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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 46672 (05)
- University: Sharif University Technology
- Department: Electrical Engineering
- Advisor(s): Oraee Mirzamani, Hashem
- Abstract:
- Because of environmental problems of fossil fuel energies and the rise in petroleum products, the tendencies to the renewable sources like wind power and solar power have been increased. In some particular applications like electric vehicles, satellites power system and all stand-alone unites that are using solar and wind powers are the only solutions. On the other hand, because of intermittent behavior of renewable sources, use of back-up supplies e.g. batteries are necessary to make a balance in power consumptions and productions. To interface between different ports some independent two port converters are used in traditional techniques. Multiport converters, used in multi-input/multi-output power electronic systems, have low cost, low weight, low mass integrated control system. Besides these converters offer bidirectional and isolated ports, which are inevitable in some applications. TPHBCs are the ones which have the lowest component count. But these converters suffer from a low ZVS range that is lost in medium to low load powers, besides asymmetric characteristic of these converters lead to high transformer magnetizing DC current. Low ZVS range and high DC current cause low efficiency, especially in low output powers.
In this thesis a modified pulse width modulation technique is introduced to increase the ZVS range of main switches which results higher efficiency and lifetime of the converter. A new method based on converter DC characteristics and control techniques is introduced to eliminate DC bias current of the transformer. A reduction in the DC bias current would change some other parameters like ZVS, which is studied in detail. To have better control over the output parameters like output voltage, first and second port voltage and magnetizing current a good dynamic model of control object should be obtained, therefore state-space averaging model is applied. The interference of control loops is compensated with a decoupling network that is used as a pre compensator. Different control strategies are implemented, such as to achieve maximum power from solar/wind port, to maintain battery port voltage in a specific range, to limit transformer's DC off-set current and to regulate output voltage. All above-mentioned predictions are validated with simulations - Keywords:
- Pulse Width Modulation (PWM) ; Zero Voltage Switching (ZVS) ; Multi-Port Converter (MPC) ; Transformer Dc-Offset Current ; Three Port Half Bridge Converter with Primary Freewheeling (TPHBC-PF)
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