A Nonlinear Load Current Feedforward Strategy for the Charge-Controlled LLC Converter and Its Digital Implementation to Improve the Dynamic Response
A Nonlinear Load Current Feedforward Strategy for the Charge-Controlled LLC Converter and Its Digital Implementation to Improve the Dynamic Response
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DOI：
10.1109/tie.2022.3217596
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发表时间：
2023
影响因子：
7.7
通讯作者：
Qingyuan Xu;Rongyan Zou;Tingting Wen;Shixiang Du;Xiang Li;Daorong Lu;Haibing Hu
中科院分区：
文献类型：
--
作者：
Qingyuan Xu;Rongyan Zou;Tingting Wen;Shixiang Du;Xiang Li;Daorong Lu;Haibing Hu
与传统的LLC变换器单电压环控制策略相比，电荷控制LLC变换器具有一阶特性，可以显著提高其动态响应。通常，负载电流前馈方法可以改善变换器的动态响应。然而，对于LLC变换器，由于负载电流和控制变量之间的关系不清楚，这几乎是不切实际的。为了建立这种关系，推导出负载电流变化与控制变量之间的数学表达式，可以精确地抵消负载扰动，实现更快的动态响应。导出的关系是非线性的，有关的输入和输出电压和开关频率，并适合于数字实现。为了进一步分析系统的动态响应，建立了负载电流前馈控制前后的输出阻抗模型并进行了分析，通过计算输出阻抗和负载变化频谱，直观地展示了系统在时域上的动态改善。最后，一个120 W的LLC的原型与标称48 V输入和12 V输出，以验证非线性负载电流前馈控制及其分析。
Compared with the traditional single-voltage loop control strategy in LLC converters, the charge-controlled LLC converter can significantly improve its dynamic response due to its model having the first-order feature. Generally, a load current feedforward method could improve the converter's dynamic response. However, for the LLC converter, it is almost impractical due to the unclear relationship between the load current and the control variable. To build this relationship, a mathematical expression between the load current change and the control variable is derived that can precisely offset the load disturbance and achieve faster dynamic response. The derived relationship is nonlinear, related to both input and output voltages and switching frequency, and is suitable for digital implementation. To further analyze the dynamic response, the output impedances with and without the load current feedforward control are established and analyzed, which visually demonstrate the dynamic improvement in the time domain through the calculation of the output impedance and load change spectrum in the frequency domain. Finally, a 120 W LLC prototype with nominal 48 V input and 12 V output is built to verify the nonlinear load current feedforward control and its analysis.