Resonance suppression method and resonance adaptive control method and device based on resonance suppression method

Abstract

The invention relates to a resonance suppression method. The resonance suppression method comprises the following steps of performing fussy control on a voltage of a power grid accessed by a photovoltaic grid-connected inverter and eliminating system resonance. A resonance adaptive control method based on the resonance suppression method comprises the following steps: judging whether the photovoltaic grid-connected inverter is under a resonant mode; if so, then adopting the resonance suppression method to eliminate the system resonance; if not, then adopting a PI double loop control method to control the voltage. A resonance adaptive control device comprises a judgment module used for judging whether the photovoltaic grid-connected inverter is under the resonant mode; a fussy control branch used for performing fussy control on the voltage of the power grid to eliminate the system resonance; and a conventional grid-connected branch used for performing conventional grid-connected control on the voltage of the power grid. The scheme of the invention can automatically distinguish whether a grid-connected system is resonant and use different control strategies, which can not only guarantee an output characteristic under a normal grid-connected condition, but can also guarantee the stability of the system under a high-impedance state and other resonant states.

Description

technical field [0001] The invention belongs to the field of photovoltaic power generation, and in particular relates to a method and a device applied to a situation where a photovoltaic inverter generates resonance under the conditions of high impedance of a power grid or parallel connection of multiple machines. Background technique [0002] For photovoltaic grid-connected inverters, resonance is a problem that needs to be solved urgently. The occurrence of resonance is likely to cause the inverter to go off-grid, resulting in great economic losses. The resonance of the photovoltaic grid-connected inverter is roughly caused by two situations: the first situation is that there is a high impedance in the line from the inverter to the power grid, which forms an LCL network with the filter inductance and capacitance of the inverter itself, and the output current of the inverter When the high-order harmonics contained are exactly the same as the resonant frequency of the LCL ne...

AI Technical Summary

Problems solved by technology

The second case is that when multiple inverters are working in parallel, there is a common impedance at the output grid-connected end, which causes multi-machine resonance between parallel inverters

Therefore, the phenomenon of grid-connected resonance has certain randomness

[0004] Therefore, on the one hand, the existing technology may affect the filtering performance of the inverter, on the other hand, it will also increase the system loss and reduce the system efficiency, and the resonance suppression technology often sacrifices the output characteristics of the inverter. Grid friendliness cannot be guaranteed

Therefore, the existing technology cannot meet the grid-connected requirements of various types of grids at the same time

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