Research on the Interaction Between Multiple Timescales of the Grid-Tied Voltage Source Converter
Du Buyang1, Shao Dejun2, Zhu Jianhang1, Shi Mengxuan2, Xu Youping2
1. State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan 430074 China; 2. Central China Branch of State Grid Corporation of China Wuhan 430077 China
Abstract:The voltage source converter's (VSC) control system and its interactions with the network are important factors that cause the instability of the grid-tied VSC. The control of VSC has a multiple timescale feature, which can be divided into DC-link voltage control (DVC) timescale and alternating current control (ACC) timescale. Most of the existing research only focuses on the stability in a single timescale, and rarely deals with the interaction between multiple timescales. In this regard, this paper investigates the quantitative indicators and influencing factors of the interaction between different timescales of the grid-tied VSC using the modal analysis method. At the same time, the applicable scope of the models in DVC and ACC timescales is clarified, and the analysis results are preliminarily explained from a physical point of view. First, this paper briefly introduces the topology and control scheme of the grid-tied VSC and illustrates its multiple timescale dynamic characteristics. Next, the small-signal models of the grid-tied VSC in multiple timescales, DVC timescale, and ACC timescale are constructed. The accuracy of the above models is verified by the electromagnetic transient simulation and eigenvalue analysis. The participation factors for state variables and modes in different timescales are used in this work, which is based on the modal analysis method, to measure the relative strength of the interaction between different timescales. On this basis, the variation law of the interaction between different timescales with the bandwidth of the phase-locked loop (PLL) and the short circuit ratio (SCR) is analyzed. By comparing the eigenvalue damping ratios and oscillation frequencies of the grid-tied VSC models in multiple timescales, DVC timescale, and ACC timescale, this paper shows that the interaction between multiple timescales has an impact on the system stability analysis results. Then, the deviations of eigenvalue damping ratios and oscillation frequencies of the models in DVC or ACC timescale are analyzed when the PLL bandwidth and SCR vary. The applicable scope of the above models in a single timescale is clarified. And the theoretical analysis results are verified by electromagnetic transient simulation. Finally, the effects of the interaction between multiple timescales are initially explained from the physical level. The main conclusions of this paper are as follows. 1) The participation factors for state variables and modes in different timescales are defined as the different-scale participation factors, and it is pointed out that the different-scale participation factors can be used as a quantitative index to measure the interaction between multiple timescales. 2) When the PLL bandwidth increases or SCR decreases, the different-scale participation factors increase, which indicates that the interaction between multiple timescales is enhanced. 3) The influence of the interaction between multiple timescales on the analysis results of system stability is studied, and the applicable scope of the models in DVC and ACC timescales is proposed. The increase of PLL bandwidth or the decrease of SCR will lead to the enhancement of the interaction between multiple timescales, thus increasing the deviation of the eigenvalue analysis results of the models in a single timescale. 4) From the perspective of the parts in DVC timescale, the inner control loops are equivalent to the damping links. Therefore, the eigenvalue analysis results of the model in DVC timescale are lower in damping ratio and higher in oscillation frequency than those in the multiple timescale model. From the perspective of the parts in ACC timescale, the outer control loops are equivalent to the excitation, so the eigenvalue oscillation frequency obtained by the model in ACC timescale is much lower.
杜步阳, 邵德军, 朱建行, 石梦璇, 徐友平. 电压源型变流器并网系统多时间尺度间相互作用[J]. 电工技术学报, 0, (): 68-68.
Du Buyang, Shao Dejun, Zhu Jianhang, Shi Mengxuan, Xu Youping. Research on the Interaction Between Multiple Timescales of the Grid-Tied Voltage Source Converter. Transactions of China Electrotechnical Society, 0, (): 68-68.
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