Fuel cell system

Patent metadata

Field	Value
Publication number	US-9728794-B2
Application number	US-201314381049-A
Country	US
Kind code	B2
Filing date	Feb 28, 2013
Priority date	Feb 29, 2012
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

A fuel cell system is configured to: calculate a target stack supply flow rate; calculate a compressor supply flow rate based on a stack supply flow rate and the target stack supply flow rate; set a larger one of the compressor supply flow rate and a lower limit flow rate, determined depending on an operation state of the fuel cell system, as a target compressor supply flow rate; control a bypass valve based on the stack supply flow rate and the target stack supply flow rate; fix the bypass valve when the stack supply flow rate is in a predetermined bypass valve fixing range, and the stack supply flow rate becomes less than the target stack supply flow rate; and release the fixation of the bypass valve when the target compressor supply flow rate becomes more than the lower limit flow rate after the bypass valve is fixed.

First claim

The invention claimed is:

1. A fuel cell system, comprising:
a cathode gas supply passage configured to supply a fuel cell stack with a cathode gas;
a cathode gas discharge passage configured to discharge the cathode gas supplied to the fuel cell stack;
a compressor provided in the cathode gas supply passage;
a bypass passage configured to discharge a part of the cathode gas discharged from the compressor to the cathode gas discharge passage while controlling the part of the cathode gas to bypass the fuel cell stack;
a bypass valve that is provided in the bypass passage and that is configured to adjust a flow rate of the cathode gas flowing through the bypass passage in a stepwise manner;
a stack supply flow rate sensor that detects a stack supply flow rate supplied to the fuel cell stack;
a controller operable to:
calculate a target stack supply flow rate to be supplied to the fuel cell stack based on a request from the fuel cell stack;
calculate a compressor supply flow rate requested by the fuel cell stack for controlling the stack supply flow rate to reach the target stack supply flow rate based on the stack supply flow rate and the target stack supply flow rate;
set a larger one of the compressor supply flow rate requested by stack and a lower limit flow rate, which is determined depending on a request from the fuel cell system, as a target compressor supply flow rate, which is a target value of the compressor supply flow rate;
control the compressor depending on the target compressor supply flow rate;
control the bypass valve based on the stack supply flow rate and the target stack supply flow rate;
change a position of the bypass valve until the stack supply flow rate reaches a bypass valve fixing range, the bypass valve fixing range being determined so as to suppress a repetition of a closing/opening of the bypass valve on the basis of the target stack supply flow rate;
fix the bypass valve so that a position of the bypass valve is not changed when the stack supply flow rate becomes less than the target stack supply flow rate in the bypass valve fixing range;
allow change in the position of the bypass valve when the target compressor supply flow rate becomes more than the lower limit flow rate after the position of the bypass valve is fixed.

2. The fuel cell system according to claim 1 , wherein when the position of the bypass valve is allowed to change by the controller, the bypass valve is closed by a unit opening degree.

3. The fuel cell system according to claim 1 , wherein when the position of the bypass valve is allowed to change by the controller, the bypass valve is fully closed.

4. The fuel cell system according to claim 1 , wherein in a case where the target compressor supply flow rate is restricted to the lower limit flow rate, only when the stack supply flow rate is less than the target stack supply flow rate, the controller carries out feedback control of calculating a time integration of a difference between the stack supply flow rate and the target stack supply flow rate, thereby calculating the compressor supply flow rate requested by stack.

5. The fuel cell system according to claim 1 , further comprising an anode gas discharge passage configured to discharge an anode gas discharged from the fuel cell stack to the cathode gas discharge passage,
wherein the lower limit flow rate comprises a target value of a compressor supply flow rate required for reducing a hydrogen density in the cathode gas discharge passage to a predetermined value or less.

6. The fuel cell system according to claim 1 , wherein the bypass valve fixing range comprises a range of from a restricted range lower limit flow rate, which is acquired by subtracting a predetermined value β from the target stack supply flow rate, to a restricted range upper limit flow rate, which is acquired by adding a predetermined value α to the target stack supply flow rate.

Assignees

• Nissan Motor

Inventors

• Asai Yoshitomo
• Takeda Hiroshi

Classifications

• H01M8/04089 Primary

  of gaseous reactants · CPC title

• H01M8/04776

  at auxiliary devices, e.g. reformer, compressor, burner · CPC title

• H01M8/04395

  of cathode reactants at the inlet or inside the fuel cell · CPC title

• H01M8/04111 Primary

  using a compressor turbine assembly · CPC title

• H01M8/04753 Primary

  of fuel cell reactants · CPC title