Centralized MPPT Controller System of PV Modules by a Wireless Sensor Network

An efficient monitoring and control system for solar photovoltaic modules, which combines the use of a non-linear MPPT backstepping controller with a custom wireless sensor network (WSN) has been developed. The infrastructure consists of a wireless smart photovoltaic system (WSPS) and a wireless centralized control system (WCC). The data of sensing, coordination and control is handled by using a WSN based on IEEE 802.15.4 technology in beacon enable mode and with guaranteed time slot. This assures the data transmission and a synchronous acquisition, which are critical elements in a wireless photovoltaic monitoring system. All measured data is gathered by an autonomous, compact and low-cost sensor node installed in each PV module, and it is transferred to the coordinator node. The power consumption of the sensor node represents only 0.25% of the power delivered by the photovoltaic module. A backstepping controller to track the Maximum Power Point (MPP) by means of a buck-boost converter derives the reference parameters to return to each PV module accordingly. The wireless solution uses low latency techniques to achieve a real-time monitoring and a stable performance of the controller. The centralized control identifies all the network nodes and significantly simplifies the maintenance operations. Experimental validation shows the robustness against interference and security in the wireless data transmission and confirms the feasibility of the proposed wireless sensor system in tracking the maximum power transfer under different weather conditions, achieving an efficiency over the 99% in the MPPT.