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.

When the switching frequency of the four-quadrant rectifiers in different multiple units deviates，the current will experience low-frequency oscillation，which is not conducive to the operation of the traction power grid. Therefore，a matrix small-signal modeling method for SPWM comparators was proposed to analyze this issue，which achieves a more accurate description of the switching frequency characteristics of the single-phase PWM rectifier. Then，the matrix small-signal modeling of parallel four-quadrant rectifiers was further established，and then the model was used to analyze the causes and rules of differential frequency oscillation during mixed running of different multiple units. Finally，the correctness of the established model and analysis conclusions were verified through experiments.

Aiming at the poor robustness and system vibration problem of asynchronous motors under the traditional sliding mode control，a variability coefficient power exponent reaching law （VCPERL） was proposed to dynamically change the control coefficients according to the position of the sliding mode surface，and the sliding mode controller was designed based on this reaching law. Firstly，according to the advantages of quick-power reaching law （QPRL） and the double-power reaching law （DPRL），which have different reaching rates at different positions of the sliding mode surface，meanwhile，the tanh（x）was used to replace the sign（x），and a variable coefficient was introduced into the reaching law. Secondly，the stability of the new reaching law was proved based on theoretical analysis and simulation. Finally，the VCPERL was applied to design the sliding mode controller according to the theory of vector control oriented by rotor magnetic chain and the dynamic mathematical model of asynchronous motor. The simulation results show that compared with the traditional PI control，QPRL and DPRL，VCPERL has strong immunity to load disturbances and fast recovery capability，which can effectively improve the dynamic response performance of the system.

In view of the need to test the operation of power electronic equipment under various working conditions in the current new power system，a control strategy using linear auto-disturbance rejection technology was proposed to study the power grid simulator with line impedance simulation function. On this basis，in order to separate and control the harmonics，the improved filter bank was used to separate and filter the grid voltage to achieve the effect of independent impedance simulation and harmonic output. Simulation and experiments show that the proposed control strategy has good output effect.