A parallel control method for multiple T-type three-level inverters using shepwm

Abstract

The invention discloses a parallel control method for multiple T-type three-level inverters using SHEPWM, which includes the following steps: determining the number of switching angles in each cycle according to the number of harmonics to be eliminated; The particle swarm optimization method solves the switching angle of the specific harmonic elimination pulse width modulation, and generates the corresponding specific harmonic elimination pulse width modulation signal; collects the midpoint voltage and zero-sequence circulating current of the T-type three-level inverter parallel system; sets Sequence: Carry out small vector control on the specific harmonic elimination pulse width modulation signal according to the set timing according to the midpoint voltage or zero-sequence circulating current, and rewrite the specific harmonic elimination pulse width modulation signal. The invention controls the midpoint voltage or the zero-sequence circulating current according to the set time sequence. Since the midpoints of multiple inverters are connected, as long as the midpoint voltage of any one of the inverters is well controlled at a certain moment, the midpoint voltage of the system will be balanced.

Description

technical field [0001] The invention relates to a parallel control method for multiple T-type three-level inverters using SHEPWM. Background technique [0002] With the large-scale access of distributed energy sources including photovoltaic power generation systems to the low-voltage distribution network, the power grid puts forward higher requirements on the output current waveform quality of grid-connected inverters. It is difficult for traditional two-level grid-connected inverters to meet large-scale Grid high power quality requirements. The emergence of T-type three-level grid-connected inverters solves the above problems, such as figure 2 As shown, compared with the traditional two-level inverter, the inverter has the advantages of small harmonics, low switching loss, and small electromagnetic interference; compared with the traditional diode-clamped three-level inverter, the inverter has The number of switches is small, the conduction loss is small, and the power lo...

AI Technical Summary

Problems solved by technology

Therefore, T-type three-level inverters have been widely used in distributed power generation occasions such as photovoltaic power generation and micro-grid, but capacity has always been the bottleneck restricting its rapid development.

[0003] The parallel connection of multi-unit T-type three-level grid-connected inverters can increase system capacity, reliability and efficiency, and has become an important choice for high-power distributed power generation. However, hardware mismatch between modules, dead time and control algorithm execution Time and other differences will produce circulation

Circulating current will increase system loss and cause grid-connected current distortion, seriously affecting the life of IGBT switch tubes, so it is of great significance to study the circulating current suppression of parallel T-type three-level inverters

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