ST_PMA_Frequency_Period_InitPars

Function block-specific structure with initialization parameters that are evaluated when the function blocks FB_PMA_Frequency_Period_1Ph and FB_PMA_Frequency_Period_3Ph are initialized.

Syntax

Definition:

TYPE ST_PMA_Frequency_Period_InitPars :
STRUCT
    nBufferLength      : UDINT := 200;   // Length of input buffer
    fSampleRate        : LREAL := 1_000; // in Hz 
    fMinFreq           : LREAL := 45;    // Min measured Freq
    fMaxFreq           : LREAL := 65;    // Max measured Freq
    nPeriods           : UDINT := 2;     // Number of periods to be considered
    nFilterOrder       : UINT  := 3;     // Filter order of butterworth lowpass filter
    fCutoff            : LREAL := 70.0;  // Cutoff frequency of filter
    eInputSelect       : E_PMA_InputSelect := E_PMA_InputSelect.Voltage; // Select input: Voltage | Current
    fMinInput          : LREAL := 200.0; // Minimal input (RMS) over one period to calculate outputs
    nRocofAvgWindow    : UDINT := 25;    // Window length of elements to calculate moving average of ROCOF
END_STRUCT
END_TYPE

Parameters

Name	Type	Parameters
nBufferLength	UDINT	Length of the input buffer
fSampleRate	LREAL	Indicates the sampling rate (samples per second) of the input signal.
fMinFreq	LREAL	Minimum expected measuring frequency
fMaxFreq	LREAL	Maximum expected measuring frequency
nPeriods	UDINT	Number of periods that influence the calculation. (Period length = sample rate/frequency)
nFilterOrder	UINT	Indicates the order of the low-pass filter. The stability of the filter must be considered for the setting. Only values up to the tenth order are allowed.
fCutoff	LREAL	Specifies the cut-off frequency of the low-pass filter.
eInputSelect	E_PMA_InputSelect	Voltage: The voltage is used as the basis for the frequency calculation Current: The current is used as the basis for the frequency calculation
fMinInput	LREAL	Minimum input value (RMS) over one period. This prevents the calculation of input values that are too small.
nRocofAvgWindow	UDINT	Window size of the sliding average value for the calculation of the ROCOF Resulting period: nPeriods * nRocofAvgWindow / avgeragedFreq)

Requirements

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