The main objective of this paper is to study and analyse the voltage output waveform of a multilevel invert er, to suggest a new approach for harmonic mitigation improving the converter performance. These last type of converters represent a new technology in the field of DC/AC electrical energy conversion, presenting advantages respect to the traditional converters. In fact, the multilevel power converters present a low harmonic content and a high voltage level. The paper considers a five-level single-phase cascaded H-bridge invert er (CHBMI) and fundamental frequency modulation techniques. The voltage waveform analysis has allowed to identify a working area of the converter where there are lowest values of the considered harmonic amplitude. The simulated behavior of the model of the converter, with the logic piloting gate signals, has been obtained in Mat lab-Sim u link environment.
- Multilevel Power Converter
- Soft switching
- Phase Shifted Voltage Cancellation
SOFTWARE: MAT LAB/SIM U LINK
Fig. 1. Single-phase five-level CHBMI
EXPECTED SIMULATION RESULTS:
Fig. 2. Gate signals H-Bridge I with a=~=30°.
Fig. 3. Gate Signals H-Bridge 2 with a=~=30°.
Fig. 4. Voltage trend over time with a=~=30°.
In this paper a fundamental switching modulation strategy for single-phase five-level CHBMI that mitigate low order harmonics is presented. The proposed method, through the control of the a and P parameters, allows the mitigation of third, fifth, seventh, ninth and eleventh harmonics. The values of the control parameters can be obtained without needs to solve a set of nonlinear transcendental equations. However, the fundamental harmonic amplitude can only be varied from 42% to 92% of 2 (V o c*4 Y r r).
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