Three-level three-phase power source transformation device capable of initiatively balancing clamp voltage of neutral points

Abstract

The invention provides a three-level three-phase power source transformation device capable of initiatively balancing a clamp voltage of neutral points and relates to a three-level neutral point clamp type PWM (Pulse-Width Modulation) inverter device which is one of power conversion devices of a connecting system, and a control (balance) device which is used in the three-level neutral point clamp type PWM inverter device and controls the voltage (current) at the neutral points of two capacitors connected in series between a positive bus and a negative bus, wherein the device consists two part devices, the first part device is of a three-phase neutral point clamp type PWM inverter device, the second part device is of a device for restraining the voltage of the natural point from deviating, the second part device is connected with the neutral point of the first part device by virtue of a serial inductor, and the device for restraining the voltage of the natural point from deviating can be used for efficiently restraining the change of the potential at the neutral point of the three-phase neutral point clamp type PWM inverter device, therefore, the safety can be improved, and the quality of output voltage can be enhanced.

Description

technical field [0001] The present invention relates to power conversion devices such as inverters and servo drives for variable-speed drive motors, three-level neutral point clamp type PWM (pulse width modulation) inverter devices as one of power conversion devices for connection systems, and The neutral point voltage (current) balancing device between two capacitors connected in series between the positive bus bar and the negative bus bar is used in the three-level neutral point clamped PWM inverter device. Background technique [0002] Such as figure 1 It is a circuit diagram showing the main circuit configuration of a three-level neutral point clamp type PWM inverter device. The three-level neutral-point clamped PWM inverter device is composed of two capacitors 7 , three-phase output terminals UVW, 12 switching elements, and 18 diodes 9 . In this three-level neutral point clamped PWM inverter device, the switching element 8 1 ,8 2 When conducting, the output terminal...

AI Technical Summary

Problems solved by technology

Its shortcoming is that when controlling the neutral line current, the method of changing the ratio of the voltage vector will cause the output line voltage and part of the common mode voltage to degenerate into the line voltage and the output line voltage of the two-level PWM inverter. The common mode voltage is the same, which not only brings the complexity of control, but also produces more harmonics and strong electromagnetic interference

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