PV Power Plant (Generic)

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
PV Plant (Generic)		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.

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 reference 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 Table 6.

• 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 Table 7.

PV Power Plant (Generic) power stage

The power stage is shown in Figure 2. 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.

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.Table 2 describes the input signals and their order, while Table 3 describes the output signals and their order. Lastly, Table 4 describes 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 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.

* If the values for inputs 10 to 15 are all zeroes, default values will be used.

Table 5. PV Power Plant (Generic) UI subsystem

PV Power Plant (Generic) UI	PV Power Plant (Generic) UI internals

PV Power Plant (Generic) operational states

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.

Tab: "2 - PV"

In this component tab, parameters that are related to the PV side of the converter can be specified.

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.

Implementation details for the LVRT unit are given on the LVRT in generic DER components page.

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 $Q_{max}=\left(1+opc\_pu\right)* Q_{nom}$ , where opc_pu is the overpower capability.

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 $P_{max}=\left(1+opc\_pu\right)* P_{nom}$ , where opc_pu is the overpower capability.

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 $P_{max}=\left(1+opc\_pu\right)* P_{nom}$ , 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.

Tab: "5 - Grid Extras"

In this component tab, additional parameters that are related to the grid can be specified.

Example

Overall behavior and control methodologies can be better understood with the use of the given example:

Model name: pv_plant_gen.tse

SCADA interface: SCADA_Panel.cus

Path: /examples/models/microgrid/pv_plant//pv_plant (generic)