A Current Adaptive Control System of Grid-Connected Converter to Suppress High-frequency Oscillation of the System

Abstract

The invention discloses a self-adaptive current control system for inhibiting system high-frequency oscillation. The self-adaptive current control system comprises three main parts of dual-PI control under conventional rotational coordinates, a harmonic wave online detection link, special frequency band gain adjustment of a current loop, and the like. The value of amplitude of a harmonic component is obtained by detecting current waveform, during operation, of a filter capacitor of the grid-connected inverter in real time and analyzing harmonic wave components in the waveform; and when the detected value of amplitude of the harmonic component is greater than a set threshold value, the gain, at the harmonic wave frequency, of a current controller is inhibited by regulating a wave trap corresponding to the output end of the current controller, thereby preventing the grid-connected inverter from interacting with the system at the frequency point, and amplifying the harmonic waves. According to the control method disclosed by the invention, under different power grid harmonic oscillation environments, the automatic adjustment for the gain, at the harmonic oscillation frequency point, of the current controller can be realized, thereby improving the stable operation capacity of the grid-connected inverter.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and more specifically relates to a current adaptive control system of a grid-connected converter that suppresses high-frequency oscillation of the system. Background technique [0002] With the decline of fossil energy, new energy power generation has been greatly developed in recent years. At the same time, it can be expected that new energy power generation will occupy a considerable proportion in the energy structure of various countries in the future. Today's new energy power generation mainly includes wind power and photovoltaic power generation. In order to realize the smooth feeding of new energy to the grid, power electronics technology is generally used in the grid-connected device of the new energy power generation unit, and the grid-connected converter has become one of its core equipment. As the installed capacity of new energy power generation continues to increase, the de...

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Problems solved by technology

However, this oscillation suppression method needs to know detailed system parameters, equipment parameters, etc., these parameters are difficult to obtain when the new energy power station is not built, and the actual grid conditions change with the running time, which makes the original Well-designed passive filters may fail

[0005] On the other hand, the existing current controller schemes generally only focus on the single resonance frequency point introduced by the converter filter when dealing with high-frequency oscillation problems. Most active damping schemes are only designed for this situation and are not applicable Suppresses high-frequency oscillations caused by external network resonance

And more high-frequency resonance suppression algorithms are generally only effective for fixed network resonance. If the system resonance frequency shifts, the suppression effect will be greatly reduced

[0006] To sum up, the existing high-frequency oscillation suppression schemes can only be aimed at specific grid conditions. Once the grid environment connected to the converter changes, the equipment may still have high-frequency oscillations with the system, and the actual power system itself will change with time, so it is urgent to invent an effective current adaptive control algorithm to adapt to changes in the grid

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