Based on the reservoir conditions of tight conglomerate reservoirs in the Mahu area of the Junggar Basin, an experiment was conducted to study the interaction between tight conglomerates, CO₂, and water. The results indicate that after CO₂ dissolves in water to form carbonic acid, it primarily reacts chemically with feldspar and calcite in the cement between the conglomerate grains. This leads to significant around-grain dissolution, with dissolution being the main process and precipitation being secondary. Ultimately, this increases the porosity and permeability of the rock, enhancing the reservoir fluid seepage capacity. The maximum increases in porosity and permeability are 3.65% and 87.36%, respectively. Additionally, the surface roughness of the rock increases after the interaction, with hydrophilic mineral quartz exposed on the surface. The water-phase wetting contact angle of the rock decreases by 7.4°, enhancing hydrophilicity. The CO₂ huff and puff process has a positive effect on improving oil recovery, with the main oil-increasing mechanisms being the enlargement of pore space to enhance fluid seepage capacity and the improvement of rock water-phase wettability, which increases reservoir water-phase imbibition capacity and crude oil mobility, thereby improving oil recovery.

Due to the similarity in site selection between underground pipelines and power facilities such as high-voltage power lines and urban rail transit power supply systems, underground pipelines are increasingly affected by stray currents generated by power facilities. The impact of AC stray currents on the corrosion rate of pipeline coating defects were simulated and analyzed. The effects of parameters such as AC current magnitude, soil conductivity, internal pressure of the pipeline, stress, distance to grounding electrode, and pipeline radius on corrosion were investigated in the study. The results indicate that when the stress on the pipeline is less than the yield strength, the effect of stress on the corrosion caused by AC stray currents is relatively small. However, after the deformation of the pipeline increases, serious corrosion will be induced by stress. The greater the AC current, the greater the corrosion at the defects of the pipeline coating. The lower the AC frequency, the greater the corrosion at the defects of the pipeline coating. The closer the distance to the grounding electrode, the greater the corrosion at the defects of the pipeline coating. The higher the soil conductivity, the greater the corrosion at the defects of the pipeline coating. The smaller the pipeline radius, the greater the corrosion at the defects of the pipeline coating. These research findings are of significant importance for ensuring the safe operation of oil and gas transportation pipelines under the influence of AC stray currents.

Macro-encapsulated phase change material (PCM) capsules are the core components that form the heat storage tank of the packed bed. In order to enhance the heat storage rate of the packed bed tank, it is necessary to optimize the heat storage and discharge rate of individual PCM capsules. Four different encapsulated shapes of PCM capsules were established while ensuring the uniform volume of individual PCM capsules. The capsules were placed in a flow field with an obstruction rate of 0.5, and the melting and solidification processes of PCM under different encapsulation shapes were analyzed with full consideration of gravity direction and heat transfer fluid flow direction in practical applications. The results show that the natural convection of liquid PCM inside the capsule can accelerate the melting and solidification process of PCM and increase the rate of charging and discharging; compared with the spherical encapsulation capsule, the heat transfer area per unit volume of cylindrical encapsulation capsule is increased by 14.47% and the melting time of PCM is shortened by 42.50%. Therefore, the cylindrical encapsulated capsule has the best thermal performance, and the cylindrical capsule can be applied to the packed-bed storage tank in future research to optimize its thermal storage performance.

In order to improve the control performance of a doubly-fed wind turbine grid-side converter under unbalanced and harmonic grid voltages, a direct power control algorithm with an improved super-helix fast terminal sliding mode was proposed. First, the mathematical model of the grid-side converter under unbalanced and harmonic grid voltages with power as the state variable was analyzed in a two-phase stationary coordinate system. Then, the power inner-loop design was carried out with a nonlinear expansion state observer for the negative sequence in the mathematical model as well as the disturbances due to each harmonic component. Secondly, to ensure that the system can reach the steady state in a shorter time, the non-singular fast terminal sliding mode surface was constructed and the sliding mode control law for the power inner loop was designed by combining with the improved super-helical sliding mode convergence law. Similarly the terminal sliding mode control rate was also designed for the voltage outer loop. The stability of the non-singular fast terminal sliding mode surface, the improved super-helix control algorithm and the nonlinear expanding state observer was also proved by using the Lyapunov function. Finally, the method was verified to have faster convergence and stronger robustness by comparing it with three different control schemes to perform simulations.

In order to improve the output performance of permanent magnet assisted synchronous reluctance motor (PMa-SynRM), a multi-objective optimization design method for external rotor PMa-SynRM based on kernel extreme learning machine (KELM) and fast non-dominated sorting genetic algorithm (NSGA-II) was proposed. Firstly, the preliminary design of the PMa-SynRM rotor magnetic barrier was carried out and the working principle of the PMa-SynRM was analyzed. Secondly, the influence of each design variable on the optimization goal was evaluated through comprehensive sensitivity analysis, and the main optimization parameters were selected. Thirdly, with high output torque, high efficiency and low torque ripple as the optimization goals, a surrogate model based on KELM was established. Finally, NSGA-II was used for global optimization, and the optimal solution was selected from the Pareto frontier generated by NSGA-II, which was verified by finite element analysis. The simulation results show that the average torque of the optimized motor is increased by 15.83%, the torque ripple is reduced by 60.27%, and the efficiency of the optimized motor is also improved compared with the initial motor, which verifies the effectiveness of the optimized design method proposed in this paper.

When the integrated energy system (IES) participates in electricity spot market transactions, the transaction price is uncertain due to changes in market supply and demand. In order to deal with this problem, a detailed analysis of the operating marginal cost of the integrated energy system was used to investigate the optimal dispatch strategy that fully utilizes the flexible resources of the integrated energy system to participate in the market. Firstly, the typical scenarios of market price uncertainty under the external spot market environment were analyzed, and the internal multiple source-load adjustable resources and operation cost structure of the integrated energy system were investigated. Secondly, a trading optimization model considering the marginal cost of the system under the condition of price uncertainty in the electric power market was established, and the sand cat swarm optimization algorithm was proposed to solve the problem. Finally, simulation verification was conducted based on actual cases. The result shows that this strategy can not only reduce the operating cost of IES, but also enhance its adaptability to market price uncertainty. The strategy provides new ideas for the operation of integrated energy systems in the power spot market environment, which is also helpful to realize the double optimization of economy and reliability of energy system participating in the market scheduling.

In order to solve the efficiency issues in distributed load responses to frequency regulation commands, an innovative strategy was introduced based on reinforcement learning for load aggregators’ pricing incentives in response to frequency commands. Within this strategy, a game-theoretic model between the load aggregators and load clusters was constructed, and the load aggregators adjust incentive prices based on frequency commands and their pricing strategies, while loads adjust their power consumption based on their own electricity costs to flexibly respond to the frequency commands. The multi-agent soft actor-critic (MASAC) algorithm was used to investigate the solution. The results show that the pricing incentive method enables effective load response to frequency commands, and the use of the MASAC algorithm not only optimizes the decision-making process but also significantly reduces computational complexity, achieving efficient dynamic adjustment. It is concluded that this method provides an effective solution for frequency regulation in power systems, offering significant theoretical significance and practical value.

Under the background that the accuracy of voltage amplitude detection is increasing year by year, a voltage amplitude detection method based on improved second-order generalized integrator was proposed to solve the problem that the existing voltage amplitude detection methods were susceptible to the interference of harmonic and DC components, which leaded to insufficient detection accuracy. First, the composition change of voltage after fault was analyzed, and the existence of harmonic component and DC component in fault voltage was proved. Then, the principle and performance of voltage amplitude detection by sine-cosine component method and traditional second-order generalized integral method were analyzed. Then, the output of traditional second-order generalized integrator without DC component was taken as the input of the improved second-order generalized integrator’s second module. In this way, the effective filtering of the DC component was realized, and the Bode diagram, zero pole and step response of the improved second-order generalized integrator under different gain coefficients were analyzed. The optimal gain coefficient was selected considering the influence of filtering effect, stability and response speed. Finally, the simulation results show that the method proposed in this chapter has stronger filtering ability and higher precision than the other two methods.

Laser ultrasonic detection technology possesses unique advantages combining ultrasonic and optical methods, enabling non-contact detection while enhancing temporal and spatial resolution. To enhance the excitation efficiency and defect detection accuracy of laser ultrasound, optimization of laser source parameters is necessary to improve energy exchange efficiency and reduce costs. Research has been conducted on the propagation characteristics of laser ultrasonic sound fields under various conditions. Numerical simulations of the process of laser ultrasonic action on X80 pipelines were performed using COMSOL Multiphysics finite element software, and the accuracy of the model was verified. The relationship between laser source parameters and ultrasonic field was studied by combining the set laser pulse width and laser spot radius, and further analysis of the relevant data was carried out using MATLAB. The analysis results indicate that when the pulse width is set to 20 ns and the spot radius is set to 300 μm, laser ultrasonics exhibit relatively optimal excitation efficiency in X80 pipelines. This provides important reference for improving the excitation efficiency of laser sources.

Aiming at the problem of frequent switching due to transient link changes in the heterogeneous network of indoor visible light communication (VLC) and radio frequency (RF) communication, a decision-making mechanism based on spatio-temporal characteristics for VLC/RF networks were proposed. Firstly, in the offline sampling stage, the database was constructed by processing and converting feature data such as spatial location, bandwidth, received signal strength, delay and signal-to-noise ratio of indoor grid points into proportional weights in the controller. Then, in the real-time decision-making phase, the terminal feeded the collected feature data back to the controller to determine the location of the user terminal by comparing it with the information in the database of the controller, and the prioritized link of the current location in the database was extracted and connected. Finally, the link decision model was used to derive the network communication index in real time, and the optimal link was solved by aggregating the proportional weights of the links in the database with the network communication index through the decision function, and the communication quality was improved using the resident timer. Simulation results show that the switching algorithm effectively reduces the average number of switching times and switching interruption probability compared with the traditional fuzzy logic switching algorithm and the vertical switching decision algorithm with equivalent signal-to-noise ratio (SNR). The algorithm can realize intelligent management of indoor heterogeneous networks and improve the quality of user experience.