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.

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.

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.

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.

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.

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.

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.

Accurately estimating the state of health （SOH）of lithium-ion batteries is crucial for optimizing energy storage systems' operation，management，and maintenance. Existing methods that extract health features from single-stage charging data fail to exploit battery aging information fully，leading to a suboptimal estimation accuracy. In addressing this issue，a SOH estimation method for energy storage systems based on the fusion of two-stage charging data for lithium-ion batteries was proposed. Combining health features from both constant voltage charging and relaxation stages，the proposed method effectively mines aging information embedded in two-stage charging data，thereby improving SOH estimation accuracy. Additionally，the introduced health feature combination does not require the use of constant current charging stage data，making it less affected by the uncertainty of charging start points and more adaptable to practical energy storage conditions. Experimental results demonstrate that the proposed health feature combination significantly outperforms single-stage feature combinations，with an average absolute error of 0.66%，mean squared error of 0.85%，and an average coefficient of determination of 0.97.

The rapid development of modern power electronics technology promotes the insulated gate bipolar transistor （IGBT）wide range of applications in the AC motor drive，inverter，switching power supply and new energy industry. In the application process of IGBT，due to the complex and varied circuit topology and system conditions，the problem of gate waveform oscillation usually exists. How to understand the oscillation mechanism and suppress methods becomes the basis of IGBT security and stability application. According to the IGBT internal parasitic parameter structure and switching process，the IGBT gate turn-on oscillation，turn-off oscillation and short-circuit oscillation were introduced in detail，the mathematical model of the gate oscillation process and the oscillation of the radio frequency （RF）positive feedback oscillation （turn-off oscillation and short-circuit oscillation） were deduced. The corrective measures of adding negative feedback or decreasing the positive feedback gain were put forward. By improving the experiment of different oscillations，the effectiveness of the suppression measures was verified，and the stability and reliability of IGBT application were improved.

A three-phase four-wire energy storage type low-voltage control device with the function of grid voltage unbalance compensation was designed. Firstly，a control method based on active voltage droop and constant power factor was introduced in detail to solve the problem of low voltage at the terminal of substation area power grid，which can compensate the low voltage at the terminal of substation area power grid. Secondly，a three-phase unbalance voltage compensation method based on negative sequence and zero sequence virtual impedance was proposed，which directly controls negative sequence and zero sequence voltage and omits the application of current sensor. Finally，a Matlab/Simulink simulation model and a 50 kW mid-point capacitor three-phase four-wire T-type three-level energy storage converter experiment platform were built，and the effectiveness of the proposed control scheme was verified through simulation and experiments.