Three-phase photovoltaic inverter anti-islanding method based on phase angle deviation positive feedback

Abstract

The invention relates to a three-phase photovoltaic inverter anti-islanding method based on phase angle deviation positive feedback, which comprises the steps as follows: carrying out disturbance to a power grid phase with T being used as a cycle, a disturbance phase angle for each time is delta theta under a grid synchronization condition of the inverter; and beginning to accumulate when a power grid voltage phase angle is 0 degree and assuming total accumulating n times within T, namely a current phase leading voltage is n*delta theta degrees, and calculating an error value delta f of the current frequency and the last periodic frequency of the power grid voltage, so that the error value is adopted as phase angle deviation positive feedback quantity. When islanding happens, the frequency of the current voltage is more than that of the last period, the delta f is positive, a control loop leads the plosive value into the positive feedback, the disturbance quantity is changed into n*delta theta+delta f at the moment, and equivalently, the forward disturbance is increased, so that the more the phase disturbance is, the more the voltage frequency deviation is, so as to form a forward deviation positive feedback system; and the system reports an overfrequency error until the frequency exceeds standard, so as to achieve the islanding protection purpose.

Description

technical field [0001] The invention relates to an anti-islanding method, in particular to a three-phase photovoltaic inverter anti-islanding method based on phase angle offset positive feedback. Background technique [0002] At present, the power generation system composed of new energy is represented by wind power and solar power grid-connected power generation; because the initial electric energy is not stable enough, it is generally used to convert it into a stable DC through power electronic technology, and then obtain a synchronous AC through the inverter. . If a line in the distribution network of the power system fails, it will be cleared by the nearest relay protection device. If there is a grid-connected power generation system in the distribution network, the distributed power supply will continue to be disconnected from the grid. Distribution network power supply, in some special cases, forms an independent small power generation system. This phenomenon is calle...

AI Technical Summary

Problems solved by technology

If a fault occurs in a certain line in the distribution network of the power system, it will be cleared by the nearest relay protection device. Distribution network power supply forms an independent small power generation system in some special cases. This phenomenon is called "island effect". Island operation will bring great harm to the power grid, users, and personal safety. Under the circumstances, the power generation equipment is still used as an isolated power supply to supply power to the load, which brings great safety hazards to the line maintenance personnel; without the support of the large power grid, the power quality of the distributed power supply cannot be guaranteed

[0003] At present, most anti-islanding methods for photovoltaic inverters use frequency disturbance plus passive detection methods. This type of anti-islanding detection method has the disadvantage of instability: when the inverter output is islanded in different power ranges (10% to 100%), there are The failure of anti-islanding poses a hidden danger to the safety of grid maintenance personnel; under normal circumstances, the disturbance is too large and too frequent, which affects the harmonics of the inverter current and the power factor of the grid

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