组串式 LC型光伏逆变器并网谐波环流及其抑制策略分析

摘要

Three‐level LC‐filter type string inverters are widely used in photovoltaic power systems . whose non‐isolated characteristic may cause differential‐mode harmonic circulating current . To analyse the influencing factors and specific forms of the harmonic circulating current , a differential‐mode harmonic circulating current model is built in ideal situations . The relations between harmonic circulating current and power device switching transient as well as relations between peak‐peak value of harmonic circulating current and carrier interleaving angle and grid vector angle are obtained . Afterward , the effects of stray parameters on high frequency harmonic circulating current in non‐ideal situations are analyzed . On this basis , the effects of three typical harmonic circulating current reduction methods on harmonic circulating current in the above model are analyzed , and the pros and cons as well as the scope of application of those methods are worked out . Finally , the analysis of harmonic circulating current and the reduction methods are verified through simulations and experiments .%组串式LC滤波型三电平并网逆变器并联入网结构广泛用于光伏发电系统中，其非隔离特性可导致逆变器之间差模谐波环流问题。为分析谐波环流的影响因素和具体形态，首先在理想情况下建立了差模谐波环流模型，得出谐波环流与功率器件开关暂态的关系，以及环流谐波峰峰值与各逆变器不同步的载波交错角度和电网矢量角度的关系，并考虑非理想情况下寄生参数对谐波环流的影响。在此基础上，分别分析3种典型的环流抑制方案对模型中输出环流的影响，得出各方法的优缺点和适用范围。