Network access current control method for single-phase less container load (LCL) filtering grid-connected inverter

Abstract

The invention discloses a network access current control method for a single-phase less container load (LCL) filtering grid-connected inverter and belongs to the field of network access current control of a grid-connected inverter. The method comprises the following steps of: feeding back six voltage and current variables which are easily measured in a single-phase LCL filter to obtain 18 feedbacks through proportion, integration and differential, and selecting a proper feedback combination to configure a characteristic equation of an LCL filter grid-connected inverter system transfer function from a third order to a fourth order so as to guarantee that four poles of the configured characteristic equation can be freely configured; further configuring a fourth-order characteristic equationin a form that two poles serve as conjugate poles at fundamental frequency and two poles serve as conjugate poles at resonant frequency; and finally, comparing to acquire various feedback coefficients in the selected feedback combination. By the method, the high gain of a system open loop transfer function on a forward path is achieved, a resonance peak at a natural resonant frequency is effectively suppressed, and the system has good steady state and dynamic responses.

Description

technical field [0001] The invention relates to a current control method, in particular to a method for controlling the grid-connected current of a single-phase LCL filter grid-connected inverter with four-pole configuration, and belongs to the field of grid-connected current control of the grid-connected inverter. Background technique [0002] Grid-connected inverter technology is one of the key technologies for distributed generation of renewable energy, and the current quality of grid-connected inverters is an important technical indicator. In order to suppress the switching frequency sub-harmonic and meet the quality requirements of the grid current, the LCL filter is a better filtering scheme for the voltage source pulse width modulation (PWM) grid-connected inverter. Compared with single-inductor filters, LCL filters have better filtering characteristics, but the resonance problem caused by its high-order characteristics puts forward high requirements for current contr...

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Problems solved by technology

However, these active damping schemes only change the damping ratio of the resonant poles, and cannot realize the free configuration of all poles, so there are still deficiencies in achieving better dynamic response and robustness of the system, especially in the filter When the ratio of the natural resonant frequency to the switching frequency is small

A state feedback method that can freely configure all poles of the system characteristic equation has received widespread attention, but the state feedback method cannot take into account the steady-state and dynamic characteristics of current control, and requires more sensors

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