PowerFactory 2020

Technical Reference

WECC Photovoltaic Templates

WECC Dist. Small PV Plants 25MVA, WECC Large-
scale PV Plant 110MVA
F2020

POWER SYSTEM SOLUTIONS

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February 10, 2020

PowerFactory 2020
Revision 1
Contents

Contents

1 Introduction 1

2 Model Usage 2

3 Model Configuration 2

3.1 Adjusting Rated Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3.2 Adjusting Power Dispatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3.3 Dynamic Model Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

4 Model Documentation 3

4.1 Large-scale PV Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

4.2 Distributed PV Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

5 References 5

List of Tables 6

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WECC Photovoltaic Templates (WECC Dist. Small PV Plants 25MVA, WECC Large-scale PV Plant 110MVA)
1 Introduction

1 Introduction

This document describes the usage of the WECC PV Power Plant models implemented in
PowerFactory .The models are based on [1].

The following plant model types defined by WECC are available in PowerFactory :

• Large-scale PV plants
• Distributed and small PV plants

Chapters 2 and 3 describe how to use and configure the models in PowerFactory . In chapter 4
the different models are described.

Note: The models which are available in PowerFactory as templates are configured with a set
of sample parameters. The user has the task to adjust static and dynamic model pa-
rameters (i.e. power rating, voltage level, reactive power limits and all parameters of the
dynamic models) to represent a specific PV plant!

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3 Model Configuration

2 Model Usage

Each of the types consist of at least two grid elements, the PV system (ElmPvsys), a terminal
and of a composite model which defines the dynamics of the PV power plant models. The com-
posite model contains the dynamic modelled built in DSL (DIgSILENT Simulation Language)
and all necessary measurement devices.

The models are available as templates and are accessible to be used in a project thought the
button General Templates in the drawing toolbox.

3 Model Configuration

The rated power, dispatched power and number of parallel machines can be adjusted as ex-
plained next.

3.1 Adjusting Rated Power

The rated power of the PV system has to be configured on the Basic Data page of the element
itself (i.e. the PV system doesn’t need a type). The rated active power is calculated via the
nominal apparent power “sgn” and the power factor “cosn”.

3.2 Adjusting Power Dispatch

The dispatch of the PV plant can be entered on the Basic Data page. The default input mode
is “P, cos(phi)”, which allows to enter the operation active power and power factor. The reactive
power can be limited by the reactive power capability curve which can be also voltage depen-
dent. It is also possible to coordinate the reactive power output of several PV systems by using
a station controller (ElmStactrl).

3.3 Dynamic Model Configuration

The dynamic simulation is started from steady state, which is the load flow result. It is therefore
important to check the load flow configuration of the elements as mentioned in the previous
sections.

The dynamic model can either be accessed via the generator element in the single line diagram
or via the data manager.

• Via Element: Open the element. Go to the Basic Data page and click on the arrow button
after “Model”.
• Via Data Manager: Search the corresponding composite model , right click and select
“Edit”.

After opening the composite model the different dynamic (common) models can be accessed
via a double click on the 2nd column.

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4 Model Documentation

The dynamic (common) models can be configured via scalar input parameters. These parame-
ters are displayed after opening a common model on the General page.

4 Model Documentation

In the following sub-sections the different types are described. In Table 4.1 the different dynamic
models are listed.

DSL Model Block Definition Large- Distributed

scale PV Plant
PV
Plant
REEC B Electrical Control Model REEC B X
REGC A Generator-Converter Model REGC A X
PVD1 Distributed PV Model PVD1 X
Protection Model Protection X
Voltage Source Reference Voltage Source Reference (X)
Plant Control Frame WECC Plant Control (X)
Table 4.1: Block Overview

4.1 Large-scale PV Plant

The Large-scale PV plant model is represented in the network via the PV system element.
The initial settings for the load flow calculation and dynamic simulation are done in the same
element, configuration of the grid element is described in 3.

The model is recommended to represent aggregated plants where a single equivalent PV gen-
erator is enough to represent the total output power and dynamics, the model as build in Pow-
erFactory consist of the following components:

• Large-scale PV Plant.
• REGC A. This implements the fast converter controllers and takes care of the reactive
current during high voltage and active current during low voltage sags.

• REEC B. This implements the electrical controls of the inverter, calculating active and
reactive current references based on power references, voltage and power measures.
Different control modes are allowed depending on the flag settings as shown in Table 4.2.
• Protection. This model implements protection functions with disconnection from the grid
in case of over- or under- frequency, over- or under- voltage. The protection model is in
the template by default out of service.
• Voltage Source Reference. This optional component enables a controlled Voltage Source
representation of the model. The controlled Voltage Source shows a more robust perfor-
mance in dynamic simulations, especially in cases of extreme low voltages. The model
can be found in the global “DIgSILENT Library/Dynamic Models/DIgSILENT” folder. If
a model representation as controlled voltage source is preferred then this model has to
be selected and the “Voltage Source” option on the RMS simulation page of the static
generator has to be selected.

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4 Model Documentation

• Plant Control. This implements the plant controller which calculates the commanded ac-
tive and reactive current. The plant control is available as template in the templates folder
“Plant Controllers”.
• Voltage and power measurement.

Control Mode PfFlag Vflag Qflag

Local constant Q control 0 1 0
Local constant pf control 1 1 0
Local voltage control 0 0 1
Local coordinated Q/V control 0 1 1
Table 4.2: PQ Control modes for Large-scale PV Plant model [2]

Note: In the local voltage control mode the reactive power reference is taken as reference as
specified by WECC [1]

4.2 Distributed PV Plant

The distributed PV plant model is represented in the network via the PV system element. This
model represents a large number of PV systems connected to distribution systems symbolising
the PV generation at an equivalent medium voltage feeder. The model as build in PowerFactory
consist of the following components:

• Distributed Small PV Plants.

• PVD1. This is a simple representation of the basic control of PV generation connected to

distribution system. Offering options such as volt/var control, active power controls and
disconnection of generation.
• Protection. This model implements protection functions with disconnection from the grid
in case of over- or under- frequency, over- or under- voltage. The protection model is in
the template by default out of service.
• Voltage and power measurement.

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5 References

5 References
[1] WECC - PV Power Plant Dynamic Modeling Guide; Issued april, 2014, 2014.
[2] Model User Guide for Generic Renewable Energy System Models. Technical Report
3002006525, EPRI, June 2015.

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List of Tables

List of Tables

4.1 Block Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

4.2 PQ Control modes for Large-scale PV Plant model [2] . . . . . . . . . . . . . . . 4

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