Direct-current overvoltage control system of uncontrollable rectification unit of cascade high-voltage transducer

Abstract

The invention relates to a direct-current overvoltage control system of an uncontrollable rectification unit of a cascade high-voltage transducer, comprising a phase-shift multi-winding rectifier transformer, a power module group and a CPU (Central Processing Unit), wherein the CPU measures that capacitor voltage udc in a power module is between UL and UH2, normal PWM (Pulse Width Modulation) pulse drives each IGBT (Insulated Gate Bipolar Translator) module in the power module; when udc is less than UL or udc and is more than UH3, each IGBT module in the power module group is locked; when udc is more than UH2 and less than UH3, current flows into a left inverter bridge arm from the alternating current side of a single-phase bridge-type inverter, and the upper IGBT module and the lower IGBT module in the left inverter bridge arm are controlled to cut off and conduct; and meanwhile, the upper IGBT module and the lower IGBT module in the right inverter bridge arm are controlled to respectively conduct and cut off; and normal PWM pulse drives each IGBT module in the power module until udc is more than UL and less than UH2.

Description

technical field [0001] The invention relates to the technical field of cascaded high-voltage frequency converters, in particular to a DC overvoltage control system for cascaded high-voltage frequency converters that does not control rectification units. Background technique [0002] At present, when domestic 10kV motors are used for frequency conversion and speed regulation, cascade type (power module series type) high-voltage frequency converters are used most. Such as figure 1 As shown, the cascaded high-voltage inverter is mainly composed of a phase-shifting multi-winding rectifier transformer T, a power module group (A1~A8, B1~B8, C1~C8) and a control system. On the input side, the phase-shifting multi-winding transformer T steps down the 10kV high voltage to 740V to supply power to each power module. The secondary windings of the phase-shifting multi-winding transformer T are divided into 3 groups. According to the voltage level and the number of modules in series, Ge...

AI Technical Summary

Problems solved by technology

For these large inertial loads, the motor will be in the generator state (the motor rotor flux speed is faster than the stator flux speed) when the frequency conversion speed regulation is performed; because the high-voltage inverter power module adopts diode uncontrolled rectification, DC The side energy cannot be fed back to the grid. If the speed drops too fast, it will cause overvoltage on the DC side of the power module due to the fast energy feedback of the drag system.

[0005] Due to the decentralization of components and control, and the separation of the DC capacitors of the power modules, it is easy to cause unbalanced voltages of the capacitors of each unit (that is, lead to overvoltage of the power module), and the related solutions in the prior art, From the perspective of cost, device control complexity and power consumption, it is not suitable for cascaded high-voltage inverters

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