A switching cycle optimization space vector pulse width modulation method and modulator

Abstract

The invention discloses a switching period optimizing space vector pulse width modulation method and a modulator. Average switching frequency is controlled through time windows of width adaptive regulation, and the switching periods in different time windows are mutually independent; switching periods in the same time window are correlated, optimizing rules between the switching periods by means of the time windows, switching period coefficients, modulation rates and phase angles control the switching periods, peak values of cluster harmonic waves in SVPWM can be significantly reduced, total harmonic distortion is greatly reduced, and the quality of output voltage is improved. The average switching frequency is controlled through the time windows of the width adaptive regulation, frequency ranges of a power switch tube is sufficiently utilized, and cost performance of a variable frequency system is improved. The modulator can sufficiently utilize flexible circuit customization characteristics of an FPGA, and integrates other circuits and algorithms of a speed regulating system into one FPGA; the speed for controlling software execution is improved, and guarantee is provided for application of the modulator in the variable-frequency speed control system.

Description

technical field [0001] The invention belongs to the technical field of AC frequency conversion, and in particular relates to a switching period optimization space vector pulse width modulation method and a modulator capable of reducing harmonic distortion and cluster harmonic peak values. Background technique [0002] Such as figure 1 The shown two-level three-phase inverter and space vector PWM (SVPWM) are widely used in various aspects of industrial and agricultural production. SVPWM is based on the basic principle of "volt-second balance", which uses voltage pulses with continuously changing widths to equivalent command voltages required, so harmonics are inevitable. Harmonics cause energy loss and cause motor heating; low-frequency harmonics can also cause torque ripple, which in turn leads to mechanical vibration; steep pulses can also cause serious electromagnetic interference, affecting the normal operation of other electronic equipment. [0003] In response to the ...

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Problems solved by technology

[0007] However, in the motor closed-loop control system, such as the vector control system of electric vehicle electric drive, because the command torque changes continuously with the throttle, the command voltage vector output by the controller changes continuously, and the command voltage vector no longer rotates at a constant speed with equal amplitude

At this time, the three-phase command voltage is no longer a sine wave, which causes the average switching frequency of the power tube (such as IGBT) to be uncontrollable

If the switching frequency is too high, the power tube may be burned; if the switching frequency is too low, the switching frequency that can be used to reduce harmonics cannot be fully utilized

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