ADE5166 datasheet(65/156 Pages) AD

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ADE5166/ADE5169/ADE5566/ADE5569

Rev. B | Page 65 of 156

Reactive Power Gain Calibration

Reactive Power Sign Detection

Figure 72 shows the signal processing chain for the ADE5169/

ADE5569 reactive power calculation. As explained in the Reactive

Power Calculation (ADE5169/ADE5569) section, the reactive

power is calculated by applying a low-pass filter to the instanta-

neous reactive power signal. Note that, when reading the waveform

samples from the output of LPF2, the gain of the reactive energy

can be adjusted by using the multiplier and by writing a twos

complement, 12-bit word to the var gain register (VARGAIN,

Address 0x1E[11:0]). Equation 23 shows how the gain adjust-

ment is related to the contents of the var gain register.

The ADE5169/ADE5569 detect a change of sign in the reactive

power. The VARSIGN flag (Bit 4) in the Interrupt Status 1 SFR

(MIRQSTL, Address 0xDC) records when a change of sign has

occurred according to the VARSIGN bit (Bit 5) in the ACCMODE

Interrupt Enable 1 SFR (MIRQENL, Address 0xD9), the 8052 core

has a pending ADE interrupt. The ADE interrupt stays active until

the VARSIGN status bit is cleared (see the Energy Measurement

Interrupts section).

Output VARGAIN =

⎟

⎠

⎞

⎜

⎝

⎛

⎭

⎬

⎫

⎩

⎨

⎧ +

VARGAIN

Power

Reactive

(23)

When the VARSIGN bit (Bit 5) in the ACCMODE register

(Address 0x0F) is cleared (default), a transition from positive to

negative reactive power sets the VARSIGN flag (Bit 4) in the

Interrupt Status 1 SFR (MIRQSTL, Address 0xDC).

When VARSIGN in the ACCMODE register (Address 0x0F)

is set, a transition from negative to positive reactive power sets

the VARSIGN flag in the Interrupt Status 1 SFR (MIRQSTL,

Address 0xDC).

The resolution of the VARGAIN register is the same as the

WGAIN register (Address 0x1D) (see the Active Power Gain

Calibration section). VARGAIN can be used to calibrate the

reactive power (or energy) calculation in the ADE5169/ADE5569.

Reactive Power No Load Detection

Reactive Power Offset Calibration

The ADE5169/ADE5569 include a no load threshold feature on the

reactive power that eliminates any creep effects in the meter. The

ADE5169/ADE5569 accomplish this by not accumulating reactive

energy when the multiplier output is below the no load threshold.

When the reactive power is below the no load threshold, the

RNOLOAD flag (Bit 1) in the Interrupt Status 1 SFR (MIRQSTL,

Address 0xDC) is set. If the RNOLOAD bit (Bit 1) is set in the

Interrupt Enable 1 SFR (MIRQENL, Address 0xD9), the 8052

core has a pending ADE interrupt. The ADE interrupt stays

active until the RNOLOAD status bit is cleared (see the Energy

Measurement Interrupts section).

The ADE5169/ADE5569 also incorporate a reactive power offset

ment, 16-bit register that can be used to remove offsets in the

reactive power calculation (see Figure 72). An offset can exist in

the reactive power calculation due to crosstalk between channels

on the PCB or in the IC itself. The offset calibration allows the

contents of the reactive power register to be maintained at 0 when

no power is being consumed.

The 256 LSBs (VAROS = 0x0100) written to the reactive power

offset register are equivalent to 1 LSB in the WAVMODE register

(Address 0x0D).

The no load threshold level can be selected by setting the

VARNOLOAD bits (Bits[3:2])in the NLMODE register

(Address 0x0E). Setting these bits to 0b00 disables the no load

detection, and setting them to 0b01, 0b10, or 0b11 sets the no

load detection threshold to 0.015%, 0.0075%, and 0.0037% of

the full-scale output frequency of the multiplier, respectively.

Sign of Reactive Power Calculation

Note that the average reactive power is a signed calculation.

The phase shift filter has −90° phase shift when the integrator

is enabled and +90° phase shift when the integrator is disabled.

Table 47 summarizes the relationship of the phase difference

between the voltage and the current and the sign of the resulting

var calculation.

Table 47. Sign of Reactive Power Calculation

Angle

Integrator

Sign

0° to +90°

Off

Positive

−90° to 0°

Off

Negative

0° to +90°

Positive

−90° to 0°

Negative

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