Research on Coordinated Control Strategy of DFIG-ES System Based on Fuzzy Control

Abstract

As the penetration rate of wind power systems is rising, which causes the overall system’s inertia to decline, the power system’s capacity to regulate frequency will be negatively affected. Therefore, this paper investigates the inertia control of doubly fed induction generation, and an energy storage system is installed in the wind farm to respond to the frequency deviation. First, a fuzzy control-based virtual inertia adaptive control strategy is presented. The goal of dynamic adjustment of the virtual inertia coefficient is realized by taking into account the uncertain factors of wind speed and frequency change rate. A recovery strategy based on the energy storage system’s level of charge is employed to prevent overcharging and over-discharging of the battery. Then, a weight factor based on frequency deviation is introduced to combine the droop output of the energy storage system with the virtual inertia output of the doubly fed induction generation, and the joint output mode of the wind storage system is determined in each stage of primary frequency regulation. Finally, the simulation verification is performed using the wind storage system simulation model created by MATLAB. The comparison results with other control methods prove that the proposed method is effective.

Novel Fuzzy Logic Controls to Enhance Dynamic Frequency Control and Pitch Angle Regulation in Variable-Speed Wind Turbines

“…Using FLC to estimate adaptive droop coefficients should be an appropriate solution. For instance, references [45,[63][64][65] applied FLC for the adaptive droop gain, which considers the required reserved power according to wind speeds and de-loading ratios. However, the previous studies provided complex calculations and resulted in slow responses for frequency controls.…”

“…To avoid signal delays and minimize possible noises, a filter is added in the control loop. Compared with traditional fuzzy adaptive droop controls [44,[62][63][64], the proposed method can simplify the implementation of frequency regulation and improve the frequency response of VSWTs. The proposed control method is illustrated in Figure 10, where the ROCOF serves as one of the fuzzy inputs, providing a rapid response to disturbances.…”