基于扩张状态观测器的牵引逆变器中点平衡控制策略

Control Strategy for Neutral-point Potential Balance of the Traction Inverter Based on the Extended State Observer

针对中点箝位型三电平牵引逆变器由于自身拓扑主电路结构而存在的中点电位不平衡问题,对其中点电位平衡的优化控制策略进行了研究。在三电平逆变器旋转坐标系电压电流双闭环控制的基础上,提出了一种基于扩张状态观测器的三电平逆变器中点电位平衡控制策略。基于等效电路模型建立中点电位的一阶数学模型,采用二阶非线性扩张状态观测器实现中点电位扰动的实时估计,之后利用PI控制器实现中点电位波动的补偿,对逆变器电压外环控制策略进行了优化,最后在MATLAB/Simulink环境下进行了仿真建模。仿真结果表明优化控制策略具有较好的中点电位平衡能力。

With regards to the unbalance of neutral-point potential of the neutral-point-clamped three-level traction inverter due to its main circuit topology,the optimization control strategy for neutral potential was discussed. On the basis of double closed-loop control of voltage and current in the rotating coordinate system of the three-level inverter,a neutral potential control strategy for the three-level inverter based on the extended state observer was proposed. Furthermore,based on an equivalent circuit model,we established a first-order mathematical model for neutral potential. Use a second-order nonlinear extended state observer to realize real time estimation of neutral potential disturbance,and use a PI controller to realize compensation for neutral potential fluctuation,thus optimizing the outer loop control strategy for inverter voltage. Finally,simulation modeling was completed in MATLAB/Simulink environment. Simulation results show that the proposed optimization control strategy has a good ability to balance neutral point potential.