Embedding Power Line Communication in Photovoltaic Optimizer by Modulating Data in Power Control Loop
In Photovoltaic (PV) system, dc-dc power op-timizer (DCPO) is an option to maximize output power. At the same time, data links among DCPOs are often required for system monitoring and controlling. This paper pro-poses a novel power line communication (PLC) method for the DCPOs, in which the data of a DCPO is modulated into the control loop of power converter, and then transmitted through the series-connected dc power line to other DCPOs. In the process of communication, differential phase shift keying (DPSK) modulation and discrete Fourier transformation (DFT) demodulation are employed. To ana-lyze the quality of communication, the communication model of the system is built, based on small-signal model. Furthermore, the noises of the system, including switch-ing, maximum power point tracking (MPPT) and additive white Gaussian noise (AWGN), are discussed and meas-ured to evaluate the signal-to-noise ratio (SNR). At last, an experimental system including 6 DCPOs is established and tested, which verifies the feasibility and effectiveness of the proposed method.