Capacitor voltage feedforward control method of grid-connected inverter under weak power grid

Abstract

The invention relates to a capacitor voltage feedforward control method of a grid-connected inverter under a weak power grid. The method belongs to the field of grid-connected inverter control, and comprises the following steps: S1, performing feedback control by using inverter side current i1, and performing phase locking, active damping and feedforward compensation by using capacitor voltage uCto obtain a capacitor voltage feedforward control system of a grid-connected inverter under a weak power grid; S2, performing active damping negative feedback design under a weak power grid on the capacitor voltage feedforward control system obtained in the step S1; and S3, on the basis of the step S2, designing a capacitor voltage feedforward compensation control strategy for the capacitor voltage feedforward control system. On the premise of ensuring the performance of the control system, the use of voltage and current sensors is reduced, and the hardware cost of the system is reduced; and the dynamic performance and stability of the control system are improved, so that the grid-connected inverter always has enough stability margin under the characteristic that the impedance of the powergrid changes in a relatively wide range.

Description

technical field [0001] The invention belongs to the field of grid-connected inverter control, and relates to a method for feedforward control of the capacitor voltage of a grid-connected inverter under a weak grid. Background technique [0002] Grid-connected inverter, as the core device connecting the new energy power generation system to the grid, is related to the stable operation of the power system. When the transmission and distribution lines are long and there are many isolation transformers in the regional power grid, the power grid is prone to appear a weak power grid characterized by "low short-circuit ratio". If the grid-connected inverter is connected to a weak grid, it is easy to cause stability problems such as excessive harmonic content of the grid-connected current. [0003] In order to solve the stability problem, the existing literature has proposed many schemes to improve the stability, including adding compensation links in the current loop, optimizing t...

AI Technical Summary

Problems solved by technology

However, limiting the resonant frequency will lead to problems such as too slow dynamic response

To avoid this problem, it is necessary to add an additional damping link to ensure the stability of the system, but the traditional active damping will increase the number of sensors and the capacitance-voltage damping approximation link is difficult to achieve in engineering

In addition, the current feedback control strategy on the inverter side has the advantages of small distortion and good system stability, but it will introduce a positive feedback loop related to the grid impedance, which will affect the system stability

[0004] In order to achieve effective control of the system, the traditional inverter-side current feedback control strategy requires three sets of state variables: inverter-side current, grid-connected point voltage, and capacitor current, which means that three sets of sensors are required, and the cost is relatively high

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