Focusing on the central position of AC power frequency converter in the development of the national economy，emphasizingd their critical impact on the safety and efficiency of industrial production. In view of the rapid development of power electronics technology，the field of AC power frequency converter has made remarkable progress，but also faces many challenges，such as uneven product quality，and there is an urgent need to optimize the industry order to improve the overall quality level. By comparing and analyzing the development status quo of power supply systems at home and abroad，the high standard of product reliability required by the international community was revealed，and provided an in-depth analysis of the problems that exist in China's AC power frequency converter products in terms of reliability，standardization and regulation. In order to promote the high-quality development of the industry，a series of strategies were put forward：strengthening product reliability technology research and development，building a standardized evaluation system，ensuring the effective implementation of standards，promoting the power supply product certification system，and strengthening the operation and maintenance regulatory mechanism. These comprehensive measures are aimed at optimizing the industry ecosystem，improving product quality and safety，and thus promoting the high-quality，sustainable development of the AC power frequency converter industry.

Aiming at the problem that the circulating currents analysis of modular multilevel matrix converter（M3C） is not deep enough and the frequency component of circulating currents is not clear，the coupling process of submodule capacitor voltage fluctuation，bridge voltage fluctuation and circulating currents in M3C was deeply analyzed，and the primary coupling model of M3C circulating currents and its four main frequency components were obtained. The analysis results provided a theoretical foundation for using PR controller to suppress the circulating currents of corresponding frequency components. The theoretical analysis and suppression of circulating currents were verified by experiments. The experimental results prove that the theoretical analysis of the frequency components of circulating currents is correct，and it is also proved that the PR controller designed according to the analysis results has better suppression effect on circulating currents than the P controller.

As the penetration rate of new energy in the power system continues to increase，the large-scale grid connection of wind power is one of the important factors affecting the stable frequency operation of the power system. Configuring energy storage can provide transient frequency support for the system，improve wind power fluctuations，and enhance the stability of wind power generation. Firstly，by considering the primary frequency regulation requirements of wind farms and starting from the operating status of batteries，a state of charge （SOC）control strategy taking into account charge coefficient and discharge states was proposed，and a battery service life model was established. On this basis，with the overall goal of minimum sum of annual comprehensive costs of wind storage systems，a power and capacity optimization configuration model for energy storage systems was constructed that taken into account the state of charge and battery life. Secondly，the ant lion algorithm was used to solve the optimization results，and the effect of complex cost，battery life，and charge status on the optimization result was analyzed. Finally，the effectiveness of the results through simulation was validated.

The stability analysis of power system transient voltage，power angle，and frequency is often based on short-time-scale electromechanical transient simulation，which requires a relatively accurate large-scale simulation model，which not only has low simulation efficiency but also takes a long time，thus giving rise to the demand for dynamic equivalence of large power grids. However，as the proportion of new energy increases，the power system gradually presents some unique characteristics of new power systems，with more significant differences in system inertia，frequency spatiotemporal distribution，and frequency modulation resource distribution. Conventional dynamic equivalence methods based on slow coherence theory are gradually difficult to ensure accuracy. To solve these problems，based on previous work，a large power grid dynamic equivalence method based on random forest algorithm was proposed. First，the large power system was divided into the study area and the external area. Then the external area on the opposite side of the study area tie line was equivalent to several nonlinear dynamic loads controlled by the random forest algorithm. The random forest algorithm was trained using the original model tie line's voltage/reactive power and frequency/active power relationships. A joint simulation model based on PSS/E and Matlab platform was established to achieve equivalent simplified electromechanical transient simulation，and Python environment was used to achieve information exchange and simulation control between them. Simplified results for the Northeastern United States power grid was presented and compared them with existing methods. The results show that the proposed method can effectively balance simulation accuracy and control stability.

In order to reduce the loss of electric energy in the process of energy conversion and improve the energy efficiency of aluminum air battery，an energy efficiency model based on the internal resistance characteristics of aluminum air battery was established，and the variations of operating conditions （operating temperature，electrolyte concentration），internal resistance characteristics，output characteristics and energy efficiency were studied. In order to improve the energy efficiency of aluminum air battery，an improved pollination algorithm was adopted to obtain the optimal working temperature and electrolyte concentration under constant current density output. The validity of the model and method was verified by simulation and experiment. The results show that the energy efficiency can be improved by co-optimizing the operation conditions，and the total internal resistance can be reduced and the output performance can be improved by increasing the energy efficiency.

While a large number of distributed generator （DG） keep penetrating into distribution networks，the problems such as voltage violation and network power congestion become more and more serious. Soft open point（SOP） can quickly achieve flexible interconnection and accurate power flow control，effectively addressing the challenges caused by the integration of DG. Considering the installation priority of SOP on branches where active power is heavily affected by loads，an intelligent soft switch site slection and capacity determination strategy based on branch active power sensitivity analysis was proposed. Firstly，a load growth factor was introduced into the power flow equations，and the branch power sensitivity，which reflects time series variation of DG output and load，was theoretically derived. The selection of SOP sites was then ranked according to this sensitivity value. Secondly，the model of SOP site slection and capacity optimization was established，which was solved using a second-order cone algorithm. Finally，validation was conducted on the improved IEEE 33 node distribution system. Results show that the proposed method can affectively save annual comprehensive operation cost of distribution networks，reduce system network losses and improve node voltage deviation.

Aiming at the problem that the photovoltaic grid-connected inverter system operates under multiple disturbances，an linear active disturbance rejection control （LADRC） grid-connected strategy combined with photovoltaic system was proposed.Firstly，the dynamic process of PV grid-connected system was analyzed and modeled，and the LADRC-PM structure was designed according to the model characteristics of the photovoltaic system，further improving the speed on the basis of the classical structure. And then，the structure was introduced on the basis of the double closed-loop control framework，so that the system could compensate the disturbance through the feedforward way to enhance the system ability to suppress the uncertainty. Furthermore，the mathematical model of the proposed control strategy was dynamically analyzed using frequency domain analysis method，and its engineering stability，tracking convergence，and disturbance rejection superiority were theoretically verified，and the guidance of adjusting some parameters was given. Finally，the advantages of LADRC-PM control strategy was verified by the Matlab/Simulink simulation in various working conditions.

The development of modern power systems with wide span，low inertia，and complex structure makes the frequency stability problem increasingly prominent，and the spatial-temporal distribution characteristics of frequency are distinct. Taking the actual power grid as the object，the impacts of large-scale new energy access and DC power control on the grid frequency response under disturbances and the characteristics of frequency spatial-temporal distribution were analyzed. Firstly，based on the detailed time-domain simulation model，the causes of the spatial-temporal distribution of node frequency were discussed from the perspective of the distribution differences of disturbed power，inertia，and frequency regulation resources. The system-level and node-level frequency response indicators that reflect the overall trend and distribution differences of grid frequency response were proposed. Then，the impact mechanisms of factors such as the new energy power proportion，the distribution of synchronous，the primary frequency regulation of new energy，and DC frequency limit control on the grid frequency response under disturbances were analyzed. Finally，through simulation results of real power grid cases，the impact of various factors on the grid frequency response and its spatial-temporal distribution characteristics was quantitatively analyzed.

It is an important means to improve the anti-G ability of pilots to simulate the flight G-load characteristics of aircraft in full envelop flight on the ground through centrifuge. With the great improvement of maneuvering performance of manned aircraft，it is extremely difficult to accurately analyze its flight G-load characteristics and convert them into centrifuge control instructions for continuous and effective flight G-load characteristics simulation. The exact kinematics and dynamics equations of the aircraft were established，the corresponding G-load characteristics of the aircraft in full envelop flight were analyzed in detail. Then the mechanical and kinematic characteristics of the centrifuge were analyzed. Then，the transfer relationship between the earth coordinate system，the aircraft body coordinate system and the pilot coordinate system were used to obtain the extraction method of the aircraft G-load characteristics to the centrifuge control command. Finally，for a three-axis centrifuge with rotation，roll and pitch axis，the digital simulation experiments of flight attitude，G-load calculation and centrifuge control commands for the full flight envelop were carried out. The experimental results show that the proposed simulation method of G-load in full envelop flight of aircraft is feasible and effective.

With the accelerated construction of new power systems，the scale and complexity of transmission systems are constantly increasing. Therefore，it is urgent to study transmission line fault diagnosis algorithms that utilize multi-source data as driving sources and meet requirements for accuracy and low time consumption. A multi-source information fusion transmission line fault diagnosis method based on the improved NRBO-XGBoost algorithm was proposed. Firstly，by analyzing the measured electrical quantities and action switch quantities on both sides of the line protection，the correlation features of time/frequency domain differential current and differential voltage，transient polarity，and action signals under internal and external fault scenarios were decoupled. Then，the decoupled multi-source fault feature vectors were input into the XGBoost serial learning algorithm，and the NRBO algorithm was introduced to globally optimize the training parameters of XGBoost. Finally，based on the identification output of the improved NRBO-XGBoost algorithm，a complete transmission line fault diagnosis model for internal and external faults was obtained. An IEEE-30 standard node transmission system model was constructed using PSCAD/EMTDC. Through testing in four typical scenarios，the results demonstrated that the proposed multi-source information fusion algorithm achieves a line fault diagnosis accuracy of 99%，meeting the required threshold. Additionally，it exhibits certain advantages in terms of diagnosis speed compared to traditional intelligent algorithms.

A fusion prediction method was proposed to predict and correct the calculation deviation of the top transformer oil temperature model in IEEE guideline，so as to realize the more precise prediction of the transformer top oil temperature（TOT）.Firstly，the characteristics of the transformer TOT model and the extreme learning machine（ELM） prediction model was introduced. Secondly，in order to avoid the problem of slow operation speed caused by double level intelligent prediction，the weighted multi-point extrapolation method combined with the load curve clustering algorithm was used to obtain the future load coefficient of the transformer which introduced as the load prediction level of the model. Finally，based on the calculation of thermal model，which the ELM was used to predict the deviation between the calculated value of thermal model and the measured value，and finally the accurate predicted value of the TOT of the transformer was obtained.The simulation platform was built and the simulation results show that the average prediction error rate of the proposed prediction method is only 0.59%，and the root mean square error is only 0.47 ℃. Compared with the other three methods，it has higher prediction accuracy and stability. The model training speed and prediction speed are only 1.21 ms and 0.39 ms，respectively，which proves that the fusion prediction model proposed and established has high prediction accuracy，stability and operation speed.

An anti-interference domestic variable frequency multi-drive system solution for the five-stand continuous cold rolling line in the steel strip cold rolling field was presented. Firstly，the mechanical equipment and rolling process of the 900 mm five-stand continuous rolling line was introduced，and matched the models of domestic AC drive devices according to the motor table. The parallel connection mode of modular rectifier feedback power supply and inverter and the fiber optic communication were briefly described. Then，the problem of instantaneous drop of the incoming grid voltage encountered by the common DC bus system and how to improve the system stability by adding capacitor banks were discussed. At the same time，the method of using encoder isolation distribution board was introduced and providing separate power supply for the encoder to solve the encoder signal interference problem. Finally，the anti-interference performance of the system was verified by comparing the speed and torque accuracy before and after the improvement.