面向长航时高空无人机燃料电池级联系统优化与控制研究

High-altitude fuel cell unmanned aerial vehicle (UAV) has become an important development direction of high altitude aircraft due to the low infrared characteristics, low operation noise and long flight time. This project aims to study the optimization and control strategy of UAV based on fuel cell cascade system, targeting to achieve the reliable and long-haul UAV. The research contents are as follows: the first is to establish the fuel cell aging mechanism model to explore the influence of high-frequency current ripple on the fuel cell lifetime, to finally provide a guide for design optimization of zero-current ripple DC-DC converter with fuel cell lifetime consideration. Secondly, the fuel cell air supply subsystem is unable to overcome the anti-oxygen-starvation by itself in the high-altitude complex environment. Therefore, the oxygen-starvation control strategy based on the zero-current ripple DC-DC converter is put forward to ensure the bus voltage stability, because of the time-varying, nonlinear and multi-modal system characteristics. The third is to ensure the stability of the whole multi-load cascade system of anti-oxygen-starvation. this project studies the reduction and simplification method for the cascade system with multi-timescale constant power load. The obtained reduced order model can be used for system stability analysis. The fourth is to establish an experimental platform based on dSPACE to validate the reliable operation of the long voyage of high altitude UAV powered by post-optimized system, and also to accelerate the practical process. This research of project will promote the development of the long-haul high-altitude fuel cell UAV.

高空燃料电池无人机由于红外特征低、运行噪声小、留空时间长等特性，成为高空飞行器一个重要发展方向。项目以高空无人机燃料电池级联系统为研究对象，以实现无人机长航时可靠飞行为研究目标，研究燃料电池级联系统优化与控制策略。主要研究内容有：为探究高频电流纹波对燃料电池寿命影响机理，建立燃料电池老化机理模型，优化设计零电流纹波直流变换器，延长燃料电池寿命；为解决高空复杂环境下燃料电池供气系统自身已无法克服氧饥饿的问题，基于零电流纹波直流变换器，针对系统时变性、非线性、多模态等特点，提出系统直流变换器的抗氧饥饿控制策略，保证母线电压稳定；为分析抗氧饥饿的高空无人机燃料电池多负载级联系统稳定性，研究多时间尺度恒功率负载级联系统模型降阶与简化方法，获取用于系统稳定性分析的降阶模型；为验证优化后的系统长航时可靠运行，搭建dSPACE的实验平台，加快实用化进程。本项目将推动我国长航时高空燃料电池无人机的发展。

高空燃料电池无人机由于红外特征低、运行噪声小、留空时间长等特性，成为高空飞行器一个重要发展方向。项目以高空无人机燃料电池动力系统为研究对象，以燃料电池动力系统的“耐久性”与“长航时”两个科学问题为基础，开展以下三个方面的研究：.(1) 燃料电池动力系统高频电流纹波抑制方法研究.鉴于无人机对燃料电池长寿命的需求，本项目拟通过实验测试分析并优化燃料电池二维模型，探究高频电流纹波对燃料电池性能及寿命影响的机理。为抑制高频电流纹波，考虑到无人机对机载设备体积和重量的严苛要求，提出含纹波消除网络的交错并联式变换器优化拓扑方案，达到燃料电池零高频电流纹波的目的，并探究纹波消除网络对变换器动静态特性的影响。.(2) 燃料电池动力系统抗氧饥饿控制策略研究.高空复杂环境及负载大范围快速变化，导致燃料电池系统易出现氧饥饿，造成燃料电池电压下降及母线电压波动。针对带纹波消除网络交错升压变换器的时变、非线性、多模态等特点，首先，采用开关网络平均法建立零电流纹波变换器的微分模型；其次，明确燃料电池氧饥饿对供电系统的扰动界限，开展高空燃料电池无人机抗氧饥饿控制策略研究，实现稳定燃料电池供电系统母线电压的目标，满足高空无人机长航时可靠运行的需求。.(3) 燃料电池动力系统稳定性分析及谐振抑制技术研究.在燃料电池动力系统中，级联结构是其最典型的组合方式。为了减小或消除动力系统中的电磁干扰，论文提出了两种有源解决方案。研究了控制策略的实现方法，分别建立了两种不同控制方案下系统的数学模型，利用经典控制理论和现代控制理论相关知识对所建数学模型进行稳定性分析，证明了所提算法的有效性。.通过上述三个方面内容的研究，主要完成如下任务：燃料电池用功率变换器高频电流的零纹波设计、动力系统抗氧饥饿响应速度小于1秒、动力系统稳定裕度显著增高。