A bidirectional isolated resonant converter with variable mode and wide voltage range was proposed. The proposed converter has the advantages of BOOST circuit and flyback current feed topology. By reusing the pre-storage and flyback energy feedback of the resonant inductor，it can improve the gain from the battery side to grid side and the power density of the converter，while also reducing the current circulation. The converter adopts fixed frequency pulse width modulation and has multiple working modes，which is suitable for wide range output. the working principle of the converter was first introduced and the output gain when the energy flows in different directions was analyzed. Finally，on the premise of meeting the charge and discharge of the battery in the home distributed energy storage system，the devices and control parameters were designed to verify the correctness of the theoretical analysis.

The power transmission and transformation system is an important link of power transmission. In order to reduce the cost of operation and maintenance and improve the recognition effect，an application method of automatic identification and control of transmission and transformation vulnerable lines was proposed based on artificial intelligence （AI）technology. Using the greedy decision tree algorithm （ID3）of AI to measure the amount of information between different operation characteristics of the line，it got the line characteristics，introduced mutual information feature selection （MIFS）to optimize the decision tree，balanced the redundancy between the line operation characteristics by using the adjustment coefficient and penalty term，and introduced the weighted degree，measured the node weight and focused on the total active power of all connecting lines. Based on the comprehensive analysis of the permittivity and weighted degree，the comprehensive automatic identification index of vulnerable lines was obtained，the identification model was established，and finally the power flow transmission and load change of transmission and transformation lines were changed to achieve control. The experiment shows that the proposed method can accurately identify the location of vulnerable lines，which is effective and feasible，and its control application also effectively reduces the operation and maintenance costs.

In the grid load control and planning of distribution network，in order to optimize the grid structure of distribution network，such as line loss，power supply quality and load，a grid load control and planning technology based on differential evolution algorithm was proposed. For all kinds of power generation devices in the distribution grid，the power grid planning model was established，the initial population was set and constructed，and the appropriate differential initial vector was selected for mutation processing. On the premise of forming a new individual under the difference increment，in order to improve the diversity of the population of future generations，the differential individual was cross trained by using cross factors to form a new distribution individual. Finally，the greedy selection model was used to evaluate and retain the offspring population，control the active power of controllable load and uncontrollable load，and complete the grid planning. The experimental results show that the load control and planning of distribution grid using differential evolution algorithm are better，the robust performance is superior，and the iteration speed is faster.

Aiming at the problem of large output voltage fluctuation and long recovery time of three-phase pulse-width modulation （PWM）rectifiers when the load changes，an improved single-neuron gradient learning control strategy was proposed. Due to the poor adaptability of the traditional PI controller parameters when the load changes，a single neuron PI control was adopted in the voltage outer loop，and the gradient descent method was used to adjust the weight parameters online. In order to avoid falling into a local optimal solution during the solution process，a stochastic gradient descent algorithm with restart function （SGDR）was used，and cosine annealing was used to change the learning rate of the weights to improve the convergence performance of the algorithm. Through Matlab and hardware-in-the-loop simulation experiments，the dynamic response performance of the voltage outer loop of the three-phase PWM rectifier under different control algorithms was compared and analyzed. The results show that the three-phase PWM rectifier controlled by the improved single neuron PI algorithm has smaller voltage fluctuation，faster dynamic response and more stable operating state when the load changes.

Electrically assisted manufacturing （EAM）is a promising and rapidly developing metal processing method.The power supply is a key sub-system for EAM，which needs to be designed properly.the model-based design of a low-voltage high-current pulse power supply used for EAM was proposed based on converter-level electro-thermal modeling.The thermal stress of key components was obtained by converter-level finite element simulations.A simplified thermal modeling method was proposed to reduce the computation burden of the finite element modeling（FEM） simulation to obtain the dynamic thermal profile under pulse current operation.The impact of the duration of the current pulse on the maximum temperature and temperature variations of MOSFETs was investigated based on the thermal model.A case study of a 10 V/500 A pulse power supply was presented to demonstrate the theoretical analyses and verification. The outcomes contribute to the design optimization and virtual prototyping of pulse power supplies for EAM applications.

The telecommunication power supply applied in 5G base stations can save energy consumption by reducing the output voltage when the equipment works in standby state. Nevertheless，frequent and rapid output voltage regulating of the converters is challenging. To solve this problem，the concept of partial power conversion was adopted in the design of power supply converters. A partial voltage regulating circuit was added at the output side of the converter，and fast output voltage regulating was realized with control of outer voltage loop，inner current loop，load current feedforward and output voltage feedforward loop. At the same time，higher energy conversion efficiency was guaranteed. A 1 kW DC/DC converter was built and verified the effectiveness of the proposed topology and control strategy.

DC high current comprehensive characteristic test device is used to detect the released characteristics of DC low-voltage electrical overcurrent protection electrical device，which is used in low-voltage electrical industry for DC products for long time delay，short time delay，instantaneous tripping test and short circuit test. With the wide application of DC low-voltage electrical products in non-ferrous metallurgy，chlor-alkali chemical industry，low-voltage power distribution，DC transmission and distribution，new energy and railway applications，the DC high current comprehensive characteristic test device used for DC electrical product testing needs to be traced regularly to ensure that it can meet the accuracy requirements of the test detection capability. In the field of measurement calibration，the present situation of relevant calibration methods was analyzed，and the research direction of calibration methods of this test device was reviewed. According to the corresponding product of the test device and the national standard，a new calibration parameter was proposed. Aiming at the calibration problem of the DC high-current device，the measurement method of optical fiber current sensor was proposed，so as to evaluate the uncertainty of the data generated.

With the rapid development of the society and economy and the accelerated construction of new power systems，flexible interconnection has gradually become an important technical means for upgrading the structure and enhancing the flexible regulation ability of distribution network. A power coordinated control strategy for engineering applications was proposed to address the power control requirements of multi-terminal flexible interconnection systems，including heavy-load limiting control for the rational power distribution when some feeder lines were heavy-loaded，and power balance control for power flow optimization distribution when all feeders were heavy-loaded. A flexible interconnection coordinated control device was developed based on the proposed strategy and applied to practical engineering. The case analysis based on the real load data and the measured data of the project verify that the proposed strategy can deal with different flexible interconnection scenarios with different load/power characteristics，effectively solve the problems of unbalanced feeder load and reverse PV power flow in the distribution network，and improve the power supply efficiency and security.

Considering that the problem of voltage fluctuations on the DC side caused by the three-phase imbalance of the AC grid of the flexible interconnection device，a DC voltage fluctuation suppression strategy for flexible interconnection device based on the Torricelli point was proposed. Firstly，by defining the Torricelli point of the triangle formed by the voltage vector in the three-phase unbalanced fault system as the "new neutral point"，the voltage amplitude asymmetry and phase angle drift faults in the traditional three-phase coordinate system were transformed into voltage amplitude faults in the Torricelli point coordinate system； secondly，the relationship between the active power oscillation of the three-phase power system and DC fluctuations was analyzed，a new control strategy was established to suppress the voltage fluctuations of the DC bus voltage by suppressing the fluctuation of double frequency component of active power effectively. Finally，the proposed method was proved to be effective by the Matlab/Simulink simulation model.

A dual active bridge （DAB） DC-DC converter voltage control strategy based on double-integral sliding mode control was proposed，which can obtain good control effect under the condition that the model accuracy requirements are low and the controller design process is simple. Firstly，the reduced-order model of the converter was established based on the single-phase shift modulation mode. Then，the output voltage controller of the converter was designed by using the double-integral sliding mode control theory. The design process introduced the time domain analysis method to analyze the sliding surface coefficients. Finally，simulation and experimental results show the effectiveness of the proposed control strategy.