Controllable rectifier arrangement for hydrogen electrolysis

A method of controlling electrical current for hydrogen electrolysis, the method comprising:

• providing a rectifier arrangement comprising:
• a transformer having a primary winding for connecting an input alternating voltage and a secondary winding for providing an output alternating voltage, and a rectifier connected to the secondary winding, wherein the rectifier comprises a single-phase or multi-phase passive diode bridge rectifier;
• configuring the primary winding to comprise a first partial winding having N winding taps where N>1, and a second partial winding having M winding taps where M>1;
• providing a first on-load tap-changer connected to a controller and configured to switch the winding taps of the first partial winding without interruption;
• providing a second on-load tap-changer connected to the controller and configured to switch the winding taps of the second partial winding without interruption;
• connecting the first partial winding in series with the second partial winding via the second on-load tap-changer such that a transformation ratio of the transformer is switchable in N×M steps;
• generating an output direct current IDC of more than about 600 A at an output direct voltage UDC in the range of about 300 V to 1500 V for hydrogen electrolysis;
• and
• controlling the output direct current by operating the controller to adjust the on-load tap-changers through a coarse adjustment to +/−10% and through a fine adjustment to +/−1%.