A single-phase off-grid inverter system and its control method

Abstract

The invention relates to a single-phase grid-connected and off-grid inverter system and a control method thereof. The inverter system comprises a single-phase grid-connected and off-grid inverter, a switch circuit, a switch circuit control module and a signal acquisition module, wherein the signal acquisition module comprises an external direct current voltage acquisition circuit, an inversion output voltage acquisition circuit, an external power grid current acquisition circuit and an external power grid output voltage acquisition circuit; the input end of the single-phase grid-connected and off-grid inverter is connected with the output end of an external direct current voltage supply device, the output end of the single-phase grid-connected and off-grid inverter is connected with the input end of the switch circuit, the output end of the switch circuit control module is connected with the switch circuit, and the output end of the switch circuit is bidirectionally connected with an external power grid; the external direct current voltage acquisition circuit is connected with the external direct current voltage supply device, the inversion output voltage acquisition circuit is connected with the output end of the single-phase grid-connected and off-grid inverter, the external power grid current acquisition circuit is connected with the output end of the switch circuit, and the external power grid output voltage acquisition circuit is connected with the external power grid.

Description

technical field [0001] The technical solution of the present invention relates to a grid-connected and off-grid inverter system and its control method, specifically a single-phase grid-connected and off-grid inverter system and its control method. Background technique [0002] One of the key technologies of grid-connected and off-grid inverters is the mutual switching between island mode and grid-connected mode. In the normal working mode, the microgrid runs in parallel with the large grid. When the large grid fails or the power quality fails to meet the requirements, the inverter device is isolated from the grid through the isolation device and operates in an isolated island. When the grid fault is eliminated, the inverter device will re-synchronize with the external grid to realize grid-connected operation. [0003] At present, there are three control modes for the control structure of distributed generation system operation mode switching: voltage mode control, indirect ...

AI Technical Summary

Problems solved by technology

The control method adopts a double closed-loop feedback control program based on the mixed voltage and current control mode. This control method can accurately and quickly realize the synchronization of the amplitude and phase of the inverter output voltage and the output voltage of the external grid, and can realize the switching between the island mode and the grid-connected mode. The smooth transition of the load voltage and load current during the process overcomes the defects of the existing voltage control mode technology that the dynamic performance of the system will deteriorate and the quality of the load voltage will be poor during the switching process

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