For regional integrated energy system containing a high proportion of renewable energy, "quantity" and "quality" of energy are both discussed under "Exergy" concept and a twolayer optimization method considering exergy efficiency is proposed. Firstly, a model of multi – energy coupling of electricity, gas, heat and cold was established, and exergy analysis of energy and equipment is implemented. Then, a twolayer optimization model is established that considers system capacity planning and dispatching operation. The upper layer takes exergy efficiency and economy as the optimization goal for capacity allocation, while the lower layer takes the lowest operating cost as the optimization goal for unit output, therefore the best capacity allocation and operation scheduling scheme are obtained. Finally, a regional integrated energy system case is selected, and different schemes are analyzed for comparison. The result shows that the twolayer optimization method proposed in this paper can provide a better planning and scheduling scheme for the regional integrated energy system, while the exergy efficiency can characterize the actual level of energy utilization precisely and achieve highquality energy use.

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.

At the present stage, the construction and operation cost of optical storage DC microgrid is high and the lack of overall planning, so it is urgent to carry out the optimization planning research of optical hydrogen storage DC microgrid. Considering the fluctuation of photovoltaic power output power and the uncertainty of load change in light hydrogen storage DC microgrid, an optimization planning method of light hydrogen storage DC microgrid based on opportunity constraint is proposed. Based on the opportunity constraint planning, the optimization planning model of optical hydrogen storage DC microgrid with the lowest construction and operation cost is constructed, and the energy storage capacity configuration of the microgrid is optimized. Through the sequence operation, the constraints containing random variables in the model were used for deterministic transformation, and the CPLEX solver was called to solve the model. Through simulation calculation and analysis, the effectiveness and practicability of the optimization planning method of optical hydrogen storage DC micro grid based on the sequence operation algorithm were verified.

To improve the fragmentation rate , particle size uniformity, and stability of straw micropulverization, a composite pulverizing method of moving and fixed cutter impact shear was proposed for the physical properties of straw, and a curved serrated blade pulverizing cutter was designed. The main factors affecting the pulverizing performance of straw and the way of fragmentation were clarified through the analysis of the shear mechanics of straw, the analysis of impact dynamics, and the mechanical analysis of pulverizing moving cutter. Based on EDEM numerical simulation, the effects of the serrated blade and smooth blade cutters on the pulverizing performance of straw were compared and analyzed. The simulation results show that when pulverizing corn straw with a moisture content of 20%, the number of connective keys of the serrated blade is 16.76% less than that of the smooth blade, the particle motion speed is increased by 15.9%, the total energy of particles is increased by 25.05%, and the impact force on the pulverizing chamber wall is reduced by 33.69% , and has a smoother working condition and lower energy consumption.

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.

With the largescale access of new energy into the power grid, traditional power flow calculation can no longer meet the needs of the distribution network, and the effectiveness of reactive power allocation of the distribution network is reduced, thus affecting the safety and stability of the entire distribution network. Therefore, this paper analyzes the influence characteristics of power flow in substations including new energy stations, establishes the PCC node model of new energy stations connected to the regional power grid, and uses the branch forward pushback method as the power flow calculation method of distribution network. The characteristics of reactive power compensation in substation with new energy station access are analyzed, and the reactive power compensation capacitors are planned based on equal quantity grouping. Finally, taking a substation as an example, the feasibility of the proposed calculation method is verified, which fully proves the effectiveness of the proposed calculation method.

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%.

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.