Class I Item no.: 0001-9447 V04 GENERIC USER MANUAL

Item no.: 0001-9447_V04

GENERIC USER MANUAL

Date: 2011-08-22

Issued by: Technology Class: I

Type: Page 2 of 30

Class I

Item no.: 0001-9447_V04

2011-08-22

GENERIC USER MANUAL Simulation model

Version 7

In DIgSILENT PowerFactory®

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DISCLAIMER

VESTAS MAKES NO WARRANTY OR REPRESENTATION EITHER EXPRESS OR IMPLIED IN RESPECT OF

THE POWERFACTORY MODEL, INCLUDING WITHOUT LIMITATION AS TO ACCURACY, COMPLETENESS,

FUNCTIONALILTY, PRECISION, USEFULNESS, FITNESS FOR A PARTICULAR PURPOSE OF THE

POWERFACTORY MODEL OR OTHERWISE. THE POWERFACTORY MODEL IS PROVIDED “AS IS” AND

VESTAS SHALL HAVE NO RESPONSIBILITY OR LIABILITY WHATSOEVER FOR RESULTS OF USE OR

PERFORMANCE OF THE POWERFACTORY MODEL. TO THE MAXIMUM EXTENT PERMITTED BY LAW, IN

NO EVENT VESTAS SHALL BE LIABLE FOR ANY CONSEQUENTIAL DAMAGES, DIRECT, INDIRECT,

SPECIAL, PUNITIVE OR OTHER DAMAGES WHATSOEVER ARISING OUT OF OR IN ANY WAY RELATED

TO THE USE OF OR INABLITY TO USE THE PSS/S MODEL, WHETHER BASED IN CONTRACT, TORT,

NEGLIGENCE, STRIT LIABILITY OR OTHERWISE.

For the avoidance of doubt, Vestas makes no warranty or representation either express or implied as to

the performance of the wind turbine model in terms of it being in accordance with the performance of the

actual wind turbine generator, as other circumstances, including, but not limited to deviations in the

markets and optional features might have influence on the performance of the actual wind turbine

generator. The performance of the wind turbine model is expected only to be indicative to the

performance of the actual wind turbine generator.

Copyright Notice

The documents are created by Vestas Wind Systems A/S and contain copyrighted material,

trademarks, and other proprietary information. All rights reserved. No part of the documents may be

reproduced or copied in any form or by any means—such as graphic, electronic, or mechanical,

including photocopying, taping, or information storage and retrieval systems—without the prior written

permission of Vestas Wind Systems A/S, and its respective parent companies, subsidiaries, affiliates,

successors, assigns, licensees, representatives and agents (together "Vestas"). The use of these

documents by you, or anyone else authorized by you, is prohibited unless specifically permitted by

Vestas. You may not alter or remove any trademark, copyright or other notice from the documents.

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History of this Document

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History of this Document

Rev. no. Date Description of changes

00 2008-08-14 -

01 2009-04-15 Disclaimer and copyright update

02 2009-06-08 Change from Class II to I

03 2010-12-28 Updated to cover more turbines in the generic model structure

Added information about spikes at switching events at LVRT

04 2011-08-22 Updated to cover more turbines in the generic model structure

Table of Contents

1 Introduction .......................................................................................................................... 6 2 Example project ................................................................................................................... 7 3 Static model set-up ............................................................................................................ 10 3.1 WTG PWM converter Data .................................................................................................. 10 3.2 WTG Terminal ..................................................................................................................... 12 3.3 Internal DC node and DC Voltage Source ............................................................................ 12 4 Dynamic model set-up ....................................................................................................... 12 4.1 Bus Voltage Slot .................................................................................................................. 15 4.2 WTG Element Slot ............................................................................................................... 15 4.3 Frequency Measurement Slot .............................................................................................. 16 4.4 PQ Grid Slot......................................................................................................................... 17 4.5 WTG Slot ............................................................................................................................. 18 4.6 External Grid ........................................................................................................................ 19 5 Vestas V80 2MW VCS 50Hz model .................................................................................... 20 5.1 Control Parameters .............................................................................................................. 20 5.2 Model Input Signals ............................................................................................................. 23 5.3 Model Output Signals ........................................................................................................... 24 6 Integration of the model to a user network model ........................................................... 24

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Table of Figures

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Table of Figures

Figure 1 - Example project tree and model grid contents ........................................................................ 7

Figure 2 - Terminal and Point-terminal graphic elements ........................................................................ 8

Figure 3 - WTG Static Element with Vestas-defined Symbol................................................................... 8

Figure 4 - Vestas Frame Version 7 ....................................................................................................... 13

Figure 5 - ―Frame WTG Vestas V80‖ Composite model: location in the example project tree ............... 14

Figure 6 - ―Frame WTG Vestas V80‖ Composite model: contents and edit dialog window .................... 15

Figure 7 - Vestas V80 2.0 MW 50Hz Model Dialog ............................................................................... 18

Figure 8 - Event Definition Page ........................................................................................................... 21

Figure 9 - Unit Trip Events Definition .................................................................................................... 22

Figure 10 - User Project and Grids ....................................................................................................... 25

Figure 11 - User Grid ............................................................................................................................ 26

Figure 12 - User Grid (Detail)................................................................................................................ 27

Figure 13 - WTG Composite Model ...................................................................................................... 28

Figure 14 - Connection of grids "Part 1" and "Vestas V80 2MW VCS 50Hz" ......................................... 29

Figure 15 - Load Flow Results with WTG Model ................................................................................... 30

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Introduction

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Vestas Wind Systems A/S · Alsvej 21 · 8900 Randers · Denmark · www.vestas.com

1 Introduction

This document provides guidelines for the user to include the Vestas WTG dynamic simulation models in a network model, using the DIgSILENT PowerFactory® software tool.

This user manual refers to model version 7 and makes reference to the example project “Vestas V80 2MW VCS 50Hz”. This example contains the WTG model set-up for load flow and dynamic simulation, using the single machine – Infinite Bus network model.

The Vestas type specific simulation model is provided along with this document to be used as a tutorial and for the user to import the WTG model to other projects in DIgSILENT PowerFactory® software tool.

The WTG model may be used both for steady state analysis purposes (Load Flow and other related calculations), and for dynamic stability studies with a time range in excess of 10 seconds. The model supports aggregation of wind turbines in order to simulate a whole wind park with a minimum number of individual elements. The model not only simulates the response of the WTG to changes in the grid voltage and frequency, but can also initiate disconnections of the WTG groups according to its defined protection criteria.

The model is intended to be linked to a static network element representing the current/power injection of the WTG group to the grid. For this purpose, a PWM converter element (ElmVsc) is used in association with the dynamic model.

DIgSILENT GmbH developed this implementation based on a model description provided by VESTAS.

This model has been developed for PowerFactory® version 14.

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Example project

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2 Example project

The single machine – Infinite Bus network model provided in the simulation model file

consists of two separate grids:

- ―Grid‖ represents a generic external grid - ―WTG VXX contains the Vestas WTG model.

This set-up facilitates the creation of remote system stages to include the WTG model into

the user’s existing grid models.

Two separate library folders are provided in the network model. The library folder ―Vestas

Library‖ contains the DSL model and frame specific to the WTG model are stored.

Figure 1 indicates the elements in the example project tree.

Figure 1 - Example project tree and model grid contents

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The static element selected for this example to represent the WTG group in a network model

is the ―PWM-converter‖-Element, which allows for various modes in load flow setup. This

model behaves like a controllable current source in dynamic simulation. Such PWM-

converter element will be connected to a node/busbar representing the WTG terminal. The

terminal can be alternatively represented in the graphic by means of a point-terminal graphic element, as shown in Error! Reference source not found..

Figure 2 - Terminal and Point-terminal graphic elements

The PWM-converter element graphic symbol can be changed by a Vestas-defined symbol,

so that the element will look as shown in Figure 3.

Figure 3 - WTG Static Element with Vestas-defined Symbol

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The procedure to change the symbol is quite straightforward:

- Multi-select the PWM converter, DC node and DC voltage source.

- Right-click the selection.

- On the pop-up menu, select ―Group as new symbol‖.

- Select the symbol ―VestasWTGcomp‖ on the menu appearing.

- Press ―OK‖.

The data needed for setting up the PWM converter, internal DC node and internal DC

voltage source elements will be described in the following chapter.

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3 Static model set-up

3.1 WTG PWM converter Data

For the set-up of the PWM-Converter element, some issues have to be considered:

- WTG General Settings, Rated AC Voltage: This value should be equal to the AC

terminal voltage of the WTG, in this case 0.69 kV.

- WTG General Settings, Rated DC Voltage: This value corresponds to the rated

voltage of the internal DC node, in this case 1.0 kV.

- WTG General settings, Rated Power: this value must be equal to the rated power of

the WTG units group, i.e., if the rated power of a single WTG is 2.0 MVA, and a

group of 5 units is represented, the Rated Power of the PWM must be 5*2.0 = 10.0

MVA

- WTG General Settings, Short circuit impedance: This value can be set to 5%.

- WTG General Settings, Modulation: Sinusoidal PWM.

- WTG control mode: in the load flow edit dialog, the control mode for the WTG

element should be set to P, Q mode, in order to define both the active and reactive

setpoints of the element.

- WTG active power setpoint: The PWM element must represent an active power

injection to the grid. The desired total output active power of the WTG group should

be defined in the load flow edit dialog of the PWM converter, in the field active power

setpoint. (Example: if 4 units are considered to be in the group, and generation of 1.5

MW per each machine is desired, the PWM element active power operating point

should then be 4*1.5 = 6.0 MW.)

- WTG reactive power setpoint: The PWM element must represent a positive or

negative reactive power injection to the grid. The desired total output reactive power

of the WTG group should be defined in the load flow edit dialog of the PWM

converter, in the field reactive power setpoint. (Example: if a single unit is considered

to be in the group, and absorbing 0.2 MVar in under-excited operation, the PWM

element reactive power operating point should then be -0.2 MVar).

In the example grid, the output of the WTG group is set to 2.0 MW / 0 MVar (power factor

=1). At this point in time, no specification has been made concerning the number of units

in the group, so that the load element could either represent a single unit at full load, or,

for example, two units at 50% load.

The user will be warned if they introduce P reference values in the load element over the capability limits defined in the DSL WTG model. The limits are defined by the parameter Nunits (see Chapter 5) and the following message will be shown in the output window when calculating initial conditions:

DIgSI/pcl - message: Warning: WTG initialized at P>1

In the same manner, if Q reference value is out of the capability limits defined by parameter Nunits and beyond the V80 2MW VCS 50Hz PQ capability chart (found in standard product documentation) the following message will be shown:

DIgSI/pcl - message: Warning: WTG Q limits exceeded

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After executing the ―Calculate Initial Conditions‖ command, the following text messages will appear in the display window as a result of the successful initialization of the model:

DIgSI/info - Derivative of a not equal 0!

DIgSI/info - Derivative of b not equal 0!

DIgSI/info - Derivative of vd_dynamic not equal 0!

DIgSI/info - Derivative of vq_dynamic not equal 0!

DIgSI/info - Derivative of xRateLimiter not equal 0!

DIgSI/info - Derivative of xRdummy not equal 0!

DIgSI/info - Derivative of xlvrtprot not equal 0!

DIgSI/info - Derivative of xril not equal 0!

DIgSI/info - Derivative of xusuago not equal 0!

DIgSI/info - (t=-02:000 s) Initial conditions calculated

When running the simulation the user will get similar DSL messages as the simulation model enters different control modes, timers and limiters being activated etc. These messages can be used to monitor the state of the model during dynamic events.

The reactive power output of the model in dynamic LVRT simulations sometimes can show small spikes after fault insertion and right after fault clearance. These spikes are due to the fact that no time delays are considered in the model for voltage measurements or for enabling AGO2 in the WTG. Due to the numerical properties of the PowerFactory® solution algorithm, enabling AGO2 and fault insertion/removal is not always executed simultaneously and hence, these small spikes in reactive power can occur. These spikes are a numerical artefact and do not represent the real performance of the WTG.

As the simulation model is a reduced model and applies switched logics during LVRT the user might get the following warning on non-convergence during such a switched event. By reducing the simulation integration step size these warnings and the derived spikes in simulation results can be mitigated. In general short spikes <10ms after switching operations do not necessarily reflect the real turbine behavior. In general a simulation integration step size of 1 ms or less is recommended.

DIgSI/wrng - (t=801:000 ms) No convergence in iteration-loop

These warnings do not bring the general stability of the model, or the general validity of the results into question.

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Dynamic model set-up

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3.2 WTG Terminal

To represent the stator terminal of the WTG, either a terminal bus element or a station bus

element can be used. In this case, a bus terminal has been used. The only parameter

needed for this element is the nominal voltage, which must be equal to the rated WTG

voltage in kV (0.69 kV).

3.3 Internal DC node and DC Voltage Source

The nominal voltage of the DC node and DC source should be compatible with the voltage

defined as the Rated DC voltage of the PWM Converter.

4 Dynamic model set-up

In order to connect the WTG dynamic model to the network element representing the WTG

power injection to the grid, a model frame (composite model) is needed. Figure 4 shows the

use of the frame.

This frame can be found in the project library folder ―Vestas Library‖, sub-folder ―Frame‖

under the name ―Vestas Frame Version 7‖.

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Vestas Frame Version 7:

WTG Converter ElementWTG Model

PowerMeasurement

Stator Frequency Measurement

Stator Voltage Measurement

Qgrid

Pgrid

Frequency measurementElmPhi*,ElmPll

0

1

2

WTGmodelElmV*

Pset

Reactive_ref

0

1

2

3

4

5

0

1

6

7

PQ gridStaPqmea

0

1

Bus VoltageStaVmea*

0

1

2

WTGelementElmVsc*

0

1

2

3

Vestas Frame Version 7:

sinr

e.. co

sre.

.

ur

ui

us

f

iq_ref

id_ref

DIg

SIL

EN

T

Figure 4 - Vestas Frame Version 7

A composite model element, named ―Vestas Frame v7‖ has been created in the grid ―WTG V80‖ from the frame in Figure 4. Its content and edit dialog are shown in Figure 6 and Figure 6.

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Figure 5 - “Frame WTG Vestas V80” Composite model: location in the example project tree

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Figure 6 - “Frame WTG Vestas V80” Composite model: contents and edit dialog window

Each one of the elements needed by the composite model will be discussed in the next

sections.

4.1 Bus Voltage Slot

The slot identified as ―Bus Voltage‖ contains the element representing the measurement of

generator terminals voltage. The element used for this purpose will be a ―Voltage

Measurement‖ element (element StaVmea) and is stored inside the Composite Model folder.

This slot will provide the stator voltage in p.u. of the unit rated voltage (variables us, ur, ui).

4.2 WTG Element Slot

This slot contains the PWM Converter element (ElmVscmono) representing the WTG in the

grid. Since this element is external to the composite model, the selection has been made by

right-clicking the corresponding field. The WTG dynamic model will feed to this element the

required active and reactive reference currents (WTG dynamic model output variables id

and iq).

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4.3 Frequency Measurement Slot

This slot contains an element providing the stator frequency in Hz for use of the WTG

dynamic model (variable “f”), and the voltage reference angle to the PWM element (PWM

converter input variables cosref and sinref). The element foreseen for the purpose is a

―Phase Measurement Device PLL_Type‖ (ElmPhi_pll), and has been created inside the

composite model itself, so that the selection can be made simply by clicking the ―Slot

Update‖ button in the composite model edit dialog.

This element mimics a frequency/angle measurement device, and it is to be preferred rather

than obtaining the frequency directly from the bus, since in the latter case, discontinuities in

the grid will appear as ―spikes‖ in the frequency values.

In this element, the measurement point must be defined: in this case, the WTG terminal.

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4.4 PQ Grid Slot

This slot contains an element providing the feedback active and reactive power measurements from the static element representing the WTG to the dynamic model (variables Pgrid and Qgrid). For this purpose, a ―PQ measurement‖ (ElmStaPqmea) element is needed.

In the example project, for this element, the measurement point of the active and reactive power injected to the grid is left blank in the PQ measurement element dialog, being such measurement point the cubicle where the element is stored (the cubicle to which the WTG PWM converter element is connected). The Power Rating of the element should be set to 1 MVA, and the measurement should be ―Generator oriented‖, so to compensate for the inverse sign convention of the load element.

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4.5 WTG Slot

This slot contains the actual simulation model for the specific Vestas wind turbine, and therefore is the key element for the overall WTG model set-up. The ―Common Model‖ element (ElmDsl), named ―Vestas V80-2.0 MW 50Hz‖ has been created inside the composite model folder from the DSL model with the same name that can be found in the library folder ―Vestas Library‖, sub-folder ―WTG Model‖. The input and output signals, as well as the parameter needs for this model will be described in detail in chapter 5. Figure 7 shows the edit dialog for the common model element of the Vestas WTG, as it can be found in the composite model ―WTG V80-2.0 MW VCS 50 Hz.

Figure 7 - Vestas V80 2.0 MW 50Hz Model Dialog

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4.6 External Grid

The WTG model must be connected to a grid model.

The example provided presents, as stated before, a single unit-Infinite Bus system. The external grid, identified simply as ―Grid‖ in the example, is composed of:

- External network element (ElmXnet). Since the External network must represent an infinite bus, its acceleration time constant has been defined as ―very large‖ (9999 s). The MVA rating has been set at 1000 MVA, and the R/X ratio at 0.1, but these two last parameters can be set at other values representing the conditions at the point of common coupling (PCC).

- HV connection bus for the WTG (HV Bus, ElmTerm). The HV bus representing the high voltage connection point (PCC) of the WTG has been set with a nominal voltage of 33 kV

- Step-up transformer. ―Grid‖ includes a 2 winding transformer element (ElmTr2), representing the parallel aggregation of nacelle transformers. The example project uses the type ―2-Winding Trafo 33/0_69 kV 2.1MVA Dyn5‖ that can be found in the ―Grid Library‖ Folder. That type definition is based on generic transformer characteristics, and cannot substitute more accurate data available from specific transformer models.

The step-up transformer element can be parameterized in the element edit dialog to represent up to 99 parallel identical units, in the example project it represents 1 unit.

The user can introduce other transformer types corresponding to different MV levels and different transformer characteristics contemplated as options by Vestas specifications.

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Vestas V80 2MW VCS 50Hz model

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5 Vestas V80 2MW VCS 50Hz model

This section presents how to use the Vestas simulation model.

5.1 Control Parameters

This category includes parameters governing the modes of operation of the WTG model.

They are settable by the user according to its specific requirements. Table 1 lists such

parameters. A detailed description is also given in this chapter.

Name Description value units

Nunits Number of Units Conforming the WTG group >=1

ModeSel PF or Q Model selector 1/0

AGO_enable LVRT Functionality Enable/Disable Flag 1/0

Prot_enable Protection Trip Enable/Disable Flag 1/0

Table 1 : “Vestas V80 2MW VCS 50Hz” Model Control Parameters

Nunits:

The model allows aggregation of units in a group. This parameter defines the number of

units in the group. This parameter is set to 1 in the example project.

Mode_Sel:

The reactive power reference for the group of units can be calculated to obtain Defines the

way in which model input signal Reactive_ref (see section 5.2) provides an external power

reference to the model:

- A constant reactive power at the generator (ModeSel = 0).

- A constant power factor (ModeSel = 1).

In the example project, the value of ModeSel is set to 1.

AGO_enable:

The AGO functionality of the model (LVRT conditions detection, switching between power

and current control, and activation of the LVRT Under-voltage protection) is enabled

(AGO_enable = 1) or disabled (AGO_enable = 0) by this user flag. By default, AGO_enable

is set to 1.

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Prot_enable:

This flag allows the user, when set to 1, to activate the actual trip (disconnection) of the unit

group whenever the protection module settings are exceeded. Such disconnection can be

performed locally in the model by defining the appropriate event(s) in the ―Events‖ definition

page of the model dialog. The event(s) must be named ―SwitchGen‖.

An example of this is given in the provided network model. Figure 8 shows the model dialog

event page. It can be seen that three events have been defined in this case.

Figure 8 - Event Definition Page

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Figure 9 - Unit Trip Events Definition

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Figure 9 shows the definition of such events. As it can be seen, the first event (event

―SwitchGen‖, element EvtSwitch), causes the breaker connecting the WTG element to the

grid to open. This event is in principle enough to ensure the disconnection of the unit group.

The second event (event ―SwitchGen(1)‖, element EvtOutage) takes the WTG simulation

model out of service. This last event is not strictly necessary, but it has been included as a

security measure to prevent eventual numerical problems that may arise (but not necessarily

so) when the model is running with its associated element not connected.

It is to be noted that, when the protection trip is disabled by setting the flag Prot_enable to

0, as is the case in the example project, warning messages indicating that protection limits

have been exceeded will nevertheless be issued in the output window.

5.2 Model Input Signals

As from Figure 4, the following input variables and set-points to the model can be identified:

us, ur, ui, f, Pgrid, Qgrid, Pset, Reactive_ref. Of all these, the input variables obtained

from the grid are:

us: Stator voltage in p.u., from the Bus Voltage slot (Stator terminal bus).

ur: Stator voltage (real part) in p.u., from the Bus Voltage slot (Stator terminal bus).

ui: Stator voltage (imaginary part) in p.u., from the Bus Voltage slot (Stator terminal bus).

f: Stator frequency in Hz, from the Frequency Measurement slot (stator terminal bus).

Pgrid: Active Power input in MW (Grid active power feedback from the WTG element), form

the PQ Grid slot.

Qgrid: Reactive power input in MVAR (Grid reactive power feedback from the WTG

element) from the PQ Grid slot.

The set-points for the WTG are automatically defined by the model at initial conditions time

from the power values defined by the user for the WTG load element associated to the

model, and considered to be constant, therefore are not linked to any other slot/model:

Pset: Active power set-point in MW.

Reactive_ref: Reactive power set-point reference, either in MVAR or as Power Factor.

The model will issue warning messages to the output window whenever the initial settings of

active and reactive power defined for the load element exceed the WTG internal constraints.

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5.3 Model Output Signals

From Figure 4 it can be seen that the model has two main output variables, and an auxiliary

one.

The main output variables are:

- id: Active Power reference current to be fed into the PWM converter model to obtain

the desired active power injection to the grid, in p.u.

- iq: Reactive Power reference current to be fed into the PWM converter model to

obtain the desired reactive power injection to the grid, in p.u.

The auxiliary variables are defined as:

- Pgout: WTG active power output to the grid, in p.u. of the WTG. This variable is

used mainly for supervision and testing purposes.

- Qgout: WTG reactive power output to the grid, in p.u. of the WTG. This variable is

used mainly for supervision and testing purposes.

- Trip: Protection trip signal for the unit/group: this variable will initiate the unit/group

disconnection by means of a user-defined event defined locally in the model, as will

be described at a later time, and it is made available for eventual external models.

6 Integration of the model to a user network model

To integrate the hereby presented WTG model to an existing network model, it is not

necessary to create from scratch the previously described elements and models, but, by

creating a remote system stage, this same model in the example network can be included

easily in a large existing network model. The procedure will be illustrated by means of an

example.

We will start from supposing that a user wants to include the V80 2MW VCS 50Hz v6.1.0

model to the project ―User Project‖. The Network in this project consists of two grids, named

―Part 1‖ and ―Part 2‖, activated by the study case ―Case1‖ (see Figure 10).

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Figure 10 - User Project and Grids

By opening the single-line diagram of the grid ―Part1‖, we can see that a current source is

connected to the bus‖BusBar1‖ of the substation ―Station 4‖, with a nominal voltage of 11 kV.

The Current source is injecting 1.9 MW / 0 MVar. We will suppose now that this current

source is a simplified representation of a WTG that now we need to model in a more detailed

way using the Vestas model, (see Figure 11 and Figure 12), using as WTG element a PWM

converter.

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Figure 11 - User Grid

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Figure 12 - User Grid (Detail)

The first steps are:

- Deactivate the User Project, so to enable the data import.

- Import the file ―Vestas V80 2MW VCS 50Hz‖.

- Activate again the User Project

Once the example project is part of the user data manager tree:

- Right click the ―Vestas V80 2MW VCS 50Hz‖ grid in the ―Vestas V80 2MW VCS

50Hz‖ project.

- Select ―Add to Study Case‖ in the pop-up menu that will appear

A ―remote system stage‖ will appear in the user project‖, called also ―Vestas V80 2MW VCS

50Hz‖. This name may be changed by editing the remote system stage. The contents of the

remote system stage and the WTG composite model current definition are shown in Figure

13.

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Figure 13 - WTG Composite Model

Since all elements of the WTG are contained in the grid ―Vestas V80 2MW VCS 50Hz‖, and

all element and links in the remote system stage are maintained, no further adjustment are

needed in this sense.

Also, a new graphic tab is now present in the original project graphics board, corresponding

to the ―Vestas V80 2MW VCS 50Hz‖ grid single line diagram.

The WTG model is now included in the user’s grid, but it is still not connected to it. To do so,

it is possible, for example, to create in the single line graphics an 11 kV/0.69 kV step-up

transformer connecting the WTG terminal to the ―Station 4/Busbar 1‖ 11 kV busbar, and at

the same time taking out of service the current source. The grids ―Part 1‖ and ―V80 2MW

VCS 50Hz‖ in the user project will now look as in Figure 14.

To finish the integration of the WTG model to the user grid, it is only needed to define (if it

doesn’t already exists in the user library) a type for the step-up transformer, assign it , and

set the WTG Element operating point according to the power injected by the current source.

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Figure 14 - Connection of grids "Part 1" and "Vestas V80 2MW VCS 50Hz"

Grid ‖Part 1‖

Grid ‖Vestas V80 2MW VCS 50Hz‖

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Figure 15 - Load Flow Results with WTG Model

The WTG model is now fully integrated to the user grid. It is to be noted that, because of the

presence of the transformer, setting the reactive power in the PWM converter at 0 MVar as

in the current source will not result in a 0 reactive power injection to the grid. To obtain the

desired injection at the PCC, the reactive power operating point should be adjusted

accordingly (Q = 0.12 in this case)

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Aggregated WTG representation

An aggregated WTG group representation can be created by changing accordingly the

following settings:

- Parameter “Nunits” in the WTG model.

- Number of step-up transformers in parallel.

- Rated power of the WTG PWM-Converter Element.

In case that more than one WTG group has to be represented individually, than the WTG

model elements (PWM converter, DC node, DC source elements, Terminal and Composite

model) in the ―Vestas WTG V80 2MW 50Hz‖ grid can be created by ―copy/paste‖ of the

existing WTG element and model.

It must be noted that, when doing so, the contains of the ―WTG Element‖ slot, along with the

measurement point definition of the voltage measurement, phase measurement etc.

elements in the newly replicated composite models, and the events in the WTG models must

be updated, linking all of them to the corresponding new elements and cubicles.

The connection of the so created WTGs to the desired busbar (PCC) can be defined, for

example, as an arrangement of step-up transformers and cables, as per the user

requirements.

Documents

Class I Item no.: 0001-9447 V04 GENERIC USER MANUAL