JP5392592B2 - Fuel cell system and impurity concentration estimation method - Google Patents

Description

  The present invention relates to a fuel cell system and an impurity concentration estimation method.

  2. Description of the Related Art Conventionally, a fuel cell system including a fuel cell that generates power by receiving a supply of reaction gas (fuel gas and oxidizing gas) has been put into practical use. It is known that impurities such as nitrogen gas accumulate over time in the fuel cell of such a fuel cell system and in the circulation path of the fuel off gas with power generation. At present, for the purpose of stabilizing the operation state of the fuel cell, a purge valve is provided in the discharge channel connected to the circulation channel, and the purge valve is controlled to open and close to discharge impurities (purge). Fuel cell systems have been proposed.

At present, various techniques for estimating the impurity concentration in the fuel gas system have been proposed for the purpose of realizing accurate control of the purge timing and purge time. For example, the difference between the amount of nitrogen in the fuel gas system before purging and the amount of nitrogen discharged during purging is estimated as the residual nitrogen amount, and the nitrogen concentration in the fuel gas system is estimated based on this residual nitrogen amount The technique which performs is proposed (for example, refer patent document 1).
JP 2005-327596 A

  By the way, in recent years, development of a fuel cell system employing a modulatable pressure valve (injector or the like) that performs a modulatable pressure of fuel gas supplied from a fuel supply source to the fuel cell has been advanced. Thus, in the fuel cell system that performs a modulatable pressure of the fuel gas system, the amount of exhausted nitrogen at the time of purging changes due to the modulatable pressure, so that the conventional impurity concentration estimation as described in Patent Document 1 described above is performed. When the method is employed, it has been difficult to accurately estimate the impurity concentration.

  The present invention has been made in view of such circumstances, and an object of the present invention is to achieve accurate estimation of impurity concentration in a fuel cell system that performs a modulatable pressure of a fuel gas system.

  In order to achieve the above object, a fuel cell system according to the present invention includes a fuel cell, a fuel gas system having a fuel gas supply channel for flowing fuel gas supplied from a fuel supply source to the fuel cell, and a fuel. A controllable pressure valve for controlling the controllable pressure of the fuel gas flowing through the gas supply channel, a purge valve for discharging the gas from the fuel gas system, and a pressure command value for the fuel gas supplied from the controllable pressure valve to the fuel cell And a control means for controlling the opening / closing operation of the modulatable pressure valve and the purge valve based on the discharge amount command value of the gas discharged from the purge valve, wherein the control means has a discharge amount command value The gas residual rate in the fuel gas system after the gas is discharged from the purge valve is calculated based on the gas residual rate, the impurity partial pressure in the fuel gas system is calculated based on the gas residual rate, and the impurity partial pressure is calculated as a pressure command value. To divide by Ri, and calculates the estimated impurity concentration in the fuel gas system.

  Further, the impurity concentration estimation method according to the present invention includes a fuel cell, a fuel gas system having a fuel gas supply channel for flowing fuel gas supplied from a fuel supply source to the fuel cell, and a fuel gas supply channel. A method for estimating the impurity concentration of a fuel cell system, comprising: a modulatable pressure valve that performs a modulatable pressure of fuel gas flowing through the gas; and a purge valve for exhausting gas from the fuel gas system. Based on the gas discharge command value, the first step of calculating the gas residual rate in the fuel gas system after gas discharge from the purge valve, and the gas residual rate calculated in the first step, By dividing the impurity partial pressure calculated in the second step and the second step of calculating the impurity partial pressure in the fuel gas system by the pressure command value of the fuel gas supplied to the fuel cell from the adjustable pressure valve Estimated impurity concentration in the fuel gas system A third step of calculating the one in which comprises a.

  By adopting such a configuration and method, even in a fuel cell system that performs a variable pressure of the fuel gas flowing through the fuel gas supply flow path, information on the pressure adjustment value of the fuel gas (pressure command value) and information on the purge amount (discharge) Based on the quantity command value), the impurity concentration in the fuel gas system can be accurately estimated.

  In the fuel cell system, an injector can be adopted as the adjustable pressure valve.

  An injector is an electromagnetically driven opening and closing that can adjust the gas state (gas flow rate and gas pressure) by driving the valve body directly with a predetermined driving cycle with electromagnetic driving force and separating it from the valve seat It is a valve. The predetermined control unit drives the valve body of the injector to control the fuel gas injection timing and injection time, whereby the flow rate and pressure of the fuel gas can be accurately controlled.

  According to the present invention, it is possible to achieve accurate estimation of impurity concentration in a fuel cell system that performs a modulatable pressure of a fuel gas system.

  Hereinafter, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an example in which the present invention is applied to an on-vehicle power generation system of a fuel cell vehicle will be described.

  First, the configuration of the fuel cell system 1 according to the embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 1, the fuel cell system 1 according to the present embodiment includes a fuel cell 2 that generates power by receiving supply of reaction gas (oxidation gas and fuel gas). Gas to the fuel cell 2 and the oxidizing gas system 3 for discharging the oxidizing off gas from the fuel cell 2, hydrogen gas as the fuel gas to the fuel cell 2 and hydrogen off gas as the fuel off gas to hydrogen gas In addition, a fuel gas system 4 to be circulated to the fuel cell 2 is connected. The fuel gas system 4 has an exhaust drain valve 29 that can discharge hydrogen off gas from the fuel gas system 4, and the hydrogen off gas discharged from the exhaust drain valve 29 is discharged from the oxidizing gas system 3 in the dilution section 5. It can be discharged to the outside after being mixed with (air). The entire system is centrally controlled by the control unit 6.

  The fuel cell 2 is formed of, for example, a solid polymer electrolyte type and has a stack structure in which a large number of single cells (cells) are stacked. The unit cell (cell) of the fuel cell 2 has an air electrode (cathode) on one surface of the solid polymer electrolyte membrane, a fuel electrode (anode) on the other surface, and further includes an air electrode and a fuel electrode. A pair of separators are provided so as to be sandwiched from both sides. The fuel cell 2 generates electric power by supplying the fuel gas to the flow path of the separator on the anode side and the oxidizing gas to the flow path of the separator on the cathode side. The fuel cell 2 is provided with a temperature sensor 2a that detects its operating temperature. Information on the operating temperature of the fuel cell 2 detected by the temperature sensor 2a is transmitted to the control unit 6 and used for control of the hydrogen circulation system.

  The oxidizing gas system 3 has an air supply passage 11 through which oxidizing gas supplied to the fuel cell 2 flows, and an exhaust passage 12 through which oxidizing off-gas discharged from the fuel cell 2 flows. The air supply flow path 11 includes a compressor 14 that takes in the oxidizing gas, and a humidifier 15 that humidifies the oxidizing gas pumped by the compressor 14. The exhaust passage 12 includes a back pressure adjustment valve 16 and is connected to the humidifier 15, and the oxidizing off gas flowing through the exhaust passage 12 passes through the back pressure adjustment valve 16 and is used for moisture exchange in the humidifier 15. After that, it is transferred to the dilution unit 5.

  The fuel gas system 4 includes a hydrogen tank 21 as a fuel supply source storing high-pressure hydrogen gas, and a hydrogen supply flow path 22 as a fuel gas supply flow path for supplying the hydrogen gas in the hydrogen tank 21 to the fuel cell 10. And a circulation flow path 23 for returning the hydrogen off-gas discharged from the fuel cell 2 to the hydrogen supply flow path 22. Instead of the hydrogen tank 21, a reformer that generates hydrogen-rich reformed gas from a hydrocarbon-based fuel, a high-pressure gas tank that stores the reformed gas generated by the reformer in a high-pressure state, and Can also be employed as a fuel supply source. A tank having a hydrogen storage alloy may be employed as a fuel supply source.

  The hydrogen supply flow path 22 is provided with a shutoff valve 24 that shuts off or allows the supply of hydrogen gas from the hydrogen tank 21, a regulator 25 that adjusts the pressure of the hydrogen gas, and an injector 26. A pressure sensor 27 that detects the pressure of the hydrogen gas in the hydrogen supply flow path 22 is provided on the downstream side of the injector 26 and upstream of the junction between the hydrogen supply flow path 22 and the circulation flow path 23. ing. Information on the pressure of the hydrogen gas detected by the pressure sensor 27 is transmitted to the control unit 6 and used for controlling the hydrogen circulation system.

  The regulator 25 is a device that regulates the upstream pressure (primary pressure) to a preset secondary pressure. In the present embodiment, a mechanical pressure reducing valve that reduces the primary pressure is employed as the regulator 25. The mechanical pressure reducing valve has a structure in which a back pressure chamber and a pressure adjusting chamber are formed with a diaphragm therebetween, and the primary pressure is reduced to a predetermined pressure in the pressure adjusting chamber by the back pressure in the back pressure chamber. Thus, a publicly known configuration for the secondary pressure can be employed.

  The injector 26 is an electromagnetically driven on-off valve capable of adjusting the gas flow rate and the gas pressure by driving the valve body directly with a predetermined driving cycle with an electromagnetic driving force and separating it from the valve seat. In the present embodiment, as shown in FIG. 1, an injector 26 is disposed on the upstream side of the junction between the hydrogen supply flow path 22 and the circulation flow path 23. The injector 26 includes a valve seat having an injection hole for injecting gaseous fuel such as hydrogen gas, a nozzle body for supplying and guiding the gaseous fuel to the injection hole, and an axial direction (gas flow direction) with respect to the nozzle body. And a valve body that is slidably accommodated and opens and closes the injection hole. In the present embodiment, the valve body of the injector 26 is driven by a solenoid that is an electromagnetic drive device, and the opening area of the injection hole is made two or more stages by turning on and off the pulsed excitation current supplied to the solenoid. It can be switched. By controlling the gas injection time and gas injection timing of the injector 26 by the control signal output from the control unit 6, the flow rate and pressure of the hydrogen gas are controlled with high accuracy. The injector 26 directly opens and closes the valve (the valve seat and the valve body) with an electromagnetic driving force, and has a high responsiveness because its driving cycle can be controlled to a highly responsive region.

  The injector 26 changes the opening area (opening) and / or the opening time of a valve provided in the gas flow path of the injector 26 in order to supply the required gas flow rate downstream thereof. The gas flow rate (or hydrogen molar concentration) supplied to the (fuel cell 2 side) is adjusted. Since the gas flow rate is adjusted by opening and closing the valve of the injector 26 and the gas pressure supplied downstream of the injector 26 is reduced from the gas pressure upstream of the injector 26, the injector 26 is regulated by a pressure regulating valve (pressure reducing valve, regulator). Can also be interpreted. Further, in the present embodiment, a variable pressure control valve capable of changing the pressure adjustment amount (pressure reduction amount) of the upstream gas pressure of the injector 26 so as to match the required pressure within a predetermined pressure range according to the gas requirement. Also works.

  A discharge channel 30 is connected to the circulation channel 23 via a gas-liquid separator 28 and an exhaust drain valve 29. The gas-liquid separator 28 collects moisture from the hydrogen off gas. The exhaust / drain valve 29 operates according to a command from the control unit 6, and discharges moisture collected by the gas-liquid separator 28 and hydrogen off-gas (fuel off-gas) including impurities in the circulation channel 23 to the outside. (Purge) functions as one embodiment of the purge valve in the present invention. By performing such purging, the impurity partial pressure and the impurity concentration are reduced, and the concentration of hydrogen gas supplied to the fuel cell 2 is increased. The impurity partial pressure is, for example, nitrogen gas contained in hydrogen gas supplied from the hydrogen tank 21, nitrogen gas supplied from the oxidizing gas system 3 through the solid polymer electrolyte membrane to the fuel gas system 4, fuel It is the sum of partial pressures of gases other than hydrogen gas such as water vapor generated by power generation of the battery 2. In addition, the circulation channel 23 is provided with a circulation pump 31 that pressurizes the hydrogen off-gas in the circulation channel 23 and sends it to the hydrogen supply channel 22 side. The hydrogen off-gas discharged through the exhaust drain valve 29 and the discharge passage 30 is diluted by the diluter 5 by joining with the oxidizing off-gas in the exhaust passage 12.

  The control unit 6 detects an operation amount of an acceleration operation member (accelerator or the like) provided in the vehicle, and receives control information such as an acceleration request value (for example, a required power generation amount from a load device such as a traction motor). Control the operation of various devices in the system. In addition to the traction motor, the load device is an auxiliary device required for operating the fuel cell 2 (for example, a motor of the compressor 14 or a motor of the circulation pump 31), various devices ( It is a collective term for power consumption devices including actuators used in transmissions, wheel control units, steering devices, suspension devices, etc., air conditioners (air conditioners) for passenger spaces, lighting, audio, and the like.

  The control unit 6 is configured by a computer system (not shown). Such a computer system includes a CPU, a ROM, a RAM, an HDD, an input / output interface, a display, and the like. The CPU reads various control programs recorded in the ROM and executes a desired calculation, thereby performing a purge described later. Various processes and controls such as control are performed.

  Specifically, the control unit 6 determines the pressure command value (hydrogen pressure regulation value) of the hydrogen gas supplied from the injector 26 to the fuel cell 2 according to the load (required power generation amount from the load device), and the exhaust gas. An emission amount command value (purge amount) of the gas discharged from the drain valve 29 and a command value (circulation amount) of the flow rate of the gas sent from the circulation flow path 23 to the hydrogen supply flow path 22 are set in a predetermined map ( Set based on FIG. And the control part 6 controls operation | movement of the injector 26, the exhaust drain valve 29, and the circulation pump 31 based on each set control parameter (hydrogen pressure regulation value, purge amount, and circulation amount).

  Further, the control unit 6 calculates the gas residual rate in the fuel gas system 4 after purging (after exhausting the gas from the exhaust drain valve 29) based on the set purge amount, and based on this gas residual rate, calculates the fuel residual rate. The impurity partial pressure in the gas system 4 is calculated. Then, the control unit 6 calculates the estimated impurity concentration in the fuel gas system 4 by dividing the impurity partial pressure by the set hydrogen pressure adjustment value. That is, the control unit 6 functions as an embodiment of the control means in the present invention.

  Here, the design method of the map (FIG. 6) used for the setting of the control parameter of the fuel cell system 1 according to the present embodiment will be described with reference to FIGS.

<Room temperature: Design in low load range>
First, the operating temperature of the fuel cell 2 is the design of a typical low-load region when the ambient temperature T ₁ (the required power generation current value A _L of the fuel cell _2). In the low load region, as shown in the flowchart of FIG. 2, first, the hydrogen stoichiometric ratio _RS is set (stoichiometric ratio setting step: S1). Here, the hydrogen stoichiometric ratio is a ratio between the amount of supplied hydrogen gas and the amount of consumed hydrogen gas (a value obtained by dividing the amount of supplied hydrogen gas by the amount of consumed hydrogen gas). After setting the hydrogen stoichiometric ratio R _S in the stoichiometric ratio setting step S1, the purge amount _EL is set so that the concentration of the hydrogen gas discharged during the purge is less than a predetermined environmental reference value (purge amount setting). Step: S2).

Then, the purge amount E _L set in the purge amount setting step S2, the hydrogen loss is to set the hydrogen pressure regulation value that minimizes (hydrogen pressure regulation value setting step: S3). Here, the hydrogen loss is a cross leak loss (a value obtained by multiplying a hydrogen permeation coefficient, an anode-side hydrogen partial pressure, the number of cells, and an electrode area) and a hydrogen discharge loss (a gas discharge amount from the exhaust drain valve 29 to a fuel). The value obtained by multiplying the hydrogen concentration at the outlet of the battery 2) and the circulation pump power loss (theoretical hydrogen consumption estimated based on the power of the circulation pump 31). In the low load region, the relationship between the hydrogen pressure (hydrogen gas supply pressure in the hydrogen supply flow path 22) and the hydrogen loss is substantially linear as shown in the graph of FIG. Therefore, setting the minimum value P _L of the hydrogen pressure in the graph of FIG. 3 as the hydrogen pressure regulation value.

Next, the hydrogen stoichiometric ratio R _S set in the stoichiometric ratio setting step S1, the purge amount E _L set in the purge amount setting step S2, and the hydrogen pressure adjustment value P _L set in the hydrogen pressure adjustment value setting step S3. Based on this, the circulation amount _CL is set (circulation amount setting step: S4). Each parameter of the hydrogen stoichiometric ratio, purge amount, hydrogen pressure adjustment value, and circulation amount is a parameter relating to operating conditions of the hydrogen circulation system of the fuel cell system 1, and when any three parameters are determined, the remaining 1 It is assumed that two parameters are automatically determined.

Next, an impurity partial pressure P _NH at the outlet of the fuel cell 2 when operating based on the parameters set in the stoichiometric ratio setting step S1 to the circulation amount setting step S4 is calculated (impurity partial pressure calculation step: S5). The impurity partial pressure can be calculated mainly based on the nitrogen gas partial pressure and the water vapor partial pressure. The nitrogen gas partial pressure can be calculated mainly from the nitrogen content contained in the hydrogen gas supplied from the hydrogen tank 21 and the nitrogen content that permeates from the cathode side to the anode side. It can be calculated from the saturated water vapor pressure at the temperature of the battery 2.

With the above procedure, the design in a typical low load region (required power generation current value A _L to the fuel cell 2) at normal temperature is completed. Purge amount set in the purge amount setting step S2 E _L in the map of FIG. 6 (A), hydrogen pressure regulation value P _L set in the hydrogen pressure regulation value setting step S3, the map of FIG. 6 (B), the circulation amount circulation amount C _L set in setting step S4, the map of FIG. 6 (C), the so that the respective plotted.

<Normal temperature: Design in medium load range to high load range>
Next, a load region exceeding a typical low load region, that is, a value A corresponding to a high load region through values A _M1 , A _M2 ,... Design in the load region up to _H. In these load regions (medium load region to high load region), as shown in the flowchart of FIG. 4, first, the impurity partial pressure P _NH set in the impurity partial pressure calculation step S5 in the low load region is maintained. , Purge amounts E _M1 , E _M2 ,..., E _H are set (purge amount setting step: S11).

Next, a hydrogen pressure adjustment value that minimizes hydrogen loss is set at the purge amounts E _M1 , E _M2 ,..., E _H set in the purge amount setting step S11 (hydrogen pressure adjustment value setting step: S12). In the medium load region to the high load region, the relationship between the hydrogen pressure and the hydrogen loss is substantially linear or non-linear as shown in the graphs of FIGS. For this reason, in the graphs of FIGS. 5A to _5G , the hydrogen pressure (P _M1 , P _M2 ,..., P _H ) that minimizes the hydrogen loss is set as the hydrogen pressure adjustment value. Next, the purge amounts E _M1 , E _M2 ,..., E _H set in the purge amount setting step S11, and the hydrogen pressure adjustment values P _M1 , P _M2 ,..., P _H set in the hydrogen pressure value setting step S12, Based on (and the hydrogen stoichiometric ratio R _S set in the stoichiometric ratio setting step S1), circulation amounts C _M1 , C _M2 ,..., C _H are set (circulation amount setting step: S13).

With the above procedure, the design in the medium load region to the high load region at normal temperature is completed. The purge amounts E _M1 , E _M2 ,..., E _H set in the purge amount setting step S11 are shown in the map of FIG. 6A in the hydrogen pressure adjustment values P _M1 , P _M2 , .., P _H are plotted on the map of FIG. 6B, and circulation amounts C _M1 , C _M2 ,..., C _H set in the circulation amount setting step S4 are plotted on the map of FIG. Thus, the design of the map in the entire load area is completed. The impurity partial pressure P _NH in the full load region is constant as shown in the graph of FIG.

<High temperature: Design in full load range>
Subsequently, design is performed when the operating temperature of the fuel cell 2 reaches a temperature T ₂ higher than the normal temperature T ₁ . At such a high temperature, first, parameters (hydrogen pressure adjustment value P _L , purge amount E _L , circulation amount) set in a typical low load region (required power generation current value A _L to the fuel cell 2) at normal temperature. The impurity partial pressure P _NH ′ at the outlet of the fuel cell 2 when operated based on C _L ) is calculated (impurity partial pressure calculating step: S21). The impurity partial pressure P _NH ′ calculated in the high-temperature impurity partial pressure calculation step S21 is such that the partial pressure of water vapor is increased by the amount by which the operating temperature of the fuel cell 2 is increased. higher than the impurity partial pressure P _NH calculated in calculation step S5.

Next, purge amounts E _M1 ′, E _M2 ′,..., E _H ′ are set so as to maintain the impurity partial pressure P _NH ′ set in the impurity partial pressure calculation step S21 (purge amount setting step: S22). Thereafter, the purge amount _E M1 set in the purge amount setting step _{S22 ', E M2', ...} , and _{E H} ', the hydrogen pressure regulation value _{P M1,} P M2, ..., and _{P H,} (more stoichiometric ratio setting step Based on the hydrogen stoichiometric ratio R _S set in S1, the circulation amounts C _M1 ′, C _M2 ′,..., C _H ′ are set (circulation amount setting step: S23). In this embodiment, in order to simplify the design, hydrogen pressure values P _M1 , P _M2 ,..., P _H at normal temperature are employed even at high temperatures.

With the above procedure, the design in the entire load region at high temperature is completed. Purge amount _E M1 set in the purge amount setting step _{S22 ', E M2', ...} , is plotted _{E H} 'in the map of FIG. 6 (A), the purge amount at high temperature _{T 2} (broken line), normal temperature T _It can be seen that the purge amount at ₁ is increased (solid line).

  Next, a control method of the fuel cell system 1 according to the present embodiment will be described using the flowcharts of FIGS. 9 and 10.

  First, as shown in FIG. 9, the control unit 6 of the fuel cell system 1 receives a signal from an accelerator sensor or the like provided in the vehicle and calculates a load (required power generation current value) to the fuel cell 2 ( Load calculation step: S31). Moreover, the control part 6 detects the operating temperature of the fuel cell 2 using the temperature sensor 2a (temperature detection process: S32).

Next, the control unit 6 determines the hydrogen pressure adjustment value, the purge amount, the circulation amount based on the load calculated in the load calculation step S31, the temperature detected in the temperature detection step S32, and the map of FIG. Are set (control parameter setting step: S33). For example, a calculated load is A _M, when the detected temperature is T _1, as shown in FIG. 6 (A) ~ (C) , hydrogen pressure regulation value is P _M, the purge amount E _M The circulation amount is set to _CM , respectively. When the calculated load is A _M and the detected temperature is T ₂ , the purge amount is set to E _M ′ as shown in FIG.

  Next, the controller 6 estimates the impurity concentration in the fuel gas system 4 based on the hydrogen pressure value and purge amount set in the control parameter setting step S33 (impurity concentration estimation step: S34). Information relating to the impurity concentration estimated in the impurity concentration estimation step S34 is reflected in the control of the injector 26, the exhaust / drain valve 29, and the circulation pump 31 in the next step (circulation control step S35).

  Here, the details of the impurity concentration estimation step S34 will be described with reference to the flowchart of FIG.

First, the control unit 6, the purge amount set by the control parameter setting step S33 (the discharge amount command value), divided by the total volume of the fuel gas system 4 calculates the purge rate R _P (purge ratio calculating step : S41), further, by reducing the purge rate R _P 1, to calculate the gas residual ratio R _R of the fuel gas system 4 after the purge (residual percentage calculation step: S42). The residual ratio calculating step S42 corresponds to the first step in the present invention.

Then, the control unit 6, the gas residual ratio R _R calculated in residual percentage calculation step S42, by multiplying the impurity partial pressure P _NHn-1 in the previous control loop, the impurity partial pressure P _NHn in the present control loop Calculate (impurity partial pressure calculation step: S43). Then, the controller 6 divides the impurity partial pressure P _NHn calculated in the impurity partial pressure calculation step S43 by the hydrogen pressure value (pressure command value) set in the control parameter setting step S33, so that the fuel gas system 4 The estimated impurity concentration is calculated (estimated impurity concentration calculation step: S44). The impurity partial pressure calculation step S43 and the estimated impurity concentration calculation step S44 correspond to the second and third steps in the present invention, respectively. After the above process group, the impurity concentration estimation process S34 is completed.

  Subsequent to the impurity concentration estimation step S34, the controller 6 controls the operations of the injector 26, the exhaust drain valve 29, and the circulation pump 31 based on the control parameters set in the control parameter setting step S33 (circulation). Control step: S35). In the circulation control step S35, the control unit 6 calculates the deviation between the pressure value of the hydrogen gas detected by the pressure sensor 27 and the hydrogen pressure adjustment value (control parameter), so that the injector 26 reduces the deviation. Perform feedback control. In the circulation control step S35, the control unit 6 calculates the gas discharge amount from the time when the exhaust drain valve 29 is opened, and when the calculated gas discharge amount reaches the purge amount (control parameter), the exhaust gas is discharged. The drain valve 29 is closed. In the circulation control step S35, the control unit 6 sets the rotation speed of the circulation pump 31 so that the flow rate of the gas sent from the circulation pump 31 to the hydrogen supply passage 22 becomes the circulation amount (control parameter).

  In the fuel cell system 1 according to the embodiment described above, the fuel gas is controlled based on the hydrogen pressure adjustment value and the purge amount while performing the variable pressure control of the hydrogen gas flowing through the hydrogen supply flow path 22 using the injector 26. The impurity concentration in the system 4 can be accurately estimated. Therefore, accurate purge control can be realized using accurate estimation information related to the impurity concentration.

  In the above embodiment, an example in which the exhaust drain valve 29 for realizing both exhaust and drainage is provided in the circulation flow path 23 as a purge valve is shown. However, moisture recovered by the gas-liquid separator 28 is externally supplied. It is also possible to separately provide a drain valve for discharging the gas and an exhaust valve (purge valve) for discharging the gas in the circulation channel 23 to the outside, and the control unit 6 can control the exhaust valve.

  Moreover, in the above embodiment, although the example which mounted the fuel cell system which concerns on this invention in the fuel cell vehicle was shown, it concerns on this invention to various mobile bodies (a robot, a ship, an aircraft, etc.) other than a fuel cell vehicle. A fuel cell system can also be installed. Further, the fuel cell system according to the present invention may be applied to a stationary power generation system used as a power generation facility for a building (house, building, etc.).

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. 3 is a flowchart for explaining a map design method (normal temperature: low load region) of the fuel cell system shown in FIG. 1. 2 is a graph for explaining a map design method (normal temperature: low load region) of the fuel cell system shown in FIG. 1. 2 is a flowchart for explaining a map design method (normal temperature: medium to high load region) of the fuel cell system shown in FIG. 1. 2 is a graph for explaining a map design method (normal temperature: medium to high load region) of the fuel cell system shown in FIG. 1. FIG. 2 is a map used for setting control parameters of the fuel cell system shown in FIG. 1, (A) is a map showing the relationship between load and purge amount, and (B) is a map showing the relationship between load and hydrogen pressure regulation value. (C) is a map showing the relationship between the load and the circulation rate. 2 is a graph showing an impurity partial pressure in a full load region of the fuel cell system shown in FIG. 1. 2 is a flowchart for explaining a map design method (high temperature: full load region) of the fuel cell system shown in FIG. 1. 2 is a flowchart for explaining a control method of the fuel cell system shown in FIG. 1. 2 is a flowchart for explaining an impurity concentration estimation step of the fuel cell system shown in FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 4 ... Fuel gas system, 6 ... Control part (control means), 21 ... Hydrogen tank (fuel supply source), 22 ... Hydrogen supply flow path (fuel gas supply flow path), 26: Injector (modulable pressure valve), 29: Exhaust drain valve (purge valve).

Claims (3)

A fuel cell, a fuel gas system having a fuel gas supply channel for flowing a fuel gas supplied from a fuel supply source to the fuel cell, and a modulatable pressure of the gas flowing through the fuel gas supply channel A controllable pressure valve, a purge valve for discharging gas from the fuel gas system, a pressure command value of fuel gas supplied from the controllable pressure valve to the fuel cell, and a discharge amount of gas discharged from the purge valve A fuel cell system comprising: control means for controlling opening and closing operations of the modulatable pressure valve and the purge valve based on a command value;
The control means includes a map that defines a relationship between the required generated current value and the pressure command value and a relationship between the required generated current value and the emission command value, and the pressure is determined by the required generated current value and the map. A purge rate is calculated by setting a command value and the discharge amount command value, and dividing the discharge amount command value by the total volume of the fuel gas system. By subtracting this purge rate from 1, the purge valve A gas residual rate in the fuel gas system after the gas is discharged is calculated, an impurity partial pressure in the fuel gas system is calculated based on the gas residual rate, and the impurity partial pressure is divided by the pressure command value. by state, and are not for calculating the estimated impurity concentration in the fuel gas system,
The map includes a normal temperature / low load region where the operating temperature of the fuel cell is a first temperature and a required generated current value to the fuel cell is a first value, and the operating temperature of the fuel cell is the first temperature. A normal temperature / medium / high load region in which the required power generation current value to the fuel cell exceeds the first value, and the operating temperature of the fuel cell is a second temperature higher than the first temperature. The required power generation current value for the fuel cell is designed in each of a high temperature and full load region in which the first value or higher is greater than or equal to the first value.
Fuel cell system.   The fuel cell system according to claim 1, wherein the modulatable pressure valve is an injector. A fuel cell, a fuel gas system having a fuel gas supply channel for flowing a fuel gas supplied from a fuel supply source to the fuel cell, and a modulatable pressure of the gas flowing through the fuel gas supply channel The relationship between the controllable pressure valve, the purge valve for discharging the gas from the fuel gas system, the required power generation current value and the pressure command value of the fuel gas supplied from the controllable pressure valve to the fuel cell, and the required power generation current A map for defining a relationship between a value and an emission command value of a gas discharged from the purge valve, respectively, and an impurity concentration estimation method for a fuel cell system comprising:
The pressure command value and the discharge command value are set according to the required power generation current value and the map, and the purge rate is calculated by dividing the discharge command value by the total volume of the fuel gas system. A first step of calculating a gas residual ratio in the fuel gas system after gas discharge from the purge valve by subtracting from 1;
A second step of calculating an impurity partial pressure in the fuel gas system based on the gas residual ratio calculated in the first step;
A third step of calculating an estimated impurity concentration in the fuel gas system by dividing the impurity partial pressure calculated in the second step by the pressure command value ,
The map includes a normal temperature / low load region where the operating temperature of the fuel cell is a first temperature and a required generated current value to the fuel cell is a first value, and the operating temperature of the fuel cell is the first temperature. A normal temperature / medium / high load region in which the required power generation current value to the fuel cell exceeds the first value, and the operating temperature of the fuel cell is a second temperature higher than the first temperature. The required power generation current value for the fuel cell is designed in each of a high temperature and full load region in which the first value or higher is greater than or equal to the first value.
Impurity concentration estimation method.

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