This document describes the implementation and validation of a three-phase average value model (AVM) of a voltage source converter high voltage direct current (VSC-HVDC) system using Modelica. The VSC-HVDC model is composed of controlled voltage and current sources that approximate the internal behavior of a modular multilevel converter. Each component of the model, including controls, is implemented and validated separately against an EMTP-RV reference model. System-level validation is also performed by connecting the VSC-HVDC model to a two-node power system and simulating the transfer of 1000MW active power while controlling voltage. The results show good agreement with EMTP-RV. A key benefit of the Modelica implementation

1. A Three-Phase VSC-HVDC Average Value Model
Implementation using Modelica and Software-
to-Software Validation using a Power System
Domain Specific Simulator
Luigi Vanfretti
Royal Institute of Technology
(KTH)
1
Md Ahsan Adib Murad
University College Dublin
(UCD)

2. Outline
• Motivations
• Description of VSC-HVDC Model
• Implementation Modelica
• Model Validation
• Conclusion
2

3. Introduction and Motivations
 Proof of concept, Three phase AVM VSC-HVDC model
implemented in Modelica
3
1http://www.itesla-project.eu/
 VSC-HVDC models ‘trusted’ by users
were available in EMTP-RV
 Dynamic security assessment
carried out using the iTesla1 toolbox,
requires phasor time-domain models
 An VSC-HVDC AVM model for
phasor time-domain simulation was
implemented in Modelica
 Control gain parameters are
calibrated using the RaPId toolbox
Why not use Modelica for
modeling and model exchange of
EMT-like models? Specially for
control systems of power-electronic
devices?
 Advantage: model defined in one
language, does not need to be
maintained in multiple platforms
(e.g. Modelica export to FMI, FMI
supported in EMTP, Simulink, etc…)

4. VSC-HVDC Model
4
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SM2ua
SMNua
SM1ub
SM2ub
SMNub
SM1uc
SM2uc
SMNuc
SM1la
SM2la
SMNla
SM1lb
SM2lb
SMNlb
SM1lc
SM2lc
SMNlc
Vdc
vc
vb
va
Larm Larm Larm
Larm Larm Larm
iua iub iuc
ila ilb ilc
ic
ib
ia
Idc
VuaVla
MMC Topology
AC Side
Phase A
VDC
Varef
Vac AC Side
Phase B
VDC
Vbref
Vac AC Side
Phase C
VDC
Vcref
Vac
Larm Larm Larm
AC
AC Side of AVM
IDC
DC_SideVaref
Vbref
Vcref
Ia
Ib
Ic
Req_DC
Leq_DC
C1
P
N
DC Side
Different kinds of VSC based MMC
models are available.
 In Average Value Models (AVMs), the
power electronic switches (IGBTs) and
diodes are not modeled in detail.
 MMC behavior is represented using
controlled voltage and current sources.
 An ideal behavior of the internal
variables of the MMC is assumed.

5. VSC-HVDC Control
5
 The AVM and this control is already available in EMTP-RV
which are implemented in Modelica using Modelica
Standard Library library.

6. Implementation in Modelica
6
 Each component is implemented
separately in Modelica .
 After implementing each component,
validation is carried out with reference
models.
Models implemented in Modelica
Three phase equivalent generator &
two winding transformer
Clark transformation
P/Q/VAC calculations
d/q transformations
Outer control , inner control
Synchronization block (PLL)
Linearization's and d/q to abc
 For Example: PI control block

7. VSC-HVDC in Modelica
7

8. Model Validation
8
Equivalent Generator
and Transformer
Each component is validated against
EMTP-RV
Phase Lock Loop

9. Model Validation
9
 Two Node power system is implemented and used for system level
validation.
 Converter 1 (VSC1) controls the active power and Converter 2 (VSC2)
controls the DC voltage.
 1000 MW active power is transferred from VSC1 to VSC2.
 The user can select which controller should be active in each VSC.

10. Simulation Results
10
 Step change in active power reference from 1000 MW to 500 MW at 0.8
second

11. Conclusions
11
 Potential use of the Modelica language to model EMT-type models of
VSC-HVDC systems.
 The Modelica implementation was compared to the EMTP-RV
software, provides similar results.
 The major benefit of the work reported herein is that the control
system implemented can now be exchanged with different tools that
support the FMI standard, including:
Simulink and
EMTP-RV,
which makes it possible to keep and maintain a single version of the
control system model implemented (i.e. the one in Modelica)

12. 12
Questions?
• The VSC HVDC models presented here can be found on-line at Github:
https://github.com/SmarTS-Lab/2017_ModelicaConf_VSC-
HVDC_AVM_Model