# Research on Optimal Voltage Control of Distribution Network with the Participation of EVs and PVs
## 5 Conclusions  
Due to the intermittent power generation of distributed PV systems and the spatiotemporal uncertainty of uncontrolled EV charging, the accelerating grid penetration of EVs and PVs brings in severe voltage deviations and voltage fluctuations. The conventional voltage regulation resources in distribution networks include OLTC transformers and CBs, which are featured by slow response and limited lifetime duration with the increased number of operations. Compared to OLTC transformers and CBs, PVs, and EVs get connected to the power grid via fully controllable power electronic converters, making them ideal voltage support resources. In this context, a two-stage control scheme for the voltage regulation of distribution networks is proposed and is made of day-ahead control and intraday control. The day-ahead control is for mitigating the potential voltage violations via the optimal operation settings of OLTC transformers and CBs. The intraday control is for further alleviating the voltage deviations and fluctuations based on the voltage drop control of PV systems and the ROCS-based EV charging/discharging schedule. To evaluate the feasibility of the proposed two-stage voltage regulation scheme, case studies are performed on the IEEE 123-node test feeder with EVs and PVs connected. The simulation results demonstrate that the proposed control scheme can effectively improve the grid voltage distribution patterns.  
In future works, the proposed two-stage control scheme will be combined with the voltage adaptive dynamic partition methods to improve its applicability for large-scale distribution networks. In addition, as the aggregate voltage support capability will vary with different functional subareas of the city, subarea aggregation models will be developed for EVs and PVs, with the time and space couplings among agents fully considered. Ultimately, the voltage support capability of EV chargers and PV inverters is limited due to the constraints of fulfilling EV charging tasks and avoiding PV active power curtailments. To further enhance the voltage support capability of EV chargers and PV inverters in future studies, a mild decoupling between fully controllable PE converters and the power grid is required, which can be achieved by adequately designed battery energy storage systems integrated into EV charging stations and PV parks.  
**Author Contributions:** Conceptualization, Y.Z. and F.G.; methodology, Z.Z.; software, S.Z.; validation, X.X., Y.Z. and Z.Z.; formal analysis, F.G.; investigation, X.X.; resources, S.Z.; data curation, X.X.; writing--original draft preparation, S.Z.; writing--review and editing, H.M.; visualization, X.X.; supervision, Z.Z.; project administration, Y.Z.; funding acquisition, H.G. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was supported by the Science and Technology Project of State Grid Jiangsu Electric Power Company, Ltd., (no: J2022136).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data are contained within the article.  
**Conflicts of Interest:** The authors declare no conflict of interest.