为同时满足光伏并网系统中逆变器升压和消除漏电流的要求,提出一种基于开关电容的双接地五电平光伏逆变器。所提逆变器拓扑具有自主升压、器件数量少、电容电压自动平衡和可扩展等优点。此外,双接地结构彻底消除了共模电压引起的漏电流,进而降低了电路的电磁干扰和功率损耗,并提高了系统的安全性。针对所提逆变器拓扑,采用一种包含移相载波的混合调制策略,解决了开关电容长时间连续放电的问题,从而减小电容电压纹波,提高输出SPWM电压波形质量。此外,通过与其他五电平逆变拓扑的比较,表明所提逆变器在结构、升压能力和减小电容电压纹波方面的优势。最后,通过实验验证所提逆变器拓扑的可行性及混合调制策略的有效性,结果表明所提逆变器具有较好的静态、动态特性和较高的转换效率。
Abstract
In order to meet the requirements of voltage boosting and leakage current elimination in grid-connected photovoltaic inverters, a common-ground five-level inverter based on switched-capacitor （SC） is proposed in this paper. The proposed topology possesses the advantages of self-boosting voltage, less components, capacitor voltage self-balance and scalability etc. Meanwhile, the leakage current caused by the common mode voltage （CMV） is eliminated by the common-ground structure, thereby reducing the electromagnetic interference and power loss of the inverter, and improving the safety of the system. Then, a hybrid modulation strategy with phase-shifted carriers is adopted to prevent the switched-capacitor from continuously discharging, which not only reduces the voltage ripple of the switched-capacitor, but also improves the quality of SPWM output voltage waveform. Furthermore, the advantages of the proposed topology have been demonstrated by comparing with other five-level topologies in terms of the circuit structure, voltage-boosting capability and reducing capacitor voltage. Finally, the feasibility of the proposed inrerter and the effectiveness of the hybrid modulation strategy are verified experimentally. The results show that the proposed inverter has better static and dynamic characteristics as well as higher conversion efficiency.
关键词
光伏 /
逆变器 /
开关电容 /
多电平 /
双接地
Key words
photovoltaic /
inverter /
switched-capacitor /
multilevel /
common-ground
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基金
国家自然科学基金（51907033）; 广州市科技项目（202102020780）
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