A tool for stability and power sharing analysis of a generalized class of droop controllers for high-voltage direct-current transmission systems
For power systems engineers, this provides a theoretical framework for analyzing droop controllers in HVDC systems, but the results are incremental and lack concrete performance numbers.
The paper addresses primary control of high-voltage direct current transmission systems, proposing a new nonlinear model and deriving necessary conditions for equilibrium existence, power sharing, and stability. Numerical results on a four-terminal example illustrate the theoretical findings.
The problem of primary control of high-voltage direct current transmission systems is addressed in this paper, which contains four main contributions. First, to propose a new nonlinear, more realistic, model for the system suitable for primary control design, which takes into account nonlinearities introduced by conventional inner controllers. Second, to determine necessary conditions - dependent on some free controller tuning parameters - for the existence of equilibria. Third, to formulate additional (necessary) conditions for these equilibria to satisfy the power sharing constraints. Fourth, to establish conditions for stability of a given equilibrium point. The usefulness of the theoretical results is illustrated via numerical calculations on a four-terminal example.