Neutral Potential Balance Control Method of T-Type Three-Level Inverter with Zero-Sequence Voltage Injection
Zhang Jianzhong1, Hu Lucai1, Xu Shuai2
1. Jiangsu Provincial Key Laboratory of Smart Grid Technology and Equipment Southeast University Nanjing 210096 China; 2. State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031 China
Abstract：Three-level T-type inverters are widely used in low-voltage and high-current fields due to small number of power devices, low switching losses, and high power density. The neutral potential balance control of the three-level T-type inverter is one of its key technologies. The imbalance of neutral potential will lead to an increase of harmonics in the output voltage and current, which will reduce the life of the dc-link capacitors. Based on the traditional zero-sequence voltage injection method, a zero-sequence voltage injection that combines feed-forward with feed-back compensation loops is studied to control the balance of neutral potential as well as the suppression of low-frequency voltage ripples. In this paper, by establishing the switching model and neutral potential model of three-level T-type inverter, the equilibrium mechanism of neutral potential is analyzed in detail, and then the relationship between three-phase modulation voltage and injected zero-sequence voltage is derived. This method avoids complicated duty cycle calculation, which can realize neutral potential balance control and suppression of low-frequency voltage ripple. The correctness and effectiveness of the proposed control method are verified by experiments.
张建忠, 胡路才, 徐帅. 一种零序电压注入的T型三电平逆变器中点电位平衡控制方法[J]. 电工技术学报, 2020, 35(4): 807-816.
Zhang Jianzhong, Hu Lucai, Xu Shuai. Neutral Potential Balance Control Method of T-Type Three-Level Inverter with Zero-Sequence Voltage Injection. Transactions of China Electrotechnical Society, 2020, 35(4): 807-816.
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2020, Vol. 35 
