摘要
在弱电网条件下,由于并联逆变器之间以及逆变器与电网之间的耦合作用,系统会产生谐振。同时,实际系统中的电网阻抗以及逆变器到并网点处的线路阻抗又会导致谐振点发生偏移,加剧系统谐振失稳。以单台并网逆变器为基础,建立考虑电网阻抗和线路阻抗的多逆变器并联数学模型,通过探讨弱网下并联系统的谐振形成机理以及分析电网和线路阻抗对系统谐振产生的影响,研究一种进网电流全前馈与PCC点并联虚拟导纳相结合的谐振抑制方法。在Simulink中搭建3台基于LCL滤波器的T型三电平逆变器并联系统仿真模型并进行仿真。仿真结果表明该方法可以有效抑制LCL型并网逆变器的自身固有谐振以及弱电网引发的谐振,同时还可以有效提高系统稳定性,增强多机并联系统对线路阻抗和电网阻抗变化的鲁棒性。
Under weak grid conditions,the system generates resonance due to the coupling between parallel inverters and between inverters and the grid.At the same time,the grid impedance in the actual system and the line impedance from the inverter to the grid connection point cause the resonant point to shift,aggravating the system resonance instability.Under the background,a multi-inverter parallel mathematical model considering grid impedance and line impedance is established on the basis of a single grid-connected inverter firstly.Then,the resonance formation mechanism of the parallel system under weak grid is discussed and the influence of grid and line impedance on system resonance is analyzed.Meanwhile,a resonance suppression method is proposed by combining the full feedforward of the incoming current and the virtual admittance in parallel at the PCC point.Finally,three parallel system simulation models of T-type three-level inverters based on LCL filters are built in Simulink.The simulation results show that this method can effectively suppress the inherent resonance of the LCL grid-connected inverter and the resonance caused by the weak grid.In addition,the method can also effectively improve the system stability and enhance the robustness of the multi-machine parallel system to changes in line impedance and grid impedance.
作者
曹芸凯
赵涛
朱爱华
孙权
CAO Yunkai;ZHAO Tao;ZHU Aihua;SUN Quan(School of Automation,Nanjing Institute of Technology, Nanjing 211167, China;Shaoxing Power Supply Company,State Grid Zhejiang Electrical Power Co., Ltd., Shaoxing 312000, China)
出处
《电力科学与技术学报》
CAS
北大核心
2022年第2期188-196,共9页
Journal of Electric Power Science And Technology
基金
国家自然科学基金(61901212)。
关键词
谐振
多逆变器并联
LCL滤波器
弱电网
resonance
paralleled connection of multiple inverters
LCL filter
weak grid