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.

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.

The integrated energy system contains adjustable resources and flexible operating modes，which to a certain extent play a supporting role in the power grid and assist in optimizing its operation. Based on this，an optimal operation model of integrated energy system considering support capacity to power grid was proposed. Firstly，the electric-heat integrated energy system（EHIES）was considered as the research object and the EHIES model was established. Secondly，considering the expected support demand of external power grid and aiming at meeting the expected support demand of external power grid，the optimal operation model of EHIES was established. Considering the complexity of the model，the Bacterial Colony Chemotaxis optimization algorithm was used to solve it. Finally，an integrated energy system in northern China was considered as an example and the effectiveness of the proposed model was verified. By adjusting the flexible operation of the EHIES，it can effectively meet the expected support needs of the external power grid and play an external support role.

In order to solve the problems of high subjective misjudgment rate and low efficiency in manual hand touch and auscultation methods for acoustic quality detection of micro motors，while taking into account the accuracy of detection results and the fast construction of detection models，a small sample machine learning detection method was proposed. Based on the physical model of micro motor transmission chain，multi-dimensional acoustic fault features were extracted，particle swarm optimization was used to optimize the core parameters of support vector machine，a small sample learning method，so as to improve the accuracy of model discrimination.The experimental results show that this method can effectively distinguish abnormal vibration and sound of micro motors，with an accuracy rate of over 95%.

Permanent magnet synchronous machines（PMSM）has serious chattering problem when traditional sliding mode observer（SMO）is applied to low-speed operation with fixed sliding mode gain. To solve this problem，a full-order sliding mode observer（FSMO）with fuzzy adaptive adjustment of sliding mode gain was proposed，which can improve the chattering suppression performance in a wide speed range. First，a FSMO was constructed with stator current and extended back-EMF as observation objects. In addition，the fuzzy control rules were constructed by using the error and error change-rate of the actual and observed values of the stator current as the input，and the adaptive adjustment of the sliding mode gain was realized according to the different speed of the motor. Then，the soft switching continuous sliding mode control was realized by using hyperbolic tangent function instead of traditional sign function. Moreover，in order to eliminate the influence of variable speed，the normalized orthogonal phase-locked loop was used to obtain the accurate rotor position from the extended back-EMF. Finally，the PMSM drive test platform was built，and the performance of low speed and medium-high speed was tested. The experimental results show that the proposed algorithm has significant advantages in wide speed range over traditional algorithms.

To solve the chaos problem of inverter in new energy generation system，a regulation scheme of H-bridge inverter based on active disturbance rejection control（ADRC） was proposed. Aiming at the phenomenon of poor steady-state and dynamic characteristics of inverters in chaotic state，a discrete model of the inverter was developed to control the chaos by establishing tracking differentiators，extended state observers，and state error feedback control laws. Through bifurcation diagram，folding diagram and simulation，the results show that the stability range of the H-bridge inverter based on ADRC control is expanded by 45% compared with the H-bridge inverter based on proportional control，which effectively suppresses the occurrence of chaos. It can be concluded that the control strategy can restrain the chaotic behavior of the system and broaden the stable working range of the system.

In order to monitor current distribution state of parallel silicon carbide（SiC）devices in photovoltaic inverter，a contactless monitoring solution based on anisotropic magnetoresistive sensor was proposed. According to practical position of SiC devices on PCB board，multiphysics simulation tool COMSOL was employed to analyze magnetic distribution around SiC devices. Then，the best location of magnetoresistive sensor was determined. Current monitoring unit consisting of magnetoresistive sensor，signal conditioning circuit and data communication interface was formed. Testing of a 1.5 kW photovoltaic inverter prototype was implemented. The experimental results demonstrate the contactless current mismatch monitoring solution features high bandwidth，high sensitivity，good linearity and simple circuit structure.

In order to address the issue of large output voltage variation from self-powered current transformer in smart measurement switch，ultra wide input voltage range post-stage DC-DC module is required to generate stable system voltage rails. A ultra wide input DC-DC module based on constant on-time control and asynchronous Buck circuit operating in discontinuous mode was proposed. Accroding to the gap between intput voltage and output voltage，variable frequency control and quasi-fixed freqency control were combined. With large voltage gap conversion realized，this DC-DC module also features super fast dynamic response. PSIM software was used to analyze and verify the characteristics of the propsed DC-DC module. A 5 W hardware prototype was fabricated and tested to produce key experimental waveforms. The experimental results demonstrate that the proposed DC-DC module has features of ultra wide input range，super fast dynamic response and high stability.

Junction-case thermal resistance has always been a highly concerned thermal parameter of power semiconductor devices，which is also the standard to weight the heat sink performance of power semiconductor devices. Heat-sink design should be considered in order to prevent device overheating damage. Therefore，accurate measurement of thermal resistance is particularly important for system heat-sink. The difficulty of devices thermal resistance measurement lies in the junction temperature measurement because it is difficult to measure junction temperature directly without destroying the devices package. Found through experiment that when the conduction voltage under small constant-current was used as the temperature-sensitive parameter，the conduction voltage and temperature had good linearity，which can be used for junction temperature measurement. Finally，the thermal resistance measurement can be completed based on the thermal resistance formula when the junction temperature was known.