Variable frequency modulation method for inverter switching signal and OPWM inverter

Abstract

The invention relates to a variable frequency modulation method for an inverter switching signal. The method comprises the following steps: calculating a peak value of a variable frequency triangular carrier at each frequency value according to a modulation signal, and generating the variable frequency triangular carrier accordingly, calculating a corresponding instantaneous value of a digital modulation wave at each frequency value of the variable frequency triangular carrier according to an analog modulation wave and the peak value of the variable frequency triangular carrier, and generating the digital modulation wave accordingly; comparing the digital modulation wave with the variable frequency triangular carrier to generate a first switch control signal, negating the digital modulation wave, and comparing the negated digital modulation wave with a voltage value of the variable frequency triangular carrier to generate a second switch control signal; inputting the first and second switch control signals and first and second pulse signals to a driving circuit, controlling the on-off of an H bridge switching tube, and obtaining positive and negative current signals at both ends of a load; and repeating the above steps to obtain alternating current signals at both ends of the load. The variable frequency modulation method provided by the invention is used for inhibiting the electromagnetic interference of the output current signal of the inverter, so that the output current signal is closer to an ideal signal.

Description

technical field [0001] The invention relates to an electrical detection instrument in geophysical detection, in particular to an inverter switching signal frequency conversion modulation method and an OPWM inverter suitable for a time-domain electromagnetic transmitting circuit. Background technique [0002] The switching signal of the traditional PWM inverter is generated by comparing the fixed-frequency triangular carrier wave with the modulation wave, that is, the inverter works at a fixed carrier frequency. After being applied to the transmitter, the output current of the transmitter contains a phenomenon of large-amplitude harmonics. It will not only cause electromagnetic interference, but also increase the switching loss of the bridge power device, which has a certain gap with the ideal output current signal. In addition, some large-amplitude intermediate-frequency harmonic components in the current are likely to cause mechanical resonance and reduce system stability. ...

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Problems solved by technology

However, its research mainly focuses on the composition of the composite signal and the effect of the maximum frequency deviation of the composite signal on harmonic peak suppression, and does not give how to quantitatively design the maximum frequency deviation according to the required spectrum distribution and how to choose two periodic signals

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