Datasheet

Data Sheet ADE5166/ADE5169/ADE5566/ADE5569
Rev. D | Page 67 of 156
REACTIVE ENERGY CALCULATION
(ADE5169/ADE5569 ONLY)
As for active energy, the ADE5169/ADE5569 achieve the integra-
tion of the reactive power signal by continuously accumulating
the reactive power signal in an internal, nonreadable, 49-bit energy
register. The reactive energy register (VARHR, Address 0x04)
represents the upper 24 bits of this internal register. The VARHR
register and its function are available in the ADE5169/ADE5569.
The discrete time sample period (T) for the accumulation register
in the ADE5169/ADE5569 is 1.22 µs (5/MCLK). As well as
calculating the energy, this integration removes any sinusoidal
components that may be in the active power signal. Figure 72
shows this discrete time integration or accumulation. The
reactive power signal in the waveform register is continuously
added to the internal reactive energy register.
The reactive energy accumulation depends on the setting of
SAVA RM (Bit 2) and ABSVARM (Bit 3) in the ACCMODE
register (Address 0x0F). When both bits are cleared, the addition
is signed and, therefore, negative energy is subtracted from the
reactive energy contents. When both bits are set, the ADE5169/
ADE5569 are set to the more restrictive mode, which is the
absolute accumulation mode.
When the SAVA RM bit (Bit 2) in the ACCMODE register
(Address 0x0F) is set, the reactive power is accumulated
depending on the sign of the active power. When active power
is positive, the reactive power is added as it is to the reactive energy
register. When active power is negative, the reactive power is
subtracted from the reactive energy accumulator (see the Var
Antitamper Accumulation Mode section).
When the ABSVARM bit (Bit 3) in the ACCMODE register
(Address 0x0F) is set, the absolute reactive power is used for the
reactive energy accumulation (see the Var Absolute Accumulation
Mode section).
The output of the multiplier is divided by VARDIV. If the value
in the VARDIV register (Address 0x25) is equal to 0, the internal
reactive energy register is divided by 1. VARDIV is an 8-bit,
unsigned register. After dividing by VARDIV, the reactive energy is
accumulated in a 49-bit internal energy accumulation register.
The upper 24 bits of this register are accessible through a read to
the reactive energy register (VARHR, Address 0x04[23:0]). A read
to the RVARHR register (Address 0x05) returns the contents of
the VARHR register, and the upper 24 bits of the internal register
are cleared.
As shown in Figure 72, the reactive power signal is accumulated in
an internal 49-bit, signed register. The reactive power signal can be
read from the waveform register by setting the WAVMODE reg-
ister (Address 0x0D) and setting the WFSM bit (Bit 5) in the Inter-
rupt Enable 3 SFR (MIRQENH, Address 0xDB). Like the current
and voltage channel waveform sampling modes, the waveform data
is available at sample rates of 25.6 kSPS, 12.8 kSPS, 6.4 kSPS, and
3.2 kSPS.
Figure 67 shows this energy accumulation for full-scale signals
(sinusoidal) on the analog inputs. These curves also apply to the
reactive energy accumulation.
Note that the energy register contents roll over to full-scale
negative (0x800000) and continue to increase in value when
the power or energy flow is positive. Conversely, if the power is
negative, the energy register underflows to full-scale positive
(0x7FFFFF) and continues to decrease in value.
Using the Interrupt Enable 2 SFR (MIRQENM, Address 0xDA),
the ADE5169/ADE5569 can be configured to issue an ADE
interrupt to the 8052 core when the reactive energy register is
half full (positive or negative) or when an overflow or under-
flow occurs.
VARGAIN[11:0]
VARDIV[7:0]
LPF2
CURRENT
CHANNEL
VOLTAGE
CHANNEL
OUTPUT LPF2
TIME (nT)
5
MCLK
T
REACTIVE POWER
SIGNAL
+
+
V ARHR[23:0 ]
UPPER 24 BITS ARE
ACCESSIBLE THROUGH
VARHR[23:0] REGISTER
23 0
48 0
WAVEFORM
REGISTER
VALUES
%
VAROS[15:0]
2
6
sgn 2
5
2
–6
2
–7
2
–8
+
+
FOR WAVEFORM
SAMPLING
HPF
PHCAL[7:0]
90° PHASE
SHIFTING FILTER
OUTPUTS FROM THE LPF2 ARE
ACCUMULATED (INTEGRATED) IN
THE INTERNAL REACTIVE ENERGY
REGISTER
TO
DIGITAL-TO-FREQUENCY
CONVERTER
07411-047
2
Figure 72. Reactive Energy Calculation