The Economic and Efficient SOP Based on the Hybrid Transformer With Combination Control

The soft open point (SOP) can improve the dynamic regulation capability of distribution networks and mitigate the adverse impacts of distributed generations (DGs). The back-to-back (B2B) link of voltage source converters has been regarded as the sole SOP topology for a long time, but the high cost hinders the application of SOPs and the upgradation of distribution grids. Some new topologies, such as the solid-state transformers (SSTs) with serial shunt structures, have been discussed as alternative SOP solutions recently. In this work, a cost-effective solution of the SOP based on the hybrid transformer (HT) is proposed. The combination control of the HT, including voltage coordination and power regulation, is analyzed for stable operation under steady and dynamic conditions. The performance is also investigated and compared with that of the B2B and SST schemes. The total converter capacity of the HT-based SOP is highly reduced. It is only sixteen percent of that of the B2B scheme and twenty-eight percent of that of the SST scheme. Efficiency can also be enhanced by 2.7% and 0.9%, respectively. Simulations and experiments have been completed to verify the effectiveness of the proposed solution.