Active damping of resonances in DFIG system with cascade converter under weak grid

Abstract

Summary The interaction of impedance between the doubly fed induction generator (DFIG) system and series‐compensated weak grid gives rise to an issue of subsynchronous resonance (SSR). Likewise, the high‐frequency resonance (HFR) occurs when a DFIG system is connected to parallel‐compensated weak grid. This paper proposes an improved method to mitigate the caused resonance. The improved method, based on impedance modeling, utilizes an additional cascaded converter (CC) at Y‐point of DFIG stator winding with virtual impedance implemented at the CC control unit, which reshapes the DFIG impedance for effective mitigation of both SSR and HFR. The virtual impedance is disabled when DFIG operated in series‐compensated weak grid, while enabled when working in parallel‐compensated weak grid, which effectively damps the HFR. A detailed theoretical explanation and impedance modeling of the CC has been given. The effectiveness of the proposed method has been validated through MATLAB simulations based on a 2‐MW DFIG system.

Recent development and future trends of resonance in doubly fed induction generator system under weak grid

“…The HFR has been studied in the grid connected converter [214–221]. However, the HFR in the DFIG system is quite a new phenomenon, which has been researched recently [222–242]. The impedance based modeling approach is used for the analysis of HFR.…”

“…So, the control complexity and the burden on the traditional RSC and GSC control might be increased. The novel cascade converter (CC), that is, the hardware-based solution, is proposed by authors in [242] to damp the HFR in the DFIG system. The proposed CC is serially connected at the Y-point of the DFIG's stator winding, as shown in Figure 39a.…”

Impact of Phase Locked Loop with Different Types and Control Dynamics on Resonance of DFIG System

“…The subsynchronous resonance (SSR) [5][6][7][8][9][10][11] and high frequency (HFR) [12][13][14][15][16] may occur, when the DFIG system operates under a series and parallel compensated weak grid, respectively.…”

“…Literature [5], further reports that the high bandwidth PLL, i.e., the larger values of K pPLL and K iPLL , increases the probability of the SSR incidence in the DFIG system due to the low phase margin [27] studying the effect of PLL parameters on the SSR in a type-4 wind turbine. However, the impact of PLL on the impedance modeling has been ignored for the analysis and damping of HFR in the DFIG system [12][13][14][15][16].…”