Voltage balancing method and system for a direct-current side series capacitor of three-level inverter circuit

Abstract

The invention belongs to the field of three-level inverter circuits, and discloses a voltage balancing method and system for a direct-current side series capacitor of a three-level inverter circuit, and the method comprises the steps: obtaining the voltage of a first capacitor and the voltage of a second capacitor; when the difference between the voltage of the first capacitor and the voltage of the second capacitor is positive, switching off a switching tube directly connected with the second capacitor, calculating a first duty ratio according to the difference between the voltage of the first capacitor and the voltage of the second capacitor, and switching on the switching tube directly connected with the first capacitor according to the first duty ratio; when the difference between thevoltage of the first capacitor and the voltage of the second capacitor is negative, switching off the switching tube directly connected with the first capacitor; and calculating a second duty ratio according to the difference between the voltage of the second capacitor and the voltage of the first capacitor, and switching on a switching tube directly connected with the second capacitor according to the second duty ratio. The switching tube directly connected with the first capacitor and the switching tube directly connected with the second capacitor are independently controlled, so that the problems of relatively large current and serious heating of the balance circuit during light load are solved.

Description

technical field [0001] The invention belongs to the field of three-level inverter circuits, and relates to a method and system for voltage balancing of capacitors connected in series on the DC side of a three-level inverter circuit. Background technique [0002] Since the three-level inverter circuit is directly connected to the capacitor on the DC side, there is a problem of inconsistent capacitor voltage, so certain measures need to be taken to maintain voltage balance. [0003] Commonly used methods include adjusting the way of sending waves, adding a balance circuit and other methods. Among them, the wave-adjusting method cannot be used in the three-phase four-wire circuit due to the complexity of the voltage vector in the three-dimensional space. Although the method of adding a balanced circuit can achieve capacitor voltage balance, the conventional balanced circuit control method has the problem that the balanced circuit current at light load is close to that at full ...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to overcome the shortcomings of serious heating and low efficiency of the balance circuit in the prior art, and provide a voltage balance method and system for the DC side series capacitors of the three-level inverter circuit

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