Rapid robustness single-current feedback control method of LCL type grid-connected inverter

Abstract

The invention discloses a rapid robustness single-current feedback control method of an LCL type grid-connected inverter. Single-current feedback control is introduced, a rapid robustness PWM modulation method is combined, and grid-connected control of the inverter is realized. According to the method, the grid-connected current is sampled, extra sensors are not needed, the hardware cost is reduced, and the system reliability is improved. According to the rapid robustness PWM control method, the duty cycle limitation is not introduced, the calculation time delay of one-step delay of a grid-connected current outer loop and an active damping inner loop is completely eliminated, the essential requirement that the positive and negative dividing frequency of an equivalent damping resistor is higher than the design range of the LCL resonant frequency is realized, the method allows half of the switching period of sampling and duty cycle calculating time, and the overall robustness and the dynamic performance of the grid-connected inverter are enhanced.

Description

technical field [0001] The invention relates to the field of PWM inverter control and new energy sources thereof, in particular to a fast and robust single current feedback control method for an LCL type grid-connected inverter. Background technique [0002] Grid-connected inverters, as the core device connecting distributed energy sources and public grids, play a vital role in distributed power generation systems. Its output filter adopts LCL type filter, which can effectively suppress the high-frequency harmonics output by the inverter, reduce the volume and quality of the filter, and has important application value in engineering. However, the LCL filter is a low-damping third-order system, which has resonance problems, which can easily lead to instability of the grid-connected inverter. Now there are a lot of literature to discuss and solve the resonance problem of the LCL-type grid-connected inverter, mainly including the capacitor branch The passive damping method of ...

AI Technical Summary

Problems solved by technology

[0004] The technical problem to be solved by the present invention is to analyze the influence of control delay on the stability of the grid-connected inverter system and provide a fast and robust single-current feedback control method for LCL-type grid-connected inverters. , to solve the problem that the grid-connected inverter will have inherent control delay under digital control and will change the size and positive and negative directions of the equivalent virtual damping resistance, and completely eliminate the grid-connected current outer loop and the active damping inner loop. Lag calculation delay, and allow 0.5 times the switching cycle sampling and duty cycle calculation time, while solving the problem that the current LCL grid-connected inverter needs additional sensors or the introduction of single current feedback parameters is difficult to select

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