Small-Signal Stability of a Grid-Connected PMSG Wind Farm Dominated by Dynamics of PLLs under Weak Grid Connection
Dong Wenkai1, Du Wenjuan2, Wang Haifeng1,2
1. State Key Laboratory of Alternate Power Systems with New Energy Resources North China Electric Power University Beijing 102206 China; 2. School of Electric Engineering Sichuan University Chengdu 610065 China
Abstract：This paper investigates the small-signal stability (SSS) of a grid-connected wind farm (GCWF) with direct drive permanent magnet synchronous generators (PMSGs) dominated by the dynamics of phase-locked loops (PLLs) under the condition of weak grid connection. To do so, the full-order linearized state-space model of a GCWF with N PMSGs was established at first. To analyze the impact of the strength of the AC system on the SSS of the GCWF, the full-order model was equivalently transformed into N independent subsystems, each of which was comprised of a single grid-connected PMSG, based on similar transformation of a matrix under the condition that the linearized models of the PMSGs in the GCWF were identical. Secondly, the 2th characteristic equation of the equivalent subsystem with only the dynamics of PLL and transmission line retained was established and the conditions under which the equivalent subsystem was stable were obtained. Thus, the critical condition of small-signal stability and reasons for and mechanism of the small-signal instability of the GCWF dominated by the dynamics of PLLs under the condition of weak grid connection were studied. It is indicated that, as the strength of the AC grid decreases, the network structure of the GCWF changes or the integral gain Ki of the PLL increases, the risk of small-signal instability of the GCWF dominated by the dynamics of PLLs increases. Finally, the effectiveness of the methods proposed and conclusions obtained were validated via study cases.
董文凯, 杜文娟, 王海风. 弱连接条件下锁相环动态主导的并网直驱风电场小干扰稳定性研究[J]. 电工技术学报, 2021, 36(3): 609-622.
Dong Wenkai, Du Wenjuan, Wang Haifeng. Small-Signal Stability of a Grid-Connected PMSG Wind Farm Dominated by Dynamics of PLLs under Weak Grid Connection. Transactions of China Electrotechnical Society, 2021, 36(3): 609-622.
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2021, Vol. 36 
