Selective Harmonic Optimization for Flexible Single-Phase Operation of Cascaded H-Bridge Multilevel Inverters
In this research work, a generic output signal model of a multilevel inverter are mathematically modeled and compared with harmonic based decomposition conventional signal model. The mathematically modeled signal are used for the formulation of selective harmonic optimization and it is solved using one of the stochastic evolutionary algorithms. Below images are few simulation results showing the comparison of various signals (actual, desired and obtained) for various extents of switching.
3-level single-phase inverter
Voltage Output of a 3-level single-phase inverter
5-level single-phase inverter
Voltage Output of a 5-level single-phase inverter
7-level single-phase inverter
Voltage Output of a 7-level single-phase inverter
Simulation Results
Case–1.a.
THD≈13% [Too high]
5 voltage levels
Transitions per cycle is 8
Max. inst. Fswitching= 500 Hz
Case-1b
THD<5% [within limits]
7 voltage levels
Transitions per cycle is 12
Max. inst. Fswitching= 800 Hz
Case-2
THD is high [expected ]
9 voltage levels
Transitions per cycle is 50
Signal with harmonics is presented here
