Abstract: Provided is a fuel cell system capable of supplying electric power to external loads without excess or deficiency even when switching between operation states is carried out. A warm-up timing judgment part judges whether or not it is time to carry out warm-up based on the temperature of a fuel cell stack. A target shift voltage determination part determines a target output voltage of the fuel cell stack used during a warm-up operation, and a voltage change speed determination part determines a voltage change speed based on electric power required from the fuel cell stack, the target output voltage of the fuel cell stack used during the warm-up operation which is output from the target shift voltage determination part and a current output voltage detected by a voltage sensor. A voltage decrease execution part carries out voltage decrease processing in accordance with the voltage change speed indicated by the voltage change speed determination part.

Abstract: A fuel cell system increases an output voltage of a fuel cell if an electric power generation command value Pref for the fuel cell abruptly reduces while the fuel cell is being warmed up at a low-efficiency operation, which has lower electric power generation efficiency than that of a normal operation. Thus, the surplus electric power Ws corresponding to the difference between an electric power generation amount Pmes of the fuel cell and the electric power generation command value Pref is stored into a capacitive component of the fuel cell, thereby matching the electric power supplied to an external load of the fuel cell (Pmes-Ws) with the electric power generation command value Pref. This makes it possible to conduct control not to supply the surplus electric power to the external load when the electric power required from the fuel cell suddenly reduces during the low-efficiency operation.

Abstract: A fuel cell system capable of carrying out a proper current limiting even when decreasing a cell voltage through, e.g., a rapid warm-up is provided. When a rapid warm-up is started, an acceptable cell-voltage value setting part sets a acceptable lowest-cell-voltage value in accordance with the operation state of a fuel cell. Meanwhile, a target cell-voltage value setting part sets an initial value for a target lowest-cell-voltage value. The target cell-voltage value setting part then compares a lowest cell voltage detected by a cell monitor with the set target lowest-cell-voltage value, and judges whether or not the lowest cell voltage is near the target lowest-cell-voltage value continuously for a given time period. If the result of the judgment is positive, the target cell-voltage value setting part updates the target lowest-cell-voltage value with a value obtained by decreasing the target lowest-cell-voltage value only by an update width.

Abstract: Provided is a fuel cell system that can suitably control a voltage converter in response to a judgment that an abnormal condition occurs in a power detection unit that detects a power passing through the voltage converter. The fuel cell system has: a first power detection unit that estimates an effective value of a converter input power by multiplying the converter input power, which is obtained from a battery voltage and a battery current, by a converter efficiency; a second power detection unit that estimates a converter output power from a fuel cell voltage, a fuel cell current and a driving motor load power; and a third power detection unit that estimates a converter flowing power from a current of a reactor measured by a current sensor (shown in a separate drawing). The fuel cell system also has similar detection units for current, and using one of the detection units or a combination of some of them, specifies a malfunctioning sensor and prohibits correction of parameters.

Abstract: A fuel cell system capable of improving the voltage controllability of a converter provided in the system is provided. A controller judges whether or not a passing power of a DC/DC converter falls within a reduced response performance area for the number of active phases as of the present moment. When the controller determines that the passing power of the DC/DC converter falls within the reduced response performance area, the controller determines the number of phases which avoids the driving within the reduced response performance area, and outputs a command for switching to the determined number of phases (phase switching command) to the DC/DC converter.

Abstract: Provided is a fuel cell system capable of making a shift of an operation state while optically controlling an output voltage and an output voltage of a fuel cell. When an ECU judges that the time when an operation should be shifted from a low-efficiency operation to a normal operation has come, the ECU performs, as preprocessing prior to a shift to a ?V control, processing of increasing an oxidant gas supplied to a fuel cell stack by a predetermined amount. After this processing, the ECU detects output power, calculates an output power deviation, and then compares the output power deviation with a set deviation threshold. When the output power deviation exceeds the deviation threshold, the ECU carries out the ?V control, and then carries out an I-V control. Meanwhile, when the output power deviation does not exceed the deviation threshold, the ECU judges that the time when the ?V control is carried out has not come yet, and automatically starts the I-V control without carrying out the ?V control.

Abstract: In a fuel cell system comprising a fuel cell with plural cells and performing processing for limiting a supply current to a load by performing a compensation computation with respect to a system-request current corresponding to a system-request power requested by the system based on the lowest cell voltage in the cells, the compensation computation being performed for limiting the supply current through a PI compensation using, as a reference value, a current value of the system-request current as of the time when the lowest cell voltage falls below a predetermined lowest-cell-voltage acceptable value, values for gains in the PI compensation for limiting the supply current are different from values for gains in the PI compensation for restoring the supply current.

Abstract: An object is to miniaturize device size in a vehicle mounted converter. The vehicle mounted converter includes a plurality of inductors, a switching unit for switching current path, an external power acquisition unit for acquiring alternating current power from a power generation source provided separately from the mounted vehicle, and a switching means for switching a circuit connection state to a connection state of either a boost connection state for connecting one end of the inductors to a path to a battery for vehicle drive power supply and connecting the switching unit to the other end of the inductors, or a charging connection state for connecting one end of one of the plurality of inductors to the path to the battery, disconnecting one end of the remaining inductors from the path to the battery and connecting to the external power acquisition unit, and connecting the other end of the inductors to the switching unit.

Abstract: The theme of the present invention is a fuel cell system capable of avoiding a disadvantage caused by the maintaining of a low-efficiency operation to improve the safety of a system operation. The fuel cell system is configured to perform the low-efficiency operation having a large power loss as compared with a usual operation at a predetermined low temperature to raise the temperature of a fuel cell in a short time as compared with the usual operation. The fuel cell system prohibits the low-efficiency operation to execute the usual operation, in a case where predetermined conditions are established at the predetermined low temperature. The predetermined conditions include a time when the generated power of the fuel cell cannot be consumed, a time when this generated power cannot be accumulated in a battery, or a time when the flooding of the fuel cell is generated.

Abstract: Provided is a fuel cell system which can perform sufficient scavenging during a current system operation even if required sufficient scavenging during the previous system stop is not performed. When a control device detects that a system start command is input and a low temperature mode flag is turned “ON”, the control device compares a measured impedance during the previous system stop stored in a measured impedance memory to a low temperature start target impedance It stored in a reference impedance memory, to judge whether or not a scavenging process performed during the previous system stop has been insufficient. When the control device judges that the scavenging process is insufficient, an immediate warm-up operation is executed during the current system operation to immediately raise the temperature.

Abstract: A fuel cell system includes; a fuel cell which generates electricity by using a fuel gas and an oxidant gas as reaction gases; current control means which controls current of a fuel cell; voltage control means which controls voltage of the fuel cell; and heat value control means which calculates a heat value required by the fuel cell system and decides a target current value of the current control means and a target voltage value of the voltage control means so as to generate the calculated necessary heat amount, thereby controlling the heat value. Thus, it is possible to supply a heat required for the fuel cell system without increasing the size of the fuel cell system.

Abstract: Provided is a temperature control system which can suppress a cell voltage fluctuation even in the case of starting under a low-temperature environment. The temperature control system for a fuel cell according to the present invention circulates a heat transfer medium through the fuel cell to control the temperature of the fuel cell. The system is characterized by including circulation control means for circulating, through the fuel cell, the heat transfer medium having a flow rate larger than that for a normal operation during a low-temperature operation. According to such a constitution, the flow rate of the heat transfer medium (cooling water or the like) for low-temperature start is set to a flow rate larger than that of the heat transfer medium for normal start, so that a temperature fluctuation among cells can be suppressed even in the case of warm-up for the low-temperature start, and as a result, the cell voltage fluctuation can be suppressed.

Abstract: Disclosed is a fuel cell system including a fuel cell which generates a power, and control means for decreasing the amount of a reactant gas to be supplied to the fuel cell to an amount smaller than that during normal power generation to realize low-efficiency power generation of the fuel cell. The control means sets the voltage lower limit value of the fuel cell so that the amount of an anode gas (pumping hydrogen) to be formed in a cathode of the fuel cell during the low-efficiency power generation is a predetermined amount or less.

Abstract: Provided is a fuel cell system capable of accurately estimating I-V characteristics of a fuel cell. An impedance measurement section measures an impedance of the fuel cell and obtains a voltage drop caused by a direct-current resistance. An air stoichiometry judgment section detects the amount of oxidant gas supplied to the fuel cell and thereby judges whether or not the air stoichiometry ratio is 1 or higher at this time point. An estimated I-V characteristics line creation section determines that the remaining voltage component consists entirely of an activation voltage when the air stoichiometry ratio notified by the air stoichiometry judgment section is 1 or higher, while determining that the remaining voltage drop component includes the combination of the activation overvoltage and voltage drop corresponding to the change in the electromotive voltage when the notified air stoichiometry ratio is below 1.

Abstract: A control unit 80, when calculating a request current I0 according to a system request electric power Preq and calculating a target current I1 by correcting the request current I0 with PI compensation calculation based on a minimum cell voltage Vm detected by a cell monitor 101, variably changes a proportional gain Kp according to the current value at the present time when calculating a current limit value ?I as the amount of correction of a request current I0 according to the equation ?I=?V×Kp+??V×Ki, thereby enhancing controllability to control the current of a fuel cell 20 to a target current value I1. When controlling the current of a fuel cell by determining a target current value by correcting a request current by PI compensation using the difference between a minimum cell voltage and a threshold voltage, controllability to control the current of the fuel cell to the target current value can be enhanced.

Abstract: A fuel cell system is configured to have: a voltage superimposing unit that superimposes a predetermined AC signal on an output voltage of a fuel cell; a unit that detects an output voltage value of a battery device, the output voltage value varying as the fuel cell output voltage value on which the AC signal has been superimposed varies; a battery device voltage comparison unit that compares the detected battery device output voltage value with a predetermined threshold voltage; and a measurement permission determination unit that determines whether the AC impedance measurement is permitted or not based on whether or not the battery device output voltage value exceeds the threshold voltage. The fuel cell system can protect the battery device in the impedance measurement of the fuel cell based on an AC impedance method.

Abstract: A DC/DC converter includes a reactor, IGBT devices, a dead time generation unit, and a DC-CPU. The dead time generation unit operates in response to a reference signal for a duty ratio, to output first and second activation signals provided with an inactive period corresponding to a dead time preventing both of the IGBT devices from conducting. The DC-CPU corrects a tentative duty ratio calculated as based on a voltage control value, in accordance with a value of a current flowing through the reactor, to output the reference signal. Preferably the DC-CPU associates the value of the current of the reactor with three states and when the value approaches a value at which a state transitions to a different state, the DC-CPU gradually switches a correction value.

Abstract: Output voltage of a fuel cell 2 is decreased by a converter 51 to conduct an activation treatment to catalyst of the fuel cell 2, while measuring reduction current by a current sensor 2a while scanning output voltage of the fuel cell 2 over a certain range by the converter 51 as measurement of cyclic voltammetry under the condition that supply of oxidation gas to the fuel cell 2 is stopped from a compressor 31, and this measurement value is integrated by a control device 6. The control device 6 finds a charge amount of electrode catalyst of the fuel cell 2 based on this integration value, decides whether this charge amount is smaller or not than a degradation decision value, and displays this decision result on a display 55. A decision can be made precisely as to whether the electrode catalyst of the fuel cell is degraded or not.

Abstract: When a request power for a fuel cell is smaller than a predetermined value, a fuel cell system stops the supply of an oxidizing gas to the fuel cell and lowers the output voltage of the fuel cell from a use upper limit voltage to a reduction voltage to perform catalyst activation processing. When the output voltage of the fuel cell lowers to an air blow voltage because of the shortage of the oxidizing gas, the fuel cell system re-supplies the oxidizing gas to recover the output voltage of the fuel cell.

Abstract: A fuel cell system capable of reducing time spent before actual execution of low-temperature countermeasure processing is provided. At the time of activation, a control unit for the fuel cell system refers to, for example, a detected FC temperature and judges whether or not the low-temperature countermeasure processing is necessary for the activation. If the control unit determines that the low-temperature countermeasure processing is necessary, it controls an output voltage of the fuel cell to be a target voltage for the low-temperature countermeasure processing, without having the fuel cell enter an OCV state, and then executes the low-temperature countermeasure processing.