Wind Turbine Ramping Control Considering Load Optimization

With the rapid development of new energy technologies, the capacity of integrated wind power is increasing. Winds are volatile and uncertain, so the output of wind turbine is also showing a time-varying characteristic. When the wind speed changes dramatically in a short time, wind power fluctuates largely which may cause wind power ramping events. If system reserve capacity is not enough or associated control is not applied to wind power before ramping events, the safe and stable operation of power system will be seriously affected. At the same time, due to the changes of external wind speed, wind turbine load environment becomes more complex. If the load of wind turbine is too large, it may cause blade damages and tower vibration, which shortens the life of wind turbine. In order to ensure the safe and stable operation of power system and improve wind turbine reliability and economy, it is important to study wind turbine ramping control strategy and load optimization plan.Based on momentum and blade element theory, solving processes of axial inducible factor and circumferential inducible factor are given by iterative method. Expressions of wind turbine aerodynamic load, gravity load and centrifugal load are provided. Wind turbine load models are established by MATLAB software. Aerodynamic performance and aerodynamic load of wind turbine blades are simulated and studied. After analyzing the relevant expressions of blade aerodynamic load, it concludes that the factors which affect aerodynamic load are wind wheel rotation angular velocity, wind velocity and pitch angle. Influence characteristics of each factor are analyzed by simulation study.For wind turbine ramping events in low wind speed, power output reduction control strategy of wind turbine is introduced. Optimal models are solved by PSO and the effectiveness of the proposed control strategy is verified. Different from the disadvantages of traditional power control, coordinated control strategies of wind turbine rotation speed and pitch angle are implied in this paper. Wind turbine loads are optimized. In order to avoid the negative influences of wind turbine ramping events in high wind speed, under the premise of contributing power as much as possible, ramping rate is minimized. Based on the above control strategy, optimization model is established, simplified and solved. Compared by optimization results of different weight coefficients, effects of weight coefficient are analyzed from the theory and simulation results two levels.Assessment results of wind power capacity credit can be used for providing preferences for wind power ramping events early warning and decision and ramping control. Based on Monte Carlo simulation, power system reliability evaluation method is given. Under the premise of reliability levels remaining same, wind power capacity credit assessment methods and indexes are proposed, which contain Effective Load Carrying Capability, Equivalent Firm Capacity and Equivalent Conventional Capacity. The differences between various methods and indexes are compared by MATLAB simulation and analyzed in theory.Some research results of wind turbine load models, influence factors and characteristics of load, wind turbine ramping control and load optimization and wind power capacity credit are achieved in this paper. The research can provide references for wind farms and farm groups ramping control and joint optimization of wind turbine power output and load in high wind speed.