A system for electrolysis power conversion includes electrolyser cells arranged as controllable series connected cell groups, a unit for electrolysis operation at a first voltage in the range of 1.0-2.5V per cell and a unit for at least intermittently drawing current from the cell groups at a second voltage at 0.4-1.0V per cell. The system includes at least one capacitor bank maintained at the first voltage and a capacitor bank maintained at the second voltage, the capacitor banks and cell groups having one pole in common and a bidirectional non-isolating DC/DC converter for connecting the first and second voltage capacitor banks. The system further includes a controller for the first and second voltages levels and a half-bridge switch pair for each controllable cell group for individually alternating between the first and second voltage levels being applied to the cell groups to prevent escalating unbalances and cell degradation.

A control method and system of a fuel cell system is provided. The control method includes detecting, by a controller, a voltage of a fuel cell stack when power generation of a fuel cell is stopped while a fuel cell vehicle is being driven. In addition, hydrogen supply pressure at an anode side is adjusted based on a variation in the detected voltage.

A power conditioning system that includes a fuel cell to be connected to a load, a fuel cell converter connected between the fuel cell and the load, the fuel cell converter converting an output voltage of the fuel cell at a predetermined required voltage ratio, a battery connected in parallel with the fuel cell with respect to the load, the battery serving as a power supply source different from the fuel cell, a battery converter connected between the battery and the load, the battery converter converting an output voltage of the battery at a predetermined required voltage ratio. The power conditioning system includes a converter direct coupling unit configured to directly couple an input side and an output side of the fuel cell converter during startup of the power conditioning system and a fuel cell output voltage increasing unit configured to increase the output voltage of the fuel cell to a predetermined voltage by supplying oxidant gas during startup of the fuel cell.

A drive system includes a drive device including an electric power generator; a fuel cell; a secondary battery; a fuel cell step-up converter including a diode; a relay connected to wiring between the fuel cell step-up converter and the drive device; a secondary battery step-up converter connected; a fuel cell voltage sensor; a secondary battery voltage sensor; and a controller. The controller stops the secondary battery step-up converter when a short-circuit fault of the diode is detected, disconnects the relay when a voltage of the fuel cell is higher than a voltage of the secondary battery after stopping the secondary battery step-up converter, and when the voltage of the secondary battery is higher than or equal to the voltage of the fuel cell, executes a voltage control process which increases the voltage of the fuel cell relative to the voltage of the secondary battery, and disconnects the relay.

A motor drive control method is provided for controlling a speed of a motor such that a measured speed value of the motor follows a speed command value. The motor drive control method includes an on/off driving operation of driving a torque of the motor based on the speed command value in such a way that the torque of the motor is repeatedly turned on/off on preset cycle and duty. The motor drive control method and system can markedly enhance efficiency of a motor by reducing switching loss and current ripple loss of an inverter in a low-speed driving period of a high-speed motor.

A device for converting voltage for a drive. The device comprises a first DC voltage converter and a second DC voltage converter. The first DC voltage converter can be set or configured and operated as an inverse converter or as a boost converter.

The drive may be for a forklift truck with a fuel cell system, a battery, at least one electrical element and the device.

A fuel cell vehicle includes a cell stack, a DC level converter, an output unit, a first switching unit disposed between a positive output terminal of the DC level converter and a positive input terminal of the output unit, a second switching unit disposed between a negative output terminal of the DC level converter and a negative input terminal of the output unit, a resistor and a third switching unit connected to each other in series between the positive output terminal of the DC level converter and the negative output terminal of the DC level converter, a fourth switching unit disposed between a contact point between the resistor and the third switching unit and the positive input terminal of the output unit, and a controller for controlling switching operation of the first, second, third and fourth switching units according to an operation mode.

The invention relates to a pre-charging switching device and a fuel cell device for automatically adjusting an output voltage of a fuel cell system and a battery voltage of a battery connected in parallel with respect to a load without a DC-to-DC converter connected therebetween. The invention further relates to a motor vehicle equipped therewith. The pre-charging switching device comprises an input connection for connecting the fuel cell system, an output connection for connecting to the battery and the load and an adjustment switching unit connected therebetween. The adjustment switching unit has a controllable limiting element and a regulating device coupled thereto and is configured for damped adjustment of the voltages by regulating a direct current carrying behavior of the limiting element depending on a fuel cell system current detected on the input side.

A shut down system of a fuel cell vehicle includes: a fuel cell configured to output a high voltage; a rechargeable high voltage battery; a bidirectional converter arranged between an output terminal of the fuel cell and the high voltage battery; a first relay arranged between the fuel cell and the bidirectional converter; and a controller configured to control a voltage of the bidirectional converter when the fuel cell vehicle stalls to reduce a voltage of the output terminal of the fuel cell and turn off the first relay when a voltage value of the output terminal of the fuel cell is below a preset voltage reference value.

A system and method are disclosed for using regenerative braking power to start a fuel cell stack for system restart during a start/stop operation of a fuel cell hybrid vehicle. The method includes disconnecting the fuel cell stack from a high voltage bus for the start/stop operation and using regenerative braking power provided by an electric traction system to recharge a battery in the hybrid vehicle during the start/stop operation. The method also includes reconnecting the fuel cell stack to the high voltage bus and providing at least some of the regenerative braking power from the electric traction system to a compressor that provides cathode air to the fuel cell stack when the stack is reconnected to the high voltage bus at the end of the start/stop operation. A bi-directional DC converter selectively distributes the power to the compressor and the battery.