Increasing solar PV penetration by improving feeder voltage and congestion through novel SST control strategies

While actively reducing carbon emissions in the electric power field and continuing to install renewable energy (RE) facilities, the stability of the power system faces significant challenges. Due to overvoltage and feeder congestion, the PV hosting capacity is limited in meeting the grid code. In general, STATCOM and smart inverters are employed for seamless voltage regulation, and storage systems enable energy time shifting to enhance PV hosting capacity. However, an alternative solution is proposed. This paper aims to increase solar PV penetration by improving the voltage and congestion of the feeder simultaneously using solid-state transformers (SSTs). For distinct applications, a grid-forming (GFM) SST model and a grid-following (GFL) SST model are presented. In this article, a GFM SST is used to connect traditional ac loads and PV systems, while a GFL SST is used to connect two separate distribution systems that contain distinct power sources. Compared to legacy distribution systems, the addition of the SST in various placements can solve different problems. Basically, through reactive power control methods, various voltage issues can be mitigated to prevent PV curtailment. More importantly, a GFL SST that works as a power flow controller to alleviate feeder congestion and increase PV hosting capacity is proposed for the first time. It is validated that the feeder can maintain voltage and thermal stability while doubling its PV hosting capacity compared to the original design. • Voltage and congestion issues are key factors affecting the development of solar PV. • A grid-forming and a grid-following SST models are presented for distinct use cases. • This article demonstrates voltage regulation methods through an SST. • A grid-following SST that works as a power flow controller can alleviate congestion. • The PSO method is utilized for optimal planning of PV or SST sizing and placement.