| Distributed power generation systems make good use of the energy from the distributed energy systems by converting all kinds of the energy into the electricity, and it has become one of the most efficient ways for the energy conversion. Distributed Generation (DG) raises more and more concerns by its environmental and economical efficiencies with the increasing percentage of the DG systems in power systems, and it would have great influence on the power system. In this case, it is of great significance to use safe excitation control systems that are flexible in operation mode switches. This paper designs a new excitation system based on the modern power electronic technology to satisfy such requirements, and makes inner research to the designed system.Firstly, this paper makes a deep research into the DC-DC converter and its control, and then designs a new excitation system based on the uncontrolled rectifier and the DC-DC converter. After that, PID control is taken into the system and we adopt PWM to realize the flexible excitation control in certain operation modes by regulating the duty cycle of the IGBT.Secondly, according to the excitation system designed in this paper, we set up a model in PSCAD, and test the characteristics by making a comparison with the traditional self-shunt excitation system.Finally, we set up a model for the governing system in PSCAD. Taking the effects of the governor into consideration, this paper simulates the excitation starting and the load operation. The last part is about synchronization and we analyze the static stability of the single-machine infinite bus system by small-signal analysis.This paper verifies the effectiveness of the new excitation system based on the theory of chopper by general testing. The excitation system would take good advantage of its characteristics about safe operation and flexible operation mode switches. In this way, it would play an important role in distributed power generation systems in the near future. |
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