A mid-point voltage balance control method of T-type three-level inverter using shepwm

Abstract

The invention discloses an SHEPWM (selective harmonic elimination pulse width modulation) adopted T type three-level inverter neutral-point voltage balance control method. The number of switching angles in each period is determined according to the number of harmonic orders needing to be eliminated; a selective harmonic elimination pulse width modulation switching angle is solved based on a multi-objective particle swarm optimization method to generate a corresponding selective harmonic elimination pulse width modulation signal; the T type three-level inverter neutral-point voltage is collected; the signal is optimized; if the T type three-level inverter neutral-point voltage is within a threshold value range, the T type three-level inverter is not changed and the signal directly enters the three-level inverter; and or otherwise, the switching state is replaced by a corresponding low-vector signal to modify the selective harmonic elimination pulse width modulation signal. The control method provided by the invention has the same function of eliminating low-order harmonics as the conventional SHEPWM; and in addition, the control method can maintain the neutral-point voltage balance and can enable the T type three-level inverter to operate stably and efficiently.

Description

technical field [0001] The invention relates to a middle point voltage balance control method of a T-type three-level inverter adopting 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 1 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, an...

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Problems solved by technology

[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 Power grid high power quality requirements

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