The instantaneous heat collection of the nontracing compound parabolic concentrator is greatly affected by the incident angle. Therefore, in this paper, the PV module with a mirror on its backside was arranged above the focal spot of the traditional compound parabolic concentrator to realize the reuse of the escaped light and improve the solar energy conversion efficiency of the device. The ray tracing of the novel compound parabolic concentrator based on photothermal photovoltaic coupling energy supply was carried out with optical software, and the influence of radial incident angle on the light receiving rate was compared and analyzed. In the actual environment, the variation of the inlet and outlet temperature, instantaneous heat collection and output power of the novel compound parabolic concentrator with time were tested and studied. The results indicate that the light receiving rate of the novel compound parabolic concentrator is consistent with that of the traditional compound parabolic concentrator. When the radial incident angle is 20°, the light receiving rate of the novel compound parabolic concentrator is 89.00%, which is 72.82% higher than that of the traditional compound parabolic concentrator. In sunny days, the maximum outlet temperature, the photothermal conversion efficiency and the daily output power of the novel compound parabolic concentrator. are 34.20 °C, 73.40% and 118.40 W, respectively.

This study addresses challenges associated with conventional parabolic trough solar power systems, including limited operating temperature and excessive thermal stress caused by uneven energy flux density distribution on the vacuum absorber tube's surface. Rather than altering the parabolic trough collector's structure, we introduce an innovative vacuum absorber tube design. This design involves reducing the diameter of the inner metal tube, shifting it downward, and adding a hyperbolic secondary concentrator above it to enhance solar energy concentration and improve energy flux distribution on the inner metal tube's surface. Simulation results for the new vacuum absorber tube yield promising outcomes. Optically, this novel design increases the concentration ratio from 62 to 71 and improves the uniformity of energy flux distribution by 55.05%. Importantly, these improvements come at the cost of only a 1.88% reduction in optical efficiency compared to traditional vacuum absorber tubes. Consequently, these modifications offer a substantial boost to the overall performance of the parabolic trough collector.

Pitch control of large wind turbine is a complex nonlinear control task. How to achieve power regulation and load reduction under system constraints and wind speed disturbance has become a problem. For this problem, a controloriented linear parameter varying (LPV) model is constructed by using mechanism and parameter identification methods. The gap metric theory is introduced to reduce the complexity of the model, which provides a more accurate linear model for control design. Based on the obtained optimal states, an adaptive model prediction pitch controller (MPC)is proposed with the change of realtime wind speed. The coordinated control of powerload for large wind turbine can be realized under the conditions of system constraints. The simulation examples of OpenFAST show the effectiveness of the proposed model and controller.

In the construction of floating wind farms, various soil conditions may be faced. Based on the needs in practice, a kind of anchor named gravity penetration column anchor is proposed for the soil with high permeability, where has high risk of installation by suction. The finite element method was used to analyze the penetration process and bearing characteristics of this kind of anchor. The analysis results show that in the coarse sand, the gravity penetration column anchor can penetrate to the design depth by its own weight. Unlike ordinary gravity anchors, which mainly provide anti sliding force through friction at the anchor bottom, the gravity penetration column anchor is shallow failure under horizontal load, and can mobilize more soil resistance during the failure improving its anti sliding ability effectively. The gravity penetration column anchor can provide a horizontal bearing capacity of more than 2 000 t, which is nearly twice that of conventional gravity anchors, and can meet the bearing requirements of floating wind turbine. This kind of anchor could provide more choices for offshore floatingturbine in China.

In response to stability issues caused by the dynamic response of wind turbines, in order to study the numerical response of the wind turbine under different wind speeds, a threedimensional structural model of the wind turbine is established based on SolidWorks, the blade root and tip particles are extracted, and the stress and displacement trends under different wind speeds are analyzed by using the finite element analysis method. The wind speed attenuation in the pendulum direction and the brandishing direction of the wind turbine is studied and the shear stress distribution of the flow field near the blade surface is discussed. The results show that the stress and displacement of blade tip and blade root have certain regularity under different wind speeds. When the natural wind passes through the wind turbine, the wind energy is effectively captured, and then shows regular attenuation. This study provides reference value for the dynamic parameters of wind turbine operation and improves the stability of wind turbine operation.

Offshore wind turbines installed close to earthquakeprone zones are not only affected by wind and wave loadings, but also threatened by earthquakes. In order to reduce the earthquake impacts on the structural vibration and load of largescale wind turbines, a seismic coupled analysis and structural control architecture has been developed by improving FAST based on the modal acceleration method and the Tuned Mass Damper (TMD). The control effects of TMD on tower vibration and load reduction of the IEA 15 MW monopile wind turbine due to different ground motions are investigated. The results show that the TMD can significantly reduce the towertop displacement and towerbase load for each examined ground motion. The best effect on alleviating towertop vibration is achieved when the tuning frequency ratio of the TMD is 0.9, reducing the tower top displacement by 89.8%. The fluctuation amplitude of towerbase bending moment following the earthquake event is significantly reduced by the TMD with a tuning frequency ratio of 0.8 that is capable of reducing the standard deviation by up to 99%.

With the continuous development of renewable energy, a large number of inverter interfaced distributed generations (IIDG) are connected to the distribution network, which puts forward new requirements for the traditional relay protection technology. In order to improve the power supply reliability of distribution network and adapt to the new power system with large penetration of renewable energy, an adaptive distance protection is proposed for distribution network with Tconnected IIDG. Firstly, the influence of fault at different locations on the protection is analyzed. According to the output characteristics of IIDG in case of system fault, the output current of IIDG is calculated by BP neural network using the local electrical information of the protection, and the action value is set immediately. Because this method does not need to communicate with the remote, the action speed is fast, and the investment of the communication system is reduced. Finally, the 10 kV distribution network model with Tconnected IIDG is established in MATLAB, and compared with the traditional distance protection to verify the superiority of this protection method.

The solar heating system coupled with seasonal thermal storage is a promising solution to solve the seasonal mismatch between the solar energy supply and heating demand. The thermal performance of the system in the heat storage season has a significant impact on the system's annual operation performance, and has a direct impact on the discharging process of the seasonal storage in the heating season. Therefore, based on the solar heating system coupled with seasonal thermal storage in Fanshan Town, Zhangjiakou, a dynamic simulation platform is built. The influence of different operation strategies on the performance of the system is analyzed by experiment and simulation methods. Results showed that the control strategies were significant for improving the heat collection performance of solar receiver and the exergy efficiency of the UWPS. The stratification of the seasonal storage has an impact on the collection efficiency of the receiver, especially at the end of the nonheating season. In addition, at the end of the nonheating season in typical year, the monthly solar collection efficiency could be increased by 4.8% in variable flow control compared to the temperature difference control.

Due to the intermittency and uncertainty of wind power on the time scale and complementarity on the spatial scale, the line capacity is underutilized and the cost of wind power is high in traditional planning. Combined with the output characteristics of largescale wind power, considering the smoothing effect, the construction cost of transmission projects, the cost of wind power curtailment, and the income, the economic evaluation model of offshore wind farm aggregation system is established, and the model is solved by using an improved genetic algorithm. The genetic algorithm is improved based on the minimum spanning tree of dynamic weight variation, and the coding, selection, crossing, and mutation links in the genetic algorithm are improved to promote the efficiency of the algorithm. Taking a wind farm cluster in Jiangsu Province as an example, the topology of wind turbines and the convergence and connection mode of wind farms are optimized, and the results show that the proposed algorithm has good optimization and convergence. And the established topology optimization model of wind farm and internal wind turbines can effectively reduce the engineering investment.

This thesis constructs a coupling system inactive adjustment model for system voltage output of wind power fluctuations in renewable energy and thermal power generation coupling systems, and constructing coupling system reactive modulation models, on the basis of considering communication delays, The voltage deviation is quantified index to analyze the effect of reactive power control on voltage stability in coupling system. A coupling system bilateral reactive control optimization strategy for fusion SVG and wind turbines as reactive modulated resources is proposed. The upper layer is based on SVG as an inactive adjustment device, and the system's overall power factor optimization model is constructed by the respective node voltage deviation. The lower layer is a node having a large voltage deviation. The wind turbine near the node is used as an inactive adjustment device. The system voltage deviation is optimal, and the wind turbine reactive optimization model is constructed, and the algorithm combined with Ybus and LinWPSO is used. Solve the optimization model and derive the wind power unit reactive reference value. The case simulation results show that the twolayer reactive policies mentioned in this paper make full exertion of the powermodulated potential of the wind and motor sets, which can take care of the voltage fluctuations and web damage of the coupling system, and reduce the disturbance of the renewable energy power fluctuations on the coupling system, improve coupling the voltage stability of the system.