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Average-Value Rectifier

Convert three-phase AC voltage to DC voltage with fixed power loss

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Semiconductors

Description

The Average-Value Rectifier block models an average-value, full-wave, six-pulse rectifier. It converts instantaneous three-phase AC voltages to DC voltage and DC power demand to three-phase AC power demand. The corresponding AC power demand is equal to the sum of the fixed power loss and the DC power demand.

You can use the Average-Value Rectifier block only as a six-pulse rectifier. You cannot combine two Average-Value Rectifier blocks to represent a twelve-pulse rectifier.

The figure shows the equivalent circuit for the rectifier as a full-wave, six-pulse rectifier. The Average-Value Rectifier block does not yield the harmonics that are typically associated with the detailed representation, however, because it performs an average-value power conversion.

Electrical Defining Equations

The voltages are defined by:

vref=va+vb+vc3,

VRMS=(vavb)2+(vbvc)2+(vcva)23,

vDC=32πVRMS,

vp=vref+vDC2,

and

vn=vrefvDC2,

where:

  • va, vb, vc are the respective AC phase voltages.

  • vref is the DC offset on the AC side. In a balanced AC power system with no DC bias, vDC is 0 V.

  • VRMS is the RMS AC line-line voltage.

  • vDC is the voltage difference between the positive and negative terminals of the rectifier.

  • 32/π is the vDC /VRMS ratio for a full-wave, six-pulse rectifier.

  • vp, vn are the voltages at the positive and negative terminals of the rectifier.

The resistance, power, and currents are defined by

Rfixed=VRated2Pfixed,

PDC=vpipvnin,

RAC=VRMS2PDC+VRMS2Rfixed,

and

[iaibic]=[vavbvc]vrefRAC,

where:

  • VRated is the rated AC voltage that you specify on the block mask.

  • Pfixed is the fixed power loss that you specify on the block mask.

  • Rfixed is the fixed per-phase series resistance in an equivalent wye-connected load.

  • ip, in are the currents flowing into the positive and negative terminals of the rectifier.

  • PDC is the power output on the DC side. PDC has a minimum limit of 0 W.

  • RAC is the per-phase series resistance in an equivalent wye-connected load.

  • ia, ib, ic are the respective AC phase currents flowing into the rectifier.

Parameters

Rated AC voltage

Rated voltage of the AC system. The default value is 4160 V.

Fixed power loss

Minimum power drawn on the AC side at rated AC voltage. When the instantaneous AC voltage is equal to the value you specify for the Rated AC voltage, the AC power demand equals the value you specify for the Fixed power loss plus DC power demand. The default value is 1e3 W.

Ports

The block has the following ports:

~

Expandable three-phase port

+

Electrical conserving port associated with the positive terminal

-

Electrical conserving port associated with the negative terminal

Introduced in R2014b

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