High-frequency filter applied to grid-connected inverter

Abstract

The invention relates to the field of passive filters, in particular to a high-frequency filter applied to a grid-connected inverter. The high-frequency filter comprises an IGBT converter, a first inductor (L1), a second inductor (L2) and an RC damping branch, wherein the output of the IGBT converter is connected with the first inductor (L1); an output end is connected with a power grid through the second inductor (L2); the RC damping branch comprises a fifth capacitor (C5) and a damping resistor (R7); the fifth capacitor (C5) is connected with the damping resistor (R7) in series; a high-frequency component output from a bridge side of an IGBT is by-passed on a null line through the RC damping branch; the high-frequency filter is characterized in that the RC damping branch is connected with two paths of LC tuning branches respectively composed of a fourth inductor (L4), a seventh capacitor (C7), and a third inductor (L3) and a sixth capacitor (C6) in parallel; the fourth inductor (L4) is connected with the seventh capacitor (C7) in series; and the seventh capacitor (C7) is connected with the third inductor (L3) in series. The high-frequency filter applied to the grid-connected inverter hardly generates losses; due to the value of a resonance resistor R, the damping action of a resonance point position is the strongest; the system has relatively high damping characteristics; and the voltage of the damping resistor can be sampled for an active damping algorithm.

Description

technical field [0001] The invention relates to the field of passive filters, in particular to a high-frequency filter applied to grid-connected inverters. Background technique [0002] The grid side of the grid-connected inverter generally adopts an LCL type passive filter, but a pure LCL filter has a resonance point, so an RC type damping circuit is generally used on the high frequency branch of the filter. However, the damping resistor in the RC circuit has losses, and its power depends on the average effective value of the high-frequency current. When the output current of the active filter approaches the rated value, because the inductance tends to be saturated, the high-frequency current component increases sharply. The power dissipation in the damping resistor can reach hundreds of watts. Therefore, we will find that when many filters are finally damaged, their damping resistors are often burned. The control algorithm using active damping can prevent the equipment...

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Problems solved by technology

However, the damping resistor in the RC circuit has losses, and its power depends on the average effective value of the high-frequency current. When the output current of the active filter approaches the rated value, because the inductance tends to be saturated, the high-frequency current component increases sharply. Power dissipation in damping resistors can be hundreds of watts

Therefore, we will find that when the final damage of many filters is often caused by the burning of the damping resistor

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