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 dis. 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.••••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.Renewable energy integrationSmart energy systemsDistribution automationVoltage regulationHigh PV penetration on distribution feeders leads to voltage fluctuations and operational challenges due to the intermittent nature of solar generation. Legacy regulation devices such as on-load tap changers (OLTC) and capacitor banks have relatively slow responses and can alleviate only slow-moving voltage fluctuations. Electric utilities typicall. 2.1. Model development methodologyThe proposed VVC model is developed in MATLAB/Simulink using realistic data collected from an experimental testbed of a real-world PV system connected to a smart distribution feeder with multi-string inverters, as described in Section 3.1. The VVC algorithm code is compiled using Simulink PLC coder to develop a prototype for experimental testing and validation. Quantitative validation is performed to assess the agreement between the simulated and experimental results as shown in Fig. 3.2.2. X/R based volt/var control algorithmIn this section, a deterministic mathematical model is developed for adaptive volt/var control of PV inverters based on the X/R ratio at the point of PV connection to the distribution feeder for autonomous voltage regulation. The X/R-based voltage regulation of a PV inverter can be formulated using a simplified two-node feeder model. The substation bus voltage is assumed to be constant at the nominal voltage with a magnitude of 1 per unit (p.u.) and the conventional inductive power output of the inverter is taken as the negative value, as shown in Fig. 4.Fig. 4. Simplified model of radial distribution feeder.
