本文针对应用于三相非隔离光伏并网发电逆变器中三电平Boost直流变换器启动建压过程时,可能出现的中点(Neural-Point, NP)电位不平衡问题和后级逆变电路调制策略对中点电位的影响,在三电平Boost直流变换器功率级提出了一种实现中点电位平衡的模糊控制策略。采用模糊控制器可自适应地改变三电平Boost直流变换器开关管的占空比大小,不仅在启动过程中(直流母线建压时),而且在并网逆变器稳定工作时,都能实现直流侧输出电容的均压,并获得良好的动态和静态性能。论文中为三电平Boost直流变换器设计了模糊控制器,给出了控制规则。最后通过仿真和实验验证了该方法的可行性和可靠性。
Aiming at the neutral-point (NP)
imbalance and the influence of the modulation strategy of the post-stage
inverters on the neutral-point potential when the three-level Boost DC
converter is used in the three-phase non-isolated grid-connected PV power
generation inverters to start the voltage-building process, a fuzzy control
strategy is proposed to realize the neutral-point potential balance at the
power level of the three-level Boost DC converter. The duty cycle ratio of the
switch of three-level Boost DC converter can be adaptively changed by using the
fuzzy controller. Not only in the start-up process (when the DC bus is
voltage-building), but also in the stable operation of grid-connected
inverters, the voltages across output capacitors can be equalized and good dynamic
and static performance is obtained. In this paper, a fuzzy controller is
designed for three-level Boost DC converter, and the control rules are given.
Finally, the feasibility and reliability of the method are verified by
simulation and experiment.
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Xia, C.L., Gu, X., Shi, T.N. and Yan, Y. (2010) Neutral-Point Potential Balancing of Three-Level Inverters in Direct-Driven Wind Energy Conversion System. IEEE Transactions on Energy Conversion, 26, 18-27.
https://doi.org/10.1109/TEC.2010.2060487