直流变换器模式快速识别PI自适应控制策略

Fast mode identification PI adaptive control strategy for DC/DC converter

针对三电平H桥直流变换器在传统的PI控制下,受到电流连续模式和电流断续模式切换大扰动时动态性能较差的问题,提出了一种新颖的模式快速识别PI自适应非线性控制策略。采用状态空间平均法和开关网络平均法,建立了变换器在两种模式下的数学模型,并设计了数字控制器。控制器有效提取了电感电压特征,能在一个开关周期内对模式进行快速识别,克服了依据电感电流检测模式速度慢且准确性不高的问题,从而根据模式实时改变PI参数以实现最佳的动态性能。将新型控制策略和传统PI控制进行了对比实验研究,实验结果表明变换器在突加50%负载工况后,采用新型控制的输出电压最大跌落较传统控制降低了25.2%,从而验证了该新型控制策略的可行性和有效性。

The good dynamic performance is hardly reached with traditional PI controller when the three- level H-bridge DC/DC converter meets the large disturbance of the changing between continuous conduc- tion mode（CCM） and discontinuous conduction mode（DCM）. Aiming at it, a PI adaptive non-linear control strategy based on fast mode identification is proposed. The small signal models were built in CCM and DCM with average state space method and average switched network method, and the controller was designed. The controller extracted the mode characters from the inductance voltage, and sent the mode information in less than a switching period. The mode identification method was much faster and more correct than the method based on the inductance current. Therefore, the PI parameters were instantane- ously changed by mode signal to achieve the best dynamic property. The experiment results show that the new controller has better performance compared to the conventional one. And the output voltage droop re- duce 25.2% compared to the common PI controller. Finally, the operation principle and analytical result of the control strategy are verified.