A high-permeability photovoltaic access method to prevent overvoltage at the neutral point of the main transformer

Abstract

The invention discloses a method for preventing overvoltage of the neutral point of a main transformer in high-permeability photovoltaic access. The method is based on a traditional photovoltaic grid-connected decoupling double closed-loop control method, and can be divided into 3 states: in a state 1, the voltage of the neutral point of the main transformer is over the rated voltage but the overvoltage is within an allowable range, and a traditional grid-connected control method is adopted; in a state 2, the voltage of the neutral point of the main transformer rises to the phase voltage and does not reach the breakdown condition, the voltage and current of the grid connection point and the voltage of the neutral point of the main transformer are collected, the photovoltaic grid connectionphase angle is adjusted to limit the voltage of the neutral point of the main transformer within a safety range, and active power output of photovoltaic grid connection is ensured; and in a state 3,the voltage of the neutral point of the main transformer is broken down, the photovoltaic power supply operates in an off-grid mode, the voltage of the neutral point of the main transformer decreasessubstantially, and the photovoltaic system is connected with an energy storage device through a DC converter. By changing the photovoltaic grid-connected control strategy and adding a supporting energy storage device, the problem that transformer damage is caused due to too high voltage of the neutral point of the main transformer during operation of a high-permeability photovoltaic access grid infault can be solved.

Description

technical field [0001] The invention relates to a high-permeability photovoltaic access method for preventing overvoltage at a neutral point of a main transformer, which belongs to the grid control technology. Background technique [0002] In recent years, solar energy, as a renewable and clean energy, has attracted much attention and has been widely used and connected to the grid. At the same time, with the large-scale access of photovoltaics, the penetration rate of photovoltaics relative to the grid continues to increase, which has brought many problems to the stable operation of the grid, such as the increase of feeder voltage and the impact of relay protection setting configuration. For a transformer whose neutral point is not grounded, when a single-phase ground fault occurs in the power grid, the neutral point voltage will rise to the phase voltage. When the power grid does not contain distributed power sources such as photovoltaics, the power grid can still run cont...

AI Technical Summary

Problems solved by technology

Neutral point overvoltage protection is an important part that cannot be ignored in the operation of the entire power grid. If insufficient attention is paid, it may cause serious accidents to the entire power grid

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