Coordinative Control Strategy of Virtual Inertia and Primary Frequency of DFIGs Based Wind Farms

Xinshou Tian, Weisheng Wang, Yan Li, Haiyan Tang, Yongning Chi, Yukun Wang and Zhen Wang
State Key Laboratory of Operation and Control of Renewable Energy & Storage Systems China Electric Power Research Institute Beijing 100192, China e-mail:xinshoutian@
Abstract—The mechanical parts of doubly fed induction generators (DFIGs) is decoupled from electrical parts, which makes the output active power hard to respond the frequency change of power grid, it becomes a new challenge to frequency stability of power grid with large scale wind power grid integration. A coordinative control strategy of virtual inertia and primary frequency of DFIGs based wind farms is given, and its principle is analyzed in the paper. The primary frequency control is a slow process, which is mainly implemented by control level of DFIGs based wind farms, and the DFIGs is cooperative. The virtual inertia control is a fast process, which is only implemented by control level of DFIGs. The theoretical analysis and time domain simulation show that the proposed control strategy can guarantee the frequency stability of power grid with large scale wind power integration. Index Terms—DFIGs; wind farms; virtual inertia; primary frequency; coordinative control strategy.
2016 IEEE PES Asia-Pacific Power and Energy Conference – Xi’an – China
Coordinative Control Strategy of Virtual Inertia and Primary Frequency of DFIGs Based Wind Fbit through adding active power frequency control module. The disadvantage of this method is that the frequency regulation of wind turbines is limited in low wind speed condition because of lower rotor speed, and the decreased rotor speed makes wind power obtained capability decrease in the process of frequency regulation, which may cause secondary frequency disturbance. Secondly, primary frequency control technology uses reserved active power of wind turbines to participate in frequency control of power grid [10-18] . The de-load operation of wind turbines in normal condition, and the wind turbines can provide continuous active power support by releasing active power reserve when there is a frequency disturbance. The current researches mainly focus on frequency response characteristics or frequency control of single wind turbine. But the capacity of wind turbine is limited, the frequency control contribution of wind turbine is limited, and the frequency control of large scale wind power may bring other frequency stability of power grid, so the frequency control of large scale wind power need unified consideration. The fast response characteristic of virtual inertia control of DFIGs is an advantage, but lacking continuous active power support. Meanwhile, the primary frequency control of DFIGs can provide continuous active power support. So we need to coordinated consider the characteristics of virtual inertia control and primary frequency control. According to the above analysis, a novel coordinative control strategy of virtual inertia and primary frequency of DFIGs based wind farms is proposed based on the researches of variable parameter virtual inertia control strategy of DFIGs in paper [9] and practical primary frequency controller of DFIGs in paper [18]. The purpose of this paper is to provide a useful frequency control strategy of DFIGs based wind farms for improving the frequency stability of power grid with large scale DFIGs integration. The main work of this paper can be described as follows: section 1 gives a review of research on domestic and aboard and shortcomings. A coordinative control strategy of virtual inertia and primary frequency of DFIGs based wind
I.
INTRODUCTION
With the increasing of wind power, the proportion of thermal power is decreasing. At the same time the output active power of thermal power is declining due to the requirements of improving regional renewable energy consumptive level. These factors lead to frequency stability problem of power grid with large scale wind power integration exposed, and the frequency control of wind power is urgently needed. Currently, the limited output active power of wind power phenomenon is widespread in the area of large scale wind power development, which provides a chance of engineering applications for frequency control of wind power. In recent years, the frequency stability of power grid integrating large scale wind power has drawn great attention to the engineers and scientists of power systems [1,2]. Now, two aspects work have been done on frequency influence characteristics and frequency control of wind power. Firstly, virtual inertia control technology uses rotational kinetic energy of wind turbines to participate in frequency control of power grid [3-9]. The own inertia of wind turbines at maximum power tracking control operation mode does not reduce, and the