Medium-voltage frequency converter capable of realizing AC-AC (alternating-current) direct transformation

Abstract

The invention provides a medium-voltage frequency converter capable of realizing AC-AC (alternating-current) direct transformation, belonging to the technical field of frequency converters and comprising a reduction transformer and three converter arrays, wherein three three-phase secondary windings of the reduction transformer are respectively connected with input ends of the three converter arrays. The medium-voltage frequency converter is novel in conception, strong in generality and simple in overall structure, and can improve power factors of network sides.

Description

technical field [0001] The invention relates to a device in the technical field of frequency converters, in particular to a medium-voltage frequency converter for AC-AC direct conversion. Background technique [0002] In the field of three-phase medium-voltage frequency conversion speed regulation, a cascaded inverter of multi-stage series voltage source inverter is commonly used, which belongs to the high-low-high type, and the maximum input voltage is 10kV. Generally, uncontrolled rectifiers are used, and a few use three-phase controlled rectifiers. High-low-high type cascaded inverter, the general structure includes 3x stages of three-phase uncontrolled rectifiers, 3x stages of single-phase voltage source inverters, a step-down transformer with high-voltage input and low-voltage output, and the characteristics of the step-down transformer The primary is a Y-connected three-phase winding, and the secondary is a number of meandering three-phase windings with 3x series. The...

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Problems solved by technology

[0003] After searching the existing technical literature, it was found that the Chinese patent application number: 02104140.7, the patent titled "High Voltage High Power Frequency Converter Without Harmonic Pollution"; "Research on Technology" (Shanghai University Doctoral Dissertation. February 2006) also discloses the application of cascade multiplexing, that is, multi-stage series connection in a certain range, which plays the role of frequency conversion, voltage regulation and speed regulation, energy saving and consumption reduction, both in theory and practice. It proves that the cascaded inverter structure with multiple stages in series is a feasible circuit structure, but there are still existing problems that cannot be ignored in the power structure, such as: the design of the step-down transformer is complicated, which is manifested by the design of the secondary winding winding; the three-phase rectifier The quantity is large; the load of the rectifier is unbalanced, and a large-capacity electrolytic capacitor is required; the whole machine is large in size, low in efficiency, high in cost, complex in control, and poor in performance; higher voltage output requires more inverter series series

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