A frequency-responsive power-smoothing scheme of a doubly-fed induction generator for enhancing the energy-absorbing capability. (October 2021)

• Record Type: Journal Article
• Authors: Choi, Seungho; Kang, Yong Cheol; Kim, Kyu-Ho; Lee, Young-Il; Terzija, Vladimir
• Is Part Of: International journal of electrical power & energy systems. Volume 131(2021)
• Publication Date: 2021-10
• Subjects: Frequency deviation loop -- Frequency fluctuations -- Frequency-regulating capability -- Frequency-responsive power smoothing -- Variable control gain; Electrical engineering -- Periodicals; Electric power systems -- Periodicals; Électrotechnique -- Périodiques; Réseaux électriques (Énergie) -- Périodiques; Electric power systems; Electrical engineering; Periodicals; 621.3
• DOI: 10.1016/j.ijepes.2021.107053
• Languages: English
• ISSNs: 0142-0615

Abstract

Highlights: Continuously varying wind speeds cause the frequency fluctuation. Power smoothing can maintain the frequency within a narrow range under normal operation of a power grid. The rotating masses of a WTG can be effectively used as an ESS for the frequency regulation. The proposed scheme can improve the flexibility of a power grid, particularly in a higher penetration level of wind power. Abstract: Continuous wind speed variations fluctuate the active power of a wind turbine generator (WTG), thereby causing grid frequency fluctuations. Difficulty arises in alleviating the frequency fluctuations during normal operation, if WTGs continue to operate maximum power point tracking even for a high wind penetration level. This paper proposes a novel frequency-responsive power-smoothing scheme for a doubly-fed induction generator (DFIG) that can maintain the frequency deviations within a narrow range during normal operation of a power grid. To decrease the frequency in the overfrequency section, the proposed scheme decreases the DFIG active power, thereby absorbing energy into the rotating masses of a DFIG. To increase the frequency in the underfrequency section, the proposed scheme increases the active power, thereby releasing energy from the rotating masses. In the medium and high rotor speed regions, to improve the frequency-regulating capability, the proposed control gain increases as a fourth-order polynomial of the rotor speed. To avoid overdeceleration in the low rotor speed region, the control gain decreases as a sixth-order polynomial of the rotor speed as the rotor speed decreases. The simulation results clearly demonstrate that the proposed scheme significantly mitigates the frequency fluctuations under various wind conditions even in high wind penetration levels.