Adaptive control method and control system for grid-connected converter under weak power grid

Abstract

The invention discloses an adaptive control method and control system for a grid-connected converter under a weak power grid. The steps are as follows: an adaptive control module is added to the control structure of a grid-connected converter, wherein the input signal of the adaptive control module is the voltage of the point of common coupling (PCC) and the grid current; a grid voltage estimationsignal is obtained through an adaptive algorithm; the grid voltage estimation signal instead of a PPC voltage sampling signal is sent to a feed-forward compensation module and a phase-locked loop module respectively; and finally, the duty cycle of the grid-connected converter is generated through current control, carrier interception and other modules. The adaptive control method is simple and easy to implement. A grid-connected converter based on the method has excellent grid current quality and system stability under wide change range of grid impedance. The method and the system are suitable for grid voltage synchronous control and grid current control in grid-connected inverters, rectifiers, reactive power compensators and other grid-connected AC equipment.

Description

technical field [0001] The invention belongs to the field of current control of grid-connected converters (including inverters, rectifiers, reactive power compensators, etc.), and particularly relates to a current control method of grid-connected converters suitable for weak grid occasions. Background technique [0002] In the new energy distributed grid-connected power generation system, how to improve the output current of the grid-connected converter, that is, the quality of the grid current, has received extensive attention and discussion. First of all, grid-connected converters using pulse width modulation technology will generate a large number of switching frequency sub-harmonics. Inserting a filter between the converter and the grid can effectively suppress switching frequency harmonics. Currently, commonly used filters include LCL filter as well as higher order filters with additional harmonic trapping in the LCL. Secondly, in order to achieve the desired grid-conn...

AI Technical Summary

Problems solved by technology

Although the existing optimal control methods for grid-connected converters can achieve system robustness under a certain range of grid impedance changes, the existing methods generally have problems such as narrow range of adaptation to grid impedance, complex control and design, etc., and their practical applications are limited.

If the grid impedance further increases, the grid-connected converter may experience harmonic amplification or even resonance near a lower frequency (close to 100Hz)

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