March 20, 2019
March 20, 2019
March 22, 2019
This paper presents the results of an interdisciplinary undergraduate research project that investigated the economic cost and benefits of implementing Volt-VAR optimization (VVO) on distribution feeders with an emphasis on the Pacific Northwest region. The team comprised of two undergraduate students, an electrical engineering professor, and engineers from a local utility. Volt-VAR optimization is the combination of both conservation voltage reduction (CVR) and volt-ampere reactive (VAR) optimization. The goal of CVR is to reduce energy consumption by lowering the voltage magnitude toward the lower limit of the ANSI C84.1 range (i.e., 114 V). This scheme uses End of Line (EOL) measurements to control the substation voltage regulators so that the appropriate voltages are set. To implement VAR optimization, utilities switch shunt capacitors onto distribution system feeders to reduce the amount of power losses resulting from reactive power flow. Implementing both CVR and VAR optimization in tandem by using advanced communication and control schemes comprise the complete VVO system.
Time series data were collected from simulations conducted using GridLAB-D software at step sizes of 1 minute for an entire year. Loads on the distribution system were modeled using both the traditional static ZIP model, whose weights were determined through a least squares fit. Thermostatically controlled loads were modeled using the equivalent thermal parameter (ETP) model. The closed-loop control equations were described using differential equations due to their time varying nature. Finally, a composite model was developed by combining the two different types of loads that appear on a distribution system to develop a representative building load. The loads were then aggregated together and through the law of large numbers, appear identical to the actual behavior of loads on a distribution system. The relative weights of different loads were varied until they were found to match that of actual supervisory control and data acquisition (SCADA) data. Simulations on 24 prototypical distribution feeders were performed using GridLAB-D both with VVO and without. The resulting energy consumption was then analyzed for both cases. Estimation for the economic costs and benefits of VVO in the Pacific Northwest was done by combining both simulation data and past survey data from the Snohomish PUD. Energy cost savings are then converted to dollar amounts using market rate electricity prices for each region (i.e., typically 10 cents per kWh). It is found that implementing VVO technology can save utilities up to 4 percent per year on energy losses.
The challenges, opportunities, and student experiences of this research is also presented. As the nature of this research was interdisciplinary, it required significant cross-collaboration as well as background knowledge in both engineering and economics. The students performed extensive literature review on these topics before reaching out to the engineers from local utilities for guidance. The results of this research is highly beneficial to the students as well as to the utility. Along the way, the students develop communication, project management, and soft skills that will serve them well into their professional careers.
Jiang, X., & Bolstad, A. (2019, March), COST AND BENEFITS OF VOLT-VAR OPTIMIZATION ON ELECTRIC POWER DISTRIBUTION SYSTEMS: An Undergraduate Research Experience Paper presented at 2019 ASEE PNW Section Conference, Corvallis, Oregon. https://22.214.171.124/31872
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