Seamless switching control system and method based on hybrid control strategy

Abstract

The invention discloses a seamless switching control system and method based on a hybrid control strategy. The system and method can realize automatic switching from current source control to voltage source control based on droop control of an inverter when switching from grid-connected operation to isolated island operation, thereby improving load voltage quality in the process of switching from a grid-connected mode to an isolated island mode. Slave inverters are divided into two kinds, wherein the first kind of slave inverters are based on conventional PQ control and adopt current source control, and are named as slave inverters-type 1; and the other kind of slave inverters are based on PQ control and droop control, and are named as slave inverters-type 2. When island occurs, the slave inverter-type 2 is switched from the PQ control to the droop control and operates in a voltage source mode, and can realize power equalization without fast communication lines; and the slave inverter-type 2 can serve as a main inverter after switching to the droop control, thereby playing a role in maintaining grid voltage amplitude and frequency stability. Existence of a plurality of main inverters enhances reliability of a micro-grid system during isolated island operation.

Description

technical field [0001] The invention belongs to the research field of grid-connected inverter control, and in particular relates to a seamless switching control system and method based on a hybrid control strategy. Background technique [0002] With the deepening of the environmental and energy crisis, new energy power generation has received more and more attention and application, and the grid-connected inverter is an indispensable interface device for the new energy power generation system to transmit electric energy to the grid. The performance of the inverter will have an important impact on the stability of the power generation system and the grid. [0003] When the grid is normal, the grid-connected inverter should be able to run in parallel with the grid, and supply power to the load together with the grid. When the grid fails, the distributed generation unit should immediately disconnect from the grid and supply power to the load independently, forming an island ope...

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Problems solved by technology

[0004] The purpose of the present invention is to overcome the above-mentioned problem that the main inverter fails and the whole microgrid system cannot work in the improved indirect current control, and proposes a seamless switching control system and method based on a hybrid control strategy, which can realize inverters in parallel The seamless switching between the grid mode and the island mode improves the quality of the load voltage during the switching process, and in the island mode, the microgrid system operates in a multi-master and multi-slave structure, which improves the reliability of the system

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