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CPES Patent Information
US Patent: 9966874
Power-Cell Switching-Cycle Capacitor Voltage Control for Modular Multi-Level Inverters
Jun Wang, Rolando Burgos, Dushan Boroyevich, Bo Wen
Issued: May 08, 2018
Abstract:
In a modular multi-level power converter, additional switching states are interleaved between main switching states that control output voltage or waveform. The additional switching states provide current from a DC-link to charge capacitors in respective modules or cells to an offset voltage from which the capacitor voltages are controlled toward a reference voltage during each switching cycle rather than being allowed to build up over a period of an output waveform of variable line frequency, possibly including zero frequency. Since the switching cycle is much shorter than the duration of a line frequency cycle and the capacitor voltages are balanced during each switching cycle, output voltage ripple can be limited as desire with a capacitor of much smaller value and size than would otherwise be required.
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