功率双向流动时背靠背变流器稳定性分析

doi:10.12204/j.issn.1000-7229.2021.07.009

摘要/Abstract

摘要：

背靠背变流器作为区域电网互联的关键器件,其自身稳定性是保证电网间稳定运行的重要前提。文章主要从变流器直流端阻抗的角度研究了功率双向流动时背靠背变流器稳定性问题,分析显示背靠背变流器直流端在功率正向传输的稳定性劣于功率反向运行。针对功率双向运行对系统产生的稳定问题,提出在逆变器中引入直流电流内环控制从而对逆变器直流/交流端阻抗进行重塑校正,使得直流端输入阻抗由原本在低频段的负阻抗变为感性阻抗特性,从而提高了背靠背变流器运行的稳定裕度。最后,在Matlab/Simulink仿真平台建立背靠背变流器系统进行仿真验证,结果验证了理论分析及所提控制方案的可行性。

关键词: 背靠背变流器, 功率方向, 阻抗重塑, 直流电流, 稳定性

Abstract:

As the key component of regional power grid interconnection, the stability of back-to-back converters is an important prerequisite to ensure the stable operation of regional power grids. In this paper, the stability of back-to-back converter with bidirectional power flow is studied mainly from the perspective of the DC terminal impedance of the converter. The results show that the stability of the back-to-back converter is better when power reverses. To alleviate the stability problem of the back-to-back converter caused by bidirectional power flow, the DC current inner loop is introduced into the inverter to reshape the AC/DC impedance of the inverter, which makes the DC terminal input impedance change from the original negative impedance in the low frequency band to the inductive impedance characteristics, so as to improve the stability margin of the back-to-back converter. Finally, the model of back-to-back converter is established in the Matlab/Simulink simulation platform for simulation verification, and the results verify the feasibility of the theoretical analysis and the proposed control scheme.

Key words: back-to-back converter, power flowing direction, impedance reshaping, DC current, stability.

中图分类号:

TM712

姜玉霞, 田艳军, 李永刚. 功率双向流动时背靠背变流器稳定性分析[J]. 电力建设, 2021, 42(7): 73-82.

JIANG Yuxia, TIAN Yanjun, LI Yonggang. Stability Analysis of Back-To-Back Converter with Bidirectional Power Flow[J]. ELECTRIC POWER CONSTRUCTION, 2021, 42(7): 73-82.

图/表 20

图1 背靠背变流器结构框图

Fig.1 Structure of a back-to-back converter

图2 背靠背变流器等效原理图

Fig.2 Equivalent schematic diagram of back-to-back converter

图3 整流模块控制框图

Fig.3 Block diagram of rectifier control

图4 整流模块直流端等效阻抗伯德图

Fig.4 Bode plot of equivalent impedance on the DC-side of the rectifier

图5 逆变模块控制框图

Fig.5 Block diagram of inverter control

图6 逆变模块直流端等效阻抗伯德图

Fig.6 Bode plot of equivalent impedance on the DC-side of the inverter

图7 逆变模块交流端等效阻抗伯德图

Fig.7 Bode plot of equivalent impedance on the AC-side of the inverter

图8 直流电流控制下逆变模块控制框图

Fig.8 Control block diagram of inverter under dc-current control scheme

图9 优化前后逆变模块直流端阻抗伯德图对比

Fig.9 Comparison of bode plot of DC-side impedance of inverter before and after optimization

图10 优化前后逆变模块交流端阻抗伯德图对比

Fig.10 Comparison of bode plot of AC-side impedance of inverter before and after optimization

图11 正向时优化前后变流器直流端阻抗曲线对比

Fig.11 Comparison of DC-side impedance of back-to-back converter under forward direction before and after optimization

图12 反向时优化前后变流器直流端阻抗曲线对比

Fig.12 Comparison of DC-side impedance of back-to-back converter under reverse direction before and after optimization

图13 正向时优化前后逆变模块交流端阻抗伯德图对比

Fig.13 Comparison of bode plot of AC-side impedance of inverter under forward direction before and after optimization

图14 反向时优化前后逆变模块交流端阻抗伯德图对比

Fig.14 Comparison of bode plot of AC-side impedance of inverter under reverse direction before and after optimization

图15 正反向下变流器直流端阻抗比奈奎斯特曲线

Fig.15 Nyquist curves of the DC-link impedance ratio of back-to-back converter under the different directions

图16 逆变模块交流端阻抗波德图

Fig.16 Bode plots of AC-side impedance of inverter

表1 逆变模块交流端相位裕度

Table 1 AC-side phase margin of inverter

表2 背靠背变流器主拓扑参数

Table 2 Main topology parameters of back-to-back converter

图17 优化控制前后变流器直流波形对比

Fig.17 Comparison of DC-side waveforms of back-to-back converter before and after optimization

图18 优化控制前后逆变模块交流端功率波形

Fig.18 AC-side power waveforms of inverter before and after optimization

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