FB_PMA_PowerValues_Period_1Ph

The function block FB_PMA_PowerValues_Period_1Ph calculates the power values of the connected consumer. These include the fundamental components and the phase shift angle. For this purpose, only the first harmonics of the input signal are used for the calculation in addition to the signal sequence in the time domain. The advantage of these algorithms is the high dynamics of the calculations. The results refer to a configurable number of signal periods. The period duration refers to the frequency specified at the start of the period at the input of the Call method. The statistical results refer to the entire runtime or the time at which the statistical results were last reset.

Alternatively, the function block FB_PMA_PowerValues_1Ph can be used. This uses the individual harmonics internally to calculate the power values.

The input buffer is provided via the function block FB_PMA_Source_1Ph. This can include one or more signal periods or individual fragments of oversampling values.

Syntax

Definition:

FUNCTION BLOCK FB_PMA_PowerValues_Period_1Ph
VAR_INPUT
    nOwnID                : UDINT;
    tTransferTimeout      : LTIME := LTIME#500US;
    stInitPars            : ST_PMA_PowerValues_Period_InitPars;
END_VAR
VAR_OUTPUT
    bError                : BOOL;
    ipResultMessage       : I_TcMessage;
    bNewResult            : BOOL; 
    nCntResults           : ULINT;
    fApparentPower        : LREAL;
    fApparentPower_1      : LREAL;
    fApparentPower_1_Min  : LREAL;
    fApparentPower_1_Max  : LREAL;
    fActivePower          : LREAL;
    fActivePower_Min      : LREAL;
    fActivePower_Max      : LREAL;
    fReactivePower_d      : LREAL;
    fReactivePower_1      : LREAL;
    fReactivePower_1_Min  : LREAL;
    fReactivePower_1_Max  : LREAL;
    fTotalReactivePower   : LREAL;
    fPhi                  : LREAL;
    fCosPhi               : LREAL;
    fPowerFactor          : LREAL;
    fPowerQualityFactor   : LREAL;
    bValidStatistics      : BOOL;
END_VAR
VAR_OUTPUT PERSISTENT
    stEnergy_Pos          : ST_PMA_Energy;
    stEnergy_Neg          : ST_PMA_Energy;
    stEnergy_Res          : ST_PMA_Energy;
END_VAR

Inputs

The input parameters of this function block represent initialization parameters and have to be assigned during the declaration of the function block instance (alternatively: Init method). They may only be assigned once. A change at runtime is not possible.

Name	Type	Description
nOwnID	UDINT	Identifies the function block instance with a unique ID. This must always be greater than zero. A proven approach is to define an enumeration for this purpose.
tTransferTimeout	LTIME	Setting of the synchronous timeout for internal multi-array forwardings. See Parallel Processing in Transfer Tray.
stInitPars	ST_PMA_PowerValues_Period_InitPars	Function block-specific structure with initialization parameters. The parameters must correlate to the above definition of the input and output buffers.

Outputs

Name	Type	Description
bError	BOOL	TRUE if an error occurs.
ipResultMessage	I_TcMessage	The interface offers detailed information about the return value.
bNewResult	BOOL	TRUE once new results have been calculated.
nCntResults	ULINT	Count value is incremented with new output data.
fApparentPower	LREAL	Total apparent power
fApparentPower_1	LREAL	Fundamental apparent power
fApparentPower_1_Min	LREAL	Smallest value of fApparentPower_1 that has occurred. Can be reset via bResetStatistics of the Call method.
fApparentPower_1_Max	LREAL	Largest value of fApparentPower_1 that has occurred. Can be reset via bResetStatistics of the Call method.
fActivePower	LREAL	Active power
fActivePower_Min	LREAL	Smallest value of fActivePower that has occurred. Can be reset via bResetStatistics of the Call method.
fActivePower_Max	LREAL	Largest value of fActivePower that has occurred. Can be reset via bResetStatistics of the Call method.
fReactivePower_d	LREAL	Distortion reactive power
fReactivePower_1	LREAL	Fundamental shift reactive power
fReactivePower_1_Min	LREAL	Smallest value of fReactivePower_1 that has occurred. Can be reset via bResetStatistics of the Call method.
fReactivePower_1_Max	LREAL	Largest value of fReactivePower_1 that has occurred. Can be reset via bResetStatistics of the Call method.
fTotalReactivePower	LREAL	Total reactive power
fPhi	LREAL	Phase shift angle
fCosPhi	LREAL	CosPhi (active power/fundamental apparent power)
fPowerFactor	LREAL	Power factor (active power/total apparent power)
fPowerQualityFactor	LREAL	Power Quality Factor. Represents the quality of the power supply simplified in a value range between 0 and 1. The frequency, the RMS value of the voltage and the THD of the voltage are also included.
bValidStatistics	BOOL	TRUE if the Min and Max value calculation has been performed. These values are valid.
stEnergy_Pos	ST_PMA_Energy	Energy in positive direction. The output is saved persistently and can be reset via bResetEnergyCalc of the Call method.
stEnergy_Neg	ST_PMA_Energy	Energy in negative direction. The output is saved persistently and can be reset via bResetEnergyCalc of the Call method.
stEnergy_Res	ST_PMA_Energy	Resulting energy. The output is saved persistently and can be reset via bResetEnergyCalc of the Call method.

Methods

Name	Description
Call	The method is called in each cycle to execute the calculations from the input buffer when new data is present.
Init	Alternative to the function block initialization
PassInputs	As an alternative to the Call method, the method can be called in each cycle if no calculation is to take place. The incoming input buffer is then forwarded accordingly.
Reconfigure	The method is called in order to reconfigure the function block during the runtime.
Reset	The current calculations are reset with the method.

Sample

VAR CONSTANT
    cOversamples : UDINT := 10;
    cSourceInitPars: ST_PMA_Source_InitPars := (
        nBufferLength := cOversamples);
    cFrequencyInitPars : ST_PMA_Frequency_Period_InitPars := (
        nBufferLength := cOversamples,
        fSampleRate := cOversamples * 1000,
        fMinFreq := 45.0,
        fMaxFreq := 55.0,
        nPeriods := 1,
        nFilterOrder := 2,
        fCutOff := 70.0,
        eInputSelect := E_PMA_InputSelect.Voltage,
        fMinInput := 200.0);
    cPowerValuesInitPars : ST_PMA_PowerValues_Period_InitPars := (
        nBufferLength := cOversamples,
        fSampleRate := cOversamples * 1000,
        fMinInputCurrent := 0.01,
        nPeriods := 1);
END_VAR
VAR
    aVoltage AT%I* : ARRAY[1..cOversamples] OF LREAL;
    aCurrent AT%I* : ARRAY[1..cOversamples] OF LREAL;
    fbSource : FB_PMA_Source_1Ph := (nOwnID := 1, aDestIDs := [2,3], stInitPars := cSourceInitPars);
    fbFrequency : FB_PMA_Frequency_Period_1Ph := (nOwnID := 2, stInitPars := cFrequencyInitPars);
    fbPowerValues : FB_PMA_PowerValues_Period_1Ph := (nOwnID := 3, stInitPars := cPowerValuesInitPars);
END_VAR

// Call source
fbSource.Call(ADR(aVoltage), ADR(aCurrent), SIZEOF(aVoltage), 0);

// Call algorithms
fbFrequency.Call(FALSE);
fbPowerValues.Call(fbFrequency.fFreq, FALSE, FALSE);

Requirements

Development environment	Target platform	PLC libraries to include
TwinCAT v3.1.4024.0	PC or CX (x86, x64)	Tc3_PowerMonitoring

Further Information