Pulse width modulation frequency variable power supply and dead zone compensation method thereof

Abstract

The invention relates to a pulse width modulation frequency variable power supply and a dead zone compensation method thereof. In the technical scheme, a comparison point level is arranged at the positive and negative semi-periods of a phase current respectively. When an output phase voltage reaches a predetermined value, a feedback signal level actuates to obtain a required compensation amount. The time of the positive and negative semi-periods of the phase current is determined by sampling the phase current, and the comparison point is switched around the positive and negative peaks of the phase current. The method has the following advantages that: the zero-crossing clamping problem of current can be effectively solved and the width of an output pulse can be precisely measured so as to precisely regulate the on / off time of an upper and a lower bridge arm power switching device in an inverter circuit; therefore, a desired output pulse width is obtained, and a current waveform sine degree and a control effect are improved.

Description

technical field [0001] The present invention relates to variable frequency power supply, more specifically, to dead zone compensation of pulse width modulation variable frequency power supply. Background technique [0002] Most voltage source variable frequency power supplies use PWM (Pulse Width Modulation) wave generation technology. Its main circuit topology is: through rectification and capacitor filtering to obtain a DC voltage, and then through the inverter circuit to generate pulse output with adjustable frequency and voltage. For the inverter circuit, each phase of its circuit is composed of two power switching devices with freewheeling diodes connected in series. It is usually called the upper bridge arm connected to the positive pole of the DC power supply, and the lower bridge arm connected to the negative pole. The switching of the power switching device takes a certain amount of time. Therefore, in this topology, in order to avoid the simultaneous conduction of...

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Problems solved by technology

[0012] The technical problem to be solved by the present invention is that for the pulse width modulation variable frequency power supply controlled by directly sampling the pulse width of the output voltage in the prior art, when the current in the switching device is very small, the defect that the actual turn-on time of the power switching device cannot be accurately measured, Provide a pulse width modulation variable frequency power supply, which accurately measures the width of the output pulse by setting two comparison points, and then controls the on / off time of the power switching device to obtain the desired output pulse width

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