全桥三电平DC-DC变换器优化控制策略

Optimal Control for the Full-Bridge Three-Level DC-DC Converter

针对全桥三电平(FBTL)DC-DC变换器两个占空比协调优化控制、传输功率太小以及钳位电容电压平衡等问题,该文提出一种基于查表法的FBTL DC-DC变换器优化控制策略。首先,详细分析FBTL;DC-DC变换器输入、输出特性,并设计一种钳位电容电压自平衡调制策略。其次,在所设计的钳位电容电压自平衡调制策略基础上,提出一种抗钳位电容电压扰动控制策略,并根据钳位电容输入功率差与电压最大调节能力的关系计算出占空比必须满足的条件。然后,建立一种以变压器输入电压谐波为目标函数,功率传输能力、钳位电容电压调节能力等为约束条件的优化模型,进而得到FBTL;DC-DC变换器的优化控制策略。优化占空比离线计算,然后存储在数字控制系统里,控制时直接采用查表法得到最优占空比。所提出的方法无需变换器精确模型,控制过程简单、高效,控制效果优于传统控制策略。最后,在Matlab/Simulink平台和一台实验样机上验证了所设计的优化控制策略的正确性和有效性。

In this paper,an optimal control strategy was proposed according to the problems of the full-bridge three level(FBTL)DC-DC converter,such as coordinated control of two duty cycles,small output power of the FBTL DC-DC converter and voltage balance of divided capacitors.First,the characteristics of the FBTL DC-DC converter was analyzed in detail and a self-balance modulation scheme for divided capacitor voltage was investigated.Second,a strategy to resist the voltage disturbance of the divided capacitor was proposed.At the same time,a restraint condition for the duty cycles was investigated.Third,taking the harmonics of the transformer input voltage as the objective,and taking the power of the FBTL DC-DC converter and the voltage regulation capacity of the divided capacitor as the constraints,an optimization model for the duty cycles was established.The optimal duty cycles were calculated offline and stored in the digital control system.The look-up table method was adopted to get the optimal duty cycles.The proposed method does not require an accurate model of the converter,and the control process is simple and efficient.Finally,a FBTL DC-DC converter model in Matlab/Simuink and a FBTL DC-DC converter experimental prototype were built to verify the theoretical analysis.