输入串联输出并联型三电平双有源桥变换器功率与电压平衡控制策略

Power and Voltage Balance Control Strategy of Series Input Parallel Output Type Three-Level Dual Active Bridge Converter

针对三电平半桥型输入串联输出并联(ISOP)型双有源桥(DAB)变换器的各模块参数差异而导致的模块功率不均衡传输问题,该文首先分析多模块功率不平衡原因,然后提出基于三重移相(TPS)调制的串联侧功率平衡策略。针对ISOP系统多模块间参数差异问题,提出多模块参数差异估计方法,该方法无需增加额外的电流或电压传感器,通过注入强制分量作为扰动而采集反映模块差异的特征量变化,对控制量进行补偿实现多模块功率平衡。仿真和实验结果表明,在多种扰动条件下,所提功率平衡方法可实现样机串联侧均压,在输出电压24V工况和10~435W功率范围下,系统在所提控制策略下能明显提高串联侧的电压平衡,工作效率达到90%以上。

The dual active bridge(DAB)has the advantages of high voltage utilization,high power density,and bidirectional power transfer capability.In medium and high voltage-low voltage DC power grids,the input-series output-parallel(ISOP)DAB improves the voltage of the series side and realizes a large voltage conversion ratio.However,problems such as power imbalance between modules exist.This paper analyzes the module difference and power balance control for ISOP-DAB with a three-level neutral point clamped(3L-NPC)half-bridge.Firstly,this paper compares existing multi-module power balance methods,introduces their advantages and disadvantages,and analyzes the structure and principle of the ISOP-DAB system with a 3L-NPC half-bridge-H bridge.The reasons for the power imbalance of multiple modules are analyzed,focusing on the power transmission imbalance caused by different module parameters of the three-level half-bridge ISOP-DAB converter.Secondly,this paper analyzes the relationship between voltage,current,and power among ISOP-DAB modules.The factors affecting module consistency are discussed.The self-balancing ability of the system under disturbance is analyzed,as well as the difference in control stability between series and parallel sides under bidirectional power.A power balance control strategy without sampling voltage or current module is proposed based on TPS modulation,simplifying the sampling circuit and control design.The strategy provides a backup solution in case of sensor failure.Then,an estimation method for multi-module parameter differences is proposed.Its core idea is to inject forced components as disturbance and observe feature changes reflecting module differences.Combined with the power balance control strategy,the estimation method can be extended to N modules.Three modules are simulated in Matlab/Simulink.The constraints of the control parameter are studied to avoid overpowering.The variation trend of the power boundary margin is analyzed concerning the module number and power.Finally,an ISOP-DAB converter experimental platform with field programmable gate arrays(FPGA)controllers is designed to realize the voltage conversion from 220 V to 24 V.Under four disturbances of different sizes and plus and minus,the module difference estimation method is verified.In the output voltage range of 24 V and 10~435 W,the system can significantly improve the voltage balance on the series side under power balance control,and the efficiency is higher than 90%under most powers.