IP Library › Granted Patent US 12686933
Granted Patent B2
US 12686933 · App. 17/970,698 · Granted Jul 21, 2026

Method for operating an electrolyzer, connection circuit, rectifier circuit, and electrolysis system for carrying out the method

Inventors: Alexander Unru (Baunatal, DE); Arno Gerth (Kassel, DE); Ralf Juchem (Felsberg, DE); Tobias Becker (Kassel, DE)
Assignee: SMA Solar Technology AG
C25B15/02C25B1/04H02M3/1588
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Quick Facts
Patent No.
US 12686933
App. No.
17/970,698
Granted
Jul 21, 2026
Kind
B2
Abstract

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

Claims (25)

1 . A method for operating an electrolyzer configured to generate hydrogen from water via an electrolysis reaction, and that is supplied with power from an AC voltage grid via an actively controlled rectifier circuit, wherein the electrolyzer has an input coupled to a DC converter output of an AC/DC converter, comprising:

operating the electrolyzer in a normal operating mode with an input voltage U EI applied thereto that is above a no-load voltage U LL of the electrolyzer,

operating the electrolyzer in a standby operating mode with an input voltage U EI applied thereto that is below the no-load voltage U LL of the electrolyzer, and

transitioning from the standby operating mode to the normal operating mode during a first transition duration Δt 1 , wherein the first transition duration Δt 1 is dictated by keeping the input voltage U EI at an input of the electrolyzer during the standby operating mode above a non-zero first voltage threshold value U TH,1 ,

wherein the first voltage threshold value U TH,1 corresponds to a value of at least 80% of the no-load voltage U LL .

2 . The method as claimed in claim 1 , wherein the input voltage U EI at the input of the electrolyzer in the standby operating mode is kept at least 5% below the no-load voltage U LL of the electrolyzer.

3 . The method as claimed in claim 2 , further comprising:

transitioning from the normal operating mode to the standby operating mode during a second transition duration Δt 2 , wherein the second transition duration Δt 2 is dictated by keeping the input voltage U EI at the input of the electrolyzer during the standby operating mode above the non-zero first voltage threshold value U TH,1 .

4 . The method as claimed in claim 1 , wherein the electrolyzer is additionally operated in a maintenance operating mode under specified boundary conditions, wherein in the maintenance operating mode the input voltage U EI of the electrolyzer is below a hazardous voltage value.

5 . The method as claimed in claim 1 , wherein the electrolyzer is assigned to a consumer facility and wherein operation of the electrolyzer and/or operation of components that supply electric power to the electrolyzer is controlled via a control circuit of the consumer facility that performs energy management.

6 . The method as claimed in claim 5 , wherein at least one change between the normal operating mode and the standby operating mode of the electrolyzer takes place during a calculation period with an aim of ensuring that a maximum energy ΔE agreed between the consumer facility and an energy supplier for the calculation period is not exceeded.

7 . The method as claimed in claim 1 , wherein a minimum DC voltage U W,min at the DC converter output of the AC/DC converter is above the no-load voltage U LL of the electrolyzer.

8 . A method for operating an electrolyzer configured to generate hydrogen from water via an electrolysis reaction, and that is supplied with power from an AC voltage grid via an actively controlled rectifier circuit, comprising:

operating the electrolyzer in a normal operating mode with an input voltage U EI applied thereto that is above a no-load voltage U LL of the electrolyzer,

operating the electrolyzer in a standby operating mode with an input voltage U EI applied thereto that is below the no-load voltage U LL of the electrolyzer, and

transitioning from the standby operating mode to the normal operating mode during a first transition duration Δt 1 , wherein the first transition duration Δt 1 is dictated by keeping the input voltage U EI at an input of the electrolyzer during the standby operating mode above a non-zero first voltage threshold value U TH,1 ,

wherein the input voltage U EI of the electrolyzer in the standby operating mode is kept above the first voltage threshold value U TH,1 by connecting the input of the electrolyzer to a DC converter output of an AC/DC converter within the actively controlled rectifier circuit in a clocked manner via a precharging resistor and/or an inductor.

9 . The method as claimed in claim 8 , wherein the clocked connection of the input of the electrolyzer to the DC converter output is implemented using a two-point control.

10 . The method as claimed in claim 8 , wherein a minimum DC voltage U W,min at the DC converter output of the AC/DC converter is above the no-load voltage U LL of the electrolyzer.

11 . The method as claimed in claim 8 , wherein the electrolyzer is additionally operated in a maintenance operating mode under specified boundary conditions, wherein in the maintenance operating mode the input voltage U EI of the electrolyzer is below a hazardous voltage value.

12 . The method as claimed in claim 8 , wherein the electrolyzer is assigned to a consumer facility and wherein operation of the electrolyzer and/or operation of components that supply electric power to the electrolyzer is controlled via a control circuit of the consumer facility that performs energy management.

13 . The method as claimed in claim 12 , wherein at least one change between the normal operating mode and the standby operating mode of the electrolyzer takes place during a calculation period with an aim of ensuring that a maximum energy ΔE agreed between the consumer facility and an energy supplier for the calculation period is not exceeded.

14 . The method as claimed in claim 8 , wherein the input voltage U EI at the input of the electrolyzer in the standby operating mode is kept at least 5% below the no-load voltage U LL of the electrolyzer.

15 . The method as claimed in claim 8 , further comprising:

transitioning from the normal operating mode to the standby operating mode during a second transition duration Δt 2 , wherein the second transition duration Δt 2 is dictated by keeping the input voltage U EI at the input of the electrolyzer during the standby operating mode above the non-zero first voltage threshold value U TH,1 .