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

Abstract

The invention discloses a wide-range frequency adaptive control method based on a current type grid-connected system. When an inverter is in grid-connected operation, because the frequency of the power grid changes suddenly, the output of the inverter is distorted, harmonic distortion occurs, and then current oscillation occurs. In this case, the instability of the system has a great influence onelectric equipment and an inverter module. To meet market requirements, according to the method, the power grid frequency is suddenly changed in a wider range (45Hz-55Hz), the inverter system has goodstability, and a wide-range frequency adaptive control strategy is provided on the premise of considering the sudden change of the power grid frequency, so that the stable operation of the system isrealized.

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] Single-phase grid-connected inverters use the current loop control method. Scholars at home and abroad have conducted in-depth research on the sudden change of grid f...

AI Technical Summary

Problems solved by technology

[0003] Single-phase grid-connected inverters use the current loop control method. Scholars at home and abroad have conducted in-depth research on the sudden change of 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

Images