The Capacity Credit Assessment Method Of Large-scale Intermittent Generation And Its Application

At present, environmental problems and energy crisis have become increasingly serious in human society. As the effective encouragement for clean energy by the government and the proven technique to use the new energy, the abundant natural resources of wind and photovoltaic in China are gradually developed. The installed capacity is growing rapidly in recent years. Wind power and photovoltaic generation both have the advantages of clean and renewable. But affected by natural conditions, their output has the characteristic of randomness and intermittence. For this reason, we call the wind power and photovoltaic generation of intermittent power. Their contribution to the reliability of the power system is different from traditional power forms. Capacity credit is an important indicator to measure the contribution of the intermittent power for the power system reliability. It is the traditional power capacity replaced by the intermittent power in the case of keeping the reliability of system in the same level before and after the intermittent power interconnection with grid. Calculating intermittent power credible capacity quickly and accurately is the foundation of the system planning including intermittent power.Firstly, this paper introduces the researching status and the modeling methods of the intermittent power. Especially, the review on the definition standard and calculation methods of capacity credit is carried out in this paper.Secondly, in order to evaluate the impact of the correlation between wind farms located in the same geographical region, this paper describes their correlation by using Copulas connection function, and constructs the joint probability distribution of wind farms outputs. Wind farms outputs are equivalent to the polymorphic generators and the capacity credit of wind farms is calculate by using secant method.Then, this paper presents a new method for evaluating the capacity credit of PV generation considering the characteristics of PV output and its relationship with the load. The curves of the PV output and load are split into multiple hours, and the curves fit together in the corresponding hour. The PV capacity credit model is established with the constraint of the difference between the day-peak and the night-peak of the load.Finally, this paper applies the capacity credit to the assessment of the comprehensive benefit of wind/PV hybrid system. The complementary characteristics of wind/PV hybrid system are analyzed and the capacity credit of hybrid system is calculated. Based on the electricity benefit, environment benefit and capacity benefit, this paper establishes a model of comprehensive benefit model of wind/PV hybrid system.