© Fraunhofer IEE

Researchers devel­op nov­el pow­er con­vert­ers for the grid-serv­ing oper­a­tion of electrolysers

In the medi­um term, large-scale elec­trol­y­sis capac­i­ties are to be built up both in Ger­many and world­wide. This requires new types of pow­er con­vert­ers that not only meet the require­ments of pow­er­ful elec­trol­y­sers, but also those of the pow­er grids. The Fraun­hofer Insti­tute for Ener­gy Eco­nom­ics and Ener­gy Sys­tem Tech­nol­o­gy (IEE) is now devel­op­ing such pow­er con­vert­ers togeth­er with part­ners in the H₂Gi­ga project HyLeiT. Spe­cial empha­sis is placed on the sys­tem inte­gra­tion of the con­vert­ers. The aim of the project is to halve the costs com­pared to the state of the art, to guar­an­tee a high direct cur­rent qual­i­ty and to enable the grid-serv­ing use of electrolysers.

As coor­di­na­tor of HyLeiT, Fraun­hofer IEE is col­lab­o­rat­ing on this project with SMA, Infi­neon, TU Dres­den and Bonn-Rhein-Sieg Uni­ver­si­ty of Applied Sci­ences. The project has a dura­tion of 4 years. It is fund­ed by the Fed­er­al Min­istry of Research and Education.

HyLeiT is part of the lead project H2Giga coor­di­nat­ed by DECHEMA. It aims to advance the series pro­duc­tion of elec­trol­y­sers. “With­in H2Giga, HyLeiT con­tributes in par­tic­u­lar to the top­ics of grid inte­gra­tion and the elec­tri­cal sys­tem tech­nol­o­gy of elec­trol­y­sers,” says Dr. Philipp Strauß, deputy direc­tor of Fraun­hofer IEE, who coor­di­nates the H₂Gi­ga project HyLeiT togeth­er with Dr. Nor­bert Henze.

Mod­el­ling of the net­work and the electrolysers

As part of HyLeiT, the experts are ini­tial­ly devel­op­ing lab­o­ra­to­ry pro­to­types of pow­er con­vert­ers. Infi­neon is con­tribut­ing nov­el semi­con­duc­tors that are being made suit­able for use in con­vert­ers. They meet the require­ments of both the elec­trolyz­ers and the pow­er grid bet­ter than the clas­sic thyris­tor semiconductors.

In order to be able to test and opti­mize the pow­er con­vert­ers in the sys­tem con­text, the Fraun­hofer researchers are cre­at­ing real-time sim­u­la­tion mod­els of the pow­er grid and the elec­trol­y­sis stacks. They also take into account the age­ing of the elec­trolyz­ers, as these change their elec­tri­cal behav­iour in the course of their life cycle. This must be tak­en into account when design­ing the pow­er converters.

These mod­els are then incor­po­rat­ed into a “hard­ware in the loop” plat­form. The sci­en­tists are thus test­ing the devel­oped con­vert­er con­cepts on all com­mon elec­trol­y­sis tech­nolo­gies. The focus is on the inter­ac­tions of the pow­er con­vert­er with both the elec­trol­y­sis stacks and the pow­er grid. “As the link between the elec­trol­yser and the grid, the pow­er con­vert­er is of cen­tral impor­tance for the ener­gy tran­si­tion. That’s why it’s essen­tial to take the entire sys­tem into account when devel­op­ing and opti­miz­ing pow­er con­vert­ers,” says Henze.

Pow­er con­vert­ers enable elec­trol­y­sis to serve the grid

The research team expects that the project will suc­ceed in halv­ing the sys­tem costs of elec­tri­cal engi­neer­ing from the grid con­nec­tion point to the DC con­nec­tion at the elec­trol­yser com­pared to the state of the art. A mod­u­lar and stan­dard­ised pro­duc­tion of the pow­er con­vert­ers using opti­mised semi­con­duc­tor com­po­nents is the main fac­tor con­tribut­ing to the reduc­tion in costs. Thanks to new cir­cuit­ry tech­niques for pow­er con­vert­ers, pas­sive com­po­nents such as heat sinks can also be made smaller.

Anoth­er goal of the H₂Gi­ga project HyLeiT is to design the pow­er con­vert­ers in such a way that the elec­trol­y­sers can behave in a grid-serv­ing man­ner. Pro­vid­ed that they are designed accord­ing­ly, they should even active­ly con­tribute to the sta­bi­liza­tion of the grids in the future by react­ing to crit­i­cal grid sit­u­a­tions at short notice.

Last but not least, the project also aims to improve the DC qual­i­ty for the elec­trol­yser, espe­cial­ly in dynam­ic oper­at­ing sit­u­a­tions. This increas­es reli­a­bil­i­ty and safe­ty and also extends the ser­vice life of the system.

New build­ing offers best con­di­tions for HyLeiT

In this project, the Fraun­hofer researchers ben­e­fit from the tech­ni­cal equip­ment pro­vid­ed by the insti­tute’s new build­ing in Kas­sel. “The new build­ing offers us ide­al con­di­tions. Among oth­er things, we have a gas lab­o­ra­to­ry at our dis­pos­al where we can build stacks, as well as a well-equipped lab­o­ra­to­ry for pow­er elec­tron­ics and grid inte­gra­tion,” says Strauß. The new build­ing is sched­uled to be occu­pied at the end of 2021.

Fraun­hofer IEE has been deal­ing with ques­tions of grid inte­gra­tion of elec­tri­cal equip­ment and sys­tems for many years. The researchers also have a great deal of exper­tise and expe­ri­ence in mod­el­ling, for exam­ple in the sim­u­la­tion of bat­tery cells.

About the hydro­gen lead projects:

The hydro­gen lead projects are the largest research ini­tia­tive of the Fed­er­al Min­istry of Edu­ca­tion and Research (BMBF) on the sub­ject of the ener­gy tran­si­tion to date. In the indus­try-led lead projects, indus­try and sci­ence are joint­ly devel­op­ing solu­tions for the Ger­man hydro­gen econ­o­my: series pro­duc­tion of large-scale elec­trol­y­sers (H2Giga), pro­duc­tion of hydro­gen at sea (H2Mare), tech­nolo­gies for the trans­port of hydro­gen (Tran­sHyDE).

The BMBF-fund­ed hydro­gen lead projects are the result of an ideas com­pe­ti­tion: sci­ence, indus­try and civ­il soci­ety were invit­ed to sub­mit ideas for large-scale hydro­gen projects. More than 240 part­ners have come togeth­er in this way and are to receive a total of around 740 mil­lion euros in fund­ing. The lead projects are fund­ed over a peri­od of four years.