Compliance with grid data exchange standards (i.e. CIM) can allow for sustainable software development in power systems if open and equation-based modeling languages and simulation standards are exploited . Together with my PhD student Francisco José Gómez López, we will be @RT-2014 presenting our vision and recent work carried out together with Svein Olsen: "Towards CIM-Compliant Model-Based Cyber-Physical Power System Design and Simulation using Modelica".

1. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
Luigi Vanfretti1,2, Francisco Gómez1, and Svein H. Olsen2
luigiv@kth.se , fragom@kth.se
Electric Power Systems Dept.
KTH
Stockholm, Sweden
Luigi.Vanfretti@statnett.no
svein.harald.olsen@statnett.no
Research and Development Division
Statnett SF
Oslo, Norway
Towards CIM-Compliant Model-Based Cyber-Physical
Power System Design and Simulation using Modelica

2. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
Outline
• Cyber-Physical Systems
• Key Concepts from Hybrid Systems
• Key Characteristics of Hybrid Systems
• Consequences of increased ICT
• PMU-Based Wide Area Control Systems
• Damping Controller WACS
• Cyber-Physical Systems Modeling
• Systems Data Modeling
• Model Development
• CIM for model simulation
• Modelica Simulation Engine
Towards CIM-Compliant Model-Based Cyber-Physical
Power System Design and Simulation using Modelica
Acknowledgments
• This work has been funded in part by the EU funded
FP7 iTesla project: http://www.itesla-project.eu/ and
Statnett SF, the Norwegian power system operator.
• Work related to the iTesla Modelica power systems
library presented here is a result of the collaboration
between RTE (France), AIA (Spain) and KTH (Sweden)
within the EU funded FP7 iTesla project:
http://www.itesla-project.eu/
• Special thanks for ‘special training’ and support from
• Prof. Fritzson and his team at Linköping University
• Prof. Berhard Bachmann and Lennart Ochel, FH Bielefeld

3. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
Key Concepts from Hybrid Systems
(a.k.a. cyber-physical systems)
• Physical systems evolve continuously over time, but
other systems evolve by discrete changes.
• These discrete changes, or events, occur at specific
points in time.
• Discrete event dynamic systems, as opposed to
continuous dynamic systems, may not be directly
based on physical laws derived from first principles.
• Hybrid systems contain both discrete parts as well as
continuous parts.
• E.g.: consider a digital computer system interacting
with the physical world.
• This is a simplified view of the world as discrete parts
are usually distributed together with physical
components.
Physical System
Computer
System
Actuators Sensors
Comms
Comms
010101010101
An example is a power plant where local digital controllers are
integrated as part of the generators…
http://blog.xogeny.com/blog/sensor-artifact/

4. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
Key Characteristics of Hybrid Systems
(a.k.a. cyber-physical systems)
• A reactive system is a subclass of a real-time
computer system with discrete behavior such as
the system explained above
• These systems continuously react to their environment at
a speed determined by that environment (sharp time
constraints)
• An interactive system continuously reacts to users
and to the environment, subject to a mix of user
and computer system constraints (milder time
constraints)
• We have a combination of the cases above, and
we need to address each of these characteristics
with the right architecture.
• Reactive systems have the following features:
• Concurrency
• Time Constraints
• Determinism
• Reliability
• Hardware/Software
Physical System
Computer
System
Actuators Sensors
Comms
Comms
010101010101
Environment
Output
Reactive
System
Input
Environment
Output
Interactive
System
InputInput
Output
User

5. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
Consequences of increased ICT
in Power System Operation
• Many processes in the power system are continuous, with local
control & protection systems
• Increased ICT will drive an evolution to understand power system
operation as a “hybrid system”:
• The virtual layer residing in a computer system(s) will enable new
functionalities.
• The functionalities will derive more events or discrete changes
(actions) for:
• Control, protection and optimization of the whole grid.
• Will make particular loops as reactive or interactive loops.
• Sampling and reconstruction will be needed at different sample
rates, and different granularity.
• Communication networks will transport measurements and
different types of control actions in digital telecommunication
networks (these may not follow physical laws derived from 1st
principles)
• A Smart Operation Control System is the heart into the evolution of
a high-level “hybrid system” from the operations perspective.
• One example of this transformation are synchrophasor-based
control systems that utilize remote input signals that require the
use of time-synchronized measurements, which are transferred via
communication links to a wide-area control system (WACS)
Physical System
Computer
System
Actuators Sensors
Comms
Comms
010101010101
Power System
Smart Operation
Control System
(for different tasks /
services)
Controllable
Devices
Sensors
(eg. PMUs)
CommsComms

6. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
PMU-Based Wide Area Control Systems
(challenges for design, implementation and operation)
• WACS includes an ICT platform that merges the input data
and transforms it to a useful input signal for active devices.
• WACS consists of
• (i) a number of synchronized phasor measurements units (PMUs – a
sort of GPS time-syncronized distributed sensor) from geographically
spread locations,
• (ii) a computer system termed phasor data concentrator (PDC),
• (iii) a real-time computer system where control functions are
implemented,
• (iv) a communication network, and
• (v) the power system dynamic process under control (i.e. wide-area
oscillations).
• WACS represent a true cyber-physical system that requires:
• Tools for design,
• Tools for simulation and
• Tools for hardware firmware deployment
for which technology today is not available in the power
systems domain.

7. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
Damping Controller WACS
(implemented at SmarTS-Lab)

8. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
Outline
• Cyber-Physical Systems
• Key Concepts from Hybrid Systems
• Key Characteristics of Hybrid Systems
• Consequences of increased ICT
• PMU-Based Wide Area Control Systems
• Damping Controller WACS
• Cyber-Physical Systems Modeling
• Systems Data Modeling
• Model Development
• CIM for model simulation
• Modelica Simulation Engine
Towards CIM-Compliant Model-Based Cyber-Physical
Power System Design and Simulation using Modelica

9. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
• Structural diagrams represent the
static behaviour of the system
• Object, attributes, operations and
relationships
• Class diagrams,
• Component diagrams,
• Unified Modeling Language (UML)
is a general purpose standard
modeling language
• Information model representing real
world objects
• Structured description of the
semantics of a set of information
• Information stored in XML file format
• UML is compatible with Object
Oriented software development
methods
• Behavioral diagrams represents
the dynamics of the system,
collaboration among objects
• Sequence diagrams,
• State diagrams,
• Activity diagrams
Systems Data Modeling
(uml)

10. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
• Common Information Model (CIM) is
conceived for information exchange:
power systems topology, equipment,
measurements
• Standardization of the model diagrams
for cyber-physical components,
• IEC61970 provides standard data model for
power systems components
• Components involved in the generation layer:
generators, turbine governors, etc
• Components involved in transmission and
distribution layer: capacitors, protections,
etc.
• Using UML representation to design a
structured data model: Semantic
transformation from real world to a
model
Systems Data Modeling
(CIM power systems)

11. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
• Modeling language
based on equations,
allow specification of
mathematical models
• Multi-Domain
modeling
• Visual Acausal
Hierarchical
Component Modeling
• Physical structure
• No data flow direction
• Typed Declarative
Equation-based
Textual Language
• Decopling of models
from solvers
model DCMotor
Modelica.Electrical.Analog.Basic.Resistor r1(R = 10);
Modelica.Electrical.Analog.Basic.Inductor i1;
Modelica.Electrical.Analog.Basic.EMF emf1;
Modelica.Mechanics.Rotational.Inertia load;
Modelica.Electrical.Analog.Basic.Ground g;
Modelica.Electrical.Analog.Sources.ConstantVoltage v;
equation
connect(DC.p,R.n);
connect(R.p,L.n);
connect(L.p,EM.n);
connect(EM.p,DC.n);
connect(DC.n,G.p);
connect(EM.flange_b,load.flange_a);
end DCMotor;
load
EM
DC
G
R L
Electrical
Mechanics
model GENROU
parameter Complex It=conj(S/VT) “Some comments here“;
parameter Complex Is = It + VT/Zs;
parameter Complex fpp = Zs*Is;
parameter Real ang_P=arg(fpp);
parameter Real ang_I=arg(It);
parameter Real ang_PI=ang_P-ang_I;
parameter Real psi = 'abs'(fpp);
equation
der(Epq) = (1/Tpd0)*(Efd0 -XadIfd);
der(Epd) = (1/Tpq0)*(-1)*(XaqIlq);
…
anglev =atan2(p.vi, p.vr);
Vt = sqrt(p.vr^2 + p.vi^2);
anglei =atan2(p.ii, p.ir);
I = sqrt(p.ii^2 + p.ir^2);
…
end GENROU;
Variable
declaration
DAE and ODE
Equations
Model Development
(modelica language)

12. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
• The FP7 iTESLA project
develops a high level
library for modeling power
grid components
• Generators,
• Governors,
• Controls,
• Branches,
• Loads,
• Buses,
• Events
• The library makes
available standardized
power systems models
usually available in power
system tools only
accessible through
proprietary (and
expensive) licenses
• E.g.: Model in
modelica
validated against
a PSSE model
Model Development
(power systems library)

13. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
• Modelica provides data definition
and compilers for equation based
modeling
• ModelicaML is a tool to create UML
definition for Modelica models
• Design of classes, components and
models using a data model
representation:
• Definition of start values for
components and definition of
mathematical equations
• Code generation creates classes and
models with relation between classes
• CIM and Modelica follow the
concept of Object Oriented
Programming,
• We use the CIM/UML
definition for generating
Modelica Code
CIM for Model Simulation
(uml for modelica)

14. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
• Automatic generation of Modelica code from CIM/UML
definition.
• Process Data flow
• Manual design of CIM/UML
definition and Mapping
• Loading CIM/XML and
Mapping
• Semantic transformation into
Modelica code:
• Set initial values from power
flow
• Set connection between
classes
• Simulation with Modelica
tools
• Mapping
• Relation between CIM classes and
Power system library classes
• CIM Attributes and values -> Modelica
Variables and starting values
• CIM relations between classes ->
Modelica connection between
components
or
• CIM relations between classes -> Use
of Modelica classes inside main class:
class instances
CIM for Model Simulation
(cim 2 modelica)

15. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
Modelica Simulation Engine
(simulation engine)Properties
Results
HDF5
JMOMC
PYTHON
JAVA
Dymola
• Open-source software for cyber-
physical system simulation
• Plug-in different compilers and
solvers

16. The 7th International Conference
on Real-Time Simulation Technologies
Montreal | 9-12 June, 2014
Thank you! Questions?
luigiv@kth.se , fragom@kth.se
Electric Power Systems Dept.
KTH
Stockholm, Sweden
Luigi.Vanfretti@statnett.no
svein.harald.olsen@statnett.no
Research and Development Division
Statnett SF
Oslo, Norway