A modular approach and controller area network bus implementation in an embedded system of a 3-phase 10 kVA energy efficient switchable distribution transformer

Control systems of switchable transformers play a prominent role in achieving precise timings for switching actions and providing monitoring and protection for the transformers. Since the first energy efficient distribution switchable transformer was designed and built, several designs of control system have been introduced. This paper presents a further development of the control system design which is intended to be embedded in a 3-phase 10 kVA energy efficient switchable distribution transformer. The overall new idea in this design is to implement a modular approach and CAN (Controller Area Network) bus so that multiple jobs can be handled in parallel and a better performance of a control system can be achieved. An AVR microcontroller from Atmel with a built-in CAN controller is used to handle controlling, processing and communication in each module. A physical connection called CAN bus is implemented to achieve reliable communication for up to 1Mbit/s between the modules. Furthermore, a simple protocol has been developed and tested using several microcontroller development boards. This protocol handles transfer of data which are mostly digital values as representation of physical parameters from voltage transformers, current transducers and temperature sensors. The overall system has been tested by applying multiple complex jobs that should be handled by the system, such as reading sensors, processing data, timing controls, remote monitoring and protection.