Wide-range frequency adaptive control method based on current-mode grid-connected system

Abstract

The invention discloses a wide-range frequency self-adaptive control method based on a current-type grid-connected system. When the inverter is connected to the grid, the output of the inverter is distorted due to the frequency mutation of the grid, causing harmonic distortion and then current oscillation. In this case, the instability of the system will have a great impact on the electrical equipment and the inverter module itself. In order to meet the market demand and realize the sudden change of the grid frequency in a wider range (45Hz‑55Hz), the inverter The system has good stability, and the present invention proposes a wide-range frequency adaptive control (Frequency Adaptive) strategy on the premise of considering sudden changes in the grid frequency, so as to realize stable operation of the system.

Description

technical field [0001] The invention belongs to the field of electrical control, in particular to a wide-range frequency self-adaptive control method based on a current-type grid-connected system. Background technique [0002] With the depletion of traditional fossil energy, new energy power generation systems such as photovoltaic power generation and wind power generation have sprung up, becoming a research hotspot in recent years. New energy power generation systems usually realize grid-connected operation through the inverter interface. In order to improve the current quality of the inverter grid-connected current and system stability, it is important to rationally design the control scheme of the inverter system according to different grid states and sudden changes in grid frequency. significance. [0003] The single-phase grid-connected inverter uses the current loop control method. Scholars at home and abroad have conducted in-depth research on the sudden change of th...

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Problems solved by technology

[0003] The single-phase grid-connected inverter uses the current loop control method. Scholars at home and abroad have conducted in-depth research on the sudden change of the grid frequency. However, under normal circumstances, the grid frequency changes between 49.5Hz-50.5Hz, and it is kept between 45Hz-55Hz. Wide range of grid frequency variations between, few people involved in

[0004] Most scholars use repetitive control to adapt to the frequency of the power grid. For example, in 2020, Li Weifeng and others published in "Power System Protection and Control": "New Frequency Adaptive Compound Repetitive Control and Grid-connected Inverter Application" and 2017 The “New Frequency Adaptive Repetitive Control Method for LCL Grid-connected Inverters” published by Chen Lei et al. used repetitive control, but this method usually degrades the performance of the control system, because the accuracy of the value parameters is limited, making the internal model of repetitive control The resonant frequency deviates from the actual value of the fundamental and harmonic frequencies of the power grid. At the same time, the control is complicated and the program memory is greatly increased. An internal model filter is required to improve robustness. Generally, a low-pass filter or a low-pass filter and a notch filter are used. Synthesizer, or Butterworth filter to suppress high-frequency harmonics, and the Butterworth filter is generally used above the second order. Due to the influence of the filter on the phase, an additional phase lead compensator needs to be designed to compensate for the low pass Issues such as phase lag caused by filters

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