Low-voltage ride through (LVRT) control system of photovoltaic inverter and method thereof

Abstract

The invention provides a low-voltage ride through (LVRT) control system of a photovoltaic inverter and a method thereof. The system comprises a solar cell panel, a photovoltaic inverter, a power grid and a controller, wherein the solar cell panel, the photovoltaic inverter and the power grid are sequentially connected; and the controller is respectively connected with the photovoltaic inverter and the power grid. The system and the method have the advantages that 1) when the power grid breaks down to cause power grid voltage balance sag, good dynamic response is provided, and grid-connected current can be steadily outputted by three phases of current sharing of the photovoltaic inverter; and 2) in unbalanced voltage sag, the positive and negative sequence voltage influence of the power grid can be eliminated by the control system, only the positive sequence current component is outputted, and the three-phase current sharing is ensured and has a lower harmonic component, so that the loss caused by the faults of the power grid is reduced, and the power supply reliability of the power grid is improved. The special situation of the unbalanced power grid is supported by the system, and the stable operation of the normal three-phase current sharing is guaranteed.

Description

technical field [0001] The invention belongs to the technical field of photovoltaic power generation, and in particular relates to a low voltage ride through LVRT control system and method of a photovoltaic inverter. Background technique [0002] In the solar grid-connected power generation system, one of its core components is a photovoltaic inverter. The main function of the photovoltaic inverter is to convert the direct current generated by the solar panels in the photovoltaic power station into alternating current, and then integrate the alternating current into the grid. middle. [0003] After the photovoltaic power generation is integrated into the existing power grid through the photovoltaic inverter, when the power grid fails and the voltage drops, if the photovoltaic power station is also cut off immediately, it will cause drastic changes in the entire power supply system, resulting in large-scale power outages; therefore, this At this time, the photovoltaic power ...

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Problems solved by technology

[0004] However, at present, the control system for low voltage ride through has the following defects: (1) When the power grid fails and the voltage drops, the dynamic response of the control system is slow; (2) When the grid voltage drops, the control system cannot control the photovoltaic inverter. Transformer current sharing and stable output grid-connected current

As a result, the problem of large losses caused by such faults in the power grid

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