1 Description
2 Mask and Parameters
3 Ports, Inputs, Outputs and Signals Available for Monitoring
4 Modeling Details
5 References

Description

The photovoltaic generation system (PVGS) is shown in the figure below. The PVGS features a PV array that is connected to an inverter via a boost DC-DC converter. The PV array model contains many types of modules predefined from the database of the California Energy Commission (CEC) . More than 21,000 modules from leading manufacturers are listed in this database which includes the manufacturer's specifications measured for standard test conditions (STC). meaning Irradiance of 1000 W/m2 and 25° C.

The boost converter controls the PV array in two modes of operation: maximum power point tracking (MPPT); and curtailment. In mode 1 the boost converter duty cycle is calculated by a perturb-and-observe (P&O) MPPT algorithm to ensure maximum power extraction from the array for a given solar irradiation. In curtailment mode the duty cycle of the boost converter is controlled to follow the active power reference.

Both the DC-DC converter and the three phase AC interface converter are average models. The inverter’s function is to maintain and regulate the DC link voltage and the reactive power at their respective commanded values at the point of common coupling (PCC). A RL choke filter is used to connect the inverter to the grid. The choke filter must be designed to limit the total harmonic distortion of the PVGS current injected into the grid at the point of common coupling (PCC).

The PVGS must be connected to an external step up transformer to the grid. It is recommended to use a star-delta transformer with a base power of 1.2 times the nominal power of the PVGS. The model is not compatible with load flow.

PVGS components schematic

Mask and Parameters

System Parameters

Name	Description	Unit

Name	Description	Unit
Nominal Power - Sg	Nominal power of the PVGS	VA
Nominal Voltage - Vp	Nominal AC voltage of the PVGS	V
Nominal Frequency - f	Nominal frequency of the PVGS	Hz
Nominal DC Link Voltage - Vdc	Nominal DC voltage maintained at the DC link capacitor.	V
DC link Capacitor - Cdc	DC link capacitor	F
Filter Resistance – Rgs	Filter resistance at the AC side.	Ω
Filter Inductance – Lgs	Filter inductance at the AC side	H
Switching frequency - Fsw	Switching frequency of the PWM that control the gating pulse signals of the inverter (for average inverter models, this number is only used to design the measurement filters in the control blocks).	Hz

Control Loops Parameters

Name	Description	Unit

Name	Description	Unit
Active Power Regulator**
KpP	Proportional gain PI controller for active power regulator.	-
KiP	Integral gain PI controller for active power regulator.	-
Reactive Power Regulator
KpQ	Proportional gain PI controller for reactive power regulator.	-
KiQ	Integral gain PI controller for reactive power regulator.	-
Current Regulator
KpI	Proportional gain PI controller for current regulator.	-
KiI	Integral gain PI controller for current regulator.	-
VDC Regulator
KpVDC	Proportional gain VDC Regulator	-
KiVDC	Integral gain of VDC Regulator	-
Current Limit
CL	Current Limit	pu

**D_low and D_up can be modified from the Boost Converter panel .

Cell: single unit of the photovoltaic semiconductor that converts the solar irradiance into electricity.
Module: it’s a group of cells connected in series and parallel to achieve a desired voltage and current.

The PV_Array panel is shown below. This panel contains all the parameters to tune the technology and desired output power from the PV. The panel was implemented from a MATLAB/Simulink example model available online .

PV Array Parameters

Name	Description	Unit

Name	Description	Unit
Nser	Number of PV modules connected in series.	-
Npar	Number of PV modules connected in parallel.	-
Ncell	Number of cells per module.	-
Vmp	Voltage at maximum power point for one module at nominal irradiance (1000 W/m² ) and temperature (25 °C).	V
Imp	Current at maximum power point for one module at nominal irradiance (1000 W/m² ) and temperature (25 °C).	A
Pmax	Maximum power	W
Voc	Open circuit voltage for one module.	V
Isc	Short circuit current for one module.	A
Beta	Temperature coefficient at Voc	%/°C
Alpha	Temperature coefficient at Isc	%/°C
IL	Light generated current	A
I0	Diode saturation current	A
Diode ideality factor	Ideality factor of the diode.	-
Rsh	Shunt resistance	Ω
Rs	Series resistance	Ω

PV array Database Parameters

Below figure shows the Database tab of PV model. This tab lets you choose a PV from the database of the California Energy Commission (CEC). Once the selected module, the user must click Load parameters to load the model with the respective parameter values.

Boost Converter Parameters

The boost converter control parameters contain the RLC parameters together with the duty-cycle control, this duty-cycle depends on the active power regulator.

Name	Description	Unit

Name	Description	Unit
Cpv	Boost converter DC/DC link Capacitance	F
Rpv	Boost converter DC/DC link parasitic resistance	Ω
Lpv	Boost converter DC/DC link inductance	H
D_low	Minimum duty-cycle value	-
D_up	Maximum duty-cycle value	-
delD	Duty change per time step. Increment value used to increase/decrease the duty cycle per time step. Increasing the duty cycle means decreasing the voltage reference.	-

Ports, Inputs, Outputs and Signals Available for Monitoring

Ports

Name	Description

Name	Description
PCC	Network connection; supports 3-phase connection

Inputs

Name	Description	Units

Name	Description	Units
Temperature	Temperature of the PV cell	°C
Irradiance	Sun irradiance over the PV	W/m²
Pref	Active power reference. This signal is followed if the curtailment is on and the irradiance is higher in pu than Pref.	pu
Qref	Reactive power reference.	pu
Curtailment	1- Curtailment is on, 0 curtailment is off. The PV works in MPPT mode when the curtailment is off, or when the irradiance in pu is lower than the reference active power.	-
reset	Block enabled. 1- Enable, 0- Disable.	-

Outputs

None

Sensors

Name	Description	Units

Name	Description	Units
Temperature	Temperature of the PV cell	°C
Irradiance	Sun irradiance over the PV	W/m²
Pref	Active power reference. This signal is followed if the curtailment is on and the irradiance is higher in pu than Pref.	pu
Qref	Reactive power reference.	pu
Curtailment	1- Curtailment is on, 0 curtailment is off. The PV works in MPPT mode when the curtailment is off, or when the irradiance in pu is lower than the reference active power.	-
reset	Block enabled. 1- Enable, 0- Disable.	-
Iabc0, Iabc1, Iabc2	Three-phase current through the choke filter.	A
Vdc	DC link voltage measured at the terminals of the DC capacitor	V
P	Active power absorbed/delivered by the PVGS	pu
Q	Reactive power absorbed/delivered by the PVGS	pu
V_PV	DC output voltage produced by the PV array	V
I_PV	DC output current produced by the PV array	A
dcycle	Duty cycle control of the boost converter.	-

Modeling Details

I-V Curve Characteristics

The active power regulator is a PI controller. In order to have an active power measured equal to the active power reference, it adjusts the duty-cycle of the boost converter. The diagram is shown below. The parameters D_up and D_low are located in the Boost Converter panel.

Active power regulator

The reactive power regulator diagram is presented below. This controller aims to minimize the error between the reactive power measured and the reactive power reference. It outputs the reference current in the q-axis. The reference current in the d-axis is controlled by the VDC regulator, the diagram is displayed in Figure 4. This regulator minimizes the error between the DC link voltage measured and the DC link voltage reference. Both regulators are PI controllers and produce the d and q axis current references for the current regulator. The output of both regulators is limited to respect the maximum current rating of the system.

Reactive power regulator

DC link voltage regulator

The PV generation system performs the control of its output currents in the dq reference frame. The structure of current regulator is shown in Figure 5. I_dq and V_dq are the grid currents and voltages, respectively, in the dq reference frame at the transformer secondary while V_dqi are the inverter output voltages. The d axis current corresponds to the active power and the q axis current corresponds to the reactive power.

HYPERSIM Documentation

Photovoltaic Generation System (PVGS) - Average