Tuning of a Damping Controller for Multiterminal VSC-HVDC Grids Using the Probabilistic Collocation Method

This paper presents a robust probabilistic controller tuning method to improve the damping of critical system modes through the modulation of active power injected by a voltage-source converter-based multiterminal high-voltage direct current (VSC-MTDC) grid. This methodology first establishes the probabilistic locations of the critical modes based on the known variation in power system operating conditions. Following this, the modal linear quadratic Gaussian (MLQG) controller structure is tuned for a set of probabilistic values of critical eigenvalues. The controller´s performance following small disturbances in the network for wide-ranging operating conditions is compared with the conventionally tuned MLQG controller designed for the nominal system operating point. The probabilistic collocation method is shown to facilitate robust probabilistic tuning without the need for large numbers of full system linearizations. The test system used incorporates a large wind farm with variable power output connected to the meshed ac network through the VSC-MTDC grid.