Hybrid communication topology and protocol for distributed-controlled cascaded H-bridge multilevel STATCOM

Distributed control scheme is preferred to the multiple-modules-based system because of the simple structure, low maintenance, and high scalability. This paper proposes a hybrid communication topology and a route-switching communication protocol to implement the distributed control applied in the cascaded H-bridge (CHB) multilevel static synchronous compensator (STATCOM). The hybrid topology consists of multiple paralleled synchronous communication branches and each branch has very small transmission delay, which makes it possible to apply the low-speed communication network, such as 5 Mb/s optical fiber, to reduce the cost and improve the reliability. The route-switching communication protocol promises the global fault response of the STATCOM as quick as 10 μs by switching from the long normal data to the short fault signal when the module fault occurs. Experiments based on the CHB 13-level STATCOM prototype verify the effectiveness, flexibility, and reliability of the proposed topology and protocol.