Analytical assessment of subsynchronous resonance ( SSR ) impact on doubly fed induction generator wind turbine behavior and efficient suppression of SSR oscillations

Abstract

Summary Wind‐farms are usually placed in remote areas, and thus high‐voltage AC‐based transmission systems with series capacitive compensation may be cost‐effective approaches for connection of wind‐farms to the grid over long transmission lines. However, the risk of subsynchronous resonance (SSR) is the main issue raised in series compensated transmission systems. This article first analytically investigates the effect of SSR phenomenon on the doubly fed induction generator (DFIG) dynamic behavior in a series compensated grid, and then proposes a proficient damping approach for complete suppression of SSR oscillations. The proposed damping approach is created by partial/full compensation of rotor back‐emf voltages by modifying the rotor‐side converter control. It is shown that under full compensation of rotor back‐emf voltages: (a) the rotor, stator, and grid currents become independent of SSR and (b) the DFIG and rotor circuit do not contribute to the induction generator effect, and subsynchronous oscillations have vanished quickly. In this article by the modal analysis and simulation results, it is shown that the proposed approach has a satisfactory response under different values of short circuit ratio and different series compensation levels. Next, it is shown that the proposed approach has superior performance compared to the rotor virtual resistance emulation approach.

Sub‐synchronous control interaction in power grids including doubly fed induction generator based wind turbines

“…This paper is a continuation of the previous paper by the authors [9]. The previous paper deals with the modal analysis of DFIG-based WT behaviour and damping improvement of SSR oscillations due to IGE effect.…”

“…To do this, the stator frequency is considered equal to 𝜔 res and then we write the DFIG stator and rotor voltages in the dq frame rotating at angular speed of 𝜔 res . Under the above assumptions, at steady state conditions, the derivative of the stator and rotor fluxes at the SSR frequency becomes equal to zero, and thus according to (1)-( 4) and ( 5), the stator and rotor voltages at the resonance frequency 𝜔 res can be given as (9) where subscript res represents the stator/rotor variables at the SSR frequency, L ls in ( 8) is the stator leakage inductance and E m−res = j 𝜔 res L m (i s−res + i r−res ) is the machine magnetizing voltage at the SSR frequency 𝜔 res . According to (6) and (8) and by ignoring the stator resistance and assuming L m ≈ L s , e r−res in (9) at steady state condition can be given as…”

Research on Mechanism and Damping Control Strategy of DFIG-Based Wind Farm Grid-Connected System SSR Based on the Complex Torque Method

“…The SSR suppression methods for doubly-fed wind turbines can be generally classified into the following four categories: firstly, the RSC control of doubly-fed wind turbines is directly modified. For example, in [18,19], the RSC control structure is directly modified. In [20], the excitation control is introduced for the active and reactive power of DFIG.…”