Three-level wave-by-wave current limiting control method and system

Abstract

The invention provides a three-level wave-by-wave current limiting control method and system. The method comprises the steps that when the detected first-phase current of a main power switch tube in each phase of an inverter reaches a preset first current threshold value, the main power switch tubes of the phases where the first-phase currents are located are regarded as main power switch tubes to be processed; outer main power switch tubes in the main power switch tubes to be processed are controlled to be switched off till it is detected that the first-phase currents in the corresponding phases are smaller than the preset first current threshold value; according to comparison between the number, obtained through statistics, of the first jump edges of PWM signals detected in the overcurrent period and a preset value, an appropriate time is determined for controlling the outer main power switch tubes in the main power switch tubes to be processed in the corresponding phases to be consistent with input. Thus, the output current of an electric reactor of the inverter can be gentle and will not substantially drop suddenly, the waveform quality of the current is good in the wave-by-wave current limiting period, resonance is avoided, a system is more reliable, faulty current limiting in the current limiting quitting process is avoided, and the working efficiency of the system is improved.

Description

technical field [0001] The present invention mainly relates to the field of wave-by-wave current limiting, and more specifically relates to a three-level wave-by-wave current limiting control method and system. Background technique [0002] After research, it is found that during the operation of the inverter, overcurrent phenomena usually occur due to reasons such as too small load impedance and bridge arm short-circuit, which affect the safe and reliable operation of the system. [0003] In order to realize the over-current protection of the inverter, in the prior art, when an over-current signal is detected, all main power switches of the inverter over-current phase are usually turned off, and when the over-current signal disappears and the detected When the PWM (Pulse-Width Modulation, pulse width modulation) signal of the main power switch tube enters the next switching period, the above-mentioned closed main power switch tube is turned on again. [0004] However, due ...

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Problems solved by technology

[0004] However, due to the small inductance of the three-level inverter reactor, the output voltage of the bridge arm of the over-current phase is +E / 2 or -E / 2 during the switching cycle of turning off all the main power switch tubes of the over-current phase, The output voltage will generate a large voltage difference on the reactance, which will cause a large drop in the current on the reactance, reduce the quality of the current waveform, and easily generate resonance

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