A Variety of Improvements for Solar Plant

The project is a SCADA system for a 35 MWac solar photovoltaic plant in North Carolina.

Problem: The need is to monitor in real-time the photovoltaic (PV) plant equipment to ensure high availability. This includes more than 1,700 trackers which need to be perfectly oriented. Another need is to control the performance of the PV plant. Energy production of a photovoltaic power plant depends on weather conditions (mostly solar irradiance and ambient temperature). As conditions vary throughout the day, ensuring the plant is operated at maximum achievable yield is a complex undertaking. Another need are the reports required by the utility. Finally, remote access is another important goal. The SCADA system needs to provide information about the PV plant to several stakeholders, which are mostly remote users. However, with PV plants usually being located in remote areas, data connectivity is often an issue (availability, quality of service, cost).

Solutions: Utility-scale PV plants can have thousands of devices to monitor, but the types of different devices to monitor are usually limited, as the plant is built in a modular way. Therefore, PVHardware makes intensive use of UDTs and Template Repeater functionalities. That way PVHardware can effectively configure HMI screens that display the information to the user in the compact view. PVHardware uses scripting and access to the database to calculate real-time performance indicators (performance ratio, specific power, availability, etc.). Raw data is aggregated to generate specific reports as requested by the utility. The Store & Forward Architecture is used in order to synchronize data with the cloud SCADA server and offer users a better experience. Historical data is available independently of site internet connection.

This is the first commercial project where PVHardware implemented an IoT solution. As recommended, the company built this solution in parallel to the traditional architecture. Beside the main SCADA server, there is one IoT gateway with MQTT Transmission modules that recompiles the most important tags and sends data through Sparkplug B MQTT to the remote broker. The cloud SCADA can then subscribe and serve the data to mobile clients. A big advantage of MQTT is that it doesn’t require a fixed IP at the site (only at the broker).