Henan province is a major agricultural province with abundant crop straw resources. In order to improve the comprehensive utilization rate of regional straw resources and promote the industrial layout and development of straw resource utilization, this article estimated the amount of straw resources and the nutrient content of straw of major crops in Henan province, clarified the distribution characteristics of straw resources in Henan province. At the same time, combined with the calculation of the demand for straw resource utilization in Henan province, analyzed the utilization potential of straw resources in the whole province. The results showed that the theoretical and collectable amount of the main crop straw resources in Henan province in 2022 were 103.868 8 million tons and 81.089 1 million tons respectively. The straw resources mainly distributed in Zhumadian, Nanyang, Zhoukou and Shangqiu. There is a large difference in regional straw resources. The nitrogen, phosphorus and potassium contents in collectable straws in Henan province in 2022 were 0.666 4 million tons, 0.196 6 million tons and 1.059 4 million tons respectively. Theoretically, the amount of collectable straw could replace 42.28% of the nitrogen fertilizer demand and 27.38% of the phosphate fertilizer demand in the province in that year, and could completely replace the potassium fertilizer demand in that year. The demand for livestock feed straw is 13.754 8 million tons, accounted for 16.96% of the total collectable straw resources of the province. The demand for straw resources for substrate is 1.849 5 million tons, accounted for 2.28% of the total straw resources of the province. If the collectable straw resources in Henan province was fully energy utilization, it would have potential to replace 40.862 5 million tons of standard coal.

According to the different conditions of photovoltaic resources, ongrid price, initial total investment and light abandonment rate in various regions of China, a photovoltaic economic evaluation model is constructed to analyze the ongrid situation of photovoltaic power generation parity in various regions and calculate the minimum ongrid price and the maximum initial total investment that meet the benchmark yield in each region. The results show that there are obvious regional differences in China's photovoltaic economy. Considering the abandonment of light, a total of 15 regions in the country cannot achieve grid parity access, but most of them are close to parity access. Some regions with high photovoltaic economy can achieve parity with a price of 0.05 CNY/(kW·h) below the benchmark price. The research results of this paper are helpful to the investment decisionmaking of photovoltaic projects and the formulation of relevant policies.

To evaluate the heat extraction performance and optimize the injection parameters of a singlewell ClosedLoop Geothermal System (CLGS), this paper analyzes the shortterm (thermal response testing) and longterm (one heating season) heating performance of CLGS and optimizes operation parameters including injection temperature and rate, based on wellbore reservoir coupling simulation and site operation monitoring data for a typical site in Northeast China. The results indicate that the mean heat extraction rate is 65.2 kW and the average temperature difference between the output and inlet is 4.9 °C with an average injection temperature of 7 °C and an injection flow rate of 7.7 m³/h for a vertical well of 1 700 m. At the end of a heating season, the maximum range for temperature reduction in the formation is approximately 7 m with the maximum temperature decrease up to 23 °C, and it can recovery better during the nonheating period. Without considering operating costs and sustainable development, the low injection temperature and large injection rate result in high heat extraction rate. Setting the injection temperature to 5 °C and flow rate to 6.3 m³/h can minimize operating costs while meeting heating needs, reducing costs by 20% compared to the existing solution. The optimization design that considers operating costs and sustainable development has practical significance for a single well closedloop geothermal system.

It is difficult to control and predict the solidification process and the morphology of phase transition interface in sealed directional solidification. The directional solidification (DS) process model of solargrade polysilicon is solved by analytic method, and a high precision mathematical model of solidification process is obtained. The solidification height, instantaneous solidification rate and melt temperature distribution can be calculated from the easily measured heat dissipation temperature and solidification time. By solving the Poisson equation, a 3D model of phase transition interface was established. It is revealed that the heat flow rate q value on the side wall of the melt is the key factor to influence the interface morphology, which provided quantitative analysis basis for solidification process control. The large size (0.90 m × 0.90 m × 0.35 m) ingot casting experiments were carried out using 3303 industrial silicon as raw material in YITIPV vacuum ingot furnace. For the geometrically symmetric phase transition interface, the maximum deviation between the mathematical model and the experimental curve is 4.43%; for the irregular phase transition interface, the maximum deviation is 8.68%, and the solidification process model is modified according to the experimental results. The prediction accuracy and reliability of the 3D phase transition interface model were verified by detecting the parameters such as impurity content, resistivity and minority carrier lifetime, and comparing the typical phase transition interface morphologies of the four ingots.

In view of the large number of rocksocketed demand of offshore wind power foundation in China, horizontal loading characteristics and pilerock integrated failure mode of large diameter rocksocketed monopile foundation are studied by combining physical model test and numerical simulation method, and the analysis of the influences of bedrock strength, pile foundation diameter, wall thickness and rocksocketed depth on the horizontal bearing capacity of rocksocketed pile is carried out. The research shows that the flexural capacity of pile increases with the increase of bedrock strength. The failure mode of shallow bedrock of rocksocketed pile foundation follows passive wedge failure mode, while the failure mode of deep bedrock follows rotating failure mode. The horizontal bearing capacity of pile foundation can be improved with the increase of bedrock strength, pile diameter and depth of rock socketed, but the pile thickness has little effect on it. Critical depth of rocksocketed pile is found to improve the horizontal bearing capacity of rocksocketed pile. Pile diameter and overburden thickness have little effect on critical depth of rocksocketed pile, while bedrock strength is sensitive to its change.

Generator is an important core component in wind power system, in order to improve the stable and efficient operation of wind turbine, the fault prediction of wind turbine generator is necessary. Focusing on the problem of generator machineside bearing temperature overrun fault prediction in wind power system, this paper takes into account that the collected fault characteristic signal is characterized by large noise, introduces CEEMDAN joint adaptive wavelet threshold denoising method to realize effective denoising of the signal, and at the same time establishes a fault prediction model by combining GABP neural network. By comparing the prediction indexes, error indexes and prediction effect graphs with BP neural network and GABP neural network, it is verified that the proposed algorithm can obtain better prediction effect. The error index and prediction effect are improved, and the accuracy of the prediction of generator failure of wind power system 15 days in advance reaches 92.98%.

In order to reduce external interference and ensure safe and stable power operation, a research on intelligent control of largescale wind power generation based on MQWaveNet for smart new energy is proposed. By constructing a smart new energy largescale wind turbine model, calculating the captured wind energy and blade tip speed values, adjusting the speed of the generator, and obtaining the optimal power coefficient. Input parameters such as air pressure, wind direction, and wind speed into a wavelet neural network, and obtain power values for the hidden layer and output layer based on the weights between layers; Combining multi view quantiles to form an MQWaveNet model, calculate the power generation prediction results for each quantile and clarify the temporal characteristics of wind power generation. Using Lyapunov function estimation, calculate the transformation and control vector of the sliding mode surface for wind power generation, reach the sliding mode surface within the range of multiple quantiles, and achieve intelligent and stable control of the wind power generation state. Through experiments, it has been proven that the studied model can improve the antiinterference ability of wind turbines and ensure the intelligent and stable operation of equipment.

Based on the practical problems, a dynamic model of 6.7 MW wind turbine was established, and the influence of opening trailing edge of 0, 0.1%c, 0.3%c, 0.5%c on blade aerodynamics was investigated by CFD and BEM. The result shows that the lift coefficient and liftdrag ratio of the airfoil significantly increase with the increase of the opening trailing edge; the drag coefficient is almost unchanged before stall, but slightly changed after stall; the stall angle of the airfoil is 12° and the position of the stall separation point of the airfoil moves slightly backward. Otherwise, under the influence of turbulent wind, the blade deformation and axial force increased slightly, and the maximum power generation increased by 0.88%.

With the development of regional integrated energy system, how to comprehensively evaluate the comprehensive energy efficiency of regional integrated energy system has become a widespread concern. First, consider the change of quality in the transformation process of different energies, introduce the concept of "exergy efficiency", convert different energies through the energy quality coefficient method, and establish a comprehensive energy efficiency evaluation index including economy, energy efficiency and environment on this basis; Secondly, an improved TOPSIS is established for evaluation, the results of entropy weight method and coefficient of variation method are combined by the least square method to calculate the weight, and the distance measurement method in TOPSIS is improved by using grey correlation degree; Finally, an example is given to verify the effectiveness and feasibility of the proposed method. It can provide a certain reference value for the planning and optimal operation of the highquality regional integrated energy system in the future.

An improved virtual synchronous generator (VSG) control strategy for multiinverter parallel system is proposed in this paper to suppress the circulating current caused by the impedance difference of transmission lines between PV microgrid inverters in islanded mode. Firstly, based on the traditional VSG control block diagram, each inverter counteracts the power loss on the transmission line by introducing the line power feedback, so as to improve the active and reactive power sharing accuracy, reduce the output voltage drop, and improve power quality. Then, the synchronous controller is introduced to reduce the instantaneous current and suppress the instantaneous circulating current between the multiinverter parallel system. Finally, the effectiveness of the proposed control strategy is verified by simulation and experiment.