Third Level Of The Key Technologies For High-power Medium Voltage Inverter

In recent years, with industrial development, a lot of high-voltage high-power AC variable speed equipments were used in industrial production occasions. Compared to the two-level inverter, the three-level inverter has low output voltage harmonics, high-level output voltage, output voltage closer to the sine wave, to meet the characteristics of medium voltage high power output, while optimizing run process and ncreasing productivity, been used in medium voltage high-power AC Speed occasions. So it was widely used in high voltage high power occasions. Therefore, the research on the three-level inverter has great significance. This subject researched a number of key technologies on the diode clamped three-level inverter. The major contents are as follows.Three-level inverter as one multi-level inverter was widely used in high voltage high power occasions. However, the increase in power devices, improve the system's failure rate, therefore, how to ensure stable operation of the system will become an important research question. For the three-level high-power inverter, through theoretical analysis and simulation, detailed analysis of the main circuit power device's working status and typical faults characters in the open circuit fault, and summarized the fault diagnosis rules. According to the fault diagnosis rules user can well determine the typical inverter faults. The judgment of fault types provides the basis of troubleshooting and analysis.The neutral point imbalance is there-level inverter inherent problems. Based on unipolar double-carrier SPWM modulation method, the three-level neutral point imbalance is theoretically analyzed, and analyzed of the impaction of each vector on the neutral point potential. According to the impaction of each vector on the neutral point potential, based on zero sequence voltage injection principle, the subject proposes a simple neutral point voltage balance control method and gives the choice principal of zero-sequence voltage. This approach helps to solve the three-level Neutral Point Potential imbalances, and experiment and simulation results demonstrated the effectiveness of the method.In order to improve operation and friendly interface, based on MODBUS protocol real-time communication between touch screen and three-level inverter achieved.Using C language MODBUS communication program was written, and according to the selected touch-screen interface control program prepared. Through the touch screen can be well controlled inverter operation status, change operating parameters and reflect the working status of inverter in real time. In order to verify the above results, the paper designed and builded a 690V/630kW three-phase diode clamped three-level inverter experimental platform, and given the method of choice main circuit device.Finally, based on this three-level platform experiments for the content of the research conducted the confirmatory test. Related experimental results demonstrate the correctness and validity of research findings.