STPM32 datasheet(46/121 Pages) STMICROELECTRONICS

46 / 121 page

Theory of operation

STPM32, STPM33, STPM34

46/121

DS10272 Rev 8

Results of the calculated quantities are stored in the registers as follows:

EQ1 = primary current channel reactive energy PH1 Reactive Energy[31:0]

Q1 = primary current channel reactive power PH1 Reactive Power[28:0]

q1(t) = primary current channel instantaneous reactive power PH1 Momentary Reactive

Power[28:0]

EQ2 = secondary current channel reactive energy PH2 Reactive Energy[31:0]

Q2 = secondary current channel reactive power PH2 Reactive Power[28:0]

q2(t) = secondary current channel instantaneous active power PH2 Momentary Reactive

Power[28:0].

8.4.4

Apparent power and energy calculation

The signal chain for the apparent power, energy calculations and related frequency

conversion are shown in Figure 36. The apparent power signal S is generated in two ways:



Vectorial methodology uses the scalar product of active and reactive power. The active

power is selectable through the active power mode bit (APMx in DSP_CR1 and

DSP_CR2) between wideband or fundamental.

Equation 2



RMS methodology uses the product of RMS data of voltage and current. This value can

be compensated by the apparent power offset calibration block (OFSx[8:0] in

DSP_CR10 and DSP_CR12).

Equation 3

The apparent energy is calculated from vectorial or from RMS apparent power according to

AEMx configuration bit in DSP_CR1 and DSP_CR2.

Figure 36. Apparent power and energy calculation block diagram

Svec

SRMS

VRMS IRMS



Cx RMS Data [16:0]

VxRMS Data [14:0]

Offset

√¯

APMx

S LED

AEMx

OFSx [9:0]

PHx ApparentVectorial Power[28:0]

PHx Apparent Energy[31:0]

PHx Apparent RMS Power[28:0]

PHxReactive Power[28:0]

PHx Fundamental Power[28:0]

PHx Active Power[28:0]

GIPG2803141114LM

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