Embedding OFDM-Based Carrier Communication into Power Control Loop of Converter in DC Microgrids

In direct current (DC) microgrids, communication between converters is necessary for better power distribution and finer energy scheduling. This paper proposes an orthogonal frequency division multiplexing (OFDM)-based carrier communication method for DC microgrid applications. The method integrates the communication function in the process of power conversion by modulating data into power control loop. To maximize the communication rate in a narrow band limited by PWM control, OFDM technology is applied in the data modulation process. The data is modulated to multiple low-frequency signal carriers, then the modulated wave is added to the output of the power control loop. Since no additional component is needed for sending data, this method has the advantages of low cost and simple implementation. In order to provide theoretical guidance for system design, the DC microgrid applying the proposed method is modeled. Furthermore, important issues of the communication system are discussed, including data frame for at and inter-symbol interference (ISI) problem. At last, a 2 kW DC microgrid experimental platform is established and 9.6 kbps communication rate with a transmission distance of 200 m is achieved, which verifies the feasibility of the proposed method.