FB_PMA_PowerValues_3Ph

The function block FB_PMA_PowerValues_3Ph calculates the power values of the connected consumer in a three-phase grid. These include the fundamental components and the phase shift angle. Internally, the individual harmonics and their phase angle are determined for the calculations.

Alternatively, the function block FB_PMA_PowerValues_Period_3Ph can be used for the calculation. It uses simpler calculation methods for enhanced dynamics.

The input buffer is provided via the function block FB_PMA_Source_3Ph. The size of the input buffer is half the window length.

By way of example, possible FFT and window lengths are shown in the following table:

Memory properties

Since the Welch method is used, in each case the current input buffer together with the last transferred buffer is used for the calculation.

The frequency analysis takes step changes in the time series into account. In order to achieve a correct result, the last two input buffers should therefore be consecutive without step changes.

Syntax

Definition:

FUNCTION BLOCK FB_PMA_PowerValues_3Ph
VAR_INPUT
    nOwnID                 : UDINT;
    tTransferTimeout       : LTIME := LTIME#500US;
    stInitPars             : ST_PMA_PowerValues_InitPars;
END_VAR
VAR_OUTPUT
    bError                 : BOOL;
    ipResultMessage        : I_TcMessage;
    bNewResult             : BOOL;
    nCntResults            : ULINT;
    aApparentPower         : ARRAY[0..2] OF LREAL;
    aApparentPower_1       : ARRAY[0..2] OF LREAL;
    aApparentPower_1_Min   : ARRAY[0..2] OF LREAL;
    aApparentPower_1_Max   : ARRAY[0..2] OF LREAL;
    aActivePower           : ARRAY[0..2] OF LREAL;
    aActivePower_Min       : ARRAY[0..2] OF LREAL;
    aActivePower_Max       : ARRAY[0..2] OF LREAL;
    aReactivePower_d       : ARRAY[0..2] OF LREAL;
    aReactivePower_1       : ARRAY[0..2] OF LREAL;
    aReactivePower_1_Min   : ARRAY[0..2] OF LREAL;
    aReactivePower_1_Max   : ARRAY[0..2] OF LREAL;
    aTotalReactivePower    : ARRAY[0..2] OF LREAL;
    aPhi                   : ARRAY[0..2] OF LREAL;
    aCosPhi                : ARRAY[0..2] OF LREAL;
    aPowerFactor           : ARRAY[0..2] OF LREAL;
    fSumApparentPower      : LREAL;
    fSumActivePower        : LREAL;
    fSumTotalReactivePower : LREAL;
    fSumReactivePower_1    : LREAL;
    bValidStatistics       : BOOL;
END_VAR
VAR_OUTPUT PERSISTENT
    aEnergy_Pos            : ARRAY[0..2] OF ST_PMA_Energy;
    aEnergy_Neg            : ARRAY[0..2] OF ST_PMA_Energy;
    aEnergy_Res            : ARRAY[0..2] OF ST_PMA_Energy;
END_VAR

Inputs

The input parameters of this function block represent initialization parameters and must be assigned when declaring the function block instance (alternative: Init method). They may only be assigned once. A change at runtime is not possible.

Outputs

Methods

Sample

VAR CONSTANT
    cOversamples : UDINT := 10;
    cFFT_Length : UDINT := 4096;
    cWindowLength : UDINT := 3200;
    cSourceInitPars: ST_PMA_Source_InitPars := (
        nBufferLength := cWindowLength/2);
    cPowerValuesInitPars : ST_PMA_PowerValues_InitPars := (
        nFFT_Length := cFFT_Length,
        nWindowLength := cWindowLength,
        fSampleRate := cOversamples * 1000,
        fBaseFreq := 50.0,
        nNumBands := 40,
        fBandwidth := 20.0,
        eWindowType := E_PMA_WindowType.HannWindow,
        fTimeLagCurrentTransformer := 0.0,
        fMinInputCurrent := 0.01);
END_VAR
VAR
    aVoltage AT%I* : ARRAY[0..2] OF ARRAY [1..cOversamples] OF LREAL;
    aCurrent AT%I* : ARRAY[0..2] OF ARRAY [1..cOversamples] OF LREAL;
    fbSource : FB_PMA_Source_3Ph := (nOwnID := 1, aDestIDs := [2], stInitPars := cSourceInitPars);
    fbPowerValues : FB_PMA_PowerValues_3Ph := (nOwnID := 2, stInitPars := cPowerValuesInitPars);
END_VAR

// Call source
fbSource.Call(
    ADR(aVoltage[0]),
    ADR(aVoltage[1]),
    ADR(aVoltage[2]),
    ADR(aCurrent[0]),
    ADR(aCurrent[1]),
    ADR(aCurrent[2]),
    SIZEOF(aVoltage[0]),
    0);

// Call algorithm
fbPowerValues.Call(FALSE, FALSE);

Requirements