Simplified phase-voltage reconstruction method of three-level converter

Abstract

The invention provides a simplified phase-voltage reconstruction method of a three-level converter which is applicable to the converter using a three-level topological structure. The converter can supply power for a squirrel-cage motor speed governing system, a winding motor double-fed speed governing system and a synchronous motor speed governing system. The operating method of the three-level converter comprises the following steps: dividing a vector space output by the traditional three-level converter into six small hexagons, and then carrying out corresponding output phase-voltage reconstruction algorithms in the small hexagons; and finally achieving the purpose of three-level calculation by coordinate translation and compensation amount calculation. The algorithm is relatively simple, the obtained results can fully replace the results obtained by using an output sensor, and the results are more accurate than the results obtained by directly using a SVPWM command. The method simplifies system composition and improves reliability and stability of the system.

Description

Technical field [0001] The invention relates to a simplified phase voltage reconstruction method for a three-level frequency converter, which is suitable for squirrel cage motors, winding motors and synchronous motors powered by a three-level frequency converter. Background technique [0002] In a three-level high-performance motor vector control system, the accuracy of the output phase voltage has a great impact on the performance of the system. At present, there are two traditional methods, one is to use the output voltage sensor to sample into the control system through AD. The second is to directly use the SVPWM command as the actual output phase voltage. [0003] For the first method, the number of corresponding AD channels must be increased while increasing the sensor, and the output voltage of the three-level inverter is a step wave. The value obtained by the usual instantaneous sampling A / D converter is not the actual waveform. The average value in a switching period cann...

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Problems solved by technology

[0003] For the first method, it is necessary to increase the number of corresponding AD channels while adding sensors, and the output voltage of the three-level inverter is a ladder wave, and the value collected by the usual instantaneous sampling A / D converter is not the actual waveform. The average value in a switching cycle cannot truly reflect the size of the output voltage in this switching cycle

For the second method, the narrow pulse problem is the source of its inaccuracy, because not all outputs are exactly the same as the SVPWM command given, especially in the low-speed and high-speed sections of the motor, the narrow pulse problem is more serious

[0004] At the same time, since the three-level output level is half more than that of the two-level topology, and the output voltage vector is three times that of the two-level, if the output voltage sequence is directly passed, the main vector, zero vector and sub-vector are added respectively. It is very difficult to calculate the time

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