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Real Time Simulation |
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In a Power Electronic system, three primary challenges are the hardware implementation of a switching matrix, the software problem of deciding how to operate that matrix, and the interface problem of removing unwanted distortion and providing the user with the desired clean power source. Improvements in devices and advances in control concepts have led to steady improvements in Power Electronic circuits and systems. It is predicted that, during next few years, almost all of the electrical energy will be processed through Power Electronics somewhere in the path from generation to end-use.
The greater efficiency and stringent control features of Power Electronics are becoming attractive for applications in motion control by replacing the earlier electromechanical and electronic systems. Applications in power transmission include HVDC converter stations, Flexible AC Transmission Systems (FACTS) and Static VAR compensators. In power distribution, the applications include DC-DC conversion, Dynamic filters, Frequency conversion, and Custom Power Devices.
The need for sophisticated and reliable power converting equipments become essential to meet the above requirement in the coming years. Testing and calibration of power converters largely depend on how closely we create the actual transient conditions during lab testing which is very difficult and practically impossible in many cases. Some typical cases are that of high power systems like FACTS devices, Custom Power Devices, AC/DC motor drives etc. These systems cannot be tested at full power rating in the labs, and the performance in the site will depend on many external factors like grid conditions, load characteristics etc. In many installations of AC motor drives, we come across resonance and other abnormal conditions. These situations can be avoided to a large extent by carrying out simulation of the systems in the development phase. |
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Why SEQUEL? |
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SEQUEL for Power Electronics & Power Systems
Simulation is an extremely valuable tool for designing, operating and understanding complex systems such as those frequently encountered in Power Systems and Power Electronics.
Broadly, simulation can be of two types: (a) Off-line simulation on a digital computer or workstation and (b) Real-time simulation with the help of dedicated high-speed digital processing hardware.
Off-line simulation, generally carried out with standard software packages such as Simulink, SABER etc, allows flexibility in analyzing a wide variety of components and systems. Commercial simulators that are powerful enough to tackle complex problems are expensive in the Indian context. Further, they come with a limited number of licenses. Also, component libraries in these simulators are encrypted, and so are not available to the user for viewing or modification. Updates and support services are also costly. It would be desirable to have an indigenously developed system that provides both off-line and real-time simulation capabilities at an affordable cost.
Background
Work has been going on in recent years in several institutions in India in both real-time and off-line simulation. At IIT Bombay, a software package called SEQUEL (Solver for circuit EQuations with User-defined ELements) has been developed that enables off-line simulation of a variety of systems. The circuit simulator SEQUEL is at a fairly advanced stage and has been used for several applications such as Power Electronics, Power Systems, electronic circuits, biomedical problems, switched-capacitor circuits, MEMS (Micro Electro Mechanical Systems) etc. Several students have been using SEQUEL for Power Electronics courses at IIT-B. It is also being used for research and industrial consultancy. Other academic institutes have considerable expertise in simulating Power Electronic systems using the currently available packages.
Through this Club it is proposed to build up on these capabilities at various Institutes to develop an integrated system to carry out off-line simulation. Such a platform is expected to be highly beneficial to a large number of industries, R&D labs and academic institutions. |
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SEQUEL |
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Figure shows the layout of the off-line SEQUEL circuit simulator as it exists currently. The SEQUEL preprocessor picks out the library templates that are required for simulating the circuit described in the user’s circuit file and prepares the associated element subroutines. These subroutines are linked together with the SEQUEL main program to generate the executable file. After execution, data files are generated as requested by the user, and the user can then plot the quantities of interest using an appropriate plotting program. Users can incorporate new circuit elements in the element libraries, and thus enhance the libraries.
However, in an off-line simulator there is no correlation between the simulation time and the physical time; generally, the simulation time is much larger. On the other hand, real-time simulation, as the name suggests, allows analysis of a physical system in real time (i.e., the physical time and the simulation time are the same). This helps greatly in conducting "hardware in the loop" simulation and evaluation of control hardware and software. Both off-line and real-time simulation tools are a major aid for Power Systems and Power Electronics related development activities.
In power systems, real time simulation is traditionally carried out either by using analog simulation or real time digital simulation. The idea is to build an off-line simulation package and a real time simulator for Power Electronics with libraries and application software development in SEQUEL |
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Uniprocessor Board |
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This DSP board is centered around the Texas Instruments 32-bit floating point DSP TMS320VC33. The figure
above shows the component layout of the board. This document describes the board usage. It also describes the USB based command-line program download and debugging interface. This interface consists of a host
communication program ubsl, which resides on the host computer. This board is primarily meant to be a tool for the teaching and learning of real-time computation concepts on
the TMS320VC33 DSP. In addition it can have the following uses.
• Firmware development for the Texas Instruments TUSB3210
USB peripheral controller.
• Software development for the MSP430F168 microcontroller.
• Limited closed-loop control board with six ADC inputs
and two DAC outputs.
The control system may be
implemented on the TMS320VC33 DSP, and the ADC/DAC implementation may be on the MSP430F168 microcontroller. This functionality will require drivers to be written to control the ADC/DAC on the
microcontroller, and the data communication between the microcontroller and the DSP. This document does not detail these three uses. It describes the board’s use for real-time computation.
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