Nonlinear coordination control strategy of DC power modulation in multi-infeed HVDC power systems

A novel nonlinear DC power modulation control strategy is proposed in multi-infeed HVDC power systems. The essential design idea is to drive the center of inertias (COI) of individual areas linked by AC/DC lines to a stable equilibrium point, so that the inter-area oscillations of multi-infeed HVDC systems can be damped out. COI signals are assumed to be available from the wide area measurement system (WAMS). Based on a three-area AC/DC system model derives in COI coordinate, the back-stepping method is applied to work out the nonlinear robust adaptive control law, which is adaptive to the unknown parameters and is robust to model error, disturbances and equilibrium point change. Computer simulation results of a six-generator-three-area test AC/DC system show that the proposed controller is superior to conventional DC power modulation controllers and can well coordinate to each other to damp interarea oscillations. Besides, the controller performance is not sensitive to the system structure and operation point changes. (7 pages)