topPower Converter Characteristics

CERN is realizing a laboratory for the testing of high voltage storage capacitors with big capacitance values.

The testing laboratory comprises an AC source and a DC source. The AC source is constituted by 6 single phase H bridge power converters, while the DC source is made up by 2 six pulses diode bridges powered by an adjustable 3 phase voltage source.

The two sources provide a composite stress across the capacitors, made up of an AC sinusoidal voltage superposed to a DC one.

Composite voltage

Maximum stressing values for capacitor under testing

Vdcpk 5500V
Vacpkpk 4000V
Vtotpk 7500V

topOperation Responsibles

Responsibles: Fulvio BOATTINI Fulvio BOATTINI
Charles GENTON Charles GENTON

topPower Converter Architecture

This composite voltage is meant to supply a load constituted by a set of capacitors.

The capacitance value changes depending upon the test to be effectuated, with a maximum rms current fixed in 80Arms.

Power converter architecture

Power converter architecture

topPower Part

The AC source:

The AC source is the most demanding in term of power. In-fact it has to provide all the kVAr needed by the tested capacitors.

AC source

The worst conditions are met when the testing of the fully sized element is required. To keep a limit, letís consider the present capacitor value of 2mF; the following calculations give us the power needed:

AC power needed

Pac3ph 500kVA
Vacgrid 400V
Vpll 400Vrms(line2line)
Ip 720Arms
Vsll 1850Vrms
Is 160Arms

The DC source:

The simplest DC source is a 3 phase diode bridge. For easier realization (and to keep compatibility with other testing requirements), a 12 pulse diode bridge is foreseen.

DC source

Two 6 pulses diode rectifiers are then connected in series.

The following values have to be considered for bridge sizing:

Udc= 100/2800V
Vsll 2000Vrms (line2line)
Is 10Arms
As 34kVA
Vpll 400Vrms
Ip 100Arms
Ap 68kVA

topControl & Regulation Part

Control overview

Control overview simplified schematic