Picture: TU Dortmund

Real-time sim­u­la­tion in the smart grid laboratory

How does our pow­er grid han­dle the fluc­tu­at­ing volt­age from wind ener­gy or pho­to­voltaics? How does it behave when a large num­ber of elec­tric cars are charg­ing at the same time? The new Smart Grid Tech­nol­o­gy Lab at TU Dort­mund Uni­ver­si­ty is con­duct­ing research on these cur­rent issues. At ie³, the Insti­tute for Ener­gy Sys­tems, Ener­gy Effi­cien­cy and Ener­gy Eco­nom­ics at the Tech­ni­cal Uni­ver­si­ty, var­i­ous grid sit­u­a­tions are real­is­ti­cal­ly sim­u­lat­ed in the lab­o­ra­to­ry. A trans­former that com­pen­sates for inad­mis­si­ble volt­age fluc­tu­a­tions — and does so ful­ly auto­mat­i­cal­ly on the basis of a pre­de­fined con­trol algo­rithm — was required for trans­mis­sion from the medi­um-volt­age to the low-volt­age grid in the test envi­ron­ment. Ormaz­a­bal sup­plied a con­trol­lable local net­work trans­former (rONT) for this pur­pose, the con­trol of which was spe­cial­ly tai­lored to the require­ments of the lab­o­ra­to­ry. Ormaz­a­bal was able to draw on the expe­ri­ence of its own smart grid lab­o­ra­to­ry, which the com­pa­ny oper­ates near its head­quar­ters in Spain.

With the Smart Grid Tech­nol­o­gy Lab at TU Dort­mund Uni­ver­si­ty, an infra­struc­ture has been cre­at­ed that makes it pos­si­ble to devel­op and test smart grid com­po­nents in an envi­ron­ment that cor­re­sponds to cur­rent and future grid oper­a­tions. “The spe­cial fea­ture of this lab­o­ra­to­ry infra­struc­ture is, on the one hand, the repli­ca­tion of a pow­er sys­tem across grid lev­els. On the oth­er hand, the inter­ac­tion of loads, feed­ers and stor­age sys­tems with the grid oper­at­ing equip­ment, mea­sure­ment and com­mu­ni­ca­tion tech­nol­o­gy as well as pro­tec­tion and con­trol tech­nol­o­gy is tak­en into account. Among oth­er things, these aspects are nec­es­sary for inves­ti­gat­ing the future pro­vi­sion of sys­tem ser­vices from the dis­tri­b­u­tion grid,” explains Dr. Jonas Maas­mann, research group leader at ie³. “For this pur­pose, a phys­i­cal, ‘real’ smart grid sys­tem land­scape is avail­able, which can be sup­ple­ment­ed and scaled with the help of real-time sim­u­la­tion.” The Smart Grid Tech­nol­o­gy Lab at ie³ is fund­ed by the Ger­man Fed­er­al Min­istry for Eco­nom­ic Affairs and Energy.

Want­ed: Spe­cial solu­tion with 10 kV/10 kV transformer

The TU Dort­mund com­mis­sioned the ener­gy com­pa­ny Uniper Anla­genser­vice GmbH to set up the test envi­ron­ment. In order to sim­u­late dif­fer­ent grid-stan­dard feed sit­u­a­tions, e.g. the con­nec­tion of a DC fast charg­ing sta­tion for elec­tric cars, an adjustable 10 kV/10 kV trans­former with a volt­age band of +/- 10 % should be used for the input side. A 10 kV/0.4 kV rONT was pro­vid­ed for the out­put side. “While trans­form­ers with this volt­age are stan­dard, the trans­former with 10 kV/10 kV was a spe­cial ser­vice that not every­one on the mar­ket offers,” says Ste­fan Thi­er, project man­ag­er at Uniper Anla­genser­vice GmbH. “In Ormaz­a­bal, we found a part­ner who offered us both from a sin­gle source.” Anoth­er pre­req­ui­site for use in the Smart Grid Tech­nol­o­gy Lab was that the trans­former could be switched and con­trolled remotely.

Found: Ormaz­a­bal-rONT with on-load tap-changer

The adjustable local net­work trans­former com­bines an intel­li­gent con­trol sys­tem with the so-called on-load tap chang­er (OLTC): an auto­mat­ic load tap chang­er devel­oped in-house by Ormaz­a­bal that can adjust the volt­age in steps of 2.5%. “Solu­tions with a ser­vo­mo­tor that must be exter­nal­ly reg­u­lat­ed are com­mon on the mar­ket. Com­pared to con­ven­tion­al, non-con­trol­lable trans­form­ers, our rONT can change the trans­for­ma­tion ratio from the medi­um to the low-volt­age net­work under load,” explains Ste­fan Henken­meier, sales rep­re­sen­ta­tive at Ormaz­a­bal. “In this way, the rONT com­pen­sates for unac­cept­able volt­age fluc­tu­a­tions, such as those caused by the inte­gra­tion of dis­trib­uted gen­er­a­tors, and pre­vents any result­ing dam­age at the low-volt­age dis­tri­b­u­tion lev­el.” The trans­former reacts ful­ly auto­mat­i­cal­ly and with­out man­u­al inter­ven­tion to chang­ing volt­age con­di­tions and ensures a con­stant out­put volt­age via medi­um-volt­age regulation.

train­er with remote control

A spe­cial con­trol algo­rithm makes volt­age equal­iza­tion pos­si­ble. “As part of the research facil­i­ty, there were spe­cial require­ments for com­po­nents and their com­mu­ni­ca­tion with regard to the entire sys­tem inte­gra­tion. In addi­tion, spe­cial inter­faces were nec­es­sary for research ques­tions on con­trol algo­rithms of rONTs in the smart grid,” says Dr. Jonas Maas­mann. “Here, it was impor­tant to ask about the expec­ta­tions of the oper­a­tor and the part­ners as ear­ly as the plan­ning phase,” adds Ste­fan Henken­meier. “In order to reg­u­late the con­trol of the rONT via cer­tain pro­to­cols, adjust­ments were final­ly nec­es­sary. In coop­er­a­tion with our col­leagues in Spain, the pro­gram for con­trol­ling the adjustable trans­former was rewrit­ten accord­ing­ly.” The tests can now be run remote­ly from the con­trol sta­tion of the Smart Grid Tech­nol­o­gy Lab using a SF6 gae630 switchgear. “The encap­su­lat­ed switchgear and the safe­ty con­cept imple­ment­ed by Ormaz­a­bal also ensure safe oper­a­tion of the plant,” con­firms Dr. Jonas Maasmann.

Prof­it­ing from the know-how of the group of companies

The research group leader of the TU Dort­mund Uni­ver­si­ty had vis­it­ed the Research and Tech­nol­o­gy Cen­tre (CIT) of Ormaz­a­bal near Bil­bao togeth­er with insti­tute col­leagues. A high-per­for­mance test facil­i­ty and a large-scale real-time net­work test facil­i­ty there pro­vide a safe and con­trolled envi­ron­ment for test­ing and devel­op­ing new tech­nolo­gies and prod­ucts. The expe­ri­ence gained at the CIT has been instru­men­tal in devel­op­ing an indi­vid­u­al­ized solu­tion for the Smart Grid Tech­nol­o­gy Lab. Dr. Jonas Maas­mann sums up: “Ormaz­a­bal has pro­vid­ed excel­lent sup­port to TU Dort­mund Uni­ver­si­ty as the sup­pli­er of the ‘con­trol­lable local grid sta­tion’ test stand in the devel­op­ment of the Smart Grid Tech­nol­o­gy Lab. Ormaz­a­bal did not see itself mere­ly as a sup­pli­er, but active­ly con­tributed its exper­tise in plant con­struc­tion in coop­er­a­tion with the gen­er­al con­trac­tor involved. Above all, we were also able to ben­e­fit from the expe­ri­ence of the inno­v­a­tive solu­tions from Ormaz­a­bal’s lab­o­ra­to­ry facilities”.

Sys­tem test suc­cess­ful­ly passed

From the ini­tial enquiry to the com­mis­sion­ing of the com­po­nents, just under a year passed with inten­sive con­sul­ta­tion and joint plan­ning. Dur­ing the com­mis­sion­ing of the plant, a com­plete sys­tem test was car­ried out. Both rONT were first test­ed by man­u­al­ly chang­ing the step val­ue. In a sec­ond step, the auto­mat­ic con­trol algo­rithm was test­ed by man­u­al­ly chang­ing the pri­ma­ry volt­age at one rONT. The oth­er rONT auto­mat­i­cal­ly com­pen­sat­ed for these volt­age fluc­tu­a­tions so that the sec­ondary volt­age remained with­in the defined con­trol band.

“Dur­ing oper­a­tion, it becomes appar­ent that the sys­tems brought in by Ormaz­a­bal are very reli­able and well thought-out. The sci­en­tists in the research group enjoy work­ing with the sys­tem and the coor­di­nat­ed safe­ty con­cept ensures safe oper­a­tion,” con­cludes Dr. Jonas Maas­mann. Ste­fan Thi­er from Uniper Anla­genser­vice GmbH also draws a pos­i­tive con­clu­sion: “The project went sat­is­fac­to­ri­ly, espe­cial­ly with regard to the ser­vices for the nec­es­sary adap­ta­tion of the algo­rithm. The project was very excit­ing for us, we had nev­er worked with rONT before, espe­cial­ly not in such a test world as the lab­o­ra­to­ry, far away from indus­try standards.”

Ormaz­a­bal is one of the world’s lead­ing man­u­fac­tur­ers of switchgear, com­plete trans­former sta­tions and dis­tri­b­u­tion trans­form­ers for medi­um volt­age. More than 2,200 employ­ees in over 100 cities on five con­ti­nents ensure reli­able ener­gy dis­tri­b­u­tion with high-qual­i­ty prod­ucts and ser­vices. Ormaz­a­bal is part of Vela­tia, fam­i­ly-owned and head­quar­tered in Zamu­dio, Spain. The head­quar­ters of Ormaz­a­bal’s Ger­man man­u­fac­tur­ing and sales com­pa­nies in Krefeld is also the head­quar­ters of the Cen­tral Europe region. With local know-how and glob­al expe­ri­ence, Ormaz­a­bal GmbH offers for­ward-look­ing solu­tions for all aspects of ener­gy dis­tri­b­u­tion. As a project part­ner for ener­gy sup­pli­ers, plan­ners and installers, among oth­ers, the provider responds flex­i­bly and prag­mat­i­cal­ly to indi­vid­ual cus­tomer require­ments and sup­ports projects from plan­ning to com­mis­sion­ing and main­te­nance. Ormaz­a­bal’s prod­ucts are used, for exam­ple, in the pow­er sup­ply indus­try, renew­able ener­gies, the plas­tics and auto­mo­tive indus­tries, air­ports, rail­way sta­tions, hos­pi­tals and even foot­ball sta­di­ums. For more infor­ma­tion, please vis­it http://www.ormazabal.com/de