Optimal Day-Ahead Operation Considering Power Quality for Active Distribution Networks

Battery energy storage (BES) and distributed generation (DG) play an important role in active distribution networks. However, harmonic problems could be caused by the inverters in BES and DG, resulting in a poor power quality (PQ). In addition, ensuring acceptable voltage unbalance level is also another crucial PQ issue in distribution networks. Therefore, in this paper, an optimal distribution network operational model (ODNOM) is proposed to consider PQ problems caused by BES and DG. In this model, additional network power losses due to harmonics are considered into the objective function, and the harmonic constraints and voltage unbalance constraints are also taken into account. The particle swarm optimization is used to solve the proposed ODNOM. The simulations on the IEEE 13-bus, IEEE 37-bus, and IEEE 123-bus systems show that a satisfactory PQ can be achieved by the proposed approach while optimizing the total branch active power losses. This paper aims to obtain a satisfactory PQ level while minimizing the total branch active power losses in the day-ahead dispatch of active distribution networks, since inverters-based BES and DG can inject harmonic pollution into distribution networks and voltage unbalance level is also an important issue for supplying good quality electricity to end users. To achieve such an objective, PQ constraints such as the total voltage harmonic distortion (THD) constraints, the individual voltage distortion constraints, and the voltage unbalance factor constraints are considered into the day-ahead scheduling. In addition, the network active power losses of the concerned harmonic frequencies are also considered into the objective function. The simulation results of the unbalanced IEEE 13-bus, IEEE 37-bus, and IEEE 123-bus systems show that the proposed approach can give a satisfactory day-ahead schedule of good quality power for active distribution networks. Also, the case studies indicate that total network power losses and the satisfactory PQ are the two contradictory objectives. The proposed approach can be applied to ensure a satisfactory PQ when making a dispatch plan in distribution networks with inverter-based BES and DG.