Research And Development Of Monitoring And Control System For The Modular Multilevel Converter

In recent years, modular multilevel converter(MMC) has made great application in PET, HVDC, FACTS and other fields because of its unique performance, so it is the preferred solution for high voltage power conversion. In the high voltage power system, there are large and expensive components, in addition, it requires a high level of power grid automation. Therefore, the monitoring and control system for MMC is selected to be studied in this thesis after analyzing the structure, characteristics and needs of MMC. The system can monitor MMC during its operation, and ensure safe and reliable operation of MMC.This thesis focuses on the design of the system by using multithreading technology, modularization idea and so on, mainly completes the work in the following areas:1) This thesis analyzes the current research status of the monitoring and control system and its limitations, then proposes the design ideas of this thesis.2) Based on the deep study of MMC experimental platform, this thesis describes the functional and non-functional requirements of the monitoring and control system, and introduces the serial communication protocol.3) Hardware design of the monitoring and control system is worked out in this thesis, including IGBT main circuit, DSP+FPGA control circuit and data acquisition circuit.4) This thesis designes and implements the software part of the monitoring and control system deeply, including the design of DSP software, FPGA software, harmonic analysis algorithm and upper computer software. The design of DSP software focuses on the implementation of serial communication of DSP; Based on CPS-SPWM modulation strategy, the design of FPGA software implements the PWM pulse generating; Then, the thesis studies several harmonic analysis algorithm deeply and verifies the conclusion of comparison by Matlab simulation; The design of upper computer software describes the process of serial communication of PC.5) A friendly interactive interface is designed and developed by using Visual C++ software of Microsoft corporation. It can display operating status of multilevel converter experimental platform and control the converter in time. In addition, it provides fault information display, event log analysis, power quality analysis and other functions. Based on the aboved functions, it can improve the reliability, safety and the level of automation of experimental platform, then reduce its operating costs.Finally, the overall function of the monitoring and control system is verified by using modular multilevel converter experimental platform. The result shows that the converter can output good waveforms, harmonic content of the output waveforms is consistent with the theoretical analysis, and other functions of the system meet the design requirements basically.