Development of autonomous power electronics products with communication middleware

In this paper, we introduce a communication middleware and its implementation on two kinds of inverters. This middleware provides services of an automatic and dynamic network configuration (plug-and-play) and operation mode/master switching for distributed cooperative control of electric facilities. Energy end-nodes such as photovoltaic (PV) or batteries are clustered by the middleware to form a larger power conversion system. We made two types of prototypes and compared them. The first implementation was based on an embedded processor of a commercial inverter and the other was based on an ARM/Linux control board that will be attached on the aforementioned inverter. Though both worked well, Linux and its powerful, free software offered certain advantages in terms of design and operation. Loosely coupled design was applied to an abstraction layer of an open-source framework ZeroMQ, and a standardized message format JSON with its library JSON-C were employed for the middleware. They contribute flexibility for various applications in the smart grid. A demonstration with five prototype inverters showed that our concept and implementation work well.