Method and circuit for adjusting overcurrent protection threshold value

Abstract

The embodiment of the invention discloses a method for adjusting an overcurrent protection threshold value. The method comprises the following steps of: acquiring a voltage sampling value of a direct-current bus of an inverter; calculating a difference value between the voltage sampling valve of the direct-current bus and a first voltage threshold value; calculating a product of the difference value and a derating coefficient as a derating control amount; limiting the amplitude of the derating control amount to between 0 and a second voltage threshold value; deducting the amplitude-limited derating control amount from a rated overcurrent protection voltage value to generate a bridge-arm current positive overcurrent protection voltage threshold value of an inverting bridge; and carrying out negation on the bridge-arm current positive overcurrent protection voltage threshold value to generate a bridge-arm current negative overcurrent protection voltage threshold value of the inverting bridge. The method disclosed by the invention has the advantage that the probability of damage of a switching tube in the inverter due to over-high overvoltage can be reduced. The invention also discloses a circuit for adjusting the overcurrent protection threshold value.

Description

technical field [0001] The invention belongs to the technical field of inverters, and in particular relates to a method for adjusting an overcurrent protection threshold and an overcurrent protection threshold adjustment circuit. Background technique [0002] The inverter is a device that converts direct current into alternating current, and the inverter bridge is an important part of the inverter. During the operation of the inverter, if the current flowing through the switch tube in the inverter bridge is too large, it will cause thermal failure of the switch tube. In order to avoid excessive current flowing through the switching tubes in the inverter bridge, it is usually necessary to add an overcurrent protection circuit in the inverter. When the current sampling value of the bridge arm in the inverter bridge is greater than the overcurrent protection threshold, the corresponding The switch tube limits the bridge arm current. [0003] The working principle of the over-...

AI Technical Summary

Problems solved by technology

When the voltage on the DC side of the inverter is high, if the current flowing through the switch tube is too high, it will cause the switch tube to withstand a high peak voltage when it is turned off, thereby causing damage to the switch tube

[0005] Usually, the overcurrent protection threshold set according to the thermal protection is relatively high, which leads to the fact that the switching tubes in the inverter may be damaged due to the large peak voltage before the overcurrent protection circuit starts the protection measures.

For example, when the photovoltaic inverter is in the low voltage ride through or zero voltage ride through state, when the DC side bus voltage rises to near the open circuit voltage of the battery panel due to the limitation of output active power, the switching tubes in the inverter bridge must be Under high voltage stress, if the current value of the bridge arm in the inverter bridge does not reach the current protection threshold, it will cause the active clamp circuit of the switching tube in the inverter bridge to repeatedly operate, resulting in thermal failure of the active clamp circuit, or even Cause direct overvoltage breakdown of the switching tube

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