Unit modulation degree control method of variable-frequency speed regulation inverter and application of method

Abstract

The invention provides a unit modulation degree control method for a variable frequency speed regulation inverter. The unit modulation degree control method comprises the following steps of: modulation degree unitization by obtaining a target phase voltage component, determining a control pulse duty ratio of a direct-current bus voltage reduction circuit, limiting the amplitude of the duty ratio of the control pulse and generating a step-down circuit driving pulse according to the duty ratio obtained after amplitude limiting; dead zone induced phase shift calculation by determining an expectedoutput voltage frequency of the inverter, determining dead time of the inverter, and obtaining expected output voltage fundamental wave leading phase shift caused by a dead zone; and fundamental wavephase shift compensation by obtaining a target phase voltage component polar coordinate form, rewriting a target phase voltage component phase, and calling an SVPWM or SPWM program in the permanent magnet synchronous motor control program to generate an inverter driving signal to control the permanent magnet synchronous motor. According to the method, perfect phase control is realized, accurate measurement of the position of the PMSM rotor is facilitated, the steps are simplified, the logic is clear, and the control precision of the PMSM can be improved.

Description

technical field [0001] The invention relates to the technical field of frequency conversion and speed regulation, in particular to a method for controlling the unit modulation degree of a frequency conversion and speed regulation inverter and its application, which is used for precise power supply of frequency converters. Background technique [0002] The post-stage circuit of the frequency conversion speed control inverter is a voltage source inverter, which is widely used in industrial frequency conversion speed control, frequency conversion household appliances and other application fields. As a voltage source inverter (VSI) powered by DC voltage, the same bridge When the working state of the upper and lower power switches is switched, it is necessary to set a long enough dead time to prevent the short circuit of the DC power supply caused by the direct connection of the bridge arm and cause the power switch to be damaged by overcurrent. [0003] The addition of dead time...

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Problems solved by technology

[0003] The addition of dead time will cause some problems that deviate from the ideal modulation. So far, the main concerns of people are: (1) Under the same modulation degree, the effective value of the fundamental wave of the output phase voltage (or line voltage) drops, that is, the maximum voltage The utilization rate decreases; (2) The output phase voltage (line voltage) is distorted according to the average value of the switching cycle, that is, the actual output fundamental phase voltage (or line voltage) is distorted, causing motor current distortion and torque ripple;

But up to the present, also do not appear above-mentioned corresponding compensation method, also do not find explanation or report with similar technology of the present invention, and similar data both at home and abroad

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