Control method for seamless switching between grid connection and disconnection and grid connection and disconnection of energy storage inverter

Abstract

The invention discloses an energy storage inverter grid-connected and off-grid and off-grid and grid-connected seamless switching control method. Instantaneous active power and reactive power are calculated through an inverter output voltage module value and components of the inverter output voltage module value and current in a D axis and a Q axis under a synchronous rotating coordinate system; simulating droop characteristics of the power grid, and setting reactive power and voltage amplitude droop reactive power loop output voltage and active power and frequency droop active power loop frequency; and the obtained synthesized reference voltage passes through a voltage and current double-loop controller and then is subjected to SVPWM (Space Vector Pulse Width Modulation) wave sending, sothat the output voltage of the inverter has the same droop characteristic as the power grid voltage. According to the control method, bidirectional seamless switching between grid connection and disconnection and grid connection and disconnection and connection can be achieved, the loop structure of the controller is kept unchanged before and after switching, the output voltage can be kept continuous at the moment of switching and can be stabilized to continue to operate under the off-grid condition, and seamless switching is achieved. Meanwhile, the power grid fault can be quickly and accurately judged.

Description

technical field [0001] The invention relates to the technical field of power electronics, and relates to a control method for an energy storage inverter switching from grid to grid and from grid to grid. Background technique [0002] In the traditional energy storage inverter control method, in the grid-connected mode, the inverter adopts current-type control as a current source to control the input and output power; in the off-grid mode, the inverter adopts voltage-type control, As a voltage source, it provides the load with AC voltage with stable frequency and amplitude. Switching between these two modes will inevitably lead to transient impact and oscillation, especially when switching with load is more severe, making the switching fail. [0003] Chinese patent CN 106655255 A discloses a photovoltaic energy storage inverter switching method and circuit for on / off-grid, off-grid / grid-connection, which strictly restricts the start-stop time of PCS and the action sequence o...

AI Technical Summary

Problems solved by technology

In this method, there are two modes of switching between current control and voltage control, and the continuity and stability of the switching process cannot be guaranteed. At the same time, it is not reliable to judge whether the power grid is faulty only by the voltage difference. Switching from grid-connected to off-grid cannot switch from off-grid to grid-connected under the requirement of ensuring continuous power supply of the load

[0005] Chinese patent CN 104795827 A discloses a switching circuit of an energy storage inverter and its grid-connected / off-grid switching method and device. The method only introduces The on-off grid switching circuit is introduced but there is no introduction to the control mode of the inverter in the on-off and off-grid state. Even if the switching of the filter circuit can maintain the stability of the voltage and improve the filter performance at the moment of switching on and off the grid, but after switching, whether it can be stabilized? run unknown

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