T-shaped three-level inverter and neutral-point balance control method therefor

Abstract

The invention discloses a T-shaped three-level inverter, and discloses the input / output relation of all units and the functions of each unit in detail. The invention also discloses a neutral-point balance control method for the T-shaped three-level inverter based on voltage differential prediction. The method overcomes the limitations of a neutral-point balance control method based on zero sequence voltage injection in the prior art, i.e., a zero sequence voltage component being one or zero. Although the adjustment speed is high, a system is liable to lose control and the stability of the system is not facilitated. Moreover, there are more variables in conventional detection, and the calculation burden of a computer is heavy. The method is small in number of collected signals, and the speed of reduction of neutral-point voltage fluctuation is high. The method is low in hardware cost, is simple in program, is small in calculation burden, is high in practicality, is high in robustness, and can guarantee the full-range work stability of the inverter.

Description

technical field [0001] The invention belongs to the technical field of three-level grid-connected inverter control, and specifically relates to a T-type three-level inverter, and the invention also relates to the midpoint balance control of the T-type three-level inverter based on voltage differential prediction method. Background technique [0002] In recent years, the three-level inverter has become one of the ideal choices for high-voltage and high-power applications due to its advantages of large capacity, high withstand voltage level, low output current harmonic content, and low switching loss. Among the many three-level topologies, the T-type three-level inverter uses fewer devices than other three-level inverter topologies. When outputting positive and negative levels, the current flows through fewer devices, and the corresponding The conduction loss is less, especially at present, the output voltage of the photovoltaic array does not exceed 1000V, and the T-type thr...

AI Technical Summary

Problems solved by technology

However, the midpoint voltage fluctuation problem is an important common problem in three-level inverters

This method can not only reduce the switching loss, but also balance the midpoint voltage, but the need to switch will cause control errors and the adjustment speed is poor

To sum up, the above methods all need to detect multiple variables at the same time, and the control process is relatively complicated.

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