Software protecting method for start short circuit of off-line inverter

Abstract

The invention discloses a software protecting method for start short circuit of an off-line inverter. When the inverter is started, a PMW (Pulse-Width Modulation) duty ratio is set to be zero, PWM output is enabled, a PWM counting value is set to be zero, and a given sine wave amplitude value is set to be zero by software in an open-loop control way; in a start process, the change of the given sine wave amplitude value is controlled by the software to gradually increase the given sine wave amplitude value; the software judges whether the start process is in the last period of open-loop adjustment control or not according to the PWM counting value, when the open-loop adjustment control is at a zero-over point of the last period, the software switches the inversion output from the open-loop control way to a close-loop control way, and voltage is quickly adjusted to be stable at a rated value. By the software protecting method for start short circuit of the off-line inverter, at the start or in the start process, current can be prevented from being increased suddenly in case of short circuit, so that a power pipe is prevented from being damaged by over current, and the aim of protecting a power apparatus is fulfilled.

Description

technical field [0001] The invention relates to a short-circuit protection method for an off-grid inverter, in particular to a software protection method for a short-circuit when the off-grid inverter is turned on. Background technique [0002] On April 25, 2007, the State Intellectual Property Office published an invention patent with a publication number of CN1954470 and a patent name of an inverter bridge short circuit protection scheme. The inverter bridge short circuit protection scheme has a three-phase multi-level inverter with three branches. Inverter bridges, each branch providing one of the three-phase outputs for driving inductive loads, said three-phase multilevel inverter bridge having "L" bus voltage levels (L≥3), where Two of said L levels are a minimum negative bus voltage and a maximum positive bus voltage, and the difference between any intermediate bus voltage level and any other bus voltage level is the difference between said maximum positive bus voltage...

AI Technical Summary

Problems solved by technology

However, when the load is short-circuited and the user starts working without the user's knowledge, the power device of the inverter will be damaged due to overcurrent due to untimely protection.

[0004] The traditional short-circuit protection scheme cannot completely solve the problem of machine damage caused by short-circuit. When the short-circuit is turned on, the output voltage is pulled down to close to zero. In the first few cycles, the output current does not reach the hardware trigger threshold. Under the action of the control loop , the duty cycle of the driving power device is quickly opened to the maximum, but at this time the power tube has been working outside the safe area (SOA), and when the hardware protection starts, the power tube has been damaged

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