Active balancing optimized topology and voltage balancing control strategy for three-level inverters with mid-point potential
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摘要: 针对T型三电平逆变器中点电位不平衡问题,研究了传统T型中点钳位型(NPC)三电平逆变器中点电位不平衡的形成原理。为解决直流侧电压变化导致的中点电位不平衡问题,提出一种主动平衡中点电位的改进拓扑和模糊PI控制策略。利用Matlab/Simulink建立改进拓扑的T型三电平逆变器的仿真模型,开展不同控制策略的仿真分析,并搭建相应的并网试验平台验证方案的合理性。仿真和试验结果表明,改进拓扑下模糊PI控制能有效抑制中点电压波动,兼具动态响应快、响应精度高等优点,可提高逆变器系统的抗扰性和稳定性。Abstract: Aiming at the problem of unbalanced mid-point potential in T-type three-level inverters, the principle of unbalanced mid-point potential in traditional T-type neutral point clamped (NPC) three-level inverters was investigated. To address the mid-point potential imbalance caused by voltage variation on DC side, an optimized topology with an active mid-point potential balancing strategy and a fuzzy PI control were proposed. A simulation system model of the optimized topology T-type three-level inverter was established by Matlab/Simulink, simulation analyses with different control strategies were conducted, and a grid-connected experimental platform was set up to validate the proposed methodology. The simulation and experimental results demonstrate that the fuzzy PI control under the optimized topology can effectively suppress the mid-point voltage fluctuations, with the advantages of fast dynamic response and high response precision, enhancing the disturbance resistance and stability of the inverter system.
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表 1 模糊规则表
Table 1. Fuzzy rule
系数
变化量e ec NB NS Z PS PB $ \Delta {K_{\mathrm{p}}} $ NB PB PB PS PS Z NS PB PS PS Z Z Z PS Z Z Z NS PS Z Z NS NS NB PB Z NS NS NB NB $ \Delta {K_{\mathrm{i}}} $ NB NB NB NS NS Z NS NB NS NS Z Z Z NS Z Z Z PS PS Z Z PS PS PB PB Z PS PS PB PB 表 2 仿真电路参数
Table 2. Simulation circuit parameters
参数名称 参数值 直流侧电压 U/V 1500 直流侧母线电容 C1、 C2/μF 450 电感 L/mH 1 直流侧负载电阻 R/Ω 0.1 上下母线电容带电初始值/V 100 -
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