基于对称控制的三相并网变流器单输入单输出阻抗建模与分析  

Single-Input Single-Output Impedance Modeling and Analysis of Three-Phase Grid-Tied Converter Based on Symmetric Control

作　　者：王震[1] 程鹏[1] 贾利民[1,2] Wang Zhen;Cheng Peng;Jia Limin(China Institute of Energy and Transportation Integrated Development North China Electric Power University,Beijing 102206 China;State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University,Beijing 100044 China)

机构地区：[1]华北电力大学国家能源交通融合发展研究院,北京102206 [2]轨道交通控制与安全国家重点实验室(北京交通大学),北京100044

出　　处：《电工技术学报》2024年第6期1777-1791,共15页Transactions of China Electrotechnical Society

基　　金：国家重点研发计划资助项目(2021YFB2601600,2021YFB1600203)。

摘　　要：三相并网变流器的不对称控制结构会导致频率耦合效应,降低其接入弱电网的稳定裕度,增加了阻抗分析的复杂度。首先,该文提出一种三相并网变流器的对称控制策略,以消除由锁相环和直流电压环引起的频率耦合效应。该控制策略通过在控制环路中引入直流电压环q轴补偿,以形成对称的直流电压闭环结构,同时引入对称锁相环,消除传统锁相环的非对称动态特性。因此,三相并网变流器可建模为单输入单输出的阻抗复矢量形式,进而可采用标准奈奎斯特准则进行阻抗稳定性分析,能够直观地说明控制器对系统阻抗特性的主导作用。然后,对并网变流器的阻抗特性进行分析,得出弱电网中对称锁相环的带宽对系统稳定性有着至关重要的影响,并且,不同运行工况也会改变并网变流器的阻抗特性,进而影响系统的稳定性。最后,仿真和实验结果验证了所提控制策略对频率耦合效应抑制的有效性以及阻抗特性分析的准确性。With the development of renewable energy power systems,three-phase grid-tied converters(GTCs)are widely used as grid-tied interfaces of wind,solar,and battery systems.Because renewable sources are distributed in remote areas,long-distance transmission lines result in a weak grid.In the weak grid,the asymmetric control structure of a three-phase gird-tied converter leads to frequency coupling,which is not conducive to the stability of the system and the design of the controller.Therefore,a symmetric control strategy is proposed to compensate for the asymmetry of the dq axis caused by the phase-locked loop(PLL)and DC-link voltage control(DVC).Then,the frequency coupling effect is eliminated,and GTCs are modeled as a single-input and single-output(SISO)admittance complex vector.The stability analysis based on the SISO admittance can reveal the inducement of system oscillation and simplify the parameters design of the controller.Firstly,the dq-frame admittance model of the DVC-embedded GTC with the conventional control strategy is developed,and the instantaneous power balance of the filter is considered for accuracy.Then,the unified impedance modeling approach transforms the real admittance matrix into the complex admittance.Since the dq axis is asymmetric,the complex conjugate components of the PCC voltage and current are introduced,and the frequency coupling effect is inevitable.Consequently,the symmetric PLL(SPLL)and the q-axis compensation of DVC are introduced.Compared with the synchronous reference frame PLL(SRF-PLL),SPLL controls the q-axis and d-axis of common coupling(PCC)voltage points.Therefore,the output of the SPLL is a complex vector angle that tracks the amplitude and phase of the PCC voltage.For DVC,to compensate for the asymmetry of q-axis control,q-axis voltage feedforward compensation and q-axis current feedback compensation are introduced,respectively,effectively eliminating the conjugate components of the DVC.Moreover,the accuracy of the symmetric control model is verified by the sweep frequency

关 键 词：三相并网变流器 频率耦合 对称控制 弱电网 稳定性分析 

分 类 号：TM46[电气工程—电器]