ABB Review Special Report - ABB - ABB Group

3Basic diagram of the electrical systemto 138 kV/60 Hz gridBattery strings 1 to 4Filter circuits12 x 2-phasemodules4 units3 x 1-phasetransformers4 units4 units2 unitsVoltagelimiter unitto 138 kV/60 Hz gridThe active switching devices used in theconverter are integrated gate commutatedthyristors (IGCTs), an advanced type ofgate turn off thyristor (GTO). Comparedwith other devices that can be turned off,IGCTs have the advantage of lower conductionand switching losses, plus superiorswitch-off characteristics that allow asnubberless converter design.Ease of serviceability was a primaryconsideration during the mechanicaldesign. All power semiconductors inthe stack are readily accessible, allowingeasy replacement.4Power and reactive powerperformanceThe system is designed for four-quadrantoperation. It can charge as well asdischarge the battery and it can absorbBuilding block. A double-stack water-cooled PEBB in NPC connection,forming one H–bridgeAdvantages of this converter designinclude:The three-level medium-voltage modulesare proven, highly reliable products.Low FIT values are obtainedwhen these modules are used.Use of double-stack modules shortensthe distances between the powersemiconductors, keeping stray inductanceslow, and reduces the spacerequired for the complete converter.Since the clamp diodes and capacitorsare integrated in the semiconductorstack, the stray inductance in theclamp circuit is also minimized,allowing use of higher IGCT switchoffcurrents.Using a single clamp for two phasesreduces the need for bulky and costlyclamp inductors and resistors.AC 1AC 2D C +R symC C +C C –D C –D C +R symC C +C C –D C –=Special ReportABB Review45