Distributed Modular Controller Architecture for High Power Converter Applications

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Title: Distributed Modular Controller Architecture for High Power Converter Applications
Author: Liu, Wei
Advisors: Alex Q. Huang, Committee Chair
Mesut Baran, Committee Member
Maysam Ghovanloo, Committee Member
Abstract: Modular converter is of particular interest in high power applications in order to achieve higher level of flexibility, expandability and reliability. Power electronics building block(PEBB) and H-bridge building block(HBBB) are typical modular blocks proposed for this applications. However, for converters based on the modular converter concept, the conventional controller is still not modular. The controller typically only has one single central control unit. The central controller has direct connections with each modular converter. When the controller and the power converters are placed close to each other, there will not be problem to do so despite a lot of wire connections. For high voltage and power rating converters, it is true that the power converters will consist of many modular blocks and these blocks will be placed at some distance from the controller. In this case, digital switch signals must be sent to the converters via optical fiber to improve reliability. However, the required fiber connections are too many that increase the risk of fault. Moreover, the analog signals from the sensors such as the voltage and current are usually sending back to the central controller through analog wire connections that has low electromagnetic interference (EMI) susceptibility. To solve the problems mentioned above for a high power converter system that may have multiple modular converter units, a modular controller architecture is needed and this concept is starting to be accepted specially if the system is constructed with modular converters. In this thesis, the proposed modular controller architecture includes a central controller and distributed local controllers. Each modular converter is accompanying with a local controller. The central controller performs the main control loop calculation and then sends the control commands to the local controllers. The central controller and the local controllers are communicated based on defined protocol via optical fibers. Then, the local controllers decode the command and generate the gate signals to the converter. Also, the local controllers have the function to convert analog information to digital such as voltages and currents and then feed back them to the central controller via optical fibers. The communication between the central controller and each local controller requires only two optical fibers. This largely increases the system reliability and also the flexibility to expand the system to higher power rating.
Date: 2005-12-28
Degree: MS
Discipline: Electrical Engineering
URI: http://www.lib.ncsu.edu/resolver/1840.16/1772

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