Detection method with single-phase outage of grounding transformer

Abstract

The invention relates to a detection method with a single-phase outage of a grounding transformer. A power generation system composed of the grounding transformer comprises the grounding transformer,an MVT (Medium Voltage Transformer) and an outage device; the grounding transformer, a grid-connected inverter and the outage device are connected to the low-voltage side of the MVT; and the high-voltage side of the MVT is connected to the outage device and then is connected into a power grid. The detection method solves the problem that the grid-connected inverter cannot be protected or is repeatedly connected after being protected in a traditional anti-islanding (AI) algorithm in case of the single-phase outage of the power grid containing a grounding transformer system; the content of the AI algorithm is perfected and enriched; the operation risk of grid-connected power generation of new energy is lowered; and the reliability of safe operation of the system is improved. The detection method can be widely applied to the field of a three-phase grid-connected photovoltaic inversion system, a wind power generation grid-connected system, an energy storage system and the like.

Description

technical field [0001] The invention is applied to the technical field of new energy grid-connected power generation, especially for a distributed power generation system composed of a grounding transformer GT (Grounding Transformer), a medium voltage transformer MVT (Medium Voltage Transformer) and a grid-connected inverter. Wave THDv (Voltage Total Harmonic Distortion) changes to identify whether a single-phase power outage occurs in the grid. Background technique [0002] Three-phase four-wire power distribution system is widely used in office buildings, large commercial buildings and modern factories. There are a large number of computers, office automation equipment, frequency conversion air conditioners, large display screens, uninterruptible power supplies and other non-linear electrical equipment in these buildings. Most of the equipment will generate a large number of harmonics in the power grid when they are working, which will cause pollution to the power system. ...

AI Technical Summary

Problems solved by technology

However, when a grid phase failure occurs in the system composed of GT, MVT and grid-connected inverter, due to the strong magnetic field coupling of the grounding transformer, the traditional AI algorithm cannot achieve positive feedback, which will drive the grid voltage frequency, amplitude, and phase to change.

Therefore, the traditional AI algorithm cannot identify the power grid phase failure

In the off-grid standby state, because the inverter does not output power to disturb the grid voltage and frequency, it is even more difficult to identify this type of grid fault, which will cause the grid-connected inverter to frequently reconnect to feed energy to the grid

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