Under the change of island operation conditions，the microgrid will cause that the digital twin（DT）model cannot accurately match the source domain model when migrating，which will lead to low migration efficiency and other problems.For this reason，an adaptive migration method of digital twins model under the scenario of micro grid island operation condition changes was proposed. By analyzing the operation characteristics of the microgrid under the island operation condition，the digital twin model was established，and the time-varying operation condition of the microgrid island was used to match the calculation source domain model. The adaptive migration of the digital twin model was realized by reducing the distribution difference of the source domain data under different island operation conditions of the microgrid. The experimental results show that some characteristic data such as current load and actual current have high migration effect and high migration efficiency，which verifies that the proposed migration method can adapt to different micro grid island operation conditions，and has good practicability.

At present，the traditional passive filter in on-board charger（OBC） has poor low-frequency performance，an active feedback loop was added to the traditional on-board charger passive filter，a design method of on-board charger electromagnetic interference（EMI） hybrid filter based on current sensing and current injection（CSCI） was proposed，and the structure，analysis and feedback loop design process of on-board charger hybrid filter were given.The experimental results show that compared with the existing on-board charger passive filter scheme，the new EMI filter scheme proposed has greatly improved the results of conduction test and radiation test.

Under the power grid dispatch mode of "source follows load"，different AC power supply modes are required in the market. To meet market demand，an uninterruptible power supply（UPS） system compatible with various AC power supply modes was designed. The modes of the system were selected by switching devices. According to the selected mode，different methods of driving control were carried out，and thus the compatibility of various AC power supply modes was realized. To improve the reliability of uninterruptible power supply，a fault-tolerant mechanism with compatible modes was also proposed. Finally，an experiment was conducted on a 40 kV·A/36 kW prototype. Experimental results demonstrate that the system can be compatible with various AC power supply modes，by which the correctness of the design was verified.

To address the need of carbon emission peak and carbon neutrality target on local energy systems，an optimal expansion planning method of heat pump was proposed for regional energy stations considering the benefits from ancillary services. The method was used to support the integration of new technologies such as heat pumps into existing local energy systems. Firstly，an integrated power，gas and heating system model was developed to reflect the interactions between different energy systems. On this basis，a bi-level expansion planning model that considers the benefits of grid ancillary services was proposed，taking into account the impact of factors such as energy cost，ancillary services price，existing energy storage capacity，and carbon emission cost on the planning results. Finally，a university campus energy supply station where heat pump replaces combined heat and power units was used as an example to analyze the effects of the above factors on the expansion planning results，validating the effectiveness of the proposed method.

In order to balance the output difference between renewable energy and load in the active distribution network and reduce the budget cost and user purchase cost，an optimal dispatching method of distributed generation units in the active distribution network based on power demand side response was proposed. On the premise of power demand side response，set the optimal dispatching priority of distributed generation units，combined with the objective function established with the total generation cost of active distribution network as the minimum objective，set the node voltage，power flow process，state of charge of energy storage system and power limit constraints of flexible load in all time periods of the active distribution network dispatching cycle，on this basis，the optimal dispatching model of active distribution network distributed generation units was constructed. Finally，the improved particle swarm optimization algorithm was used to solve the model and obtain the final optimized scheduling result. The experimental results show that the proposed method can effectively balance the difference in power generation output between renewable energy and load，which not only improves the absorption capacity of active distribution networks for renewable energy，but also reduces power generation budget expenses and user purchase costs.

In response to the complex working environment of pumped storage energy units，where disturbances such as temperature variations are prominent，and considering the insufficient control precision of traditional vector control for brushless doubly-fed machine（BDFM），a study was conducted on a control strategy based on linear active disturbance rejection control（ADRC）for power decoupling of BDFM.This strategy aims to mitigate disturbances，enhance control precision，improve operational characteristics，and consequently elevate the energy conversion efficiency within pumped storage energy systems.The mathematical model for BDFM in the unified coordinate system and two-phase rotating coordinate system was established.The coordinate system was determined using the power winding orientation method.The current relationship under the power winding orientation was derived，and based on this，the control winding was used to control the active and reactive power of the power winding，thereby achieving power decoupling control.To improve control performance，the speed loop and current loop were rewritten，disturbances were analyzed，state equations were formulated，an extended state observer was designed，and the control performance of the machine was enhanced using the active disturbance rejection control technique.Based on the analysis of harmonics，it is concluded that the main harmonic in the synchronous coordinate system is the 6th harmonic.To suppress specific frequency harmonics，the repetitive controller was employed.Through Simulink simulation，dynamic responses and Fourier analysis of the d-axis winding current were observed，confirming the effectiveness of the proposed active disturbance rejection power decoupling control method and harmonic suppression method.

In order to optimize the current stress of dual active bridge（DAB）converter，an improved dual phase shift （IDPS）modulation was proposed based on the traditional dual phase shift （DPS）modulation. Firstly，the working principle of IDPS modulation was introduced，its steady-state working characteristics were analyzed，and the mathematical model of current stress on transmission power was established. Then，the optimal value of current stress of IDPS modulation was obtained by using Lagrange multiplier method，and compared with traditional single phase shift（SPS） and DPS modulation methods. Finally，an experimental platform was built to verify the effectiveness of the proposed control strategy in optimizing current stress，meanwhile，the efficiency of the converter was improved.

Under digital control，the inner current loop of the LC-type inverter is affected by the control delay，which leads to the weakening of its active damping effect. Increasing the sampling control frequency can effectively reduce the negative influence of digital control delay. Furthermore，in order to suppress the high order harmonic disturbance caused by strongly nonlinear load，multiple resonant controllers are needed in the outer voltage loop. For reducing the time complexity of the outer voltage loop and increasing the quantity of the controlled harmonics，an optimal sampling digital control strategy was proposed for the current and voltage double loop control of the LC-type inverter. Specifically，the inner current loop was set to the double sampling control frequency and the outer voltage loop was set to the single sampling control frequency. The optimal sampling digital control strategy enhance the suppression ability of nonlinear load disturbance and reduce the total harmonic distortion of the output voltage while maintaining the stability margin of the inner current loop. Finally，the feasibility and effectiveness of the proposed optimal sampling digital control strategy were verified by experiments.

When the permanent magnet assisted synchronous reluctance motor（PMaSynRM）runs at high-speed with flux-weakening control，the DC bus voltage utilization is not high，and the efficiency and torque output capacity of the motor are low. Therefore，a flux-weakening control strategy of permanent magnet assisted synchronous reluctance motor based on hexagonal trajectory was proposed. Firstly，based on the d-q axis equivalent circuit of the permanent magnet assisted synchronous reluctance motor，the voltage and current constraints of the flux-weakening process were derived，and the root cause of the flux-weakening control to improve the speed regulation ability of the motor was proved. Secondly，in order to give full play to the advantages of high-power density under high-speed operation of permanent magnet assisted synchronous reluctance motor，the over-modulation algorithm was derived. It was applied to the flux-weakening operation of permanent magnet assisted synchronous reluctance motor to achieve higher DC bus voltage utilization. Finally，the effectiveness of the proposed method was verified by simulation.

The energy flow analysis method with both high precision and high computational efficiency is a basic tool to simulate the operation and analyze the interaction between the thermal and electric coupling systems. The traditional iterative numerical method is slow in computation，poor in computability for large-scale problems，and can only obtain the value of the state variable in discrete time series. Moreover，the traditional numerical method to solve electric power flow is not compatible with that to solve the dynamic flow of the heat network，so the alternating iterative solution is often adopted in the dynamic energy flow analysis，which makes the error spread in the iterative process. To solve the above problems，a dynamic energy flow analysis method was proposed based on holomorphic embedding for integrated electricity and heating systems. Through recursive calculation，the continuous analytic function of system state variable with respect to time was obtained. In the calculation process，the solution of electric power system and heating system was obtained jointly. The simulation results show that the maximum error between the algorithm and the Matlab solver is less than 3%，and the calculation speed is increased by more than 30%. Moreover，the algorithm can calculate the system state at any time in the dynamic process according to the holomorphic function.