基于LCC谐振变换器的PFU充电系统恒流特性优化  

Optimization for Constant Current Characteristics of PFU Charging System Based on LCC Resonant Converter

作　　者：段元超 王德玉[1] 高鹤 赵清林[1] DUAN Yuanchao;WANG Deyu;GAO He;ZHAO Qinglin(Key Lab of Power Electronics for Energy Conservation and Motor Drive of Hebei Province,Yanshan University,Qinhuangdao 066004,China)

机构地区：[1]燕山大学电力电子节能与传动控制河北省重点实验室

出　　处：《高电压技术》2018年第10期3275-3283,共9页High Voltage Engineering

基　　金：国家自然科学基金(51407154;51407155);河北省自然科学基金(E2014203237;E2016203237)~~

摘　　要：针对脉冲成型单元（PFU）储能电容充电环节,研究了基于LCC的串并联谐振型变换器。为解决传统恒流控制方案带来的电流输出能力低和幅值衰减的问题,满足电源对充电效率、线性度和重复频率稳定度的要求,对工作在电流断续条件下的LCC谐振变换器电流输出特性进行研究。利用临界频率控制方案：在数字控制器内部,采用分段线性函数近似拟合法对临界断续开关周期曲线进行近似拟合,随着充电电压的变化,不断修正开关周期,实现了临界开关周期曲线的在线跟踪,有效增加了输出电流占宽比,提升了电流输出能力。在控制算法上,通过引入输出电流闭环控制,实现了恒流输出,保证了充电效率和充电电压的线性度。同时,在整个充电过程中实现了全程零电流软开关。实验数据验证了理论分析的正确性和控制方案的可行性。We designed an LCC series-parallel resonant converter for the energy storage capacitor of the Pulse Forming Unit（PFU）. In order to solve the problem of low current output and amplitude damping under traditional constant-current control scheme, to meet the power supply requirements of charging efficiency and pulse to pulse repeatability, we studied the characteristics of LCC resonant converter operating in discontinuous-current-mode. Moreover, the critical switching cycle curve was fitted approximately by an approximate fitting method of piecewise linear function, and the switching cycle was corrected with the constantly changing output voltage. The results show that the critical switching cycle curve can be tracked online through digital-signal-processor, the duty ratio of the output current under critical frequency is increased, and the capability of current output is improved greatly. In order to obtain a constant current output, a charging current fed digital PI control scheme was designed. The designed power supply achieves zero current soft-switching in the whole operating process, to ensure the charging efficiency and charging voltage linearity. The validity of the theoretical analysis and the feasibility of the control scheme are verified by experimental data.

关 键 词：PFU储能系统 恒流充电 LCC谐振 软开关 临界断续电流 

分 类 号：TM46[电气工程—电器]