ADE7880 Datasheet, PDF (63/104 Pages) Analog Devices – Polyphase Multifunction Energy Metering IC

Data Sheet
ADE7880
HPGAIN HXWATTOS 2²
÷
HPGAIN HYWATTOS 2²
HXWATT
÷
HPGAIN HZWATTOS 2²
HYWATT
÷
HZWATT
HPGAIN HXVAROS 2²
÷
HPGAIN HYVAROS 2²
HXVAR
÷
HPGAIN HZVAROS 2²
HYVAR
÷
HZVAR
Figure 86. Harmonic Active and Reactive Powers Signal Processing
The harmonic distortions of the three harmonic components
HYVHD, HYIHD, HZVHD, and HZIHD 24-bit registers. The
are stored into the HXVHD, HXIHD, HYVHD, HYIHD,
distortions of the neutral current are saved into HYIHD and
HZVHD, and HZIHD 24-bit registers in 3.21 signed format.
HZIHD registers and the distortions of the ISUM are stored
This means the ratios are limited to +3.9999 and all greater
into the HYVHD and HZVHD registers. As HX is set to 1, the
results are clamped to it.
HXIHD and HXVHD registers contain 0x1FFFFF, a number
As a reference, Table 20 presents the ADE7880 harmonic engine
representing 1 in 3.21 signed format.
outputs when one phase is analyzed and the registers in which
As a reference, Table 21 presents the ADE7880 harmonic engine
the outputs are stored.
outputs when the neutral current and ISUM are analyzed and
Harmonic Calculations When the Neutral is Monitored
the registers in which the outputs are stored.
When the neutral current and the sum of phase currents are
Configuring Harmonic Calculations Update Rate
monitored, only the harmonic rms related registers are updated.
The ADE7880 harmonic engine functions at 8 kHz rate. From
The registers HX, HY and HZ identify the index of the harmonic,
including the fundamental. When a phase is analyzed, the
fundamental rms values are calculated continuously and the
results are stored in dedicated registers FIRMS and FVRMS.
the moment the HCONFIG register is initialized and the
harmonic indexes are set in the HX, HY and HZ index registers,
the ADE7880 calculations take typically 750 ms to settle within
the specification parameters.
When the neutral is analyzed, the fundamental information is
The update rate of the harmonic engine output registers is
calculated by setting one of the harmonic index registers HX,
managed by Bits[7:5] (HRATE) in HCONFIG register and is
HY or HZ to 1 and the results are stored in harmonic registers.
independent of the engine’s calculations rate of 8 kHz. The default
The maximum index allowed in HX, HY and HZ registers is 63.
value of 000 means the registers are updated every 125 μsec
The no attenuation pass band is 2.8 kHz, corresponding to a
(8 kHz rate). Other update periods are: 250 μsec (HRATE =
−3 dB bandwidth of 3.3 kHz, thus all harmonics of frequency
001), 1 ms (010), 16 ms (011), 128 ms (100), 512 ms (101),
lower than 2800 Hz are supported without attenuation.
1.024 sec (110). If HRATE bits are 111, then the harmonic
HXIRMS, HYIRMS and HZIRMS registers contain the harmonic
calculations are disabled.
rms components of the neutral current and HXVRMS, HYVRMS
The ADE7880 provides two ways to manage the harmonic
and HZVRMS registers contain the harmonic rms components
computations. The first approach, enabled when Bit 0 (HRCFG)
of ISUM. Note that in this case, the rms of the fundamental
of HCONFIG register is cleared to its default value of 0, sets Bit
component is not computed into FIRMS or FVRMS registers,
19 (HREADY) in STATUS0 register to 1 after a certain period
but it is computed if one of the index registers HX, HY and HZ
of time and then every time the harmonic calculations are updated
is initialized with 1.
at HRATE frequency. This allows an external microcontroller to
If the HX register is initialized to 1, the ADE7880 computes the
harmonic distortions of the other harmonics identified into HY
and HZ registers and stores them in 3.21 signed format into the
access the harmonic calculations only after they have settled.
The time period is determined by the state of Bits[4:3] (HSTIME)
in the HCONFIG register. The default value of 01 sets the time
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