Harmonic elimination problem using iterative methods produces only one solution, not necessarily the optimal solution. In contrast to using iterative methods, an approach based on solving polynomial equations using the theory of resultant, which produces all possible solutions, is used. The set of switching angles that produces the lowest THD is considered. This paper demonstrates how reduced harmonic distortion can be achieved for a new topology of multilevel inverters. The new topology has the advantage of its reduced number of devices compared to conventional cascaded H-bridge multilevel inverter, and can be extended to any number of levels. The modes of operation are outlined for 5-level inverter, as similar modes will be realized for higher levels. Simulation of different number of levels of the proposed inverter topology along with corroborative experimental results are presented.
1. Multilevel inverter
2. Harmonic elimination,
3. Programmed PWM.
Fig. 1: The 5-level inverter of the new topology
Fig. 2: The 7-level inverter of the new topology
EXPECTED SIMULATION RESULTS:
Fig. 3: Output voltage of 5-level inverter at Vdc=50V, and ma=0.8
Fig. 4: Load current of 5-level inverter at Vdc=50V, and ma=0.8
Fig. 5: Harmonic spectrum of output voltage of 5-level inverter at Vdc=50V, and ma=0.8
Fig. 6: Output voltage of 7-level inverter at Vdc=50V, and ma=0.8
Fig. 7: Load current of 7-level inverter at Vdc=50V, and ma=0.8
Fig. 8: Harmonic spectrum of output voltage of 7-level inverter at Vdc=50V, and ma=0.8
Fig. 9: Output voltage of 9-level inverter at Vdc=50V, and ma=0.8
Fig. 10: Harmonic spectrum of output voltage of 9-level inverter at Vdc=50V, and ma=0.8
A new family of multilevel inverters has been presented. It has the advantage of its reduced number of switching devices compared to conventional similar inverters. However, the high rating of its four main switches limits its usage to the medium voltage range. The modes of operation and switching strategy of the new topology are presented. A programmed PWM algorithm based on the theory of resultant has been applied for harmonic elimination of the new topology. Since the solution algorithm is based on solving polynomial equations, it has the advantage of finding all existed solutions, where the solution produces the lowest THD is selected. Other PWM methods and techniques are also expected to be successively applied to the proposed topology. The simulation results and experimental results show that the algorithm can be effectively used to eliminate specific higher order harmonics of the new topology and results in a dramatic decrease in the output voltage THD.
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