Stability control method for multi-inverter system based on mode adaptation in weak grid

Abstract

The invention discloses a multi-inverter system stability control method based on mode self-adaption in a weak power grid. The invention provides the multi-inverter system stability control method based on mode self-adaption for the stability of multiple inverters operating in a current source mode under the weak power grid. The method comprises the steps that the equivalent power grid impedance of the common coupling point of a grid-connected inverter in a multi-inverter system is acquired through a power grid impedance identification algorithm; if the value of the equivalent power grid impedance is greater than a set equivalent power grid impedance boundary value, other grid-connected inverters in the multi-inverter system are switched to operate in a voltage source mode one by one untilthe identified equivalent power grid impedance value is smaller than the set equivalent power grid impedance boundary value; and the grid-connected stability of the entire multi-inverter system is improved. According to the invention, the method is simple to implement; the stability margin of the multi-inverter system under the weak power grid is greatly improved; and the power grid adaptabilityof the multi-inverter system is improved.

Description

Technical field

[0001] The invention relates to a control method for grid connection of a multi-inverter system, in particular to a stable control method of a multi-inverter system based on mode adaptation in a weak grid. Background technique

[0002] With the rapid development of distributed power generation systems, grid-connected inverters have been widely used. Due to the existence of long-distance transmission lines and a large number of transformer devices in remote distributed power generation systems, the power grid presents a non-negligible equivalent impedance, which makes the power grid weak grid characteristics. At this time, a multi-inverter system consisting of multiple grid-connected inverters will form a dynamic interconnection system with the grid when it is connected to the grid. The system will exist at its point of common coupling (PCC). The grid impedance will cause the stability of the grid-connected multi-inverter system to decrease and cause the output gr...

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