Payam Niknejad - Department of Electrical Engineering, University of Guilan, Rasht, Iran
Seyed Hamid Shahalami

Multilevel inverters have benefits like reduced harmonic distortion and increased power ratings compared to their traditional two level counterparts. With development of the superconducting magnetic energy storage (SMES) technology, as High efficiency energy storage elements, current source multilevel inverters (CSI’s) will be more and more popular in power systems. A new kind of wind energy conversion system with a six-pulse rectifier and a three-phase six-level current source inverter, using staircase Phase Disposition Pulse Width Modulation (PD-PWM), is proposed in this paper which injects a multilevel semi-sinusoidal output current to the power network. The inverter topology consists of three eight-switch three-leg current source inverter bridges whose outputs are connected in parallel and six balance inductors. A novel switching strategy is used to obtain a low THD six-level output current. Three staircase six-level signals which each one has 120 degrees phase difference with two others, are employed to be compared with five triangular carrier signals to generate the control signals for the 24 switches. Simulation results are presented to confirm the operation of the new six-level topology under PD-PWM control, and to verify that little THD can be achieved.

Multilevel Inverters, Current Source Inverters, Renewable Energies, PD-PWM