Control of a High Voltage DC System Using LMI Approach

A procedure for the design and tuning of two control loops of a High Voltage DC system is presented. The controlled variables are direct current on the rectifier side and direct voltage on the inverter side. The dynamics of both control loops interact with each other and are determined by the overall properties of the combined AC/DC system. Constraints on the information available for feedback in each loop require a decentralized controller structure. The AC system impedance is determined by the transmission lines, generators and loads and can suddenly change significantly, so the designed controllers must be robust against these variations. An LMI based iterative approach - referred to as PK-Iteration - is demonstrated to be an efficient tool for the design and tuning of such a decentralized control system.