Phasor Calculation

The pmu_dft hook provides a dft based phasor calculation. The current implementation is a proof of concept but should not be used in production since this implementation is rather resource hungry.

This version supports phasor estimation for the frequency and amplitude but not yet for the phase.

This hook removes all signals fed into it and replaces it with new signals called amplitude, frequency, phase, rocof. If add_channel_name is set to false this could result in duplicate channel names.

Implementation

The source code of the hook is available here: https://github.com/VILLASframework/node/blob/master/lib/hooks/pmu_dft.cpp

Configuration

sample_rate required	integer >= 0 Default: 0 The sampling rate of the input signal.
start_frequency required	number >= 0 The lowest frequency bin.
end_frequency required	number >= 0 The highest frequency bin.
frequency_resolution required	number >= 0 The frequency resolution of the DFT.
dft_rate required	integer >= 1 The number of phasor calculations performed per second.
window_size_factor	integer Default: 1 A factor that increases the automatically determined window size by a multiplicative factor.
window_type	string Default: "none" Enum: "flattop" "hamming" "hann" "none" The window type.
padding_type	string Default: "none" Enum: "zero" "signal_repeat" The padding type.
frequency_estimate_type	string Default: "none" Value: "quadratic" The frequency estimation type.
pps_index	integer Default: 0 The signal index of the PPS signal. This is only needed if data dumper is active.
angle_unit	string Default: "rad" Enum: "rad" "degree" The unit of the phase angle.
add_channel_name	boolean Default: false Adds the name of the channel as a suffix to the signal name e.g amplitude_ch1.
timestamp_align	any Default: "center" Enum: "left" "center" "right" The timestamp alignment in respect to the the window.
phase_offset	number Default: 0 An offset added to a calculated phase.
amplitude_offset	number Default: 0 An offset added to the calculated amplitude.
frequency_offset	number Default: 0 An offset added to the calculated frequency.
rocof_offset	number Default: 0 An offset added to the calculated RoCoF. This setting does not really make sense but is available for completeness reasons"
signals	Array of strings A list of signal names to which this hook should be applied
enabled	boolean Default: true An optional field which can be used to disable a hook.
priority	integer Default: 99 The priority of this hook which determines the order in which hooks are executed. Hooks with a lwoer priority are executed before ones with a higher priority. If no priority is configured, hooks are executed in the order they are configured in the configuration file.

{

• "sample_rate": 10000,
• "start_frequency": 49.7,
• "end_frequency": 50.3,
• "frequency_resolution": 0.1,
• "dft_rate": 1,
• "window_size_factor": 1,
• "window_type": "flattop",
• "padding_type": "zero",
• "frequency_estimate_type": "quadratic",
• "pps_index": 0,
• "angle_unit": "rad",
• "add_channel_name": false,
• "timestamp_align": "left",
• "phase_offset": 10,
• "amplitude_offset": 10,
• "frequency_offset": 0.2,
• "rocof_offset": 1,
• "signals": [

  • "busA.V",
  • "busB.V",
  • "busC.V"

  ],
• "enabled": true,
• "priority": 99

}

Example

node/etc/examples/hooks/pmu_dft.conf

@include "hook-nodes.conf"

paths = (
    {
        in = "signal_node"
        out = "file_node"

        hooks = (
            {
                type = "pmu_dft"

                signals = (
                    "sine"
                )

                # Sample rate of the input signal
                sample_rate = 1000

                # Number of phasors calculated per second
                dft_rate = 10

                # Lowest frequency bin
                start_frequency = 49.7

                # Highest frequency bin
                end_frequency = 50.3

                # Frequency bin resolution
                frequency_resolution = 0.1

                # A factor with which the window will be increased
                window_size_factor = 1

                # One of: flattop, hamming, hann
                window_type = "hamming"

                # One of: signal_repeat, zero
                padding_type = "zero"

                # One of: quadratic
                frequency_estimate_type = "quadratic"

                # Signal index of the PPS signal
                pps_index = 0

                # One of: rad, degree
                angle_unit = "rad"
            }
        )
    }
)