PV inverter
This section describes the PV inverter component.
The Schematic Editor library block from the Microgrid section shown in Table 1, models a PV inverter implemented with a three-phase two-level inverter with current control loop. The DC link is fed by a PV panel source connected externally of the block. The PV inverter can only operate in grid connected mode. It operates in maximum power tracking and reactive power control mode, when grid following. This inverter is implemented in an average model. The following sections describe in more details the component parameters, inputs and outputs.
| component | component dialog window | component parameters |
|---|---|---|
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Inputs and outputs
The pv inverter component needs 2 inputs to operate. These inputs must be sent as an array, with use of a bus join component, and in the correct order. The following table describes the inputs and their order.
PV inverter inputs
| Number | Input | Description |
|---|---|---|
| 0 | Enable | A digital input that comands the On/Off state of the PV inverter. PV inverter is on when input is high. |
| 1 | Qref | An analog input that sets the reactive power reference. [VAr] |
The PV inverter model has 14 outputs. They are organized as an array and can be accessed individually through a bus split component, respecting the correct order. The following table describes the outputs ans their order.
PV inverter outputs
| Number | Output | Description |
|---|---|---|
| 0 | Connected | A digital output with a feedback of the battery inverter contactor's state. Contactor is closed when output is high. |
| 1 | Inv_On | A digital output with a feedback of the inverter on/off state. |
| 2 | Va | An analog output with the instantaneous measurement of the inverter's phase A terminal voltage. [V] |
| 3 | Vb | An analog output with the instantaneous measurement of the inverter's phase B terminal voltage. [V] |
| 4 | Vc | An analog output with the instantaneous measurement of the inverter's phase C terminal voltage. [V] |
| 5 | Vt | An analog output with the inverter's terminal peak voltage (phase to neutral). [V]; The RMS voltage can be calculated by dividing this output by a square root of 2. |
| 6 | Ia | An analog output with the instantaneous measurement of the inverter's phase A terminal current. [A] |
| 7 | Ib | An analog output with the instantaneous measurement of the inverter's phase B terminal current. [A] |
| 8 | Ic | An analog output with the instantaneous measurement of the inverter's phase C terminal current. [A] |
| 9 | f | An analog output with the measured electrical frequency. [Hz] |
| 10 | P | An analog output with the inverter's active power measurement. [W] |
| 11 | Q | An analog output with the inverter's reactive power measurement. [VAr] |
| 12 | S | An analog output with the inverter's apparent power measurement. [VA] |
| 13 | pf | An analog output with the inverter's power factor measurement. |
Component dialogue box and parameters
The PV inverter component dialogue box consists of three tabs for specifying basic and advanced parameters.
Tab: "General"
PV inverter model "General" parameters
| Parameter | Code name | Description |
|---|---|---|
| Nominal power | Sn | Battery inverter nominal power. [VA] |
| Nominal DC link voltage | Vdc | Nominal DC link voltage of the PV panel. [V] |
| Nominal line voltage | Vn | Nominal line to line grid voltage. [V] |
| Nominal frequency | fn | Nominal grid frequency. [Hz] |
| Switching frequency | fsw | Inverter switching frequency. [Hz] |
| Vdc control execution rate | Tslow | DC link voltage control execution rate. [s] |
Tab: "Filter"
PV inverter model "Filter" parameters
| Parameter | Code name | Description |
|---|---|---|
| Grid side inductance | Lg | Inductors on the grid side of the LCL filter. [H] |
| Grid side resistance | Rg | Series resistor of the inductors on the grid side of the LCL filter. [Ω] |
| Ripple attenuation | a | Ripple attenuation constant. |
Tab: "Controllers"
In this component tab, the user can specify controller parameters of the PV inverter model.
PV inverter model "Controllers" parameters
| Parameter | Code name | Description |
|---|---|---|
| Current control proportional gain | kp_i | Current control loop PI controller proportional gain. |
| Current control integral gain | ki_i | Current control loop PI controller integral gain. |
| MPPT control proportional gain | kp_v | Maximum power point tracking controller proportional gain |
| MPPT control integral gain | kp_i | Maximum power point tracking controller integral gain |
| MPPT voltage step | step | Maximum power point tracking controller voltage step. [V] |
| MPPT initial voltage | vdc_init | Maximum power point tracking controller initial voltage. [V] |
| MPPT execution rate | Ts_mppt | Maximum power point tracking controller execution rate. [s] |
Example
Overall behavior and control methodologies can be better understood with the use of the given PV inverter example:
Model name: pv_inverter_avg.tse
SCADA interface: SCADA_Panel.cus
Path: /examples/models/microgrid/pv_plant/
Folder: /pv_inverter (average)/