Low-voltage ride-through device for AC and DC input dual-backup thermal power plant inverters

Abstract

The invention relates to the technical field of electric power system voltage automatic control, in particular to a thermal power plant frequency converter low voltage ride through device with alternating-current input backup and direct-current input backup. The low voltage ride through device is arranged between a power grid power distribution cabinet and a frequency converter, and comprises a first execution unit, a second execution unit, a storage battery set, a rectifying circuit, a boosted circuit, an output execution circuit and a signal regulating board. When voltages drop, the signal regulating board controls an alternating-current power supply to be rectified through the first execution circuit and the rectifying circuit, or after the storage battery set outputs direct-current voltages through the second execution unit, pressure boosting is carried out through the boosted circuit, and a power grid is compensated through the output execution circuit. The low voltage ride through device is safe, reliable, high in sensitivity and capable of guaranteeing the continuous and stable operation of a key auxiliary machine and a thermal power generating unit.

Description

technical field [0001] The invention relates to an automatic voltage control device of an electric power system, in particular to a low-voltage ride-through device for a thermal power plant inverter with dual backups of AC and DC inputs. Background technique [0002] With the development of power electronics technology, frequency converters are widely used in power plant auxiliary machine speed control systems due to their precise speed regulation, simple use, and complete protection. The application of the frequency converter not only reduces the energy consumption of the power plant, but also improves the degree of automation of the equipment. Due to the application of power electronic devices, the inverters are equipped with low-voltage trip protection, and the fluctuation of the grid voltage often leads to the withdrawal of the inverter, resulting in the expansion of accidents. [0003] In thermal power plants, accidents of thermal power units tripping due to system low...

AI Technical Summary

Problems solved by technology

In such accidents, the internal or external faults of the power plant (lightning strike, short circuit of electrical equipment, grounding, etc.) cause a short-term drop in grid voltage, the drop rate exceeds 15%, and the duration is short. The occurrence of such faults should not have caused Auxiliary machine withdrawal, but because the frequency converter of the key auxiliary machine in the thermal power plant does not have the low voltage function, the low voltage protection of the auxiliary machine dragging the frequency converter is triggered, the frequency converter blocks the output, and the auxiliary machine stops, which eventually leads to the trip of the generator set. machine

Unplanned trips during such failures, on the one hand, affect the power generation continuity and economy of the power plant, and cause damage to the power plant’s power generation equipment. safe and stable operation

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