Low voltage ride through method for single-stage photovoltaic grid-connected inverter

Abstract

The invention discloses an improved positive-negative sequence component separation method. By adopting the method, bigger errors which are caused by a 'one-quarter cycle delay' method used in a one-quarter cycle after the happening and the ending of unsymmetrical faults are avoided, and the advantages of simplicity, high detection performance and the like of the 'one-quarter cycle delay' method are well used. The invention also discloses a method realizing low voltage ride through of a single-stage photovoltaic grid-connected inverter by using the improved positive-negative sequence component separation method. By adopting the methods, low voltage sag of an electric network can be quickly detected, the influence caused by unsymmetrical sag negative sequence components is inhibited, reactive power is provided, the voltage of a support grid connection point is recovered, and the requirement on the low voltage ride through of a high-power grid-connected inverter is met.

Description

technical field [0001] The invention belongs to the field of photovoltaic grid-connected power generation, and in particular relates to a low-voltage ride-through method for a single-stage photovoltaic grid-connected inverter. Background technique [0002] As a public power grid, the mains power system is connected to thousands of various loads. Some of the larger inductive, capacitive, switching power supply and other loads not only obtain power from the grid, but also cause serious damage to the grid itself. Impact, deterioration of the power supply quality of the power grid or local power grid, resulting in distortion of the mains voltage waveform or frequency drift. In addition, unexpected natural and man-made accidents, such as earthquakes, lightning strikes, open circuits or short circuits in power transmission and transformation systems, will endanger the normal supply of electricity, thereby affecting the normal operation of the load. [0003] Therefore, according t...

AI Technical Summary

Problems solved by technology

As more and more megawatt-scale photovoltaic grid-connected power plants are built and connected to the grid for operation, they have a profound impact on the safe and stable operation of the grid, especially when the grid fails, the sudden disconnection of photovoltaic power plants will further deteriorate the grid operating state, with more serious consequences

When the penetration rate of the photovoltaic power station is high or the output is increased, the fault of the power grid will cause the trip of the photovoltaic power station. Since the photovoltaic power station will take time to reconnect to the grid after the fault is restored, the power shortage caused during this period will cause the adjacent photovoltaic power station to trip. Cause large-scale power outages, affecting the safe and stable operation of the power grid

However, at present, photovoltaic power plants at home and abroad hardly have the ability of low voltage ride through, and there are few researches on the key technologies of low voltage ride through of photovoltaic power plants

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