实现宽输出电压范围高效率的母线电压协调控制策略

A Bus Voltage Coordination Control Strategy for High Efficiency over a Wide Output Voltage Range

摘要: 随着新能源汽车产业的蓬勃发展，新能源汽车充电模块研究也在逐渐深入。主流的新能源充电模块由前级AC/DC变换器和后级DC/DC变换器构成。本文针对宽输出电压范围下，固定母线电压导致后级全桥LLC谐振变换器偏离最佳谐振点、开关损耗剧增且效率劣化的问题，本文提出一种前级Vienna PFC与后级LLC协同的母线电压动态协调控制策略。该策略由输出电压指令设定、最佳谐振点母线电压计算、前级母线电压指令通信三大模块构成，依据后级LLC输出电压给定值，动态计算并通过SCI通信向前级Vienna PFC级发送最佳母线电压给定值，使LLC始终工作在最佳谐振点附近；同时设计斜坡缓起、步进调节的启动与模式切换流程，搭建光耦隔离的硬件与数据通信通道，保障系统稳定与通信可靠。实验结果表明，该策略在宽输出电压范围内，有效拓宽LLC软开关工作范围，显著降低开关损耗与环流损耗，提升整机工作效率，且无需额外硬件成本，工程实用性强。

Abstract: With the vigorous development of the new energy vehicle industry, research on charging modules for new energy vehicles is also in-depth. The mainstream new energy charging module consists of a front-stage AC/DC converter and a rear-stage DC/DC converter. Aiming at the problems that the fixed bus voltage causes the rear-stage full-bridge LLC resonant converter to deviate from the optimal resonant point, the switching loss to surge and the efficiency to deteriorate in a wide output voltage range, this paper proposes a dynamic bus voltage coordination control strategy for the coordination of the front-stage Vienna PFC and the rear-stage LLC. The strategy is composed of three modules: the rear-stage output voltage command setting module, the optimal resonant point bus voltage calculation module and the front-stage bus voltage command communication module. According to the given output voltage value of the rear-stage LLC, it dynamically calculates the optimal bus voltage given value of the front-stage and sends it to the front-stage through SCI communication, so that the LLC always works near the optimal resonant point. Meanwhile, a start-up and mode switching process with ramp soft start and step adjustment is designed, combined with optocoupler-isolated hardware and data communication channels to ensure system stability and communication reliability. Experimental results show that within the wide output voltage range, the strategy effectively expands the soft-switching working range of the LLC, significantly reduces the switching loss and circulating current loss, and improves the overall working efficiency. In addition, it requires no additional hardware cost and has strong engineering practicability.