economy changes of the unit before and after the low-pressure cylinder zero output were compared and analyzed. The heat supply, power generation performance and standard coal consumption of the low-pressure cylinder zero output unit under different layout schemes of draining system of heat network were simulated under multiple working conditions. The results show that the minimum standard coal consumption of power supply is reduced by 31.63 g/（kW·h）。In each draining system layout scheme, the maximum heating extraction steam is 638.26 t/h, the minimum electrical load rate is 23.05%， and the minimum standard coal consumption for power supply is 161.30 g/（kW·h）。This research can provide useful guidance for the optimal arrangement of draining system and efficient operation of the low-pressure cylinder zero-output units.

 The flow state of the tail edge airflow is controlled by adding a small cylinder at different positions above the tail edge of the S809 airfoil, and the aerodynamic performance of the airfoil under the 0-20 degree angle of attack is simulated by the N-S equation. The results show that the cylindrical spoiler can postpone the flow separation point of the airfoil and improve the vortex structure on the upper surface of the tail edge, which makes the flow around the upper surface weaken, thus increasing the velocity of the upper surface, reducing the surface pressure of the airfoil, and improving the lift of the airfoil and reducing the drag of the airfoil. At the same time, the optimal size of the small cylinder has the best control effect on the tail vortex, and the aerodynamic performance is the best.

 High-temperature corrosion on water cooled furnace wall of boiler is a paramount affecting factor on safety and economical operation of thermal power units. In this paper, the high-temperature corrosion on left and right water cooled furnace wall of a domestic 1 000 MW double-cut round boiler was researched. Influences of burner aspect ratio and secondary nozzle swing angle on the water cooled furnace wall with high-temperature corrosion was investigated by numerical simulation （commercial software:Fluent）。The numerical results show that the boiler should be applied in the burner assemble with a relatively lower aspect-ratio. When secondary air nozzle swings upward by 15， the CO concentration in near-wall region was less than 3%.In addition, oxygen content was sufficient to effectively reduce the risk of high-temperature corrosion on water cooled furnace wall.

Coal combustion coupled biomass power generation is an effective way to improve biomass utilization and reduce carbon emissions of thermal power plants. In order to explore the influence of six kinds of coal in Northeast China, such as corn stalks, Jingxi anthracite, Xishan lean coal, Longfeng Xizhong coal, Shenhua coal, Yima bituminous coal and Fengguang lignite ， on the heat transfer characteristics of furnace under different mixing ratios, a mathematical model of the influence of biomass mixed with coal on heat transfer characteristics of furnace is established in this study, and is verified its reliability. Secondly, taking a 1 000 MW ultra supercritical pressure boiler of a power plant as the research object, the heat transfer characteristics of the boiler were analyzed and calculated, and the effects of six kinds of mixed fuels on the furnace flue gas volume, furnace outlet flue gas temperature, water wall heat transfer flow, flame blackness in the furnace, average heat load of water wall, average furnace flame temperature and theoretical combustion temperature under different mixing ratios were analyzed. The results show that the mixed fuel composed of Jingxi anthracite and corn straw has the highest theoretical combustion temperature. Affected by the calorific value of the mixed fuel after mixing, with increase of mixing proportion, flue gas volume, heat transfer flow of water wall, average heat load of water wall and average temperature of furnace flame of the six mixed fuels show a downward trend.The work provides a theoretical basis for coal-fired power generation with high proportion of mixed biomass coupled combustion.

The conventional control methods used in three-phase inverter systems have limitations such as poor anti-interference capabilities and slow dynamic response after disturbances, Additionally, controller design is sensitive to parameter uncertainties in LCL filter. In this paper, a disturbance suppression strategy for LCL three-phase inverters using the super-twisting algorithm is proposed to address these issues. Firstly, a mathematical model for the Super-twisting sliding mode control of three-phase LCL inverter in the dq coordinate system is designed to optimize the voltage and current double-loop control structure. Secondly, simulation of the islanded inverter is conducted using the PLECS software to verify the insensitivity of the Super-twisting algorithm to parameter fluctuations Finally, experimental validation is carried out on the RT Box semi-physical experimental platform under load fluctuations and voltage reference experiments. The proposed Super-twisting sliding mode control method exhibits strong robustness, stability, and dynamic characteristics as compared to traditional PI control.

Based on the trapezoidal fin, a new type of plate-fin radiator with a new shape fin is proposed to optimize the heat dissipation. Based on a commercial software COMSOL Multiphysics 6.0， a heat sink model with slots between trapezoidal fins is established. The performance of different slot widths, slot heights and slot moving positions were evaluated, and the influence of fluid velocity on the heat dissipation of different fins was analyzed. The results show that the grooving between trapezoidal fins has a lower chip temperature than that without grooving, and the change of slotting width, slotting height and slotting moving position have an effect on the heat dissipation. At low fluid velocity, increasing the width and height of the slot or moving the slot down can effectively improve the heat dissipation efficiency of the radiator. The heat transfer rate of the optimized trapezoidal slotted fin radiator is 12% higher than that of the original trapezoidal radiator and 22% higher than that of the original rectangular straight fin radiator. The research results can provide reference for future research on the improvement of heat dissipation efficiency of plate-fin radiator.

The flexible DC grid is one of the effective solutions to solve the problem of large-scale new energy transmission and consumption, the DC circuit breaker is an important device for realizing the DC side fault isolation of the flexible DC grid, however, the current limit part of existing topology are less coordinated with the commutation part. Therefore, this paper proposes a multi-port circuit breaker topology with capacitors as current limiting and commutation parts. Through the cooperation of current limiting capacitor and commutation capacitor, the circuit breaker can complete current limiting and accelerate the commutation. In addition, the operation principle of the circuit breaker in the typical DC side fault is analyzed, the relationship between the voltage and current stress of the circuit breaker during operation, the energy consumption of the arrester and the parameters of system and circuit breaker is analyzed, and the design basis of circuit breaker parameters is given. Finally, the breaking and reclosing of the proposed circuit breaker are simulated and verified in PSCAD/EMTDC, and compared with the existing topology, which proves the feasibility of the proposed DC circuit breaker topology.

In order to make up for the shortcomings of the current transmission line wind deflection prevention methods, an efficient transmission line wind deflection prevention device is sought. Based on the wind-induced reaction analysis of the coupling model of tower-wire-insulator and wind-deflecting device, the wind-deflecting effectiveness of the composite wind-deflecting strut insulator and the related factors affecting its wind-deflecting effect are studied. The results show that the composite windproof skew prop insulator has a strong windproof effect, and the windproof deviation of the transmission line after installing the new device is reduced by 95.6% compared with that without installing the new device. The structural parameters have great influence on the inhibition of wind deflection；the maximum wind deflection Angle at the insulator string induced by wind decreases with the increase of the yield strength of Mr Fluid, and the decrease is 0.022° wind deflection Angle /kPa； It also decreases with the increase of the equivalent stiffness of the SMA helical spring, and the decrease is 0.073° wind deflection Angle/kN/ m.With the increase of the effective length of the piston, it decreases by 0.021° wind declination Angle/mm. It increases with the increase of piston clearance, and the increase is 0.51° wind declination Angle/mm. Therefore, in the design of transmission line anti-wind deflection with composite windproof skew prop insulators, the insulators with large yield strength of magneorheological fluid, large equivalent stiffness of SMA helical spring, long effective length of piston and small gap of piston should be selected, which can achieve better wind deflection inhibition effect without changing the external size of the insulator.

 During the ice melting process of the transmission line DC ice melting short circuit control system, the detachment of the ice coating causes the displacement and stress changes of the cantilever combining mechanism, resulting in structural instability, detachment of the moving contact and insulation failure. The analysis of the vibrational properties and the experimental investigation of the ice detachment were carried out. First, the Lagrange equation and the assumed mode method are used to create the mathematical model of the ice-shedding vibration of the combined cantilever mechanism of the ice-melting system, taking into account factors such as different ice-shedding conditions, parameter attributes, vibration directions, and the internal coupling relationship of the structure. Second, the finite element model of the ice melting system is created to perform simulation analyses. The results of the mathematical model are compared with the results of the finite element simulation analysis under the same working conditions. It is found that the maximum relative errors of displacement and tension of the cantilever combination mechanism are 5.89% and 4.62% ，respectively. The rationality of the hypothesis and the accuracy of the mathematical model are checked. Finally, the on-line vibration monitor is installed on the ice melting system, and the ice melting system vibration displacement test is performed to further verify the accuracy of the mathematical model.

With the continuous development of China's electricity market and integrated energy system, the energy consumption patterns of industrial customers have become more and more complex. Therefore ， in the current market environment, the current energy consumption behavior profiling technology can no longer meet the current development needs. In view of the above problems, this paper investigates the characteristics of multiple users' energy consumption behavior and evaluation methods. Firstly, the evaluation system of energy consumption level is constructed from six aspects； electricity load level, low carbon indicators, electricity stability, electricity interaction ability and heat/cooling characteristics； secondly, an improved AHP-CRITIC algorithm is used to calculate the weights of each index and form a user energy use profile based on the comprehensive energy use index of different users. Finally, the proposed method is verified by selecting the energy use profiles of different types of industrial users.

The transmission tower-line systems are wind-sensitive structures, which can cause severe damage by wind-induced vibration. Therefore, it is necessary to apply control techniques to mitigate the damage. In this study, a novel SMA damper is used to control the wind-induced vibration of the transmission tower-line system. A finite element model of the system is developed using finite element software. Based on MATLAB software, a linear auto regressive filter method is adopted to simulate the time series samples of random fluctuating wind loads. According to the damping principle and working mode of the SMA damper, six different layout schemes are designed and their wind-induced vibration responses are analyzed respectively. The time series of the tower top acceleration and displacement under different schemes are obtained, and the wind loads with three different wind speeds are simulated to further analyze the damping effects under different schemes. A parameter analysis of the damper is conducted according to its structure and material, changing the spring stiffness, lead block thickness, and SMA wire material of the damper, and their effects are analyzed respectively. The results indicate that； among the schemes, arranging dampers on the tower head has the best effect on controlling the tower top displacement, and arranging dampers along the tower body has the best effect on controlling the tower top acceleration. The optimal damping effect is achieved when the spring stiffness is 500 N/mm, and the optimal damping effect is achieved when the lead block thickness is 7 mm.