The Signal Conditioning Block generates the measured and conditioned values required by the Smart Inverter Control Toolbox blocks. For the grid support functions, the voltage reference can be generated as either average of three-phase RMS values or the positive sequence. The low pass filter time constant can be set for both power and DC link voltage measurement. A phase-locked loop (PLL) is implemented to obtain the frequency and instantaneous voltage angle information of the AC grid. Also, the PLL reference angle is used to perform the transformation of the voltages and currents in the ABC frame to a rectangular synchronous reference frame.
Mask and Parameters
The Signal Conditioning block contains the following tabs in the parameter configuration mask:
- Parameters
- Filters
- PLL
Parameters Tab
| Name | Description | Unit |
|---|---|---|
Nominal Operating Voltage (Vrms LL) | The nominal inverter output line to line RMS voltage | V |
Nominal DC-Link Voltage | The nominal value of DC-link voltage | V |
Nominal Frequency | System frequency | Hz |
Rated Apparent Power | Inverter nominal three-phase apparent power | VA |
Rated Active Power | Inverter nominal three-phase apparent power | W |
Grid Support Functions Voltage Reference | Choose between average of three-phase RMS or positive sequence | - |
Initial values [Freq, V, P, Q, Vdc] | Give the initializing value to the defined parameters | [Hz, pu, pu, pu, pu] |
Sample Time | Timestep of the signal conditioning block | s |
Filters Tab
| Name | Description | Unit |
|---|---|---|
Power Measurement Filter Time Constant | Specify the time constant for the power measurement first-order filter | s |
DC Link Voltage Measurement Filter Time Constant | Specify the time constant for the DC link voltage measurement first-order filter | s |
PLL Tab
| Name | Description | Unit |
|---|---|---|
Regulator gains [Kp,Ki, Kd] | Specify the proportional, integral, and derivative gains of the internal PID controller. Use the gains to tune the PLL response time, overshoot, and steady-state error performances | - |
Time constant for derivative action | Specify the time constant for the first-order filter of the PID derivative block | s |
Maximum rate of change of frequency | Specify the maximum positive and negative slope of the signal frequency | Hz/s |
Filter cut-off frequency for frequency measurement | Specify the second-order low-pass filter cut-off frequency | Hz |
Inputs, Outputs and Signals Available for Monitoring
Inputs
| Name | Description | Unit |
|---|---|---|
Vgrid | Instantaneous three phase grid voltages | V |
Igrid | Instantaneous three phase grid currents | A |
Vdc | Nominal DC link voltage | V |
Outputs
| Name | Description | Unit |
|---|---|---|
P | Per unit positive sequence active power evaluated using positive sequence voltage and current followed by a low-pass filter | pu |
Q | Per unit positive sequence reactive power evaluated using positive sequence voltage and current followed by a low pass filter | pu |
PF | Power factor evaluation using active and reactive power | - |
Vg | Three-phase instantaneous grid voltages in per unit | pu |
Vrms | RMS value of the three-phase grid voltages in per unit | pu |
Ig | Three-phase instantaneous grid currents in per unit | pu |
Vdc_pu | Nominal DC link voltage in per unit | pu |
Vrms_avg | Average of the RMS value of three-phase grid voltages in per unit | pu |
Freq | Frequency of the three-phase grid voltage obtained from PLL | Hz |
wt | Angle varying between 0 and 2*pi, synchronized on zero crossings of the fundamental (positive-sequence) of phase A voltage | rad |
Limitations
- Currently, the Signal Conditioning Block only supports three-phase balanced voltages and currents.
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