ADE7752BARW AD [Analog Devices], ADE7752BARW Datasheet - Page 19

• Manufacturer Part Number: ADE7752BARW
• Description: Polyphase Energy Metering IC with Pulsed Output
• Manufacturer: AD [Analog Devices]

ADE7752B
HPF AND OFFSET EFFECTS
Figure 24 shows the effect of offsets on the active power
calculation. An offset on the current channel and voltage
channel contributes a dc component after multiplication as
shown in Figure 24. Since this dc component is extracted by the
LPF and is used to generate the active power information for
each phase, the offsets can contribute a constant error to the
total active power calculation. The HPF in the current channels
avoids this problem easily. By removing the offset from at least
one channel, no error component can be generated at dc by the
multiplication. Error terms at cos(ωt) are removed by the LPF
and the digital-to-frequency conversion (see the Digital-to-
Frequency Conversion) section.
The HPF in the current channels has an associated phase response
that is compensated for on-chip. Figure 25 and Figure 26 show the
phase error between channels with the compensation network.
Figure 24. Effect of Channel Offset on the Active Power Calculation
{
+
V
V
V
OS
V
2
×
cos
× I
2
I
×
V × I
OS
( )
2
+
I
ω
V
×
0
t
OS
cos
+
×
V
(
2
OS
I
ω
OS
DC COMPONENT (INCLUDING ERROR TERM)
IS EXTRACTED BY THE LPF FOR REAL
POWER CALCULA TION
}
t
)
×
+
ω
{
V
I
I
V
OS
FREQUENCY – RAD/S
cos
OS
OS
× V
× I
×
( )
ω
I
t
cos
+
2ω
( )
I
ω
OS
t
}
+
=
I
OS
×
V
cos
( )
ω
t
Rev. PrA | Page 19 of 27
(9)
The ADE7752B is phase compensated up to 1 kHz as shown. This
ensures correct active harmonic power calculation even at low
power factors.
Figure 26. Phase Error Between Channels (40 Hz to 70 Hz)
Figure 25. Phase Error between Channels (0 Hz to 1 kHz)
Preliminary Technical Data