Method for improving crossing ability of grid-connected photovoltaic power generation under asymmetric operating conditions

Abstract

The invention discloses a method for improving the crossing ability of grid-connected photovoltaic power generation under asymmetric operating conditions. The method comprises the following steps: determining the optimal resistance value of a superconducting current limiter based on a superconducting current limiter resistance fixing method; setting the superconducting current limiter with the optimal resistance value in a grid-connected photovoltaic power generation system to limit the active power down level of an on-line current limiting method of the grid-connected photovoltaic power generation system during a sag period; and improving the grid-side voltage of the grid-connected photovoltaic power generation system based on the on-line current limitation method of the grid-connected photovoltaic power generation system to realize transient current limitation of the grid-connected photovoltaic power generation system. In an existing grid-connected photovoltaic power generation system, the on-line current limiting method is used to set the superconducting current limiter resistance fixing method which matches an on-line current limiting strategy, thereby ensuring the optimal selection of the resistance value of the superconducting current limiter, and saving the calculation amount. Through reasonable installation of the superconducting current limiter, the economical efficiency of a coordinated operation method is maximized, thereby improving the smooth asymmetric operating condition crossing ability of grid-connected photovoltaic power generation.

Description

technical field [0001] The invention relates to the technical field of grid-connected photovoltaic power generation system equipment, in particular to a method for improving the ability to ride through asymmetric working conditions of a grid-connected photovoltaic power generation system. Background technique [0002] Photovoltaic power generation is an important renewable energy technology. According to the installation location, it is often divided into distributed grid-connected photovoltaic power generation system and centralized grid-connected photovoltaic power generation system. Among them, centralized photovoltaic photovoltaic power generation systems are often distributed in remote areas in the central and western regions where solar energy is abundant, and are fed into the grid through long-distance transmission lines. A bipolar grid-connected photovoltaic system generally consists of a photovoltaic array, an inverter and a metering system. Generally, the centrali...

AI Technical Summary

Problems solved by technology

As a new type of power system current limiter, the superconducting current limiter can quickly limit the short-circuit current at the moment of failure when it is connected in series with the grid-connected photovoltaic system, and provide stable voltage support in the clapping steady state, especially in severe In the voltage sag event, it assists the existing asymmetric control strategy to achieve smooth asymmetric ride-through, and makes up for the weak deep voltage sag ride-through ability of the existing method

[0003] However, after the occurrence of asymmetric sag, on the one hand, due to the positive sequence voltage drop, the output power capability of the grid-side converter is limited, and the original power balance on both sides of the DC bus capacitor is broken. Lower the active power transmission level on the machine side to achieve the stability of the bus capacitor voltage

On the other hand, with the goal of eliminating ripple voltage, the grid-side converter grid-connected current contains negative sequence components, and the increase in three-phase current unbalance complicates the installation of superconducting current limiters.

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