A maximum-power-point-tracking method based on real-time resistance matching for fuel cells energy system

Abstract

燃料电池单位功率投资成本高,且寿命 有限,为充分发挥系统效能,需采用最大功率点跟踪(maximum powerpoint tracking,MPPT)控制使其连续稳定地向负载输出最大功率。该文利用燃料电池特有的物理特性和电气特性,提出一种通过检测燃料电池输出电压、电 流,实时计算内阻,根据电阻匹配的最大功率传输理论,实现燃料电池MPPT算法。若由于工作条件突变,最大功率点(maximum powerpoint,MPP)超出了燃料电池外特性的欧姆线性区,则采取自适应变步长追踪MPP。同时,该文还采用固定步长确定新MPP方向与自适应变 步长追踪新MPP相结合,实现此MPPT方法对环境的自适应能力以及解决追踪精度和速度之间的矛盾。此方法能够简单而准确地跟踪具有各种外特性的燃料电池 MPP,且在稳态下不存在功率波动。最后,在燃料电池/超级电容混合能量系统上,实验验证了理论分析的正确性。 The need to fully utilize fuel cells by operating them at the maximum power point(MPP) is motivated by their extremely high cost per unit power and limited lifetimes.According to the unique output characteristics of fuel cells,a specialized algorithm based on resistance matching was developed in this work,which is capable of tracking the MPPs of fuel cells when they exist in both the ohmic and concentration polarization regions.Under changing operation condition,a fixed step size was used to perturb the system in the direction of the new MPP,and a variable tracking step size was subsequently used to provide fast tracking of the new MPP.For validation,the proposed algorithm was implemented in a hybrid energy system that used super-capacitors for power balancing and load voltage regulation while the fuel cells constantly operated at the MPP.It was shown that the proposed algorithm is able to quickly and closely track the MPP when the fuel cells’ operating condition,such as fuels’ flow rate and environmental conditions,changes dynamically.The proposal algorithm had been verified by experiment results.