Switching frequency modulation method of two-level H-bridge converter

Abstract

The invention discloses a switching frequency modulation method of a two-level H-bridge converter. The switching frequency modulation method comprises the steps of: determining a switching frequency total threshold interval [fmin, fmax] according to factors such as an output fundamental wave range of the converter, fundamental wave modulation control precision, system efficiency and the loss of a power device; determining the minimum value fN3 of the required switching frequency by integrating a phase current ripple current effective value limit, a peak value limit and a weighting factor; determining a switching frequency real-time limit range [fmin-N, fmax-N] meeting requirements according to the switching frequency minimum value fN3 and the total threshold interval [fmin, fmax]; and within the real-time limit range [fmin-N, fmax-N] of the switching frequency, carrying out randomized selection of the switching frequency by using a random factor delta random, and finally, acting the updated switching frequency on pulse width modulation of the two-level H-bridge converter. By adopting the switching frequency modulation method, the electromagnetic compatibility and the vibration noise performance of the converter can be improved.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to a switching frequency modulation method of a two-level H-bridge converter. Background technique [0002] Compared with the two-level three-phase full-bridge main circuit structure, the two-level H-bridge converter topology can improve the utilization rate of the power supply voltage and help realize the application of electric propulsion in high-power fields such as ships and rail transit. For a long time, when performing pulse width modulation of a two-level H-bridge converter, the switching frequency is usually set to a certain fixed value. Although the fixed switching frequency will simplify the design of the output filter of the converter, it will lead to the concentration of the harmonic energy of the output switching frequency of the converter, increase the noise of high-frequency electromagnetic interference, and cause high-frequency vibration noise. ...

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Problems solved by technology

[0007] 1. Limited by factors such as modulation control accuracy, system efficiency, and power device temperature rise, the switching frequency cannot be adaptively modulated without limit, and needs to be limited within a certain threshold range

[0008] 2. The peak value and effective value of the ripple current correspond to the electromagnetic compatibility and vibration and noise characteristics of the current transformer respectively. The existing modulation method determines the switching frequency according to a single index, and does not realize the multi-objective optimal control of the switching frequency

[0009] 3. The existing modulation method is essentially based on the given voltage, by calculating the pulse vector and action time, and then predicting and controlling the peak value or effective value of the ripple current; observing from the frequency dimension of the fundamental wave output by the converter, the interval of the fundamental wave period The given voltage is the same, which means that the switching frequency calculated by the existing modulation method will repeat at the fundamental frequency, and the randomization of the switching frequency has not been realized; the regular change of the switching frequency will cause the converter to generate new Vibration noise and electromagnetic compatibility problems, which violates the original intention of the switching frequency modulation method

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