Two-Phase Short-Term Frequency Response Scheme of a DFIG-Based Wind Farm

Abstract

The kinetic energy stored in the doubly-fed induction generators (DFIG)-based wind farm can be utilized to sustain the dynamic system frequency. However, difficulties arise in determining the control gain to effectively improve the frequency nadir and smoothly return to the maximum power point tracking (MPPT) operation. This paper addresses a two-phase short-term frequency response (STFR) scheme to boost the frequency nadir and minimize the second drop in the system frequency based on a piecewise control gain. To achieve the first goal, a constant control coefficient, which is determined according to the initial operating conditions of the DFIG-based wind farm, is employed until the frequency nadir produces. To achieve the second goal, the control coefficient, which changes with time, facilitates to smoothly return to the MPPT operation. The effectiveness of the proposed two-phase STFR scheme is verified under various wind power penetration levels, wind speeds, and disturbances. The results reveal that the frequency nadir is improved, and simultaneously, it smoothly returns to the MPPT operation and minimizes the second drop in the system frequency.

Comparative Study of Grid Frequency Stability Using Flywheel-Based Variable-Speed Drive and Energy Capacitor System

“…The obtained results in the paper show considerable improvements in the power grid frequency compared to those obtained in the literature in references [30,32] with values of 59.42 Hz and 59.44 Hz, respectively, for their proposed schemes that were based on a 60 Hz frequency reference; as reported regarding frequency regulation, using DFIG as a primary frequency stability support is effective based on the concept of a pitch angle controller in settling frequency, frequency nadir, and DFIG-stored kinetic energy in a wind farm topology of maximum power point tracking.…”

“…This concept was able to improve the primary frequency response for faster recovery of the frequency variable. In a similar study carried out in [32], kinetic energy was stored and utilized in DFIG wind turbines on a wind farm to sustain the dynamics of the power grid frequency. In this study, the improvement of the frequency disturbance or nadir and smoothing of the output of the wind turbine was based on the principle of the maximum power point tracking (MPPT) operation to tackle a two-phase short-term frequency response.…”

The inertia and storage impact on the Mexican network frequency

“…Therefore, the plant system must implement additional generators with fast ramp capability to maintain system frequency stability [14]. Once they change the management strategy of VSWTGs, they will participate in frequency regulation by storing or cathartically installing on or from the rotating masses on the side of a wind turbine, gearbox, and generator rotor [15]- [16]. As in [17]- [19], the system's frequency change rate, and thus the frequency sweep management loops, often provide a frequency adjustment capability.…”

Power optimization control of VSC-HVDC system for electromechanical oscillation suppression and grid frequency control

“…Existing solutions mainly include: 1) The power system stabilizer to compensate for the negative damping, Kumar (2016); 2) The installation of synchronous condensers to improve the inertia level and damping ability of the power system to suppress electromechanical oscillations and frequency fluctuations, Nguyen et al (2019); 3) The use of reactive power compensation devices such as the static synchronous compensator to regulate the reactive power output and change the voltage level and power flow distribution of the system, thereby suppressing the grid electromechanical oscillations, Li et al (2020); 4) The use of energy storage devices to quickly emit or absorb active and reactive power to maintain the active power balance in the system and suppress power oscillations, yet energy storage devices are more expensive and difficult to apply on a large scale, Zhu et al (2019); 5) The use of the power of the new energies such as photovoltaic and wind generations to compensate for the power deficits or surpluses in the power system Yang et al (2021), but new energy generations typically operate in the maximum power point tracking mode; if used for grid frequency control and electromechanical oscillation suppression, a certain amount of capacity must be reserved for active participation in the regulation of the system dynamic process at any time, which will sacrifice their inherent power generation capacity, Li et al (2020).…”