Three-phase split phase-shifting transformer for high-voltage frequency conversion and its use

Abstract

In the transformer, line side windings connected in star type continuous form is adopted in inner side. Structure of outer side is three groups divided, N groups phase shifted cake typed line side windings. The invented transformer solves issues of harmonic polluting on power grid and harmonic wastage, possessing advantages: reliable operation, simple maintenance, small harmonic current at power grid side, low noise, low heat generated, high power factor. When being applied to high voltage frequency control, the invention solves issues: heating of motor, torque ripple, influence of dv / dr and common mode voltage on insulation of motor. The invention can reaches ideal effect of harmonic elimination even if out of balanced currents occurred, providing advantages of approximate to sinusoidal waveform output, high conversion efficiency etc.

Description

technical field [0001] The invention relates to a transformer and high-voltage frequency conversion technology, in particular to a three-phase split phase-shifting transformer for high-voltage frequency conversion and its application. Background technique [0002] At present, the energy-saving potential of frequency conversion speed regulation of high-voltage AC motors is considerable: although 50Hz is the best frequency for power generation, it is not the best frequency for all electrical equipment. Most of the on-grid AC motors, which account for 2 / 3 of the country's total power consumption, work under the conditions of full voltage, rated frequency, and constant speed, with an efficiency of only 60% and a power factor of only 0.7. If it can work at 5-45Hz, its power saving rate is 20-60%. In the total capacity of AC motors in the network, the capacity of small and medium-sized low-voltage motors accounts for 40%, and the capacity of large-capacity motors in high-voltage ...

AI Technical Summary

Problems solved by technology

From the first generation of SCR to the second generation of GTO, although the voltage level and power size can meet their requirements, the modulation frequency is low, the harmonic content is high, the power factor and efficiency are low, and the structure is complex, and the performance is not satisfactory. It was not developed until the emergence of the third generation IGBT (insulated gate bipolar transistor) and the fourth generation IGCT (integrated gate-controlled converter transistor).

Second, until the end of the 1990s, high-voltage inverters did not have a basically consistent main circuit topology like low-voltage general-purpose inverters (attached figure 1 )

[0005] The disadvantages of AC-AC are: low output frequency (less than 1 / 2 grid frequency), low grid power factor, affected by side frequency harmonics, reactive power compensation and filtering devices are required, high cost, and large area occupation

The harmonic pollution of the high-voltage frequency converter to the power grid and the impact on the motor are relatively serious

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