Robust Optimal Power Flow for Mixed AC/DC Transmission Systems With Volatile Renewables
The rising share of renewable generation increases uncertainty in power system operation. New methods are needed for secure operation of power systems under uncertainties. We present a robust optimal power flow algorithm for mixed ac and dc power transmission systems which considers uncertain renewable generation and/or load. The uncertain infeeds are assumed to lie inside a known norm-bounded set. The presented algorithm guarantees satisfaction of various steady-state power system constraints for all uncertainties within this set. In order to satisfy these constraints at minimal cost, the algorithm modifies both the redispatch and primary reserve. This is done through the optimization of setpoints and droop gains of generators and high-voltage dc converters. The algorithm is evaluated on a test system, the Cigre B4 DC grid, the IEEE RTS 96 grid, and on the Danish transmission system. In these examples, we show that redispatch costs can be reduced by additionally optimizing primary reserve, and demonstrate primary reserve sharing between asynchronous ac grids through dc grids. We illustrate the impact of the uncertainty set choice on the worst-case redispatch costs, perform a sensitivity analysis of the approach, and evaluate the computation time as a function of the number of uncertainties.