Embedding Power Line Communication in Photovoltaic Optimizer by Modulating Data in Power Control Loop

In a photovoltaic system, a dc-dc power optimizer (DCPO) is an option to maximize the output power. At the same time, data links among DCPOs are often required for system monitoring and controlling. This paper proposes a novel power line communication method for the DCPOs, in which the data of a DCPO are modulated into the control loop of a power converter, and then transmitted through the series-connected dc power line to other DCPOs. In the process of communication, differential phase-shift keying modulation and discrete Fourier transformation demodulation are employed. To analyze the quality of communication, the communication model of the system is built, based on a small-signal model. Furthermore, the noises of the system, including switching, maximum power point tracking, and additive white Gaussian noise, are discussed and measured to evaluate the signal-to-noise ratio. Lastly, an experimental system including six DCPOs is established and tested, which verifies the feasibility and effectiveness of the proposed method.