Development of a Knowledge-Based System for Power Electronics Design

Various simulation packages are being widely used to design and simulate electrical and electronic circuits. These simulators require the user to be proficient in designing the circuits and need deep training to be familiar with. Moreover, the design is based on trial and error, till the user reaches the required outputs. Despite their long use, the existing general-purpose simulation packages are still time-consuming when they are used to design power converters especially for inexperienced designers. This is because of the ad-hoc nature of the design task. An approach to overcome the drawbacks of these packages and augment their functionality is to incorporate knowledge-based techniques along with these packages. In the present work an approach to automate the design process of power converters is introduced, explained, and implemented. The presented approach integrates object-oriented paradigm within expert system techniques to develop a user-friendly tool; power electronic converters design aid system (PEDAS). Benefiting from the class builder provided in Visual Basic programming language, various class modules with their properties and methods were implemented to constitute the inference engine and represent the knowledge base. Two types of knowledge were investigated; application-based knowledge which was implemented using fourteen (14) classes and subclasses and type based knowledge which was represented by one class having eleven (11) methods. Each topology was represented by either one subclass for the first type or one method for the second type. Additionally, the tool offers an automatic selection of switching devices for a specific converter topology. The selection process is conducted within a switching devices database built for this purpose. Further, this database can be seen as an independent unit where many functions such as searching for or adding, removing devices are provided. In using this tool, the designer has firstly to choose the appropriate application of his/her converter among a given list of applications. Then he/she has to pursue interaction process to input his/her requirements and answer some questions needed for facts insertion in order to come out with the most appropriate topology that meets the entered specifications. The topology suggested for the user is formed in a schematic file accepted by the Pspice simulation package. The topology is then displayed within Schematic environment containing all the circuit parameters including the best (optimum) switching devices and the control circuit. The switching devices are stored in database module accessed by the inference engine to select the optimum switch for a certain topology. General description of the system is presented, its architecture and interaction between its various modules is dealt with in details. Finally, the issue of validating the developed tool is accomplished through many design examples, both software and hardware. The developed system still can be improved, mainly in expanding its knowledge base in its two parts; converter topologies and switching devices.

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