Keeping the lights on

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It is a hot sum­mer week­end in the year 2035. Many fam­i­lies are spend­ing time out at the lake. The beach is full, chil­dren are jump­ing off float­ing wood­en docks. Sun­light reflects on the water. There is not a cloud in the sky, but a pleas­ant, cool­ing wind is blow­ing. Solar cells and wind tur­bines are pro­duc­ing ener­gy en masse. No one on the beach spares a sin­gle thought that the line volt­age might increase to crit­i­cal ranges.

In grid con­trol cen­ters, on the oth­er hand, Ger­man sys­tem oper­a­tors are on high alert. Con­trol reserves are at the max and there is the threat of emer­gency shut-off for some ener­gy pro­duc­ers. An over­load occurs and some peo­ple will not have pow­er when they come home. Is this our future?

No stable grid without innovation

After events such as the 2011 reac­tor melt­down in Japan and recent heat waves, the Ger­man fed­er­al gov­ern­ment resolved to imple­ment a rapid ener­gy rev­o­lu­tion: by 2022, Ger­many will phase out nuclear pow­er, and by 2038 at the lat­est, it will also divest itself of coal pow­er. How­ev­er, by deac­ti­vat­ing these pow­er plants with large gen­er­a­tors, grid oper­a­tion will be more vul­ner­a­ble to inter­rup­tions. Espe­cial­ly on the extra-high and high-volt­age lev­els, trans­mis­sion grid oper­a­tors will lose an impor­tant means of keep­ing the volt­age in the trans­port lines sta­ble: reac­tive pow­er. It is reg­u­lat­ed by the gen­er­a­tors of these pow­er plants. If these go away, a replace­ment will be need­ed urgent­ly.

“With­out tech­nolo­gies to sta­bi­lize our grids, crit­i­cal sit­u­a­tions would be every­day occur­rences in the future.” Thomas Brück­n­er, Rein­hausen Pow­er Qual­i­ty

Thomas Brück­n­er of the Pow­er Qual­i­ty (PQ) busi­ness area has worked on this prob­lem exten­sive­ly. “From our con­ver­sa­tions with grid oper­a­tors, we know that there was sig­nif­i­cant trou­ble in the grid after exist­ing coal pow­er plants were deac­ti­vat­ed. With­out tech­nolo­gies to stab­ilize our grids, crit­i­cal sit­u­a­tions would be every­day occur­rences in the future.”

That is why Rein­hausen Pow­er Qual­i­ty worked with Omex­om Umspan­nwerke GmbH to offer grid oper­a­tors an alter­na­tive. Omex­om devel­ops ener­gy infra­struc­ture sys­tems for ener­gy gen­er­a­tion and dis­tri­b­u­tion. Togeth­er, the two part­ners opti­mized a tried-and-true tech­nol­o­gy for sta­bi­liz­ing the pow­er sup­ply when placed at suit­able grid nodes: MSCDN sys­tems.

MSCDN stands for mechan­i­cal­ly switched capac­i­tor with damp­ing network.“The sys­tem con­sists of a mechan­i­cal­ly switched capac­i­tor bank with a damp­ing net­work. Its pri­ma­ry task is the pro­vi­sion of reac­tive pow­er for volt­age reg­u­la­tion. If more pow­er is drawn from the grid than is pro­duced, such as because of hun­dreds of thou­sands of peo­ple con­nect­ing their cars to charg­ing sta­tions at once, the line volt­age drops. If more ener­gy is pro­duced, per­haps because the weath­er is ide­al or because con­sumers cur­rent­ly require less, the volt­age increases—in both cas­es, this can cause faults in the grid.

MSCDN sys­tems improve the pow­er qual­i­ty and
effec­tive­ly damp­en the res­o­nances in the grid. The chal­lenge for PQ and Omex­om was to opti­mize the MSCDN sys­tem so that it sat­is­fies the strict require­ments of the four trans­mis­sion grid oper­a­tors. They are respon­si­ble for near­ly 36,000 kilo­me­ters of extra-high-volt­age lines, which are ulti­mate­ly the life­lines of the econ­o­my. PQ und Omex­om there­fore per­formed numer­ous tests and sim­u­la­tions —also tak­ing into con­sid­er­a­tion future grid expan­sion sce­nar­ios. After all, in the com­ing years, sev­er­al thou­sand kilo­me­ters will be added to the trans­mis­sion grid.

An efficient system

he sys­tem has a com­pact design. It is designed as a C‑type fil­ter cir­cuit with dis­trib­uted capac­i­tances and damp­ing resis­tance. Effi­cient­ly designed reac­tors are also used that pro­duce only low loss­es. The sys­tem can be acti­vat­ed to be phase-selec­tive using a spe­cial cir­cuit break­er. In case of high uti­liza­tion, it sup­plies capac­i­tive reac­tive pow­er. With a low load, it offers pro­tec­tions against over­volt­age —which is suf­fi­cient in many sit­u­a­tions. Com­plex dynam­ic sys­tems, such as the STATCOM (rec­ti­fi­er trans­former) and sta­t­ic VAR com­pen­sators (SVC), are used for contin­uous reg­u­la­tion.

“Many solu­tions have now appeared which enable renew­able ener­gy to be imple­ment­ed even with­out cen­tral pro­duc­ers.” Volk­er Erfurth, Omex­om

The imple­men­ta­tion of these sys­tems makes Ger­many bet­ter pre­pared for the changes that come with the ener­gy rev­o­lu­tion. But this was not obvi­ous. “When renew­able ener­gy got going, all the ener­gy sup­pli­ers saw these enor­mous prob­lems and said it couldn’t be done in this time span,” says Volk­er Erfurth of Omex­om. “But since then, there have been many solu­tions that made renew­able ener­gy fea­si­ble despite non-con­tin­u­ous sup­ply from cen­tral pro­duc­ers.”

There is still sub­stan­tial need for invest­ment, as the need for elec­tric­i­ty is greater than ever—be it due to elec­tric mobil­i­ty, the increas­ing demand for hydro­gen in the future, or com­put­ing-inten­sive infor­ma­tion tech­nol­o­gy. This means there is an urgent need for action. Erfurth says, “But I am opti­mistic that tech­ni­cal solu­tions such as the MSCDN sys­tem will enable a con­tin­u­ous­ly sta­ble grid.”

The col­lab­o­ra­tion of the two com­pa­nies is thus an impor­tant step in this direc­tion. Sev­er­al sys­tems are already in oper­a­tion. Brück­n­er adds, “It is impor­tant to all of us that we make a valu­able con­tri­bu­tion to the ener­gy rev­o­lu­tion, cli­mate pro­tec­tion, and grid sta­bil­i­ty in the Ger­man, and thus also Euro­pean, com­bined sys­tem.” This means that in 2035, peo­ple will be able to enjoy the sun­shine in peace.

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YOUR CONTACT

Do you have any ques­tions about MSCDN sys­tems?
Thomas Brück­n­er would be hap­py to help:
T.Brueckner@reinhausen.com