Model-based control of cathode pressure and oxygen excess ratio of a PEM fuel cell system
Model-based control of cathode pressure and oxygen excess ratio of a PEM fuel cell system
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DOI：
10.1016/j.jpowsour.2007.08.049
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发表时间：
2008-02
影响因子：
9.2
通讯作者：
Michael A. Danzer;J. Wilhelm;H. Aschemann;E. Hofer
中科院分区：
文献类型：
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作者：
Michael A. Danzer;J. Wilhelm;H. Aschemann;E. Hofer
对于供应有空气的PEM燃料电池，压力和流量控制是高效和动态操作的关键要求，因为当阴极处的氧分压下降到临界水平以下时，燃料电池处于饥饿的风险中。为了避免氧气不足，同时为了允许燃料电池系统的动态操作，需要快速调节氧气的过量比率和阴极压力。在本文中，提出了一种基于模型的控制结构，该结构包括使用质量流量控制器（MFC）和出口节流阀作为致动器的阴极压力pC和氧过量比[公式：见正文]的多变量控制。对于这两个控制变量，可以独立地指定适当的期望值。由于推导出的送风系统的动态模型是非线性的，先进的控制技术，采用微分平坦。由于阴极流场中的氧分压是难以通过测量获得的状态变量，因此采用跟踪观测器来使用在出口节流阀处测量的空气压力来估计该压力。因此，观测器使得控制系统能够检测阴极处的氧气的暂时短缺和峰值压力两者，并相应地进行抵消。
For PEM fuel cells supplied with air, pressure and flow control is a key requirement for an efficient and dynamic operation because fuel cells are in risk of starvation when the partial pressure of oxygen at the cathode falls below a critical level. To avoid oxygen starvation and, at the same time, to allow for a dynamic operation of the fuel cell system, both excess ratio of oxygen and cathode pressure need to be adjusted rapidly. In this paper a model-based control structure is proposed that comprises a multivariable control of the cathode pressure pCand the excess ratio of oxygen [Formula: see text] using the mass flow controller (MFC) and the outlet throttle as actuators. For both controlled variables appropriate desired values can be specified independently. As the derived dynamic model of the air supply system is nonlinear, advanced control techniques using differential flatness are applied. Since the partial pressure of oxygen in the cathode flow field is a state variable that is hardly accessible by measurement, a tracking observer is employed to estimate this pressure using the measured air pressure at the outlet throttle. Thereby, the observer enables the control system to detect both temporary shortages of oxygen and peak pressures at the cathode and to counteract accordingly.