Distributed Optimization of Smart Grid Assets for Grid Operation Preserving Power System Operator Sovereignty

Distributed optimization methods promise to coordinate power system operators to improve the overall grid operation. This paper analyzes and extends existing distributed optimization methods for reactive power dispatch of multiple transmission system operators (TSOs) and distribution system operators (DSOs). For smart grid operations, reactive power provision of distributed energy resources (DERs), voltage magnitude setpoints of power plants and transformer tap positions are optimized by mixed-integer nonlinear programming (MINLP). The methods compared let the system operators (SOs) optimize and operate autonomously to preserve their sovereignty. Simulation results for a German benchmark grid with 261 buses show that all six methods compared have the potential to improve non-coordinated grid operation. One method achieves even near-optimal results. However, a discussion suggests only the investigated sequential method as a promising method for implementation in real grids, especially due to the uncertain convergence behavior of the other methods. Improving the performance of the sequential method and adding a balancing between transmission and distribution system operators' interests are pointed out for future research.