摘要
该文针对以输入串联-输出并联的双有源桥变换器为核心的直流固态变压器的控制策略展开研究。传统的由输出电压控制和输入均压控制构成的双环控制系统,各控制环的环路增益特性会随负载等工况发生显著变化,控制器参数的设计难以兼顾全工况下的动态性能。为此,该文利用双有源桥变换器的一阶模型特性,基于直流固态变压器的大信号模型,开发了一种新型的线性化控制策略,以实现输出电压控制和输入均压控制的环路模型的线性化,从而简化控制器参数的设计,并增强变换器对不同工况的适应能力。同时,该文所提出的控制策略保留了比例-积分控制的简洁性和鲁棒性,且实现了对负载的补偿作用。仿真和实验结果证实了所提的控制策略可以显著降低直流固态变压器的环路模型和动态特性对工况的敏感程度,有利于实现全工况范围内动态性能的综合优化。
The control system of the DC solid-state transformer with the input-series-output-parallel dual active bridge converters typically consists of output voltage control and input voltage sharing control.In the conventional control strategy,the loop gain characteristics of each control loop change considerably with the load and other working conditions,and the dynamic performance is ignored in the controller parameter design.This paper proposes a novel linearization control strategy to achieve the linearization of the loop models of both the output voltage control and input voltage sharing control,thereby simplifying the design of controller parameters and enhancing the adaptability of the converter.Firstly,the control command output by the PI controller of the output voltage control loop is changed from the phase shift command to a current command.A secondary-side current command is generated after the control command is superimposed with the output current.Then,the control command output by the PI controller of the input voltage sharing control loop is changed from the phase shift increment to the primary-side current increment.The method for superimposing the control commands of the two loops is changed from the phase-shift superposition to the primary-side current superposition.Finally,the phase shift ratio of each DAB is calculated based on the input current command generated by the control system,which is no longer directly output by the PI controller.In simulations,frequency sweep analyses are conducted on the output voltage control loop and input voltage sharing control loop.With the conventional control strategy,the closed-loop gain exhibits a high resonance peak with light loads.This peak disappears with heavier loads,but the bandwidth is low.In contrast,the frequency characteristics of the control loops change little with the load using the proposed linearization control strategy.An experimental prototype of a DC solid-state transformer composed of three DAB units is built.Experimental results show that under full-load conditions,the output voltage’s response speed is slow using the conventional control strategy.When the load is reduced to 10%,the overshoot significantly increases,indicating a noticeable decrease in stability.In contrast,with the proposed linearization control strategy,the output voltage’s step response waveforms under various load conditions roughly overlap,demonstrating high stability and fast response.Moreover,when switching from half-load to full-load,the voltage drop and recovery time are significantly lower than those using the conventional control strategy.The conclusions are as follows.(1)Using the conventional control strategy,the closed-loop gain's resonance frequency-domain indicators(peak,frequency bandwidth)and time-domain indicators(overshoot,rise time,and adjustment time)vary significantly with operating conditions.These dynamic performance indicators show slight variation using the proposed control strategy,facilitating the comprehensive optimization of dynamic performance.(2)The proposed control strategy enhances the suppression capability of the DC solid-state transformer against load disturbances using output current information for load compensation during the linearization process.
作者
李志祥
裴云庆
王来利
刘家豪
高韫瑶
Li Zhixiang;Pei Yunqing;Wang Laili;Liu Jiahao;Gao Yunyao(School of Electrical Engineering,Xi’an Jiaotong University,Xi’an 710049,China)
出处
《电工技术学报》
EI
CSCD
北大核心
2024年第20期6475-6487,共13页
Transactions of China Electrotechnical Society
基金
国家重点研发计划资助项目(2023YFB2407400)。
关键词
直流固态变压器
双有源桥
线性化控制
输出电压控制
输入均压控制
DC solid-state transformer
dual active bridge
linearization control
output voltage control
input voltage sharing control
