The safe and efficient operation of lithium batteries depends on accurate state of charge （SOC） estimation. However，the traditional battery model and SOC estimation have poor robustness and reliability under noise interference. Aiming at the problem of SOC cooperative estimation under noise interference，firstly，the maximum available capacity and open circuit voltage （OCV） characteristics of the battery were analyzed，and the curve characteristics of lithium battery SOC—OCV were studied. Then，the problem of online model parameter identification and SOC estimation under noise interference was studied，and a two-swarm cooperative particle swarm optimization （TCPSO） method based on adaptive dynamic sliding window was proposed. Experimental results show that the maximum SOC estimation error of the proposed method is less than 1%，which shows that the proposed method can realize online parameter identification，and it is superior to the existing collaborative estimation methods in terms of anti-noise performance and SOC estimation accuracy.

Aiming at ultra-low frequency oscillation in power system caused by hydraulic turbine governing system，an additional damping control strategy for governing side was developed. Firstly，according to the damping torque method，the negative damping generated by the hydraulic turbine governing system was regarded as the main reason for the ultra-low frequency oscillation of the power system. Secondly，the damping torque coefficient expression of the speed regulation system was derived，which proves that the coefficient is closely related to the time constant of water hammer effect and the PID parameters of the governor. Besides，based on the additional damping control strategy，the positive damping compensation was introduced in the speed control side of the system. The grey wolf optimization（GWO） algorithm was applied to optimize the PID parameters to further improve the damping characteristics of the system. Finally，simulation verification in a single-machine system and a four-machine two-area system was executed through Matlab/Simulink. The results illustrate that the proposed control strategy can significantly enhance the damping characteristics of the speed control system and effectively suppress ultra-low frequency oscillation.

In view of the frequent occurrence of omissions and false alarms of partial discharge insulation defects in on-site gas insulated switchgear（GIS），the partial discharge multi-source detection test platform was built by using true GIS to carry out the intermittent discharge test of metal contamination defect on the surface of insulator. Different partial discharge detection methods were used to study the variation of intermittent discharge characteristics of different discharge degrees. The research results show that the discharge amount of metal contamination defect shows a trend of first increasing and then decreases with the prolongation of discharge time；the overall discharge time interval shows an increasing trend；ultrasonic detection method and chemical detection method cannot realize the effective perception of intermittent discharge of metal contamination defect；the distribution law of intermittent discharge can be preliminarily obtained from the 200 frequency period ultra high frequency（UHF）phase-resolved partial discharge（PRPD）spectrum composed of 4 groups of 50 frequency period UHF PRPD spectrum data；metal contamination defect in intermittent discharge state will not gradually evolve into breakdown discharge failures. The research results are of great significance for expanding the cognition of intermittent discharge characteristics and the field detection of GIS discharge defects.

The traditional active distribution network location and capacity determination ignores the multi-energy complementary coordination characteristics of the energy system，which led to high cost. Therefore，an active distribution network location and capacity determination method based on energy interconnection was proposed. On the basis of energy interconnection，the objective function was established，and the whole life cycle cost theory was used to comprehensively consider the equipment purchase cost，installation cost，operation and maintenance cost，system operation cost and salvage value recovery. Taking the distribution network location and capacity determination comprehensive cost in the form of probability as the objective function，the necessary constraint models were constructed，including equipment configuration capacity constraint，system power supply reliability constraint，power balance constraint and equipment operation constraint. On this basis，the improved artificial fish swarm algorithm was used to solve the location and capacity determination algorithm. The simulation results show that the cost of the location and capacity determination of the active distribution network with distributed power is lower than that without distributed power. The total cost of network loss and reactive power compensation calculated by the improved artificial fish swarm algorithm is lower. Compared with other methods，the method proposed has lower loss cost and reactive power compensation cost. It shows that the proposed method can reduce the cost of active distribution network location and capacity determination，and the practical effect is better.

With the large increase of load users，the load side adjustable resources gradually increase，and the load side demand response（DR） resources are used to participate in microgrid scheduling to improve the level of new energy consumption. In order to give full play to the scheduling potential of DR resources and optimize the user side load management capability， a multi-time scale optimal scheduling strategy for microgrids that takes into account scheduling priorities was proposed. Firstly，according to the response characteristics of different DR resources，the price-based demand response（PDR） resources and incentive-based demand response（IDR） resources were subdivided into five types，and a DR model was constructed to match the scheduling period. Secondly，the multi-times cale optimal scheduling model of "day-intra-day 1 h-intra-day 15 min" was constructed，optimized scheduling of various adjustable resources in the microgrid，and established priority weights for real-time adjustable resources that have a direct impact on users' electricity consumption behavior. Finally，taking an actual microgrid as an example in Fujian，the simulation verifies the validity of the model.

In order to effectively manage the grid short-circuit current overrun problem，optimization decision-making evaluation method of short-circuit current limitation scheme based on hybrid decision model considering asymmetric closeness was designed. Considering the relevant influence of the short-circuit current limiting measures of the power grid，a four-level evaluation index system considering short-circuit current，static safety，transient stability and implementation cost was established，eight three-level evaluation index factors were simplified and analyzed，and the decision evaluation results were divided further. An improved DEMATEL+ANP index weight assignment method for balancing the interaction relationship between indexes was proposed，and a hybrid decision-making model for the optimization decision evaluation of the short-circuit current limitation scheme of power grid was established by further considering asymmetric closeness，priority and cloud theory. Combined with simulation example based on PSASP，the effectiveness of the proposed optimization decision evaluation method was verified. This method can better balance the evaluation indexes，fully consider the fuzziness and randomness in the optimization decision evaluation，not only can realize the evaluation of multiple schemes，but also can realize the evaluation of its own scheme，and improve the accuracy and applicability of the optimization decision evaluation of the short-circuit current limit scheme of the power grid.

The secondary voltage signal output by electronic capacitive voltage transformer in the primary and secondary fusion equipment is very weak，which is easy to be interfered by high-order harmonics，resulting in unstable signal transmission. In order to solve these problems，a high-order and high-precision filter based on Sallen-Key was proposed to suppress harmonics and reduce the interference to the working signals. Firstly，the working principle of the transformer was analyzed. Then，based on the principle and the working frequency band of the primary and secondary fusion equipment，the integration circuit and filter circuit were studied and designed with Matlab/Simulink simulation software. Finally，the filtering circuit was optimized and the whole circuit was simulated. The results show that the optimized circuit can suppress the interference of high-order harmonics more effectively and ensure the stable output of fundamental wave.

Aiming at the problems of three-phase load imbalance，power quality degradation and harmonic dispersion in current electronic power distribution system，a comprehensive power quality control scheme with fast dynamic response and small output harmonic was proposed，which includes comprehensive control mode and compound repeat control strategy. By example analysis，it is found that harmonic content decreases before and after compensation in a specific subharmonic compensation mode. After the unbalanced grid compensation，the current distortion was eliminated and the voltage and current were in the same phase，which indicates the effectiveness of the comprehensive management. In the experimental verification，the continuous output of 25 kW inductive reactive power to 25 kW capacitive reactive power was realized，the requirements of reactive power regulation -100%~100% in the technical index was met，and the deviation between the output power and the command value was only 0.49%，the requirements of less than 3% in the technical index were met. In addition，the compensated three-phase grid current THD was reduced to 4.7%，after unbalance compensation treatment，the unbalance degree was reduced to 1.4%，which shows the effectiveness of the device in the treatment of three-phase load unbalance，power quality degradation and harmonic dispersion.

A quasi-resonant Flyback（QR-Flyback） converter with 65 W output was designed. The valley switching principle and the switching loss reduction mechanism of QR-Flyback were analyzed，the frequency and loss characteristics of the system under different working conditions were compared，and the advantages and disadvantages of frequency conversion control were summarized. Combined with the frequency hopping control function of the NCP1380 controller，the hardware circuit parameters of each part of the system were designed and the efficiency of the system was effectively improved. Finally，the feasibility of theoretical analysis and parameter design were verified by simulation and experiment.

There are many elderly people with limb disorder in China，and exercise rehabilitation technology is an effective means of rehabilitation treatment. However，the serious imbalance of doctor-patient ratio makes it difficult for everyone to enjoy rehabilitation medical services. Impedance control technology is used for the safe interaction between rehabilitation robot and human body. However，constant impedance control is used in the existing rehabilitation robots，which has weak environmental adaptability and is difficult to be applied in clinical practice. In view of the above problems，a variable impedance control method was proposed. The user's surface electromyography signal（sEMG） was collected as input，and his upper limb motion angle was trained and recognized by the improved random forest algorithm. With the end force sensor，the motion intention was obtained，and then the rehabilitation motion was completed by the variable impedance controller. The experimental platform was built，and the track tracking and rehabilitation training abilities were verified and evaluated. The results show that the designed controller could control the robot to complete rehabilitation movement.