Reactive Power Optimization of Active Distribution Network under Parallel Condition of Solid State Transformer and On-Load Tap Changer

Parallel operation of power transformers is a common phenomenon in power networks and plays a key role in the development of active distribution network (ADN). In this paper, a parallel operation model of a solid-state transformer (SST) and an on-load tap changer (OLTC) is proposed, which can not only improve the power supply reliability of the grid, but also compensate for reactive power and maximize the use of clean energy. On this basis, the reactive power optimization (RPO) model of an ADN under the parallel condition of a SST and an OLTC is constructed. Firstly, considering the SST's own loss, a SST steady-state model is established. Secondly, to eliminate the circulation current in the parallel system, the master-slave control strategy is adopted, and the parallel model is established accordingly. In addition, a modified whale optimization algorithm (MWOA) is proposed for system RPO. Finally, an IEEE 33-bus system is used for the verification of the proposed model.