Techno-Economic Evaluation of Mixed AC and DC Power Distribution Network for Integrating Large-Scale Photovoltaic Power Generation

This paper presents a methodology for evaluating the techo-economic feasibility of mixed AC and DC distribution network to replace the existing AC distribution network with large-scale integration of photovoltaic energy sources. Economic dispatch of mixed AC/DC system is formulated in the presence of power electronic transformer (PET) for the flexible control of AC and DC power flows while maintaining the reliability constraints in terms of bus voltage, branch current carrying capacity, and the efficient operation of power electronic converters. Furthermore, the configuration of the PET and power losses of converters with a changing operation efficiency is incorporated into the optimal dispatch problem to assess the energy savings provided by the AC/DC power network. Two objectives for minimizing the operating cost and total power losses are also considered in the formulated economic dispatch. To obtain the Pareto-optimal solutions of this reliability constrained multi-objective optimization problem, the non-dominated sorting genetic algorithm-II (NSGA-II) associated with the interior-point method are applied in the proposed two-stage optimal algorithm to solve the optimization for PET configuration and operation. The method has been tested on the IEEE 33-bus radial distribution system with excessive PV installation and updated PETs. In comparison with the optimal dispatch of existing AC power distribution system, the joint optimization of PET AC/DC ports and PV inverters improves the flexibility of power flow control for both AC and DC networks and thus minimizing the PV curtailment and total operating cost.