Space Vector PWM Algorithm for Diode Clamped Multi-level Inverters using Fractal Structure
P. Satish Kumar1, Ch. Lokeshwar Reddy2, V. Ramu3
1Dr. P. Satish Kumar is with the Department of Electrical Engineering, University College of Engineering, Osmania University, Hyderabad, Andhra Pradesh, India.
2Ch. Lokeshwar Reddy is with the Department of Electrical and Electronics Engineering, Hyderabad Institute of Technology and Management, Hyderabad, Andhra Pradesh, India.
3V. Ramu is with the Department of Electrical and Electronics Engineering, University College of Engineering, Kakatiya University, Kothagudem,Andhra Pradesh, India.
Manuscript received on November 02, 2011. | Revised Manuscript received on November 14, 2011. | Manuscript published on December 30, 2011. | PP: 42-49 | Volume-1, Issue-2, December 2011. | Retrieval Number: B0130111211/2011©BEIESP

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Abstract: In this paper a space vector pulse width modulation algorithm for diode clamped multilevel inverter fed induction motor using the fractal structure has been proposed and applied for three-level and five-level inverters. In this method, fractal structure is used to represent the space vector of multilevel inverters. The switching sequence is determined without using look up tables, so the memory of the controller can be saved. The 1switching times of voltage vectors are calculated at the same manner as two-level SVPWM. It is easy to implement the triangularisation algorithm, which is used to locate the tip of the reference voltage vector. Thus, the proposed method reduces the execution time and complexity of multi-level SVPWM. This method can be extended to n-level inverter also. Based on above method, the simulation is carried out for three-level and five-level inverter fed induction motor and results are presented and analyzed. The obtained total harmonic distortions for three-level and five-level inverters are 5.70% and 3.61% respectively.
Keywords: Fractal structure, Induction motor, Multi-level inverters, Modulation index, SVPWM, THD.