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.

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.

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.

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.

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.

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.

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.

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.

In view of the problem that the transfer branch of the current high-voltage DC circuit breaker mostly adopts uncontrollable full-bridge transformer coupling energy supply，which is not conducive to controllable and stable power supply，and low energy utilization，a combined DC circuit breaker energy supply method was proposed. A bidirectional DC-DC converter topology with energy storage device （battery or super capacitor） was used to control the voltage control and energy recovery and reuse of the precharged capacitor in the resonant transfer branch of the combined DC circuit breaker. A control strategy for DC-DC energy supply using dual-active-bridge （DAB） was developed as an example. The improved energy mode of supply can not only ensure the fast and stable supply of transferred branch energy during the rapid opening of the combined high-voltage DC circuit breaker in the event of DC power grid failure，but also use the recovered energy for the reclosing process after fault recovery. The simulation and experimental results show that the proposed bidirectional DC-DC converter replaces the uncontrollable full-bridge combined high-voltage DC circuit breaker energy supply method，and the output voltage is more stable，and the energy utilization rate of the system is improved.

In order to make full use of the frequency modulation capability of the wind turbines，considering that a conventional wind-power coordinated frequency control strategy not only results in some fluctuations in the frequency of the system，but also requires high energy storage capacity and poor economic efficiency，therefore，based on the traditional wind storage coordinated frequency control strategy，an active support control strategy for wind storage coordinated regulation was proposed，which is based on a virtual synchronous generator （VSG） third-order model，and the related wind storage collaborative regulation model was built，and the control strategies for wind turbines and energy storage were designed. Based on this，the inertial response and the primary frequency response of the wind turbine and the energy storage plant to control the frequency were investigated under different control parameters. Through simulation analysis，it can be concluded that this strategy not only approximates the energy storage inverter as a synchronous voltage source，meets the inertia and damping characteristics required by the new energy grid，suppresses system frequency fluctuations，reduces energy storage capacity configuration，but also makes full use of the potential of wind farms to participate in frequency regulation，increasing the frequency stability of the electricity system.