A Sawtooth Carrier PWM Modulation Method for Symmetrical Odd Phase Two-Level Inverter

Abstract

The invention discloses a sawtooth carrier PWM modulation method for a symmetric odd phase two-level inverter. The method comprises steps that phase modulation signals are divided into odd and even arrays, two sets of sawtooth carriers are determined for the phases based on grouping of the phases, a first set of carriers and a second set of carriers of a kth phase are alternately utilized, pulse width modulation is performed with kth phase modulation signals, further, a phase bridge arm power switch control signal is obtained, a driving signal of a power switch tube is generated, in this way,suppression of the symmetric odd phase two-level inverter CMV is achieved. The method is advantaged in that through switching between mirrored symmetric sawtooth carriers, the range of the sum of allthe phase switching states during one carrier cycle is reduced, moreover, through overlapping of straight edges of the sawtooth carriers of the phases, the change frequency of the sum of all the phaseswitching states is alleviated, and a purpose of reducing the amplitude and the frequency of the CMV is achieved.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and more specifically relates to a sawtooth carrier PWM modulation method for a symmetrical odd-phase two-level inverter. Background technique [0002] Compared with the traditional three-phase transmission system, the multi-phase transmission system has the advantages of high reliability, flexible control, and small torque ripple. The multi-phase motor system powered by the multi-phase inverter has become a hot research field at home and abroad in recent years. . In addition, due to the simple topology, high reliability, and convenient control of the traditional two-level inverter, the multi-phase motor drive control mostly uses this topology. The common mode voltage (CMV, Common Mode Voltage) is a typical side effect of the pulse width modulation (PWM, Pulse WidthModulation) inverter drive system. The high amplitude and high frequency CMV will not only corrode the generator bearing, ...

AI Technical Summary

Problems solved by technology

Most of the existing software solutions use the improved voltage space vector pulse width modulation method, and the effect of reducing CMV is achieved by selecting a voltage space vector whose output is very low or even zero. However, this method needs to consider the influence of the voltage vector on multiple sub-sectors , so that the computational burden of the method grows exponentially with the number of phases

For multi-phase multi-level inverters, there is a general CMV suppression space vector pulse width modulation (SVPWM, Space Vector Pulse Width Modulation) technology that simplifies the computational complexity, but it is not suitable for the most common two-level inverter device

There are also some software solutions that use carrier-based pulse width modulation (CPWM, Carrier-Based Pulse Width Modulation) method, which is independent of the number of phases and is more suitable for multi-phase occasions. Existing solutions mostly use triangular carrier waves with uniform phase lag, which can CMV is completely eliminated in even-phase symmetric inverters, however, for odd-phase inverters, as the modulation ratio increases, the CMV suppression effect will be weakened, and the frequency of CMV cannot be suppressed

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