Low voltage ride-through control device and method of two-stage inverter

Abstract

The invention provides a low voltage ride-through control device and method of a two-stage inverter. The device includes multiple photovoltaic arrays, multiple DC / DC units, a DC bus, a DC / AC unit, a grid connection point and a power grid. The output terminal of each photovoltaic array is connected with the input terminal of the corresponding DC / DC unit. The output positive electrodes of the DC / DC units join together and then are connected to the input positive terminal of the DC bus. The output negative electrodes of the DC / DC units join together and then are connected to the input negative terminal of the DC bus. The output terminal of the DC bus is connected to the input terminal of the DC / AC unit. The output terminal of the DC / AC unit is connected with the power grid through the grid connection point. Each DC / DC unit is connected with a DC / DC control unit. The DC / AC control unit is connected with a DC / AC control unit. The invention also discloses a control method of the device. According to the invention, stability and reliability of DC bus voltage in a low voltage ride-through process is ensured effectively. At the same time, a current equalizing problem of parallel operation of the DC / DC units in the two-stage inverter is solved.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a low-voltage ride-through control device and method for a two-stage inverter. Background technique [0002] With the gradual depletion of traditional energy sources, new energy grid-connected power generation technologies represented by solar photovoltaics have been widely used. The inverter connects the DC photovoltaic array and the AC power grid, and is the core device of the photovoltaic grid-connected power generation system. A two-stage photovoltaic grid-connected inverter generally includes a DC / DC boost circuit and a DC / AC inverter circuit. The output end of the DC / DC step-up circuit is connected in parallel with the input end of the DC / AC inverter circuit to form a DC bus. The DC / DC step-up circuit can be a single DC / DC converter unit, or a parallel structure of multiple step-up DC / DC converter units. [0003] Low Voltage Ride Through (LVRT) means that when ...

AI Technical Summary

Problems solved by technology

When the grid voltage drops or recovers, it is easy to cause the DC bus voltage to overshoot or even damage the switching devices

In the prior art, there is a problem that the control mode needs to be switched during the low-voltage ride-through process, which may easily cause the DC bus voltage to be unstable.

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