Speed regulating system of high power factor load current-change synchronous motor

Abstract

A speed regulating system of a high power factor load current-change synchronous motor belongs to the technical filed of power and electron and comprises an alternating-current side LC filter, a PWM type rectification circuit directly connected in series with a full-control type power electronic device, a direct-current side filter reactor and an inverter circuit directly connected in series withal polycrystalline gate tube with 6 pulses, wherein a three-phrase input power supply is connected to the input upper end of the three-phrase PWM type rectification circuit formed by the full-control type power electronic device through the alternating-current side LC filter formed by a three-phrase inductor and a three-phrase capacitor; the PWM type rectification circuit rectifies an alternating-current power supply into a direct-current power supply with changeable amplitude values by changing trigger pulses of the full-control type power electronic device according to the computing result of a control system; and the inverter circuit controls the frequency and amplitude values of the stator current of the synchronous motor to output the frequency and the amplitude values to a stator of the synchronous motor by changing trigger pulses of a thyristor to modulate the direct current according to the computing result of the control system. The invention has the advantages that current at grid side is sine wave, and the power factor of unit power at grid side is adjustable and can approach to 1.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular provides a high power factor load commutation synchronous motor speed regulation system, which can be used in a high-power synchronous motor frequency conversion speed regulation transmission system. Background technique [0002] In the high-power industrial field, synchronous motors have been widely used due to their high efficiency and high reliability. Frequency conversion and speed regulation of synchronous motors can significantly save energy and reduce consumption, and bring huge economic benefits. At present, load-commutated inverters (Load-Commutated Inverter, LCI for short) are generally used in the occasions of high power, especially ultra-high power (over 100 MW). LCI consists of three parts: rectifier, DC filter reactor and inverter. The rectifier generally adopts a common 6-pulse thyristor rectification circuit structure, and its function is to convert f...

AI Technical Summary

Problems solved by technology

However, the main disadvantage of LCI is that its rectifier usually adopts a common 6-pulse thyristor rectification circuit structure. The input current of this rectification circuit contains a high harmonic component, and the 5th harmonic of the input current can reach 20%, and the 7th harmonic The wave can reach 12%, and it also contains high-order harmonics generated by the fast commutation of the thyristor. The total harmonic current distortion is about 30%; and in the thyristor rectifier circuit, the voltage of the intermediate DC link is proportional to the rated value of the motor line voltage Multiply by the actual power factor of the motor at the operating point, and then multiply by the percentage of speed

Therefore, for square torque loads such as fans and water pumps, the DC link voltage will drop rapidly as the speed decreases, so the input rectifier circuit must move the firing angle backwards, which will cause the input power factor to drop quickly. Therefore, in general, LCI input power factor is low and will decrease as the motor speed decreases

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