The invention relates to a method for operating a fuel cell system (100) comprising at least one stack (101) when starting the fuel cell system (100), in particular when during a cold start of the fuel cell system and/or start of the fuel cell system (100) under freezing conditions, in order to bring, in particular to adjust, a coolant temperature (TCoolIn) at the entry point into the stack (101) to a desired stagnation temperature (Ts), the method comprising the following steps: predicting the stagnation temperature (Ts) of the coolant (KM) for various rotational speeds (N) of a coolant pump (31), adjusting the rotational speed (N) of the coolant pump (31) so that the stagnation temperature (Ts) is above the desired value (Ts).

A fuel cell system includes a fuel cell, auxiliary devices, an auxiliary device controller, a secondary battery, a current sensor, a voltage sensor, and a diagnosis controller. In an output stop state where the fuel cell does not output electric power, the auxiliary device controller performs a residual water scavenging process of scavenging water remaining in the fuel cell to outside of the fuel cell system by driving the auxiliary devices using electric power supplied from the secondary battery and supplying the gas to the fuel cell. The diagnosis controller diagnoses the secondary battery using a current integrated value that is obtained by integrating amounts of current supplied from the secondary battery in a predetermined voltage range of a discharge voltage of the secondary battery that changes in response to discharge when electric power is supplied to the auxiliary devices by performing the residual water scavenging process.

A fuel cell system includes: a fuel cell stack; a voltage sensor configured to detect voltage of the fuel cell stack; a fuel cell relay connected to the fuel cell stack; a switch connected between the fuel cell stack and the fuel cell relay; an overcurrent detector configured to detect an overcurrent flowing to the switch; and a power generation stop device configured to stop power generation of the fuel cell stack when the overcurrent detector detects the overcurrent and the detected voltage becomes a specified value or less.

An apparatus for generating injection current for a fuel cell stack includes a first converter configured to convert direct current of a voltage corresponding to a battery for a vehicle, into direct current of a predetermined voltage; a second converter configured to convert the converted direct current into alternating current; a filter configured to filter a signal of a predetermined frequency band from the converted alternating current; and a control unit configured to perform a feedback control to allow the filtered alternating current to be injected without being distorted when injecting the filtered alternating current into the fuel cell stack.

A power supply includes fuel cell, secondary battery, power converter, current detecting unit and control unit. The power converter couples the fuel cell with the secondary battery, and is adapted to convert current outputted by the fuel cell into output current. The current detecting unit couples the power converter with the secondary battery and adapted to detect charging current of the output current transferred to the secondary battery. The control unit couples the current detecting unit with the power converter and is adapted to: when the charging current is greater than a charging current upper-limit-setting value of the secondary battery, a down-adjustment signal is outputted to the power converter to reduce the output current; and when the charging current is less than the charging current upper-limit-setting value, an up-adjustment signal is outputted to the power converter to increase the output current.

Ways of controlling a fuel cell and a battery are provided that include controlling a current of the battery using a current of the fuel cell and where a target battery state of charge is controlled using an actual state of charge of the battery. Systems and methods may employ an inner loop controller and an outer loop controller. The inner loop controller may be configured to control current of the battery using current of the fuel cell, where the inner loop controller includes an integrating controller operating on a time-averaged basis. The outer loop controller may be configured to control a target battery state of charge using an actual state of charge of the battery, where the outer loop controller includes a proportional controller operating using continuous modulation.

A compressor system is provided for a fuel cell system having at least one compressor stage with an electric motor. The compressor stage is set up to suck in and compress an air mass flow along a fluid path using the motor and to discharge the compressed air mass flow as a reactant feed. The compressor system also has a control unit configured to determine a current for supplying the electric motor and a rotational speed of the electric motor or a frequency of the current of the electric motor. In addition, the control unit is configured to ascertain a theoretical air mass flow value in the fluid path as a function of the current and the speed or as a function of the current and the frequency, and to control the motor as a function of the theoretical air mass flow value.

A fuel cell power controller tracks load current and fuel cell output voltage, and alerts on excessive fuel cell ramp rate, so another power source can supplement the fuel cell and/or the load can be reduced. A power engineering process makes efficient use of available fuel cell power by ramping up power flow rapidly when power is available, while respecting the ramp rate and other power limitations of the fuel cell and safety limitations of the load. Power flow decreases after an alert indicating an electrical output limitation of the fuel cell. Permitted power flow increases in response to a power demand increase (actual or requested) from the load in the absence of the alert. Power flow may increase or decrease in a fixed amount, a proportional amount, or per a sequence. A power controller relay may trip open on a low fuel cell output voltage or high load current.

In a power control device for a vehicle in which an electric motor for driving the vehicle to travel is supplied with power from a battery mounted on the vehicle and a fuel cell, a control unit sets a target charging rate (SOCt) of the battery in such a manner that the target charging rate decreases as a remaining fuel amount (Qf) of the fuel cell decreases after the power generation of the fuel cell is started during high-output/high-speed travelling and controls a power generation output (Pf) of the fuel cell based on a difference between the target charging rate (SOCt) and a current charging rate (SOC).

A method for starting the normal operation of an electrical system with a fuel cell and a transducer from a stop mode is disclosed. The transducer absorbs the electrical power of the fuel cell, in which at least one reactant supply of the fuel cell was interrupted, where the interrupted reactant supply is resumed from a restart signal, and where a fuel cell voltage is prescribed and then regulated by the transducer. The prescribed fuel cell voltage is prescribed in a way that an electrical unloaded fuel cell supplied with reactants will exceed the prescribed fuel cell voltage in every case, and the current of the transducer necessary for maintaining the prescribed fuel cell voltage is measured, where the normal operation is released as of a prescribed current necessary to that effect.