Analysis of the Propagation Characteristic of Subsynchronous Oscillation in Wind Integrated Power System

Abstract

This paper proposes oscillation propagation factors to analyze power oscillations caused by the interharmonics of doubly fed induction generators (DFIG) at different points in the power system. First, a dynamic model of the DIFG is built, including the asynchronous generator, its transmission system, converters and the control systems. Then, the state space expression is formed by deducing the input and output matrices. From this, the oscillation propagation factor is proposed and denoted to exhibit the propagation mechanism of interharmonics in the view of frequency domain, by deducing the multi-input-multi-output transfer functions matrix. Along with this, the sensitivity of propagation is calculated for adjusting the parameters to block the oscillation propagating path. Finally, the modified four machine system with two DFIGs and the New-England 39 bus system with two DFIGs is used as a test system to verify the effectiveness of the oscillation propagation factor. From this the simulation results demonstrate that the subsynchronous interharmonics of DFIGs injected into the grid will propagate to the different points of the system and results in oscillation of the power. The oscillation propagation factor could quantize the oscillation magnitude propagating from one point to other point in the wind integrated power system.

Defining SSO Power and Characterizing SSO Propagation in Power System With Wind Farms Integration

“…The impact factor of SSO power propagation is proposed to quantitatively determine which influencing element has a dominant impact under different operating conditions. The magnitude ratio of pSS_AC1(t) to pSS_AC2(t) in ( 7) is proportional to the ratio of line impedance at ωSS to line impedance at ω0, as shown in (19).…”

“…Existing literature on the SSO propagation generally concentrates on i) studying the propagation mechanism of SSO [14], ii) defining the concept of subsynchronous power [15][16][17][18], iii) identifying the influencing elements of SSO propagation [19] and iv) determining the propagation path of SSO [20]. Gong Y et al find that the oscillating current propagates along the weakly damped channel in the synchronous generator-based system [14].…”

“…In terms of instantaneous power definition, Akagi et al introduced the instantaneous power theory in the early 1980s, based on the instantaneous value, applied to non-sinusoidal circuits and various transition processes [17][18]. Wen Z et al propose an oscillation propagation factor, obtained only by the system transfer function matrix, which can represent the propagation characteristics of SSO [19]. In [20], the shunt coefficient which can characterize the SSO propagation path is proposed.…”

“…In SSO events, long-distance and cross-voltagelevel propagation of SSO is obviously beyond traditional cognition, which thinks SSO propagation is a local issue. Besides, oscillation propagation has been previously analyzed only in single oscillation frequency source systems [14][15][19][20]. The propagation mechanism of multiple oscillation sources considering the coupling effects of different frequency components has not yet been studied.…”

Identification of dominant propagation paths based on sub-synchronous oscillation using branch oscillation energy distribution coefficient

“…Reference (Wen et al, 2019) proposed a sub-synchronous oscillation propagation factor that characterizes the propagating characteristics of sub-synchronous oscillations based on frequency domain methods. This factor is obtained from the transfer function matrix of the system, but no analysis was performed on the factors that affect the propagation factor during the study.…”