Multi-inverter system dual-mode combined control method based on double-split transformer

Abstract

The invention discloses a multi-inverter system dual-mode combined control method based on a double-split transformer, and belongs to the field of electrical engineering. The invention provides a multi-inverter system dual-mode combined control method based on a double-split transformer in allusion to an extremely weak power grid. According to the method, equivalent power grid impedance of a common coupling point of a certain grid-connected inverter in a multi-inverter system based on a double-split transformer is obtained through a power grid impedance identification algorithm, and accordingto the gradual increase of the equivalent power grid impedance, the system operates in a full current source mode, a hybrid mode and a full voltage source mode in sequence, so that the stability of the multi-inverter system based on the double-split transformer under the condition of power grid intensity change is effectively improved. The method is simple to implement, greatly increases the stability margin of the multi-inverter system based on the double split transformers when the power grid impedance fluctuates greatly, particularly ensures that the system can still operate stably under anextremely weak power grid, and improves the power grid adaptability of the system.

Description

technical field [0001] The invention relates to a control method for a multi-inverter system based on a double-split transformer, in particular to a dual-mode combined control method for a multi-inverter system based on a double-split transformer, and belongs to the field of electrical engineering. Background technique [0002] At present, the development and use of renewable new energy such as wind energy and solar energy has been continuously increasing around the world. In particular, China, the United States and India have built and put into operation large-scale desert photovoltaic power plants above MW level, and the penetration rate of new energy power generation is getting higher and higher. . Moreover, for desert power stations with open sites, the structure of the centralized photovoltaic power generation system has the characteristics of simplicity, high efficiency, and easy maintenance, and has been widely used. In addition, the connection between photovoltaic g...

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Problems solved by technology

[0017] In order to overcome the limitations of the above-mentioned various technical solutions, the present invention aims at the stability problem when the multi-inverter system based on the double-split transformer adopts the traditional single current source mode or mixed mode under the extremely weak power grid, and proposes a double-split transformer-based The dual-mode combination control method of multi-inverter system, this method obtains the equivalent grid impedance of a grid-connected inverter common coupling point in the multi-inverter system based on double-split transformers through the grid impedance identification algorithm, when the equivalent The grid impedance gradually increases, that is, when the grid operates in strong grid, weak grid and extremely weak grid respectively, the system operates in full current source mode, hybrid mode and full voltage source mode in turn, thus effectively improving the multi-inverter based on double-split transformers. The stability of the inverter system in the case of changes in the strength of the power grid

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