The PV Power Plant (Generic) component, shown in Table 1, is a Schematic Editor
library block from the Distributed Energy Resources section, of the Microgrid library. It is capable of operating in grid following
mode, with active power curtailment supported.
Table 1. PV Power Plant (Generic) component in the Schematic Editor core library
component
component dialog window
component parameters
Property tabs:
1 - General
2 - PV panel
3 - Grid codes
4 - Conv. Extras
5 - Grid Extras
PV Power Plant (Generic) functional block diagram and
main control functionality
The component consists of two main parts: a high level
control subsystem and a low level control subsystem with a power stage and necessary
measurements included.Figure 1. PV Power Plant (Generic) functional block diagram
High level control subsystem main parts are:
PQ Control block - Contains regulators for active and reactive power control.
The PQ Control block receives power references and measured powers after the transformer
(grid side) and calculates refererence output currents. These current references are fed
to the low level control logic. This control block is active in the grid following mode
of operation.
Ramping elements - Limit the ROC (rate of change) of the active power
reference, reactive power reference, voltage reference, and frequency reference. The
rate of change for each function is configured through a corresponding input
signal.
Main state machine - Controls and checks overall functionality of the plant.
Operational plant states are described in Main state machine
states table.
Low level control subsystem main parts:
Currents control block - Contains regulators for inner current control loops.
Input signals to the Currents Control block are reference currents and measured currents
before the transformer (converter side).
Fault state machine - Checks all measurements, signals the fault state, and sends
an alarm message. It also immediately opens the MCB (main circuit breaker) on any detected
fault. A list of implemented faults is shown in Faults/Alarm
messages.
PV Power Plant (Generic) power stage
The power stage is shown in PV Power Plant (Generic) power stage. The main elements include the average model
of the inverter, the input L filter, the transformer, and the MCB that connects the plant to
the grid. The transformer can be excluded from the power stage if it is not necessary. Power
stage elements are parametrized from the component dialog box.
Figure 2. PV Power Plant (Generic) power stage
PV Power Plant (Generic) component inputs and outputs
This component has one user interface input, one user interface output, and one external
input. The user interface input and user interface output are each arrays of 40 elements,
while the external input is an array of 5 elements. PV Power Plant (Generic) user
interface inputs describes the input signals and their order, while PV Power Plant (Generic) user
interface outputs describes the output signals and their order. Lastly, PV Power Plant (Generic)
external inputs describe the external PV Plant input signals and their order.
All these signals are also defined in the corresponding PV Power Plant (Generic) UI
subsystem with built-in Probe components (for output signals)
and SCADA Input components (for input signals), as
shown in Table 5. These signals were split and joined by a properly
configured DER (Generic) Output Split and DER (Generic) Control Join components. The PV Power
Plant (Generic) UI subsystem is located in the same place in the Schematic Editor
library as the PV Power Plant (Generic) component, and it can be unlinked from the library
and adopted to the specific needs. Unit [pu] is associated to nominal values, which are
either inserted as general tab parameters or derived from them.
Table 2. PV Power Plant (Generic) user interface inputs
Number
Input
Description
Signal range
Default value
0
Enable
A digital input that enables the converter. The converter is enabled when the
input value is high.
0 or 1
0
1
Reset alarms
A digital input that resets alarms if the converter is in a fault
0 or 1
0
2
Pcurtailment
An analog input that limits the maximum output power. [pu]
>= 0
0
3
Qref
An analog input that sets the reactive power reference. This reference is
active in grid following and droop mode. [pu]
0
4
Pcurtailment rate of change
An analog input that sets the rate of change of the active power curtailment
reference ramping, when the active power curtailment reference value decreases.
[pu/s]
>= 0.001
0.1
5
Qref rate of change
An analog input that sets the rate of change of the reactive power reference
ramping. [pu/s]
>= 0.001
0.1
6
MPPT rate of change
An analog input that sets the rate of change of the active power when active
power is controlled through MPPT algorithm. [pu/s]
>= 0.001
0.1
7
LVRT enable
Digital input that enables the LVRT unit. The LVRT unit is enabled when the
input value is high.
0 or 1
0
8
LVRT Q contribution
An analog input that specifies additional reactive power contribution per
percent of voltage drop in the case of a LVRT event. [%]
>= 0
2
9
LVRT P set
An analog input that defines the active power reference in the case of a LVRT
event. [pu]
Digital input that enables the VoltVAr unit. The VoltVAr unit is enabled when
the input value is high.
0 or 1
0
17
HzWatt enable
Digital input that enables the HzWatt unit. The HzWatt unit is enabled when
the input value is high.
0 or 1
0
18
VoltWatt enable
Digital input that enables the VoltWatt unit. The VoltWatt unit is enabled
when the input value is high.
0 or 1
0
19-39
reserved_ins
Inputs that are not used.
0
* If the values for inputs 10 to 15 are all zeroes, default values will be used.
Table 3. PV Power Plant (Generic) user interface outputs
Number
Input
Description
0
Enable_fb
A digital output describing the converter enable/disable state. The converter
is enabled if the output is high.
1
Pref_fb_kW
An analog output with the instantaneous value of the applied power reference
in the converter. [kW]
2
Qref_fb_kVAr
An analog output with the instantaneous value of the applied reactive power
reference in the converter. [kVAr]
3
Pnom_kW
An analog output with the value of nominal active power of the converter.
[kW]
4
Qnom_kVAr
An analog output with the value of nominal reactive power of the converter.
[kVAr]
5
Snom_kVA
An analog output with the value of nominal apparent power of the converter.
[kVA]
6
Vgrid_rms_meas_kV
An analog output reporting the RMS value of the grid voltage, measured at the
grid side of the transformer. [kV]
7
Fmeas_Hz
An analog output reporting the value of the grid voltage frequency. [Hz]
8
Pmeas_kW
An analog output reporting the instantaneous value of the three-phase active
power output of the converter. [kW]
9
Pa_meas_kW
An analog output reporting the instantaneous value of the phase A active
power output of the converter. [kW]
10
Pb_meas_kW
An analog output reporting the instantaneous value of the phase B active
power output of the converter. [kW]
11
Pc_meas_kW
An analog output reporting the instantaneous value of the phase C active
power output of the converter. [kW]
12
Qmeas_kVAr
An analog output reporting the instantaneous value of the three-phase
reactive power output of the converter. [kVAr]
13
Qa_meas_kVAr
An analog output reporting the instantaneous value of the phase A reactive
power output of the converter. [kVAr]
14
Qb_meas_kVAr
An analog output reporting the instantaneous value of the phase B reactive
power output of the converter. [kVAr]
15
Qc_meas_kVAr
An analog output reporting the instantaneous value of the phase C reactive
power output of the converter. [kVAr]
16
Smeas_kVA
An analog output reporting the instantaneous value of the three-phase
apparent power output of the converter. [kVA]
17
PFmeas
An analog output reporting the value of the converter output power factor.
18
Vconv_rms_meas_V
An analog output reporting the RMS value of the converter voltage, measured
at the converter side of the transformer. [V]
19
Available_Ppv_kW
An analog output reporting the maximum amout of active power that can be
produced in current weather conditions [kW]. It limits active power
production.
20
curtailment_status
A digital output reporting if the maximum active power production is reached.
Maximum is reached if the output is low.
21
MCB_status
A digital output reporting the information about the state of the main
circuit breaker (contactor). The contactor is closed if the value is high.
22
state
An analog output reporting the code of the state of the converter.
23
alarm_msg
An analog output reporting the value of the alarm message. In order for the
converter to return to normal operation after the alarm has been triggered, all
alarms must be reset.
24
Lvrt_active_status
A digital output that signals the status of the LVRT unit. If high, the LVRT
unit is active and contributing active and reactive power to the grid, otherwise
it is not active.
25-39
reserved_outs
Outputs that are not used.
Table 4. PV Power Plant (Generic) external inputs
Number
Input
Description
0
Temperature
Ambient temperature. Affects the available power of the plant. [ºC]
1
Irradiance
Irradiance of the PV panels. Affects the available power of the plant
[W/m2]
2-4
reserved_exts
Inputs that are not used.
Table 5. PV Power Plant (Generic) UI subsystem
Figure 3. PV Power Plant (Generic) UI
Figure 4. PV Power Plant (Generic) UI internals
PV Power Plant (Generic) operational states
Table 6. Main state machine states
Code
Decription
1
Starting up state – Represents the state of the
converter between the moment signal activation is triggered and the moment when the
converter starts operating, e.g. system checking and synchronization time.
2
Running state - Represents the operational state of the
converter.
3
Disabled state - Reports if the converter is not
enabled/operational.
4
Fault state – Represents the state of the converter if
it encounters a fault. It is necessary to reset the alarms once the converter enters
this state.
Table 7. Faults/Alarm messages
Code
Description
0
None of the alarms have been triggered
1
Over current protection. Input phase currents are greater than the
maximum specified value.
2
Grid voltage out of range. Grid voltage is outside the specified range.
This protection is active in grid following mode. If the voltage restores, the fault
will be automatically reset.
3
Grid frequency out of range. Grid frequency is outside the specified
range. This protection is active in grid following mode. If the frequency restores,
the fault will be automatically reset.
4
Over power protection. Measured apparent power is greater than the
maximum allowed apparent power.
Component dialogue box and parameters
The PV Power Plant (Generic) component dialogue box consists of four tabs for specifying
parameters of the component. Unit [pu] is associated to nominal values, which are inserted
as general tab
parameters or derived from them.
Tab: "1 - General"
In this component tab, the general parameters of the PV and the grid can be specified.Figure 5. PV Power Plant (Generic) "1 - General" parameters
Table 8. PV Power Plant model "1- General" parameters description
Parameter
Code name
Description
Nominal active power
Pnom
PV Power Plant nominal active power. [W]
Nominal apparent power
Snom
PV Power Plant nominal apparent power. [VA]
Nominal converter line voltage
Vnom_LL
PV Power Plant nominal line voltage (transformer's primary side). [V]
Nominal frequency
fnom
PV Power Plant nominal frequency . [Hz]
Include transformer
include_transformer
Include the transformer in the PV Power Plant power stage model.
Nominal grid line voltage
Vnom_sec_LL
Nominal line voltage of the grid (transformer's secondary side). [V]
Tab: "2 - PV"
In this component tab, parameters that are related to the PV side of the converter can be
specified.Figure 6. PV Power Plant model "2 - PV panel" parameters
Table 9. PV Power Plant model "2 - PV" parameters description
Parameter
Code name
Description
PV Inverter load ratio (DC:AC)
ILR_factor
Factor that determines the ratio of the power that PV panels are capable of
producing (DC) at STC (standard test condition - 25ºC and 1000W/m2) and nominal
power of the inverter (AC).
Tab: "3 - Grid codes"
In this component tab, different Grid code parameters can be specified. Currently, LVRT
(Low Voltage Ride Through), VoltVAr, HzWatt, and VoltWatt functionalities are supported.
Figure 7. PV Power Plant model "3 - Grid codes" LVRT parameters
Table 10. PV Power Plant model "3 - Grid codes" LVRT parameters
Parameter
Code name
Description
LVRT requirement
lvrt_req
Automatically parametrizes voltage and time points according to the chosen
requirements. If the Custom option is selected, voltage and current points become
available for editing.
Figure 8. PV Power Plant model "3 - Grid codes" VoltVAr parameters
Table 11. PV Power Plant model "3 - Grid codes" VoltVAr parameters
Parameter
Code name
Description
VoltVAr requirement
voltvar_req
Allows for defining voltage and reactive power points. Currently, only the
Custom option is supported.
Voltage points
vs_voltvar
VoltVAr curve voltage points.
Reactive power points
qs_voltvar
VoltVAr curve reactive power points.
Preview VoltVAr curve
preview_voltvar
Displays the created VoltVAr curve.
If LVRT and VoltVAr functionalities are both enabled, then the VoltVAr curve has priority
over the LVRT reactive power contribution setting (Q_contribution).
The VoltVAr curve is linearly extrapolated for voltage values below and above the minimum
and maximum values. Also, the curve is limited by a maximum value of reactive power which
can be produced or stored. This limit is calculated as , where opc_pu is the overpower capability.
Figure 9. PV Power Plant model "3 - Grid codes" HzWatt parameters
Table 12. PV Power Plant model "3 - Grid codes" HzWatt parameters
Parameter
Code name
Description
HzWatt requirement
hzwatt_req
Allows for defining frequency and active power points. Currently, only the
Custom option is supported.
Frequency points
fs_hzwatt
HzWatt curve frequency points.
Active power points
ps_hzwatt
HzWatt curve active power points.
Preview HzWatt curve
preview_hzwatt
Displays the created HzWatt curve.
If LVRT and HzWatt functionalities are both enabled, then the
HzWatt curve has priority over the LVRT active power contribution setting.
If the frequency value is below the minimum value or above the maximum value, then the
Grid frequency out of
range error will appear. The HzWatt curve is limited by a maximum value of active
power which can be produced. This limit is calculated as , where opc_pu is the overpower capability.Figure 10. PV Power Plant model "3 - Grid codes" VoltWatt parameters
Table 13. PV Power Plant model "3 - Grid codes" VoltWatt parameters
Parameter
Code name
Description
VoltWatt requirement
voltwatt_req
Allows for defining voltage and active power points. Currently, only the
Custom option is supported.
Voltage points
vs_voltwatt
VoltWatt curve voltage points.
Active power points
ps_voltwatt
VoltWatt curve active power points.
Preview VoltWatt curve
preview_voltwatt
Displays the created VoltWatt curve.
If LVRT and VoltWatt functionalities are both enabled, then the VoltWatt curve has priority
over the LVRT active power contribution setting. But, if HzWatt and VoltWatt functionalities
are both enabled, then the HzWatt curve has priority over the VoltWatt curve.
The VoltWatt curve is linearly extrapolated for voltage values below and above the minimum
and maximum values. Also, the curve is limited by a maximum value of active power which can
be produced. This limit is calculated as , where opc_pu is the overpower capability.
Tab: "4 - Conv. Extras"
In this component tab, the additional parameters that are related to the converter can be
specified.Figure 11. PV Power Plant model "4 - Conv. Extras" parameters
Voltage margin over the minimal allowed DC link voltage. This value restricts
the maximum voltage that a converter can generate. [pu]
Overpower capability
opc_pu
Determines the overpower capability of the converter. [pu]
Shunt resistance
Rshunt_pu
The value of the shunt resistances that are used for the measurement of phase
voltages at the converter input. The position of shunts is shown in PV Power Plant
(Generic) power stage image. [pu]
Faster execution rate
Tfast
The Faster execution rate at which part of the inner signal processing of the
component will be executed. Should be approximately 5 to 10 times faster than the
Slower execution rate. [s]
Slower execution rate
Tslow
The Slower execution rate, at which part of the inner signal processing of
the component will be executed. This execution rate is inherited by the connected
UI subsystem. Should be approximately 5 to 10 times slower than the Faster
execution rate. [s]
Tab: "5 - Grid Extras"
In this component tab, additional parameters that are
related to the grid can be specified.Figure 12. PV Power Plant model "5 - Grid Extras" parameters
Short circuit apparent power of the grid that the converter is connected to.
This parameter doesn't influence the power stage of the model, only the control
part. Stable operation of the converter can be achived by tuning this parameter.
[pu]
Grid inductive power factor
PFg
Power factor of the grid that the converter is connected to. This power factor
occurs when the grid is short-circuited. This parameter doesn't influence the power
stage of the model, only the control part. Stable operation of the converter can be
achieved by adjusting this parameter. [pu]
Example
Overall behavior and control methodologies can be better understood with the use of the
given example:
