EVAL-ADE7753EB View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-ADE7753EB' PDF : 38 Pages View PDF
ADE7753
90°. The resulting waveform is called the instantaneous reactive
power signal. Equation 25 gives an expression for the instanta-
neous reactive power signal in an ac system when the phase of
the current channel is shifted by +90°.
v(t) = 2V sin(ωt + θ)
(23)
i(t) = 2I sin(ωt)
i′(t) =
2
I
sin⎜⎝⎛ ωt
+
π
2
⎟⎠⎞
(24)
where:
θ is the phase difference between the voltage and current
channel.
V is the rms voltage.
I is the rms current.
Rp(t) = v(t) × i’(t)
(25)
Rp(t) = VI sin (θ) + VI sin(2ωt + θ)
The average reactive power over an integral number of lines (n)
is given in Equation 26.
nT
∫ RP = 1 Rp(t)dt = VI sin(θ )
nT
(26)
0
where:
T is the line cycle period.
RP is referred to as the reactive power.
Note that the reactive power is equal to the dc component of the
instantaneous reactive power signal Rp(t) in Equation 25. This
is the relationship used to calculate reactive power in the
ADE7753. The instantaneous reactive power signal Rp(t) is
generated by multiplying Channel 1 and Channel 2. In this case,
the phase of Channel 1 is shifted by +90°. The dc component of
the instantaneous reactive power signal is then extracted by a
low-pass filter in order to obtain the reactive power informa-
tion. Figure 71 shows the signal processing in the reactive
power calculation in the ADE7753.
90 DEGREE
PHASE SHIFT
INSTANTANEOUS REACTIVE
POWER SIGNAL (Rp(t))
π
I
2
MULTIPLIER
++
LPF2
V
FROM
CHANNEL 2
ADC
LPF1
ZERO-CROSSING
DETECTION
CALIBRATION
CONTROL
49
0
23
0
LVARENERGY [23:0]
ACCUMULATE REACTIVE
ENERGY IN INTERNAL
REGISTER AND UPDATE
THE LVARENERGY REGISTER
AT THE END OF LINECYC HALF
LINE CYCLES
LINECYC [15:0]
Figure 71. Reactive Power Signal Processing
02875-0-070
Rev. C | Page 34 of 60
Share Link: 
