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New Power System Blockset Enables You to Model Electrical Power Systems
Simulink moves into the realm of topological modeling
By Paul Barnard
The MathWorks has just introduced the Power System Blockset (This product has been renamed to SimPowerSystems) to the modeling environment of Simulink. The Power System Blockset provides tools for modeling and simulating electrical power systems within Simulink using the standard notations for electrical circuits. Its block library contains blocks that represent standard components found in electrical power networks. You can now easily incorporate electrical systems and controllers into your complex system models.
The Power System Blockset in action
Consider for a moment the following scenario:
You are an automotive engineer working on an idle-speed control algorithm for a new vehicle. In the past, you have worked on conventional cars that had only nominal electrical loads placed on them through the alternator. This time, things are different. A major marketing shift has focused the company's vehicle line on teenagers and young adults. Now the electrical systems group is asking you to design an engine that will idle well while powering 2000 watt speakers in the back seat of the car!
This is a problem. What are the electrical transients? How well will the engine idle with the steady-state electrical load caused by a blasting CD player?
This may be an amusing story, but it is not entirely unrealistic. As automobile systems become more and more dependent on electricity, the demands for electrical power increase. The quality and reliability of that power will become more important, too. Consequently, it is no longer acceptable for engineers developing the electrical systems to be out of touch with the engineers working on the idle-speed control, for example. The Power System Blockset can help to bridge the gap in the development process between electrical and control system design, using Simulink as the common interface.
Below is a Simulink diagram representing the outcome of our story. It shows how the Simulink model for an automotive engine can be conveniently connected to a model of the electrical subsystems. Together, these subsystems form a more complete model that can help solve control and system design problems through simulation early in the development cycle.
Scenarios like these occur in many complex systems. Power utility distribution networks and self-contained power systems for ships, automobiles, aircraft, and spacecraft often include sophisticated electrical subsystems. These subsystems contain combinations of electrical circuits, as well as electromechanical devices like motors and generators. The Power System Blockset gives power systems engineers a highly efficient and intuitive environment in which to simulate and analyze complex power systems.
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| A Simulink model of an automotive engine driving an alternator that is powering various electrical loads modeled with the Power System Blockset. |
Sophisticated blocks manage diagram interpretation
The blocks in the Power System Blockset provide methods that interpret diagram connectivity in a topological manner. This capability allows you to model electrical systems without worrying about the directionality of signals and currents. You can create electrical Simulink diagrams on the computer just as you would on paper.
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| A Power System Blockset model of a motor-generator uninterruptable power supply (UPS). Using two machines connected together, this system models the mechanical and electrical transients following the fault and isolation of the motor/generator system (Click on the diagram for a larger view). |
Simulate it
The Power System Blockset is completely integrated with Simulink at the block level. Combining Power System and other Simulink blocks creates a unique environment for multidomain modeling and controller design. This environment allows the combination of electrical, power-electronic, mechanical, hydraulic, and other systems models.
For time-domain simulation, the Power System Blockset takes advantage of Simulink's powerful variable-step integrators and zero-crossing detection capabilities to produce highly accurate simulations of power system models. In addition, you have access to all of the block building and masking features, allowing you to build more complex components from electrical primitives.
Powerful analysis methods at your fingertips
The new blockset contains features that allow you to specifically analyze the electrical portions of your Simulink model. You can extract the linear portions of the electrical model into the MATLAB workspace as a state-space system for further analysis. This capability is useful if, for example, you want to examine the impedance frequency characteristics of your system.
You can work with the electrical state-space system using any of the tools from The MathWorks. If you are developing a control system for an electrical subsystem, for example, you can use one of the Control System Toolboxes to design controllers around the plant model you have extracted from the Simulink diagram.
The blockset also provides a GUI that allows you to interact directly with the blocks and states of the electrical system. You can set the state variables of the electrical system through the GUI. For example, you may want to set the states of the system (voltages or currents) to simulate some transients. The GUI also provides the steady-state values of voltage and current so that you can return to a steady-state simulation easily for other types of analysis.
Finally, to aid in working with the blockset library of machines and drives, the Power System Blockset provides a function that performs load flow analysis. Load flow analysis is done to balance the electrical and mechanical loads between machines in your model.
Conclusion
Whether you are a systems engineer working on a controller interfacing with electrical subsystems or a power utilities engineer designing a fault-tolerant power distribution network, you can now make use of the powerful Simulink environment. By using the Power System Blockset, you reach into the electrical domain with all the ease of use and extensibility of open systems that you have come to expect of tools from The MathWorks.
About the authors
TEQSIM International and The MathWorks developed the Power System Blockset. TEQSIM International is a company created by Hydro-Québec to market the Power System technologies developed by the Hydro-Québec Research Institute (IREQ).
The Power System Blockset includes blocks modeling for the following areas:
Power system networks- RLC branches and loads
- Pi section lines
- Linear and saturable transformers/td
- Surge arresters
- Breakers
- Mutual inductances
- Distributed parameter lines
- AC voltage and current source
- DC voltage sources
- Complete and simplified models of synchronous machines
- Asynchronous machines
- Permanent magnet synchronous machines
- Excitation systems
- Hydraulic turbines
- Governors
- Diodes
- Simplified and complex thyristors
- GTOs
- Switches
- MOSFETs
- Voltage and current measurements
- RMS measurements
- Active power calculations
- Timers
- Synchronized 6-pulse generators
- Triphase loads and branches
- Pi section lines
- AC voltage sources
- 6-pulse thyristor bridges
- Diode rectifiers
- Triphase transformers in Y-delta, Y-Y, and delta-Y configurations
