SVPWM method for single phase three-level NPC voltage-source rectifier

The operating principle of single phase three-level neutral-point-clamped (NPC) voltage source rectifier is analyzed firstly, and its mathematical model is founded with switching functions. According to the problem of DC-link voltage unbalance for single three-level rectifier, space vector modulation PWM method (SVPWM) and feedback neutral point potential voltage control are discussed, and the computer simulation in Matlab is carried. The simulation results show that under the two typical modes of the locomotives, traction and regenerative modes, the power factor on the line side is nearly unity by the SVPWM strategy, and the waveform of the current on the line side is nearly sinusoidal. The method is effective in discrete implementation. The capacitors voltage of the DC-link is balanced by the voltage balancing method.