并网变流器阻抗模型主要包含序阻抗和dq阻抗,两种阻抗间现有转换方法较为繁琐、通用性不强,缺乏考虑参考系初相位实际值,限制了阻抗模型的相互校验和实际应用。基于此,首先从机理上探究了参考系初相位在阻抗建模中的作用路径,接着考虑参考系初相位因素推导得出了完整的dq阻抗、多输入多输出（MIMO）及等效单输入单输出（SISO）序阻抗之间的数学关联关系,并归纳得出通用转换公式。在此基础上,通过定义负频段dq阻抗,简化了基频以下序阻抗与dq阻抗转换关系,揭示了dq阻抗的对称频率共轭特性,保证了阻抗转换公式的通用性。进一步地,阐明了参考系初相位对阻抗测量和稳定判据应用的影响,并提出参考系相位校正方法,实现了任意参考系下阻抗间的相互校验。最后,通过风电机组仿真与现场扫频试验验证了理论分析的准确性和有效性。
Abstract
The impedance models of grid-connected converters mainly include two categories： sequence impedance and dq impedance. However, the existing conversion relationship between these two types of impedances is complex and lacks universality, which does not consider the actual initial phase of the reference frame and limits the cross-checking and practical application of the theoretical impedance models. Therefore, this paper first explores the impact path of the initial phase of the reference frame on impedance modeling mechanistically, then establishes the comprehensive mathematical relationship between dq impedance, MIMO sequence impedance, and equivalent SISO sequence impedance considering the initial phases, and summarizes the universal conversion formulas. Based on this, dq impedance in the negative frequency band is defined, which simplifies the conversion between sequence impedance below the fundamental frequency and dq impedance. The symmetric frequency conjugation characteristics of dq impedance are revealed, and then the universality of the impedance conversion relationship is ensured. Furthermore, the influences of the initial phase on impedance measurement and stability criteria implementation are elaborated. A reference frame phase correction method is proposed, which achieves mutual verification between impedances in any reference frame. Finally, the accuracy and effectiveness of the theoretical analysis are verified through wind turbine simulation and on-site frequency sweeping tests.
关键词
并网变流器 /
序阻抗 /
dq阻抗 /
阻抗转换 /
参考系初相位
Key words
grid-connected converter /
sequence impedance /
dq impedance /
impedance conversion /
initial phase of reference frame
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基金
国家重点研发计划（2022YFB4202303）
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