A method and related apparatus for extending a DC voltage range of a rectifier circuit for the supply, from an AC grid, of a DC load which is connected to a DC rectifier output of the rectifier circuit, wherein an AC rectifier input of the rectifier circuit is connected via a grid connection point to the AC grid, wherein the rectifier circuit includes an AC/DC converter having an AC input and a DC output, wherein the AC/DC converter includes a converter circuit having semiconductor switches and freewheeling diodes connected in an antiparallel arrangement thereto, wherein an inductance is connected between the AC input of the AC/DC converter and the grid connection point. The method includes setting a desired DC operating voltage U.sub.DOC,soll on the DC output of the AC/DC converter or on the DC rectifier output, or both, by an actuation of semiconductor switches of the AC/DC converter, wherein, when the desired DC operating voltage U.sub.DC,soll lies below a value of an amplitude .Math..sub.4 of an alternating voltage on the AC input of the AC/DC converter, the semiconductor switches of the AC/DC converter are actuated for an exchange of reactive power Q.sub.1(t) with the AC grid, which has a voltage-lowering effect upon the amplitude .Math..sub.4 of the AC voltage at the AC input of the AC/DC converter, such that the amplitude .Math..sub.4 approaches the desired DC operating voltage U.sub.DC,soll, and wherein the exchange of the reactive power Q.sub.1(t) with the AC grid is executed during or shortly before an electrical connection or an electrical isolation of the DC load to or from the rectifier circuit.

A method and related apparatus for extending a DC voltage range of a rectifier circuit for the supply, from an AC grid, of a DC load which is connected to a DC rectifier output of the rectifier circuit, wherein an AC rectifier input of the rectifier circuit is connected via a grid connection point to the AC grid, wherein the rectifier circuit includes an AC/DC converter having an AC input and a DC output, wherein the AC/DC converter includes a converter circuit having semiconductor switches and freewheeling diodes connected in an antiparallel arrangement thereto, wherein an inductance is connected between the AC input of the AC/DC converter and the grid connection point. The method includes setting a desired DC operating voltage U.sub.DOC,soll on the DC output of the AC/DC converter or on the DC rectifier output, or both, by an actuation of semiconductor switches of the AC/DC converter, wherein, when the desired DC operating voltage U.sub.DC,soll lies below a value of an amplitude .Math..sub.4 of an alternating voltage on the AC input of the AC/DC converter, the semiconductor switches of the AC/DC converter are actuated for an exchange of reactive power Q.sub.1(t) with the AC grid, which has a voltage-lowering effect upon the amplitude .Math..sub.4 of the AC voltage at the AC input of the AC/DC converter, such that the amplitude .Math..sub.4 approaches the desired DC operating voltage U.sub.DC,soll, and wherein the exchange of the reactive power Q.sub.1(t) with the AC grid is executed during or shortly before an electrical connection or an electrical isolation of the DC load to or from the rectifier circuit.

The application describes a method for operating an electrolyzer to generate hydrogen from water using an electrolysis reaction, supplied with power from an AC grid via an actively controlled rectifier circuit. The method includes operating the electrolyzer in a normal operating mode with an input voltage U.sub.EI above a no-load voltage U.sub.LL with predominantly ohmic behavior, operating the electrolyzer in a standby operating mode with an input voltage U.sub.EI below the no-load voltage U.sub.LL with predominantly capacitive behavior, and transitioning from the standby operating mode to the normal operating mode during a first transition duration Δt.sub.1, wherein the first transition duration Δt.sub.1 is reduced by keeping the input voltage U.sub.EI at the electrolyzer input during the standby operating mode above a first voltage threshold value U.sub.TH,1 different from 0 V. The application furthermore describes a connection circuit, an actively controlled rectifier circuit and an electrolysis system for performing the method.

An apparatus for estimating electrical properties of an electrolyzer includes a data processing system for estimating electrical values, for example a membrane resistance, of the electrolyzer based on a difference voltage, a current, and an initial value and an attenuation time constant of a double-layer capacitance voltage of the electrolyzer during a shutdown of the electrolyzer. The difference voltage is a difference between a voltage of the electrolyzer and a total reversible voltage of the electrolyzer. The initial value and the attenuation time constant of the double-layer capacitance voltage are estimated based on values of the difference voltage when the current is zero and thus the difference voltage equals the double-layer capacitance voltage. The electrical values can be estimated even if a stepwise interruption of the current of the electrolyzer is not possible.

An apparatus for estimating electrical properties of an electrolyzer includes a data processing system for estimating electrical values, for example a membrane resistance, of the electrolyzer based on a difference voltage, a current, and an initial value and an attenuation time constant of a double-layer capacitance voltage of the electrolyzer during a shutdown of the electrolyzer. The difference voltage is a difference between a voltage of the electrolyzer and a total reversible voltage of the electrolyzer. The initial value and the attenuation time constant of the double-layer capacitance voltage are estimated based on values of the difference voltage when the current is zero and thus the difference voltage equals the double-layer capacitance voltage. The electrical values can be estimated even if a stepwise interruption of the current of the electrolyzer is not possible.

A device and method of controlling an electrode and electrolytic cell are provided, which independently utilizes clean energy with large power fluctuation range as an electrolysis power source for hydrogen and oxygen production. The basic number of electrodes is set by the minimum cut-in voltage value of fluctuating power sources such as wind or solar power. According to fluctuating power sources such as wind or solar power, the ratio of the minimum cut-in current and the reference current corresponding to the lowest cut-in voltage value sets the effective size of the electrodes to be connected in or cut out.

A device and method of controlling an electrode and electrolytic cell are provided, which independently utilizes clean energy with large power fluctuation range as an electrolysis power source for hydrogen and oxygen production. The basic number of electrodes is set by the minimum cut-in voltage value of fluctuating power sources such as wind or solar power. According to fluctuating power sources such as wind or solar power, the ratio of the minimum cut-in current and the reference current corresponding to the lowest cut-in voltage value sets the effective size of the electrodes to be connected in or cut out.

A controller and an operation control method for electrolysis stack module powered by a renewable energy power generation device and an electrolysis system using the same, the controller being configured to control power supply by receiving the power supply from a renewable energy generator and distributing the power supply to n (n≥2) electrolysis stacks, wherein, the controller is configured to determine whether or not to drive each electrolysis stack according to stack driving conditions, no less than two, determined on the basis of a preset minimum amount of operating power supply for each electrolysis stack, and the stack driving conditions are ranges of an amount of the power supply in which on/off of the electrolysis stacks is predetermined, and the controller is configured to control driving of the electrolysis stacks according to the stack driving conditions corresponding to the amount of supplied power from the renewable energy generator.

A controller and an operation control method for electrolysis stack module powered by a renewable energy power generation device and an electrolysis system using the same, the controller being configured to control power supply by receiving the power supply from a renewable energy generator and distributing the power supply to n (n≥2) electrolysis stacks, wherein, the controller is configured to determine whether or not to drive each electrolysis stack according to stack driving conditions, no less than two, determined on the basis of a preset minimum amount of operating power supply for each electrolysis stack, and the stack driving conditions are ranges of an amount of the power supply in which on/off of the electrolysis stacks is predetermined, and the controller is configured to control driving of the electrolysis stacks according to the stack driving conditions corresponding to the amount of supplied power from the renewable energy generator.

A load testing device includes a connection unit to which a power source being tested is connected, a hydrogen generating unit that performs electrolysis based on power supplied from the power source being tested to generate hydrogen, two or more supply units to which hydrogen obtained in the hydrogen generating unit passes and to which a portable tank is removably attached, and an operational unit that has a load amount adjustment switch and a display unit. The load amount of the hydrogen generating unit is switched depending on an operational state of the load amount adjustment switch. The display unit displays at least one of an attachment status of the portable tank and a filling status of hydrogen in the two or more supply units.