Grid-connection-to-off-grid seamless switching method suitable for hybrid energy storage all-in-one machine

Abstract

The invention relates to a grid-connection-to-off-grid seamless switching method suitable for a hybrid energy storage all-in-one machine. The method is characterized by comprising the following steps:(1) a real-time value of a power grid voltage calculated during grid connection serves as a UPS voltage reference value; a current of a load is measured to serve as an initial reference value of thecurrent at a switching moment; (2) double phase-locked loops are adopted; the phase-locked loop A is responsible for phase locking of the power grid voltage during the grid connection, and acquires aphase of a power grid in real time; the phase-locked loop B updates a sine table of the phase-locked loop B in real time by a phase of the phase-locked loop A to make phase connection preparation forgrid-connection-to-off-grid switching at any time; meanwhile, a frequency obtained by the phase-locked loop A also becomes an initial frequency of the phase-locked loop B; and (3) a state of the powergrid is judged; once the power grid is identified to be abnormal or lost, a grid-connection voltage outer loop output is switched to an off-grid voltage outer loop output, and a grid-connection stateis switched to an off-grid state to serve as an output. According to the method, voltage amplitude and frequency in the grid-connection-to-off-grid switching process are ensured not to be changed, sothat phase sudden change is avoided, and seamless switching of load power supply is achieved.

Description

technical field [0001] The invention relates to a seamless switching method suitable for grid-connected and off-grid switching of a hybrid energy storage integrated machine, which belongs to the field of electric power technology. Background technique [0002] At present, photovoltaic energy storage power generation systems can be roughly divided into: off-grid energy storage systems, off-grid power generation systems, grid-connected energy storage systems and multi-energy hybrid micro-grid systems. Among them, the grid-connected and off-grid integrated system has a variety of working modes and functions, and has great advantages and great development space in the energy storage system. However, most of the grid-connected and off-grid switching control strategies adopted by the hybrid energy storage integrated machine in the prior art are based on the ideal sinusoidal three-phase voltage of the power grid, and there are phase mutations when switching between grid and off-gri...

AI Technical Summary

Problems solved by technology

However, most of the grid-connected and off-grid switching control strategies adopted by the hybrid energy storage integrated machine in the prior art are based on the ideal sinusoidal three-phase voltage of the power grid, and there are phase mutations when switching between grid and off-grid, resulting in the inability to realize seamless switching of power supply to loads. , thus affecting system stability and reducing energy storage efficiency

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