Recently, as dependence and demand for electricity are rapidly increasing in all areas, including industry, methods for increasing capacity and reliability through parallel operations have been studied. In general, Modbus communication method with RS485 is used as a method of parallel operation for capacity increase. However, this method has a disadvantage in that it is a half-duplex communication system that cannot transmit and receive at the same time. However, the Modbus communication method is a half-duplex communication system where physical transmission and reception cannot be performed simultaneously. Therefore, as the number of power converters performing parallel operation increases, the communication period increases, which affects the power quality due to the decrease in control speed. Therefore, in this paper, we propose a hardware that can achieve a full-duplex communication method by a communication signal level to improve power quality. The characteristic of the proposed communication hardware is that the transmitter generates two-level signals for data transmission, but the receiver generates three-level electrical signals according to the state of the transmission data generated by the receiver. The generated three-level electrical signal is characterized in that the data transmission signal information of the transmitter and the data transmission signal information of the receiver occur at the same time. As a result, the communication speed is reduced by more than twice, which improves the power quality by improving the control characteristics when performing parallel operation.
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