“Good Active Filters Think for Themselves”

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What problem did Volkswagen approach you with?

Con­ven­tion­al har­mon­ic stress­es on long pow­er rail exten­sions. But Volk­swa­gen par­tic­u­lar­ly want­ed to be pre­pared for an expan­sion of the pro­duc­tion line at the Zwick­au plant; for exam­ple, with addi­tion­al weld­ing sys­tems and oth­er fre­quen­cy-con­trolled dri­ves. Our main task was to make the plant grid fit for this pur­pose.

What did you need to do this?

Sev­er­al active fil­ters in strate­gic loca­tions. When dis­rup­tive har­mon­ics occur in the plant grid, our active fil­ter feeds in tar­get­ed cur­rents of the same fre­quen­cy in phase oppo­si­tion to neu­tral­ize the inter­fer­ence. Pro­duc­tion runs smooth­ly, machines last longer, and ener­gy con­sump­tion decreas­es. That’s good, but it’s not the excep­tion­al part.

So what is the exceptional part?

Our new gen­er­a­tion of active fil­ters can think for them­selves. The active fil­ter only needs to be para­me­ter­ized once. It can then inde­pen­dent­ly adapt itself if grid con­di­tions lat­er change – for exam­ple, if pro­duc­tion lines are expand­ed or trans­form­ers are con­nect­ed or dis­con­nect­ed. And when it even­tu­al­ly reach­es its out­put lim­it, it will con­tin­ue to run at max­i­mum load and will not switch off due to over­load. In addi­tion, as the sys­tem has a mod­u­lar design, an MR ser­vice engi­neer can eas­i­ly retro­fit it in just a few sim­ple steps.

What was especially important for Volkswagen?

The „fast res­o­nance detec­tion” mon­i­tor­ing tech­nique and the Lim­it U func­tion. In large plants, such as in the auto­mo­bile indus­try, it is com­mon to have meshed grids where sev­er­al trans­form­ers feed a grid seg­ment in par­al­lel. As soon as trans­form­ers are switched off dur­ing low-load peri­ods, or some­thing else changes, the grid imped­ance also changes.

An active fil­ter can then unin­ten­tion­al­ly trig­ger a res­o­nance point in the grid. Our con­trol soft­ware detects sit­u­a­tions like this with­in sec­onds, and the active fil­ter then con­tin­ues to run nor­mal­ly with adapt­ed con­trol para­me­ters. With the Lim­it U func­tion, the cus­tomer can set the active fil­ter to damp­en a per­cent­age of the har­mon­ics rather than damp­ing them 100 percent—which saves ener­gy.

Did Volkswagen require any adjustments?

Volk­swa­gen has found that the switch­ing sys­tems in some plant sec­tions are eas­i­ly con­t­a­m­i­nat­ed with met­al dust, which increas­es the main­te­nance require­ments. There­fore, the com­pa­ny request­ed her­met­i­cal­ly enclosed hous­ings for some of the active fil­ters. That was not a prob­lem, but it did mean that air cool­ing was no longer an option. We there­fore decid­ed to go with a water cool­ing sys­tem. For this pur­pose, we sim­ply used the exist­ing cool­ing water cir­cuit of the laser weld­ing sys­tem. Reli­able vehi­cle pro­duc­tion: At Volk­swa­gen in Zwick­au, the new gen­er­a­tion of active fil­ters ensures sta­ble and clean volt­age in the plant grid. Tobias Knis­pel, Project Engi­neer at Maschi­nen­fab­rik Rein­hausen (MR), describes the sophis­ti­cat­ed tech­nol­o­gy that impressed the glob­al cor­po­ra­tion.