Advanced Inverter Voltage Controls: Simulation and Field Pilot Findings

Abstract

This report describes work performed by the Hawaiian Electric Companies and the National Renewable Energy Laboratory (NREL) to model and simulate advanced inverter grid-support utility-interactive 1 (GSUI) functions and to validate and expand on those simulations through a field pilot study. This work builds on earlier research, referred to as the Voltage Regulation Operational Strategies (VROS) study (Giraldez, et al., 2017) (and is referred to as "VROS 2017" in this report). The objective of both the original VROS 2017 study and this update is to investigate functionalities available in most photovoltaic (PV) systems equipped with advanced inverters to modulate active and reactive power autonomously based on local voltage measurements for the purpose of mitigating off-nominal grid voltage conditions. Specifically of interest are volt/volt-ampere reactive (VAR) control and volt/Watt control 2 , the effect of those functions on quasi-steady-state feeder voltages, and the impact of the functions on PV energy production. Because volt/VAR in combination with volt/Watt (volt/Var-volt/Watt) control autonomously adjust inverter output based on local conditions without requiring communication with any other devices, they are good candidates for non-wire alternatives to increase PV hosting capacity when the limiting factor is voltage constraints in a transformer secondary service with very large numbers of PV systems.

Distributed Wind Controls: A Research Roadmap for Microgrids, Infrastructure Resilience, and Controls Launchpad (MIRACL)

“…After the simulation study, NREL also performed pilot field testing at HECO feeders and collected real-time data from their grid sensors (GRID20/20 distribution transformer meters and AMI data) (Giraldez et al 2018). The plots in Figure 12 summarize the results and confirms the observation from the aforementioned simulation studies.…”

Estimation of solar photovoltaic energy curtailment due to volt–watt control

“…In our previous study [26], we simulated a very high PV penetration scenario, with 10.9 MW of total PV installations for a network with 6.5‐MVA peak load and 2.8‐MVA minimum load. A high‐voltage week was selected to capture PV production curtailed as a result of high voltage and the corresponding activation of volt–watt and volt–VAR control to mitigate the voltage limit violation.…”

“…In a previous voltage regulation operational strategy (VROS) study by Giraldez Miner et al . [26], PV energy curtailment was estimated using a detailed simulation for hundreds of customers in Hawaii with rooftop PV and advanced inverters. Curtailed PV production was estimated by computing the difference between a base case scenario simulating customer PV output without GSF activation and a scenario with GSF activation in a time‐series power flow simulation.…”

Rooftop PV and the Renewable Energy Transition; a Review of Driving Forces and Analytical Frameworks

“…ISOs also lack technologies, such as improved inverter and metering technologies, that can allow them to control the rooftop PV systems located across the distribution system, [91,92]. The absence of these devices has also been identified as an issue that impacts the ability to implement time of use tariffs, or to be externally controlled by third parties via demand response (we have adopted the definition for demand response as used by [93]: "Changes in electric usage by end-use customers from their normal consumption patterns in response to changes in the price of electricity over time, or to incentive payments designed to induce lower electricity use at times of high wholesale market prices or when system reliability is jeopardized") programs or to participate in distributed energy markets such as VPPs and P2P schemes [94].…”