Research On Multiple Solutions Of Selected Harmonic Elimination PWM For Three-level SVG

With the small voltage stress, small grid-side current harmonics, simple control, reactive power regulation continuous, and fast response characteristics, the three-level SVG has been widely used in the power system, for it can stabilize the grid voltage and improve the power factor of the system.Firstly, Selective Harmonic Elimination PWM(SHEPWM) nonlinear equations based on Diode clamped three level topology was set up. To solve that nonlinear equation, the solution of the initial value was improved. Then the result of this nonlinear equation was analyzed, a series of switching angle results under same modulation depth were obtained.Secondly, the modulation depth of three-level SHEPWM and three-level space voltage vector pulse width modulation were deduced, and the quantitative relationship is determined.Compared the switching angle trend of the three-level SHEPWM related the modulation depth,with the three-level space voltage vector distribution and modulation characteristics, the internal relationship between the three-level SHEPWM and the three-level space-voltage vector pulse width modulation strategy is studied.Finally, based on the PSIM simulation software, and three-level SVG experimental platform,in which TMS320xLF28335 DSP was selected as core controller, the solution of simulations and experiments of three level SHEPWM were completed, neutral point potential in DC side, current in grid side, and AC voltage harmonic characteristics of three-level converter were analyzed. The results show that the algorithms are correct, and the results in this paper provide a basis for the further optimization of the three-level SHEPWM.