A hybrid communication method for unit control of cascade multilevel converters

A hybrid communication method for unit control of the cascade multilevel PWM converters is proposed in this paper. The serial communication structure achieved with master and sub-controllers is employed in the converter and the data transmission is based on the Serial Peripheral Interface (SPI). With this structure, benefits of neatness, extensibility and reliability can be obtained, especially when a large number of H-bridge units are required in the high-voltage applications. In order to coordinate the time sequence of each power unit, synchronization signal and fault signal are transmitted in parallel mode, which takes account of the requirement of both the real-time and rapid response of the power electronic system. Optical fibers are used as the transmission medium to avoid the EMI problems. This hybrid serial-parallel communication method is applied to the control of cascade multilevel converters. Experimental results based on the laboratory prototypes verify the viability and effectiveness of the communication structure.