Mid-point Potential Balance Control Method for Three-level Inverter

Abstract

The invention relates to a neutral point potential balancing control system and method of a three-level inverter. The neutral point potential balancing control system and method are used for conducting effective balancing control over the neutral point potential of the high-power diode clamped three-level inverter and collecting the DC bus voltage of the three-level inverter and the neutral point voltage value of two capacitors on the DC side in real time, sending collected signals to two independent PI regulators to generate corresponding controlled quantities, determining the operating mode of the system and the corresponding on-off state of switching tubes according to the obtained controlled quantities, determining the neutral point potential by the way of meeting the requirement of the turn-off time ratio of switching devices at the same time, determining the constraint condition of a busbar voltage according to the sum of connecting time, and accordingly adjusting the duty ratio of two switching tubes in an improved three-level DC / DC module, and therefore the busbar voltage on the DC side is controlled so that the dynamic voltage-sharing process of two supporting capacitors on the DC side can be achieved. Fluctuation of the neutral point potential of the three-level inverter is effectively reduced or restrained ultimately, system performance is improved, and the responsiveness of the system and the stability of a three-level topology circuit are improved.

Description

technical field [0001] The invention relates to a power electronic technology, in particular to a three-level inverter midpoint potential balance control method based on a three-level DC / DC. Background technique [0002] Compared with the traditional two-level inverter, the multi-level inverter has the advantages of low withstand voltage of switching devices, small output voltage harmonics, and low switching frequency, so it has been increasingly used in high-power applications in power electronics. Wide range of applications. The three-level inverter is the most widely used one because of its mature topology. [0003] Due to the unique structure and control strategy of the three-level inverter topology, the circuit has the problem of the midpoint voltage offset of the DC side capacitor. This problem will increase the low-order harmonics output by the system, reduce the efficiency, and shorten the life of the capacitor on the DC side in severe cases, and even cause overvol...

AI Technical Summary

Problems solved by technology

[0005] The present invention aims at the problem of the midpoint voltage fluctuation of the DC side of the three-level inverter, and proposes a three-level inverter midpoint potential balance control system and method. Compared with the traditional three-level inverter, only Added hardware input of two switch tubes and two diodes

The control method has high precision and can effectively solve the voltage imbalance problem of the two capacitors on the DC side of the three-level inverter, so that the three-level inverter can run smoothly and safely. At the same time, the dynamic response of the system is fast, and the circuit topology and control method are easy to implement.

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