Low voltage ride through control method for high-power photovoltaic inverter

Abstract

The invention discloses a low voltage ride through control method for a high-power photovoltaic inverter. The method comprises the following steps: firstly, considering a low voltage ride through situation under the condition of grid voltage sag, particularly unbalanced sag on the basis of a high-power photovoltaic inverter structure of an LCL filter, calculating reference given values of positive sequence current and negative sequence current specific to the control aim of restraining the negative sequence current, and compensating idle work of filter capacitor absorption via a control algorithm to ensure high-power-factor grid connection while running at different power levels; secondly, designing to add a filter capacitor current feed-forward signal into a modulation signal on the basis of positive and negative sequence double current loop control, and adjusting a feed-forward coefficient to realize active damping control under unbalanced control; and lastly, designing a disturbance quantity feed-forward coefficient to restrain transient current impact. Due to the adoption of the method, current impact at the moment of grid voltage sag can be restrained effectively, three-phase balanced output of current before and after grid voltage sag is ensured, and the control effect meets the electric energy quality requirement of a power grid on the grid connection of the photovoltaic inverter.

Description

technical field [0001] The invention relates to a low-voltage ride-through control method for a high-power photovoltaic inverter, which is used for maintaining uninterrupted grid-connected operation of the photovoltaic inverter during a grid fault. Background technique [0002] As a large number of new energy sources are connected to the power system, the instantaneous removal of high-power photovoltaic energy will cause the loss of active power in the power grid, which will have a non-negligible impact on the stability and recovery of the power system. In order to maintain the safe and stable operation of the power system under the high penetration of photovoltaic energy, the new grid-connected access rules require that large and medium-sized photovoltaic inverters should have low voltage ride through (Low Voltage Ride Through, LVRT) capability, that is, to maintain The photovoltaic inverter runs continuously in grid connection. When the traditional double-closed-loop vect...

AI Technical Summary

Problems solved by technology

[0004] The technical solution of the present invention solves the problem that the existing high-power photovoltaic inverter cannot effectively suppress the instantaneous current impact caused by the voltage drop of the grid, and proposes a low voltage ride-through voltage control method, which realizes the voltage drop of the grid Stable operation of the front and rear systems, and meet the reactive power support requirements in the grid-connected rules

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