| Frequency converter is combined product of power electronics technology, microelectronic technology and control technology.In modern electric drive system, inverter is very important control equipment, the working status of which controls the effect of the whole control system. The common converter core is mainly composed by the power unit and the control unit. To make sure stable operation of converter in the system, matching design for integral part of the inverter is needed. The bus board act as high-speed data transmission backplane is very important part of the inverter control unit. The CPU veneer, IT veneer, PWM generating veneer, the power supply board are all connected to the bus board, which is a digital signal between each board and the power supply of the shared channel. In practical applications, when the high-frequency digital signal is transmitted on the bus board, reflection and ringing make the bus board exceeds the safety threshold interference untimely and cause unforeseen logical errors. Therefore, the design and the use of the related technical means to eliminate the interference of the bus board the bus board plays a crucial role for the stable and reliable operation of the entire drive.This article describes the basic structure and type of inverter and introduces the history and the development of frequency control technology and applications of speed drives. High-speed digital signal transmission line effects on the bus board is analyzed to identify sensitive factors in the signal transmission process of reflection and ringing, aimed at multi-level series cell voltage source high voltage inverter. Calculating the required parameters of inhibition and improving the impedance matching parameter of the board on the bus to inhibit the reflection and ringing phenomenon.According to the number of boards which is connected to the high-voltage inverter control unit bus board as well as the actual work requirements, this paper compares a variety of commonly used topology to determine the basic structure and size of the bus board and the appropriate choice of PCB materials of the bus board. Bus board design is completed in accordance with the requirements of the signal transmission. In order to ensure stable and reliable operation of the bus board, impedance matching is used on numbers, address, and control bus to suppress the generation of reflection and ringing theoritically.Completed load test is carried out on the disigned bus board. In order to find the cause of the malfunction of the bus board, the most accurate process of elimination is utilized to analysis the failure phenomenon which is demonstrated in the experimentsthe, including adjust the software and hardware of the upper connecting plate in the bus. Eventually, this article finds the interfering signals present on the bus which influce the stable operation of the bus board and also identifies that the cause of the failure is improper transmission line impedance matching. Using the commonly method used in engineering to determine the re-transmission line characteristic impedance of the bus board and calculate the optimal matching resistor. The load experiment is carried out, after the matched resistors on the bus board are replaced.Through the improvement of bus plate impedance matching, which could greatly reduce the noise on the bus, make the system in long-running steady state and improve security and stability of the multilevel unit series voltage source type inverter. |
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