Control method and system for improving adaptability of single-phase photovoltaic inverter to weak power grid

Abstract

The invention provides a control method and a system for improving adaptivity of a single-phase photovoltaic inverter on a weak power grid. A voltage feedback signal V<PCC-of> of a grid-connected point is processed and overlaid to the output of a current regulator; then compensation sampling and delay control are performed to realize the phase correction of the voltage feedback signal of the grid-connected point; and the adaptivity of the single-phase photovoltaic inverter on the weak power grid is improved, so that the stable operation of the inverter under the weak power grid is realized. The control method for improving the adaptivity of the single-phase photovoltaic inverter on the weak power grid comprises the following steps of S1, obtaining the voltage feedback signal V<PCC-of> and the inductive current i<L-of> of the grid-connected point, wherein the sampling delay transfer functions of the voltage feedback signal V<PCC-of> are H<v>; and the sampling delay transfer functions of the inductive current i<L-of> are H; S2, substituting the feedback signal i<L-of> into the current regulator to obtain a regulation signal V<r1>; S3, substituting the feedback signal V<PCC-of> into a phase regulator to obtain a regulation signal V<r2>; and S4, enabling V<r1> to be added to V<r2> to obtain a modulation signal V<m> which is sent to a PWM generator so as to generate PWM driving signals of each switching tube of the inverter separately.

Description

technical field [0001] The invention relates to a digital control method and system for a single-phase photovoltaic grid-connected inverter, specifically, the active damping control on the grid side is realized by constructing a phase regulator, which can effectively improve the adaptability of the inverter to a weak grid. It can still be reliably connected to the grid in a wide range of changes in the grid impedance, meeting the grid-connected standards. Background technique [0002] Distributed power generation systems represented by wind energy and solar energy, as one of the main ways of renewable energy utilization, can not only dominate the economic operation of the existing power grid, but also be clean and environmentally friendly, and their application proportion in the power system is increasing day by day. With the increase in the number of distributed power grid-connected, the grid-connected power, and the wide distribution of locations, the power grid is increas...

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Problems solved by technology

[0006] from figure 2 As can be seen in the feed-forward channel low-pass filter H v Time delay and digital control delay G d The existence of the grid-connected point voltage feedback signal v PCC_of and grid-connected point voltage v PCC and modulating signal v m and inverter bridge output voltage V ab There is a phase delay between them, especially in the high-frequency part, the delay is more serious, so when using the grid-connected point voltage feedback signal v PCC_of When feed-forward is used for active damping control, its resonance suppression effect will be affected. When the impedance of the mains changes, it may even cause downtime such as overcurrent

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