Modular Transformer Converter-Based Convertible Static Transmission Controller for Transmission Grid Management

This paper investigates the concept of convertible static transmission controller (CSTC) using modular transformer converter (MTC) as the building block. The MTC is a bidirectional back-to-back ac/ac power conversion unit and the CSTC is a versatile transmission controller asset for dynamic power flow control and contingency management of the transmission grid. The proposed CSTC with new functions has several advantages compared to existing flexible ac transmission system controllers. System modularity for manufacturers and utilities/system operators using standard high power electronic systems is one of the advantages of this structure. In this paper, algebraic models of the CSTC are derived in two different operation modes (series-shunt and shunt-shunt connecting configurations). The proposed algebraic models are used to define the reference values for the CSTC converters based on the desired operating points for the meshed power system, the power transformers in particular. The dynamic performance of the CSTC with the proposed control structures and algebraic models will be investigated based on the PSCAD simulation. To prove the CSTC as a transmission asset and to verify the control structure and algorithm, ultrahigh fidelity controller hardware-in-the-loop testing has been conducted and comparative results will be presented. Finally, lab-scale experimental results are reported on the dynamic performance of the MTC-based CSTC.