Design and field implementation of smart grid-integrated control of PV inverters for autonomous voltage regulation and VAR ancillary services

•A novel volt/var control algorithm of PV inverters based on feeder's X/R ratio.•An easy to deploy smart-grid integrated approach for PV reactive power dispatch.•IEC 61131-3 compliant prototype is developed using commercially available RTUs.•Experimentally validated voltage regulation performance on a real-world PV system. Ancillary services from Photovoltaic (PV) inverters can increase distribution system flexibility and alleviate the voltage regulation challenges associated with high PV penetration levels. However, the required communication infrastructure and smart grid integration challenges limit the broad deployment of PV ancillary services. This paper presents a cost-effective volt/var control (VVC) of multi-string PV inverters for active voltage regulation and reactive power dispatch using the existing smart distribution infrastructure to avoid the upfront costs of providing PV ancillary services. The proposed VVC model is developed in MATLAB/Simulink to adapt PV reactive power compensation according to the X/R characteristics of the distribution feeder. An IEC 61131-3 compliant prototype is designed based on Simulink PLC code and deployed to a commercially available remote terminal unit (RTU) using CODESYS standardization tool to address smart grid integration challenges. The proposed VVC scheme is tested in a real-world grid-connected PV system with multi-string inverters for experimental validation. Quasi-static time-series simulation and experimental results demonstrate the validated effectiveness of the proposed control scheme in controlling fast PV fluctuations, resolving voltage violations, voltage flickers, and enabling higher PV penetration.