Voltage transformer (TV) interturn short circuit at generator outlet will cause unbalanced voltage in system, resulting in zero sequence stator ground fault protection of generator fundamental. The external characteristics of TV fault are of great significance to stable operation of the unit. In order to understand the external characteristics of TV fault, based on Maxwell and Simplorer software, a field circuit direct coupling finite element model for the electromagnetic conversion process of single-phase voltage transformer is established, which can realize data exchange between field circuits at each calculation step. In view of the large number of turns of TV primary winding, which is difficult to model directly, winding grouping technology is proposed. An experimental platform is designed and built to verify the accuracy of the simulation model. Based on the calculation results of finite element eigenvalues, the electrical and magnetic eigenvalues of TV in different operating states are analyzed, and the analytical model of TV inter turn fault based on winding grouping technology is further given. The simulation results show that, the TV turn-to-turn fault model is accurate and effective in analyzing the primary current, circulating current and other fault characteristic quantities.

Micro-mixing combustion is a kind of potential technology to reduce pollutant emissions, and the microtube structure as a basic unit has significant influence on combustion characteristics. Taking the single microtube model burner as the object, the computational fluid dynamics (CFD) method is employed to analyze methane micro-mixing combustion characteristics with different microtube diameters, rear-section lengths, and chamber-to-tube area ratios, under the air-preheated and pressurized condition and the atmospheric condition. The numerical simulation results show that, the flame length increases obviously under the atmospheric condition, and the increase rate is greatly affected by the microtube diameter and the area ratio. With the increase of microtube diameter, the flow and temperature fields in the flame chamber are similar, and the dimensionless flame length does not change significantly. However, when the microtube diameter is smaller, the change of flame length is smaller between two working conditions, and the flexibility is better. With the increase of microtube rear-section length, the turbulence intensity at the microtube outlet reduces greatly, and the flame length increases obviously, but the change trend of flame length is consistent under two working conditions. With the increase of chamber-to-tube area ratio, the flame length decreases at first and then increases. When the area ratio is 4.0~9.0, the flame length is relatively short, and the combustion performance is relatively good. The results have reference value for the gas turbine combustor, and also have certain reference significance for free jet flame.

As a clean and efficient power generation technology, solar thermal complementary combined cycle power generation (ISCC) system is concerned widely. By taking the ISCC system containing three-pressure reheat combined cycle and trough solar field as the research object, and based on the conventional trough ISCC system (using solar energy to replace the high pressure evaporator (system 1)), two new trough ISCC system are presented, namely using solar heat collection field to replace the high and medium pressure evaporators simultaneously (system 2), and using solar heat collection field to replace the high, immediate and low pressure evaporators simultaneously (system 3). Moreover, the dynamic performances of the above three ISCC systems are analyzed under the operation condition of typical day. The results show that, with proper operation strategy presented above, the three systems can not only realize safe and stable operation, but also reduce the impact of solar energy varies on the ISCC system output power. Under the operation condition of typical day, the second type of ISCC system (system 2) has better thermal performance.

In the point cloud splicing of underground pipe gallery in power plants, an improved algorithm with 3D-Harris operator about corner detection is proposed. In this algorithm, firstly, taking multiple sets of massive point cloud data of the underground pipe gallery as analysis object, the normal information of the target detection point on the adjacent point cloud microtangent plane is obtained through principal component analysis method, thus the boundary points of the point cloud are extracted. Secondly, the covariance matrix is constructed according to the normal information of the target detection point, then the corner response intensity function is calculated and compared, and some points are selected as calculation objects to judge whether they are true corner. Thirdly, the pseudo angles are filtered out and the true angles are selected by using a pseudoangle detection method based on Gaussian curvature extreme points. At last, the fast point feature histogram method is used to match similar corners between each group, and the nearest point search point cloud registration algorithm is used to realize the splicing of multiple points and cloud in the underground pipe gallery. The results are compared with that of the conventional 3D-Harris angular point detection algorithm. It is proved that the method in paper takes less time to calculate and has a higher corner-point extraction accuracy, which can realize accurate splicing of massive point cloud of underground pipe gallery.

Large-scale grid connection of new energy power generation makes cogeneration units need flexible operation to smooth out the fluctuation brought by new energy access. In order to meet the control requirements of flexible operation of the unit and the safety of the unit operation, a flexible control strategy for cogeneration units based on flexibility evaluation is designed. Firstly, according to the response characteristics of electrical load, thermal load and throttle pressure of the unit, a calculation method of flexibility evaluation indexes which can represent the load adaptability and operation safety of the unit are proposed, and these indexes are used as the basis for selecting the optimal flexibility factors. Then, the influence of flexibility factor on the system performance under a single working condition is simulated. Finally, on the basis of determining the optimal flexibility factors under different working conditions, the adaptive flexibility factors that changing with working conditions are designed and applied to the flexible control. The simulation results show that, the control strategy can not only achieve a better control effect when the unit runs under large-scale conditions change, but also achieve a better control for the unit after the low-pressure cylinder is cut off, which can meet the control requirements of flexible operation of the unit and ensure the safety of the unit operation..

In order to improve the energy utilization efficiency of high flexibility power generation system coupled with internal combustion engine and coal-fired unit, a new thermal system combined with the internal combustion engine and the coal-fired unit was proposed. By feeding the flue gas of internal combustion engine and the waste heat of cooling water into the thermal system of coal-fired generating unit, the coal consumption of coal-fired generating unit can be reduced. EBSILON software was used to model the composite system. Steam consumption rate and heat consumption rate of the coal-fired units were taken as evaluation indexes to analyze the thermal economy of the coal-fired unit under different composite schemes. The results show that, the heat consumption rate and steam consumption rate of the coal-fired unit can be significantly reduced by combining the waste heat of the internal combustion engine into the thermal system of the coal-fired unit. The closer the compound position of flue gas waste heat is to the boiler, the smaller the proportion of feed water and condensed water involved in flue gas heat exchange, and the lower the heat consumption rate and steam consumption rate of the unit. When one part of the flue gas waste heat is used to heat the high pressure heater feed water and the other part is used to heat the low pressure heater condensed water, more waste heat will be allocated to feed water, and the heat consumption rate and steam consumption rate of the unit wil decrease. After optimization, the heat consumption rate of the combustion engine and coal-fired unit combined thermal system can be reduced by 6.62% at most.

Tibet is located in the hinterland of the Qinghai-Tibet Plateau, the area above 4 000 m accounts for 85% of the total area of the region, its geothermal resources are very rich. To realize the reasonable exploitation of geothermal resources, combined with the carbon peaking and carbon neutrality strategy, the current situation of the development and utilization of geothermal resources in Tibet is comprehensively combed, and the suggestions for the future development of the geothermal industry are put forward. The analysis shows that the geothermal resources of hydrothermal and dry hot rock in Tibet have large storage capacity, good quality, and excellent power generation potential. The shallow geothermal resources are mainly distributed in Lhasa, which can be combined with heat pump technology for local heating. At present, there are still some problems in geological exploration, technical improvement, equipment development, and operation management. It is necessary to develop ORC units, build EGS experimental platform, and scientifically develop deep geothermal energy. The research shows that the development and utilization of geothermal resources in Tibet should follow the principles of "survey-based, power generation-based, heating-assisted, equipment upgrading, and cascade utilization", promote the scientific exploitation and efficient utilization of geothermal resources, improve the geothermal industry chain, and effectively improve the energy consumption structure in Tibet.