An energy feedback type three-phase high-voltage inverter

Abstract

The invention discloses an energy feedback type three-phase high-voltage frequency converter, comprising a main transformer, three-phase reactors, three-phase low-voltage frequency converters with energy feedback functions, and three-phase output transformers. Secondary windings of the main transformer comprise M lines of symmetrical three-phase outputs which are separated from each other and are equal in phase and voltage; and one secondary winding is connected to an input end of each three-phase low-voltage frequency converter through a three-phase reactor. Output ends of the three-phase low-voltage frequency converters are connected to a load or to windings of the output transformers; and three output phases of each low-voltage frequency converter are connected to corresponding output phases of the high-voltage frequency converter in direct series connection or in series connection through coupling of the output transformers.. For three low-voltage frequency converters whose two phases among three output phases are directly connected in series to corresponding high-voltage ac output phases, public output ends of the two phases are used as output ends of the high-voltage frequency converter. According to the invention, input / output ripple current of the low-voltage frequency converters is decreased, driving performance of the load is improved, and cost of the high-voltage frequency converter is declined.

Description

technical field [0001] The invention relates to power electronics technology, in particular to an energy feedback type three-phase high-voltage frequency converter. Background technique [0002] At present, industrial energy saving has been widely valued by the society. As an important power-consuming equipment, high-voltage motors have increasingly adopted frequency conversion speed regulation technology to achieve economical operation. [0003] Since Peter W. Hammond proposed the unit series multiple pulse width modulation (PWM) high-voltage inverter in 1995, this method of realizing frequency conversion and speed regulation of high-voltage motors through low-voltage power electronic conversion technology has good output voltage waveforms and input harmonic currents. Low cost, low cost, and easy maintenance have become the mainstream of high-voltage frequency conversion speed regulation technology. The units are connected in series with multiple PWM high-voltage inverters...

AI Technical Summary

Problems solved by technology

[0009] In this unit series multiple PWM high-voltage inverter, each power unit is a single-phase output. When the output frequency is low, the DC bus voltage in the power unit fluctuates greatly, resulting in an increase in the output harmonic current of the inverter. It affects the starting performance and low-speed operation performance of the motor; increasing the filter capacitor of the power unit can improve it, but the filter capacitor capacity is too large, the price is high, and the life is short, which not only increases the cost of the high-voltage inverter, but also increases the operating time during use. maintenance workload; the main transformer is a phase-shifting transformer, the number of secondary windings of the main transformer is too many (6 circuits, 18 windings), and the manufacturing process is complicated, which increases the manufacturing cost of the main transformer; the number of power units is too large (6 ), the high-voltage inverter uses a total of 60 solid-state power switches, which also increases the material cost of the inverter; in addition, each power unit has an independent voltage and current detection and rectification control circuit, which not only increases the material cost, but also increases the cost of each power The rectification PWM synchronization of the unit is difficult, and the current ripple on the primary side of the main transformer caused by the power unit cannot cancel each other out

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