In order to overcome the problems of voltage fluctuation and network loss increase caused by random output fluctuation of photovoltaic and wind turbine equipment and load fluctuation in distribution network, it brings challenges to online reactive power optimization of distribution network. In this paper, a reactive power optimization strategy of MADDPG algorithm based on multi-agent deep reinforcement learning is designed. Compared with the traditional algorithm, this method does not need accurate power flow modeling, nor does it rely on the data prediction of day ahead load and distributed generation. The reactive power optimization problem is solved by centralized training and decentralized execution. MADDPG regards every agent as an actor. In the process of training, each actor can use a critical to train. The proposed strategy uses deep neural network to fit the action functions of switchable capacitors, voltage regulators and distributed generation inverters, and completes the training of deep neural network in the interaction process with the distribution network environment. Finally, an example is given to verify the effectiveness of MADDPG algorithm.

With the development of electric vehicles, lithium-ion batteries have been widely used. And the safety of lithium-ion batteries is the basis of the development of electric vehicles. A comprehensive review of the research on thermal runaway of lithium-ion batteries is conducted in the paper. Firstly, this paper outlines the thermal runaway of the battery under different kinds of causes. The internal short circuit and overcharge of the battery are the two major causes of thermal runaway. Meanwhile, this paper focuses on the entire thermal runaway process of the battery, including the thermal runaway mechanism of the single-cell and the propagation of thermal runaway within the battery. On this basis, this paper summarizes the way to improve the safety of lithium-ion batteries from three aspects. They are improving the temperature characteristics of battery materials, enhancing the heat dissipation capacity of the battery cooling system, and optimizing online detection, diagnosis, and prediction of battery thermal management systems. Finally, this paper summarizes the shortcomings of existing battery safety research and future research directions, aiming to provide a reference for future battery safety research.

As an intrinsic attribute of materials, activation energy can directly reflect the physicochemical characteristics of insulation aging and degradation, which presents a feasible technological route as to realize effective assessment of insulation aging, and has been a research focus among the academia and industrial sectors. In this paper three definitions plus their evolution regarding activation energy are briefly reviewed, and the physical connotation of activation energy is elucidated based on the collision theory and the activation complex theory. The methodologies to obtain activation energy of insulating materials are introduced, including the thermal analysis kinetics-based ones as well as the thermo-frequency dielectric spectroscopy scheme, moreover, significant impact of the reaction mechanism function on residual lifetime prediction is also discussed. The progressing scenario of activation energy-based applications in evaluating insulation aging and residual lifetime is summarized, and finally, several key issues of scientific and technological significance are proposed and highlighted for future studies to facilitate activation energy-based insulating assessment.

Taking two-stage grid-connected photovoltaic inverter with former stage being Boost and backward stage being full bridge inverter for example, its power losses calculation method was studied．The formula for losses calculation was derived．It shows that the losses of two-stage grid-connected photovoltaic inverter have close relationship with its middle bus voltage．Different middle bus voltage impacts the losses of switch devices，diodes and inductors, and the inverter efficiency ultimately. Based on the losses formula, the specific loss values of each device are calculated in detail. Then a method of three loop control strategy with MPPT (maximum power point tracking) in former stage and MEPT (maximum efficiency point tracking) in backward stage was proposed to search the maximum power point and efficiency point. The experiment results verified the feasibility and validity of proposed loss analysis model and MEPT control strategy.

Frequent flood disasters will lead to large-scale power outages in the distribution networks, and an effective resilience assessment system can help operation and maintenance personnel accurately predict and deal with distribution network failures caused by flood disasters and reduce economic loss. This paper first proposes a three-dimensional resilience evaluation index system, which contains 12 single indexes of state, architecture and time dimension, and can reflect the influence of rainstorm amount, distributed generation configuration, and number of operation of reconfiguration switch on the resilience evaluation of the distribution network. Then the fuzzy analytic hierarchy process(FAHP) and fuzzy membership function are used to comprehensively evaluate the resilience of the distribution network, and identify the weak links in the distribution network’s planning, operation and dispatching. Finally, a case study of Yubei district in Chongqing is carried out to verify the validity and rationality of the proposed resilience evaluation system.

A comprehensive review for isolated bidirectional DC-DC converter is presented in this paper. The research background of energy storage system and its requirement for high frequency and high power density isolated bidirectional DC-DC converter are introduced. Research progress of analysis method and control technology for CLLC and DAB converter are reviewed. This paper points out that both CLLC and DAB converter meet the requirement of future large scale energy storage system. At present, DAB converter is merging to its mature stage while CLLC converter needs to be further researched. However, CLLC converter has advantages over DAB converter in small and medium capacity applications. It still has a wide application prospects.

With a large number of electric vehicle (EV) charging interfaces connected to the grid, the stable operation of the power system is challenged. Load-side virtual synchronous machine (LVSM) technology emerged at the historic moment, which can provide inertia and damping support for the power system and help to improve the stability of the power grid. In the interconnection system of the power grid simulated by the virtual synchronous generator (VSG), the front-stage LVSM and the rear-stage EV battery charging converter, a charging and discharging strategy and implementation method for EV batteries that adapts to changes in grid frequency under three modes of constant current charging, constant voltage charging and constant current discharge are proposed in this paper. The grid frequency stability is improved through grid-load interaction. The effectiveness and correctness of the proposed control strategy and implementation method are verified by the simulation results.

The phase field method provides an effective analysis tool for the microstructure evolution process of composite materials in the mesoscale range, filling in the blank between the atomic scale microscopic simulation and the macroscopic scale simulation. This paper first summarized the theoretical basis of the phase field model, including the principle of order parameter selection, the construction of free energy functionals and the method of solving phase field dynamics equations. Then, we reviewed the application progress of the phase field simulation method in the intrinsic structure-activity relationship, breakdown evolution mechanism, and material structure design of composite insulating material. Several key issues need to be studied in-depth in the phase field simulation are generalized. The analysis points out that phase field simulation can provide basic methodology and semi-quantitative analytical means for the study of dielectric behavior of composite insulating materials, but up to now the phase field simulation method still lacks a unified simulation framework covering different modeling scales.

In view of the difficult industrial application of repetitive controller to inverter, this paper studies the repetitive controller design and the software implementation of repetitive controller. The notch filter, the low pass filter and phase lead compensator are designed respectively to meet the requirement of the inverter stability and the steady error. In this paper, an inverter repetitive controller system is built based on TMS320F28335 chip. And the software implementation of all parts of repetitive controller is elaborated. A series of experiments about the inverter repetitive control system verify the effectiveness of the proposed strategy.

Dry-type transformers are more widely used in power grids in low-voltage distribution networks, but the correlation between the intrinsic properties of the main insulation materials of dry-type transformers and the degree of aging is still not clear. The activation energy is the energy barrier that the microscopic motion unit in the dielectric overcomes during the movement, and is the microscopic intrinsic reflection of the aging state of the insulation material. In order to study the relationship between the activation energy of epoxy resin for dry-type transformers and other characteristic characterization parameters and the degree of heat aging, the epoxy resin samples for dry-type transformers are subjected to heat aging at different temperatures to measure dielectric spectrum and electrical strength of the samples. The results show that with the increase of aging time, the interfacial polarization relaxation activation energy of the sample shows a decreasing-increasing-slightly decreasing-final increasing trend due to the increase of polar groups and free radicals during aging. And reduction will deepen or reduce the depth of the trap. As the aging time increases, the relative dielectric constant and dielectric loss factor of the sample show a decreasing-increasing-slightly decreasing-final increase trend, and at the same aging time in the late aging period, the higher the temperature, the higher the relative dielectric constant and the higher the dielectric loss factor, and the breakdown field strength shows an increase-decrease-slightly increase and final decrease trend as the aging time increases. As for the dielectric parameters and electric parameters, the higher the temperature, the more severe the aging of the sample. In this paper, it is found that the activation energy, relative dielectric constant, dielectric loss factor and breakdown field strength have certain correlation with the aging time, and the relationship between the slow chemical reaction and the relaxation activation energy is established.

To study the efficient control strategy of Battery Energy Storage System (BESS) participating in the primary frequency regulation of the power grid, based on the analysis of the power system frequency modulation demand and the consideration of the state of charge (SOC) of the energy storage battery, this paper proposes a comprehensive primary frequency modulation control strategy that takes into account the grid frequency modulation demand and the SOC state of the energy storage battery, and the droop coefficient self-adaptive optimization and equalization control method are given under different states of charge. The battery can participate in the adaptive adjustment and state balance of the primary frequency modulation. Based on the regional power grid frequency modulation simulation model with energy storage batteries, the proposed control method is simulated and analyzed under step disturbance and continuous disturbance. The results show that the studied control strategy has advantages in both power system frequency adjustment and battery SOC maintenance.

LCL filters are widely used in grid-connected inverters. However, the injected grid current control does not solve the problem of current harmonics and low bandwidth caused by the LCL resonance peak. The paper proposes an AD control method for LCL inverters, which is only based on the feedback of the grid current. The feedback loop uses the first-order HPF plus the first-order LPF for frequency selection, thereby suppressing the resonance peak. Due to the widening of the bandwidth of the feedback loop, this method is suitable for the resonance frequency shift phenomenon caused by the impedance of the grid. The paper also uses a harmonic compensation control strategy with damping, and analyzes the influence of this strategy on the performance of the inverter. The results show that it can effectively suppress low-frequency harmonics and improve the stability of the system under the impedance change environment. The effectiveness of the proposed control and design has been verified by MATLAB/Simulink simulation and 2kW experimental platform.

High magnetic field plays an extremely important role in developing science and technology, gestates many significant scientific discoveries and emergences of new technologies. The generation and application of extremely high magnetic field are of great significance to extreme condition scientific facilities, biomedical engineering, and special equipment for national defense, high-precision scientific instruments and agricultural applications. Currently, many research institutes and laboratories carry out high-field superconducting magnets based on high temperature superconductors. Focusing on several research institutes and laboratories in the field of high-field superconducting magnet, this paper mainly presents their researches on high-field superconducting magnet technologies, including design schemes, technical features and latest research progress, and briefly introduces the main applications of high-field superconducting magnets.

The reliability of IGBT power module is a hot topic today, and the failure of its bonding wire is the main cause of its failure. The occurrence of the fault will cause the module to change the characteristic parameters, such as the module’s gate voltage Miller platform and the gate threshold voltage in the onoff process. The different faults of bonding wire failure are simulated by experiments, and the change of gate voltage Miller platform and threshold voltage with the severeness of the fault is analyzed. The result provides a reliable reference for the IGBT working monitoring technology.

Fast-saturation current transformer energy extraction is the main method to solve the power supply problem of intelligent circuit breaker under the condition of short circuit and voltage loss in power grid. This paper analyzes and studies the working characteristics and saturation mechanism of fast-saturation current transformer, and establishes the equivalent circuit model of current transformer energy extraction. The concept of current transformer iron core saturation is proposed, and the relationship between current transformer output power and iron core saturation is deeply studied. Through simulation research, the correctness of theoretical deduction is verified. On this basis, the design steps of the fast-saturation current transformer are put forward, including the selection of iron core working saturation, the effective magnetic conduction cross-sectional area of the iron core and the design method of secondary winding turns. The energy extraction circuit of fast-saturation current transformer is built, and the feasibility of the design method is verified by experiments.

In this paper, an improved common-mode voltages(CMV) reduction PWM strategy, called AZPWM-w strategy, which directly allocates the action time of nonzero voltage vector by parameter w, is proposed. The principle of determining the value of w is as follows: firstly, that the action time of each nonzero vector is longer than the dead time is ensured; secondly, based on the output waveform performance index HDF, the parameter w is optimized.The simulation and experimental results show that the proposed strategy can solve the dead-time peak problem in the range of full modulation ratio, and the harmonic performance is better compared with other improved strategies.

Energy storage is important for promoting the renewable energy consumption and improving the grid resilience. Cost of energy storage system is a key factor to determine whether the energy storage technology can be industrialized or not. In this paper, energy storage cost per kilowatthour and per mileage were calculated for capacitytype and powertype energy storage applications individually, based on the data from industrial research and life cycle cost analysis. Results show that the cost per kilowatthour of current electrochemical energy storage is about 0.6～0.9CNY, and there is still a gap from the target cost per kilowatthour of 0.3～0.4CNY for large scale applications. Hence, ‘low cost, long life, high safety and easy recycling’ should be regarded as the development target of energy storage technology. Research on innovative technologies and products should be emphasized on the basis of comprehensive consideration of system manufacturing, system life, safety and recycling. The energy storage cost analysis of this paper will help to build a marketoriented green energy storage technology innovation system.

Prior load identification methods have encountered a challenge in improving identification accuracy and being deployed. For example, the identification accuracy of traditional classical methods is relatively low, and advanced deep learning methods are difficult to deploy on embedded devices due to their complex models. In this paper, a novel load identification method based on high-frequency samples is proposed. The fast Fourier transform and Hilbert transform are applied to extract the features of samples both in time and frequency domain. Then, based on extreme learning machine, a feature fusion learning scheme is proposed to obtain mapping relationship between extracted features and load types. Furthermore, a window adjustment method is designed to obtain the optimal model and the most proper sampling length. In experiment, the proposed method is evaluated on two high-frequency public datasets, BLUED and PLAID. Based on the experiment results, it can be proved that the proposed method has a faster speed, better performance, and easier to be deployed on embedded devices to the previous.

Conventional LED driver is based on the electrolytic capacitor two-stage topology, which has characteristics of low efficiency and short lifetime. In order to extend the lifetime of drivers, pulsating current can be used to eliminate the electrolytic capacitor, however, this method will cause LED flicker. Thus a electrolytic-less LED driver is proposed, are the driver integrates a modified bridgeless PFC with a half-bridge LLC resonant converter into a single-stage conversion circuit, and a bidirectional boost-buck converter is utilized to solve LED flicker problem. The driver features high circuit efficiency and high power factor. Finally, a 144W prototype is fabricated and tested in the lab, with the highest efficiency up to 93.4% and the experimental results demonstrate the functionalities of the proposed LED driver.

Supercapacitor is a new type of energy storage device developed in recent decades, with the characteristics of high power density, long life and good low-temperature performance, and has been widely applied in electric power, transportation, industry and other fields. This paper introduces the types and basic principles of supercapacitors, as well as the development and market status of supercapacitor industry in recent years. Then, the main application fields and current situation of supercapacitor in China are reviewed. In the end, the relative suggestions focusing on the main defect of supercapacitor, low energy density, is proposed.

An LCC-LCC/S configurable compensation network based wireless power transfer (WPT) charging system for the electric vehicle battery is studied in this paper. The primary and secondary compensation network topology of loosely coupled transformer can be shifted from constant current-constant current (CC-CC) structure to constant current-constant voltage (CC-CV) structure by topologies switching according to battery management system to achieve CC or CV output characteristic under variable load. Furthermore, a current direction based control strategy is proposed, which can reduce the hard-switch voltage stresses on the bidirectional semiconductor switches. Specifically, the switching order in mode transition is optimized to suppress the transient voltage spikes. Finally, an 1 kW experimental prototype is built with a 400 V input and a battery-charging simulating resistor load. A CC output of 10 A and a CV output of 105 V are realized against time-variable load. The current or voltage fluctuation is tested to be small and the voltage spiker during the mode transition process is ignorable. The zero voltage switch of the inverter is realized. Experimental results verify the effectiveness and feasibility of the proposed solution.

In this paper, on the base of the future development of clean and low-carbon energy, the concept and connotation of underground energy storage engineering (UESE) was proposed and expounded, and then a review was presented for the research and development of underground pumped energy storage, underground compressed air energy storage, underground gravity energy storage and underground heat storage. Besides, we also suggested a series of comprehensive implementation schemes of underground energy storage engineering. Through the analysis, the significance and application prospect of the underground energy storage project for the transformation and development of clean and low-carbon energy in China are explained. On this basis, suggestion on the implementation of a R&D project for underground energy storage engineering is put forward, too.

In the island microgrid, using the VSG control strategy to control the inverter can effectively increase the inertia and damping of the system and improve the stability of the island microgrid system. When multiple VSGs are operated in parallel, the reactive power cannot be accurately distributed by the drooping coefficient. Aiming at this problem, this paper proposes a voltage compensation strategy based on distributed quadratic controller. The distributed secondary controller obtains the reactive power value of each VSG, adaptively adjusts the VSG stator reactance value according to the required reactive power, and indirectly controls the actual value of the reactive power output of the inverter to achieve the goal of accurate reactive power distribution. This control strategy does not require line impedance information and is robust in the event of network communication failure，and in practical applications, the bandwidth requirement for the communication network can be reduced. At the same time, the matching method of VSG parameters in parallel operation is given. Finally, three VSG parallel simulation models are built in Matlab/Simulink. The simulation results verify the effectiveness and feasibility of the proposed control strategy.

Since MAGLEV train has many advantages,many countries are busy in its study. The schemes of Germany,Japan are mature by far, and there are several typical schemes in America and some other countries. It is worthful to study these typical schemes.We can use these schemes for reference in development of ourMAGLEV. The article presents the three schemes of the high speedMAGLEV trains ofGermany, Japan and America, and the detailed comparison of the three schemes is given.We can see that the scheme of Germany is the mature one.

Aiming at the problem that the traditional thermal equivalent circuit model has large error in calculating the junction temperature of IGBT module, an equivalent thermal impedance model of IGBT module based on heat transfer research is proposed. By studying the heat transfer inside IGBT module, the heat spreading angle is determined according to the law of heat flux variation. Thermal network parameters are calculated and an improved equivalent circuit model of single chip Cauer network is established. Then, considering the thermal coupling effect between multi-chips, the self-heating thermal impedance and coupling thermal impedance are calculated and the thermal impedance matrix of IGBT module is established. The junction temperature of each chip can be predicted by using the linear superposition principle. Finally, the junction temperature calculated by the equivalent thermal impedance model is compared with the finite element simulation value, which verifies the effectiveness and accuracy of the model.

This paper briefly describes the characteristics of big data in power industry, introduces the collection, storage, processing, analysis and application of power data, then summarizes the latest research of big data in power industry from the four segments, i.e. power generation, power transmission, power distribution and power consumption, then illustrates several successful application projects. Finally the paper points out the challenges faced by the applications of big data analytic in power industry.

Aiming at the methaneair mixtures at room temperature and one bar pressure, the breakdown tests in 500μm～5mm range of clearance have been performed to study the effect of gas dielectric on the breakdown of short circuit discharge with the IEC safety spark test apparatus (IECSSTA). The experimental results show that the relationship between the breakdown voltage and gap distance fits to the typical gasbreakdown chart with changing the methaneair mixtures. For 85% methaneair mixtures, the lowest voltage is about 300v which is far larger than the operation voltage of the test circuits with IECSSTA. It is also shown that the discharge process does not belong to the category of gas discharge, and the effect of gas dielectric on the breakdown of the gap can be ignored. It is pointed out that the discharge process can be categorized into vacuum discharge rather than gas discharge, and the dominant breakdown mechanism of the discharge is the cathode electron emission. Short circuit discharge experiments of capacitive circuit in different media environment with the IECSSTA are performed, The experiment results are in good agreement with the analysis showing the feasibility of the proposed methods.

Since the 21st century，the wireless power transmission technology has entered a rapid development stage，and the related theoretical research，innovative experiments and application promotion have made great progress. With the proposal and construction of global energy interconnection，related technologies will have greater development potential and application value in the future. The paper firstly describes the birth and development of wireless power transmission. Secondly，the key research developments of inductive power transmission，capacitive power transmission，microwave power transmission，laser power transmission and ultrasonic power transmission technologies at home and abroad in the past 20 years are highlighted. Thirdly，the six major fields of electrical power system，transportation，aerospace，underwater detection，smart home and medical devices are summarized and prospected. Fourthly，specific application scenarios are discussed for different wireless power transmission technologies. Finally，the main technical challenges of different wireless power transmission technologies are discussed.

As a new intelligent power transmission equipment, power electronic transformer (PET) shows great value in the smart grid and energy Internet applications. In this paper, typical PET topologies and related control strategies are analyzed in view of medium and high voltage application. The characteristics of various topologies in terms of system efficiency, reliability and control complexity are summarized. The three-stage PET with multi-module cascade converter in the high voltage side is easy to expand, and the control is simple, but still there is room for optimization in system volume and efficiency. In this paper, two different types of converters in the isolation stage are summarized and contrasted, and the adaptability of the two different converters in medium and high voltage applications is analyzed.

This paper reviews the research status of energy storage technology for the new energy power system which contains wind power. Firstly, the great significance of energy storage technology for power system containing a high proportion of wind power is discussed. Secondly, the present research progress of various energy storage technologies are systematically compared. On one hand, the paper described the theory of various energy storage technologies and analyzed the characteristics of energy storage technologies. On the other hand, it also summarized the advantages, problem and application range of various energy storage technologies. Thirdly, it adopted a new method that coordinates a variety of energy storage technologies for new energy power system and combines energy storage technology with large capacity and quick response. Lastly, it pointed out that optimal allocation of energy storage in the new energy power system has become a subject which needs further research.

There is a strong relationship between carrier lifetime of Integrated Gate Commutated Thyristor (IGCT) physical model and dynamic or static characteristics. The existing turn-off current-tail based parameter extraction method of carrier lifetime assumes that the deceasing of current-tail mainly depends on the carrier recombination in N-base neglecting the extraction of electron from anode, therefore there is a limitation when applying to IGCT in which the extraction of electron from anode is enhanced by using transparent anode structure. In this paper, based on doping concentration dependent carrier lifetime model and Shockley-Read-Hall (SRH) recombination model, the coupled relation between carrier lifetimes in different regions is analyzed; the distribution characteristics of minority carrier and its current are discussed and analyzed by taking the PN junction near anode side as a short diode considering that the thickness of transparent anode is much less than the minority carrier diffusion length; then an improved method of carrier lifetime extraction is proposed. At last, the parameters of carrier lifetime in different region are derived from experiment as the effective carrier lifetime varying with the applied voltage; and good agreement between the experimental data and simulation results of double-pulse show the correctness of the proposed method of parameters extraction.

As one of the key technologies and bottlenecks for development and application of DC distribution network, the protection technology is still in its infancy, lack of practical experience and standards. This paper first overviews the topology structure, grounding mode, fault type and transient characteristics of the DC distribution network, which are closely related to the protection scheme design. Then, the fault identification technology of DC distribution network is summarized, and the main principles and characteristics of each type of method are analyzed. It is considered that with the development of smart distribution network, the communication-based protection technology has certain advantages. Finally, the existing fault location methods of DC distribution network are classified, and the basic principles of various location methods are illustrated. In addition, this paper summarizes the shortcomings of various fault location methods and gives possible improvements.

Wave energy power generation is an effective means of utilizing clean and renewable marine energy. Because of the instability and dispersion of wave energy, the energy conversion efficiency of wave power generation system is low, which restricts the development of wave power generation technology. Therefore, it is necessary to adopt a certain power control method to make full use of wave resources and improve wave energy conversion efficiency in wave power generation system. In this paper, the power control theory of wave power generation, amplitude-phase control and complex conjugate control, is briefly introduced. Various power control methods proposed at home and abroad in recent years are classified and analyzed. The development trend of power control research is expounded. Wave prediction and intelligent control are the research hotspots in the future, considering the large scale in the future. It is necessary to study the multi-objective optimal control problem of combining power control objectives with other control objectives for grid-connected array wave power generation devices.

Power electronic transformer (PET) is a kind of power transmission equipment combined by power electronic converters and high-frequency transformer, which has great application value in the building of Strong Smart Grid. Hot PET topologies applied to distribution system are classified and their implementations are analyzed and compared in this paper. It has been indicated that PET has great advantages in reducing its own size and weight, and power quality regulation, compared with traditional transformer. Especially for the three-stage topologies with DC link, their good controllability can make power electronic transformer achieve more functionality and also provide a channel for the integration of distributed power generation systems, which is the future development direction of PET. Finally, several key issues in practical application of PET are proposed.

The models of wind speed distribution are the important mathematic bases applying to wind resource assessment, planning and building of wind farms, and also for the reliability evaluation of power systems. Firstly, this paper reviews some models of medium-and-long-term wind speed distribution, such as Gamma distribution, Log-normal distribution, Rayleigh distribution, Weibull distribution and Burr distribution. Secondly, on the base of the Weibull distribution, kinds of parameter estimated methods are introduced. Thirdly, the characteristics of various distribution models and estimated algorithms are compared respectively. At the end of this paper the prospects of this research area are put forward.

The battery management system（BMS）is an important part of the electric vehicle energy management. It provides important parameters of the vehicle control strategy. However, BMS works in an complex electromagnetic environment of the electric vehicle, so improving the anti-electromagnetic interference performance of the BMS is extremely essential to guarantee the safe and reliable operation of the vehicle. Based on hybrid electric vehicle（HEV）platform of Changan Automobile Co., Ltd, the electromagnetic environment of HEV and its coupling mechanism to BMS are researched. By the EMC optimization design the anti-electromagnetic interference performance of the BMS is enhanced. Results show that the optimized BMS can be good adaptation in electric vehicle complex electromagnetic environment.

Energy storage technology can improve the quality of electric energy and promote the consumption of new energy. The promotion of energy storage technology is of great significance for accelerating the development of new energy industry. And the cost of energy storage systems determines the large-scale application and promotion of energy storage technology. To calculate the full life cycle cost per kilowatt hour, the investment cost, maintenance cost, replacement cost, charging cost and recovery cost of the energy storage system are respectively analyzed. The calculation method provides a reference for the cost evaluation of the energy storage system. This paper analyzes the key factors that affect the life cycle cost per kilowatt-hour of electrochemical energy storage and pumped storage, and proposes effective measures and countermeasures to reduce the cost per kilowatt-hour. Considering the actual situation of energy storage technology in application, we look forward to the prospects and development of energy storage technologies in the future.

Load identification is one of the important tasks of non-intrusive load monitoring(NILM). Considering the cost of deployment, load identification algorithms need to run on devices with limited computing power and memory. This paper proposes an identification method based on event detection and Convolutional Neural Network(CNN). The method is implemented on an embedded device based on STM32 MCU. Sliding Window with Margins method and Hotelling T2 test are used for event detection. Then the detected events are identified by the CNN models. The trained CNN models have to be compressed and then deployed to the embedded device. The performance of the overall algorithm is tested on the Blued dataset and satisfied results are obtained.

The process of big data for power grid requires the support of big data technology. The topics such as how to store the big data for power grid and how to mining out valuable information to promote the development of the grid are very hot currently. In this paper, both data storage and data retrieval function of the graph database Neo4j are introduced in detail firstly. Secondly, a method to build panoramic database based on Neo4j is proposed, which can integrate the scattered and isolated data in power grid with large-scale orderly according to the device mapping table based on power network topology. Furthermore, with the help of graph theory algorithm packaged in Neo4j, clustering methods for analysis of big data in power grid can be put forward. Finally, two real power grids are analyzed based on Neo4j, while the performance of information retrieval and data clustering analysis with Neo4j is tested as well.

Aiming at the phenomenon of the DC voltage imbalance for the cascade H-Bridge shunt active power filter(SAPF)，in order to stabilize the DC voltage，balance the DC voltage among phases and balance the DC voltage of each unit，this paper presents a three-stage balance strategy of DC voltage based on phase disposition-switching frequency optimal-PWM(PD-SFO-PWM)．When the DC voltage imbalance occurs，the strategy plays the role of regulating．Compared with the traditional balance strategy，because the modulation strategy has both the modulation function and the function of balancing the DC voltage of each unit，it avoids to design the extra strategy of balancing the DC voltage of each unit, which greatly reduces the complexity of the balance strategy．Finally，this paper conducted the simulation of seven-level SAPF and verified the feasibility of the balance strategy．In a short period of time，the balance strategy can achieve a balance effect and ensure the stability of SAPF with a smaller overshoot．