Method for controlling the start-up of electrical production in a fuel cell

Abstract

Method for controlling the start-up of electrical production in a fuel cell. The invention relates to a method and device for controlling the start-up of electrical production in a fuel cell, by effectively controlling the opening of the overall bypass circuit and the local bypass circuits during the transient start-up phase, thus ensuring a rapid and homogeneous supply of reactive power to all the individual cells. Figure for the abstract: Fig. 1

Description

- of a fuel cell (1) comprising identical elementary cells (Ci) electrically connected in series with each other, each comprising a stack including a proton exchange membrane, an anodic catalytic layer and a cathodic catalytic layer sandwiching the proton exchange membrane, - a main electrical circuit (7) comprising a device (6) electrically powered by the fuel cell, - of a global bypass electrical circuit (8) in a simple loop, in the open position, comprising a global bypass module (9) electrically connected to the terminals (2,3) of the fuel cell and comprising a global bypass load (10), - of a plurality of simple loop local bypass electrical circuits (12, k), each in the open position and comprising a local bypass module (11, k) having terminals electrically connected to the terminals of a cell module (Mk) comprising a single elementary cell or several elementary cells consecutively electrically connected in series, each local bypass module comprising a local bypass load (13, k), each cell module of the fuel cell being included in one of the local bypass electrical circuits, the method comprising measuring at different times the electrical voltage Uk across the terminals of each cell module (Mk) and implementing at least one electrical discharge sequence comprising: a) a global electrical discharge stage comprising a1) the opening of the main electrical circuit and the closing of the global bypass electrical circuit, a2) for each of the elementary cells, 1 the injection of dihydrogen on the side of the anodic catalytic layer and the injection of dioxygen on the side of the cathodic catalytic layer, the electric current produced by the elementary cells being diverted into the global bypass load, then a3) the opening of the overall bypass electrical circuit as soon as at least one overall bypass shutdown criterion is met or as soon as the start-up control end criterion is met, which is: the average voltage Umoy>k of each of the cell modules is greater than a nominal production voltage Uprod, with Umoy>k = Uk / nk, nk >1 being the number of elementary cells of the kth cell module (Mk) and if said overall bypass shutdown criterion is met,b) a local electrical discharge step as long as the average voltage of at least one of the cell modules is below the nominal production voltage Uprod, comprising: b1) the closure of each local bypass electrical circuit in which the average voltage of said at least one of the corresponding cell modules is below the nominal production voltage Uprod so as to divert the electric current produced by said cell module into the corresponding local bypass load, and b2) the progressive opening of each local bypass electrical circuit, closed in step b1) in which the average voltage of said at least one of the corresponding cell modules becomes above the nominal production voltage Uprod, so as to stop the drift of electric current produced by said at least one of the cell modules into the corresponding local bypass load,the end-of-start control criterion being met when each of the local bypass electrical circuits closed in step 1b) has been opened. [Claim 2] A method according to claim 1, wherein the nominal production voltage Uprod is greater than or equal to 0.6 V, preferably greater than or equal to 0.8 V, for example, equal to 0.8 V. [Claim 3] A method according to any one of the preceding claims, wherein in step a), the overall bypass shutdown criterion is selected from at least one of the following criteria i) to ii): i) the absolute difference between the average voltage of at least one of the cell modules and the average Vmoy of the average voltages Umoy>k of the fuel cell cell modules is greater than a predetermined dispersion voltage Udis, of , (ii) preferably Udis being greater than or equal to 100 mV, preferably greater than or equal to 200 mV; (ii) the ratio in absolute value of the difference between the time derivative of the average voltage of at least one of the cell modules and the time derivative of the average Vmoy of the average voltages of the fuel cell cell modules, to the absolute value of the time derivative of the average of the average voltages of the elementary modules of the fuel cell, is greater than 20%. [Claim 4] A method according to any one of the preceding claims, wherein the electrical resistance of the overall bypass load is chosen such that the intensity of the bypass current in the overall bypass module is at most 50%, preferably at most 10% of the fuel cell current generated under nominal operating conditions.[Claim 5] A method according to claim 1, wherein in step b), if the start-up control end criterion is not met after a predetermined start-up time of between 1 second and 60 seconds, for example 5 seconds, the flow rate of dihydrogen injected on the anodic catalytic layer side is increased by a factor of between 2 and 10. [Claim 6] A method according to the preceding claim, wherein in step b), if, within a time of between 1 second and 60 seconds, for example 5 seconds, after increasing the dihydrogen flow rate, the start-up control criterion is not met, the dihydrogen supply on the anodic catalytic layer side is stopped. [Claim 7] A method according to any one of the preceding claims, each cell module of the fuel cell comprising a single elementary cell.[Claim 8] A method according to any one of the preceding claims, the fuel cell comprising p cell modules, p > 3, the cell module of rank k=l comprising a single elementary cell and / or the cell module of rank k=p comprising a single elementary cell, the cell modules of rank k=2 to i=p-1 each comprising at least two elementary cells. [Claim 9] An electrochemical device comprising: . - a fuel cell (10) comprising identical elementary cells (Ci) electrically connected in series with each other, each comprising a stack including a proton exchange membrane, an anodic catalytic layer and a cathodic catalytic layer sandwiching the proton exchange membrane, the fuel cell being intended to be integrated into a main electrical circuit (7) to electrically power an electrical device (6), - a single-loop, open-position global bypass electrical circuit (8) comprising a global bypass module (9) electrically connected to the terminals of the fuel cell and comprising a global bypass load (10), - a plurality of single-loop local bypass electrical circuits (12, k), each in the open position and comprising a local bypass module (11, k) having terminals electrically connected to the terminals of a cell module (Mk) comprising a single elementary cell or several elementary cells connected in series, each local bypass module (13, k) comprising a local bypass load, each fuel cell cell module being included in one of the local bypass electrical circuits, - a control module (5) comprising a unit for measuring the electrical voltage Uk across the terminals of each of the cell modules, the control module being configured to open and close the main electrical circuit (7), the overall discharge circuit and the local discharge circuits (12, k) and being further configured to, according to a fuel cell power generation start-up control mode,implement at least one overall electrical discharge sequence comprising: , a) a global electrical discharge stage comprising a) the opening of the main electrical circuit and the closing of the global branch electrical circuit, a2) for each of the elementary cells, the injection of dihydrogen on the side of the anodic catalytic layer and the injection of dioxygen on the side of the cathodic catalytic layer, the electric current produced by the elementary cells being diverted into the overall divert load, then a3) the opening of the global bypass electrical circuit as soon as at least one global bypass shutdown criterion is met or as soon as the start-up control end criterion is met, which is: the average voltage Umoy>k of each of the cell modules is greater than a nominal production voltage Uprod, with Umoy>k = Uk / nk, nk >1 being the number of elementary cells of the kth cell module (Mk) and if said global bypass shutdown criterion is met, b) a local electrical discharge stage as long as the average voltage of at least one of the cell modules is less than the nominal production voltage Uprod,comprising: bl) the closure of each local branch circuit in which the average voltage Umoy>k of said at least one of the corresponding cell modules is less than the nominal production voltage Uprod so as to divert the electric current produced by said cell module into the corresponding local branch load, and b2) the progressive opening of each local branch circuit closed in step bl) in which the average voltage of said at least one of the corresponding cell modules becomes greater than the nominal production voltage Uprod, so as to stop the drift of electric current produced by said at least one of the cell modules into the corresponding local branch load, the end-of-start control criterion being reached,when each of the local bypass electrical circuits closed in step bil) has been opened. [Claim 10] An electrochemical device according to the preceding claim, comprising, in addition to the global bypass electrical circuit (8), referred to as the "start" circuit, a secondary global bypass electrical circuit (14), referred to as the "stop" circuit, in a single loop and in the open position, the global stop bypass circuit being mounted in parallel with the global start bypass circuit and comprising a global stop bypass module electrically connected to the terminals of the fuel cell and comprising a global stop bypass load. [Claim 11] An electrochemical device according to the preceding claim, the global start bypass load and the bypass load,

Claims

global stopping loads being resistive loads, the electrical resistance of the global starting bypass load is less than the electrical resistance of the global stopping bypass load. 119 mû

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