Document Type

Thesis - Open Access

Award Date

2019

Degree Name

Master of Science (MS)

Department

Electrical Engineering and Computer Science

First Advisor

Timothy M. Hansen

Keywords

Distribution locational marginal pricing, Droop control, High-Performance Computing, PV inverter control, Sustainability, Techno-economic study

Abstract

Increasing distributed solar installations in low voltage distribution grids tend to increase the feeder voltage. The rise in voltage is only acceptable to a certain limit, and control strategies are required to keep voltage within defined bounds for equipment safety and system reliability. PV inverter control strategies are cost-effective methods to prevent overvoltage. Different inverter control strategies have different impacts on their techno-economic performance, ultimately affecting their sustainability. An evaluation framework for long-term techno-economic and sustainability analysis of overvoltage prevention methods in PV-rich LV networks is proposed to decide suitable control methods by making use of quasi-steady-state time-series (QSTS) software (GridLAB-D). A power network sensitivity-based algorithm is also proposed for preventing numerical oscillation while implementing active and reactive droop-based PV inverter controllers in QSTS (i.e., GridLAB-D). Convergence of the sensitivity-based algorithm is verified using a typical radial distribution feeder for three droop-based PV inverter controllers limiting the error below 0.5%. Techno-economic performance was analyzed by looking into voltage profile, energy generation, and consumption, energy losses, impact on transformer overloading and financial impact on government, utility, and end-users. Three different sustainability metrics are proposed to quantify these impacts for inverter-based voltage control strategies. Five different PV inverter control strategies are implemented in a radial distribution feeder and power flow is analyzed for one year in a one-minute resolution to compute and compare the proposed sustainability metrics. The use of reactive power improved sustainability compared to just using active power curtailment. The trade-off of the three objectives was compared using multi-objective optimization for the highest solar irradiance day. Results showed that economic and environmental sustainability are positively correlated, and both are negatively correlated with social sustainability, indicating a required trade-off for voltage control strategies. The proposed framework can aid utilities to decide the most effective control and pricing methods, and whether investments in overvoltage prevention infrastructure can be justified under a high penetration scenario. Lastly, a distribution optimal power flow is formulated to determine the locational marginal price for distribution grid ancillary services such as active power curtailment and reactive power absorption. Additionally, a Monte Carlo based PV hosting capacity analysis is performed in Taxonomy Feeder for highest irradiance and low load day using High-Performance Computing. Results showed that overvoltage becomes an issue even at 10% penetration level.

Library of Congress Subject Headings

Photovoltaic power systems.
Electric power distribution.
Voltage regulators.
Electric inverters -- Technological innovations.
Electric controllers -- Technological innovations.
Low voltage systems.
Photovoltaic power generation.
Overvoltage -- Prevention.

Publisher

South Dakota State University

Rights

In Copyright - Non-Commercial Use Permitted
http://rightsstatements.org/vocab/InC-NC/1.0/

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