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This paper proposes a general methodology for designing hierarchical control schemes for DC microgrids loaded by constant power loads. This paper addresses issues when interfacing sources with a wide voltage range allowing for any general choice for a power source. The control strategy consists of two levels. The lower level consists of droop-based primary controllers. This controller enables current-sharing among paralleled sources and also damps limit cycle oscillations due to constant power loads. The higher level is a secondary controller which compensates for voltage deviations due to primary controller and performs voltage control of the microgrid. It also maintains the current sharing obtained in the primary stage. In the proposed secondary control, high-speed communication links to the primary controllers is implemented. The stability conditions are explained using the equivalent circuit of converters. Using this approach, stability conditions can be derived for microgrids of an arbitrary size and converter topology. The proposed control scheme is shown to be scalable and robust. The results obtained for the three basic DC-DC converter configurations are compared based on a microgrid with a parallel configuration of buck-boost converters. Simulations and experimental results are presented to verify the validity of the proposed control schemes.
Mahesh Srinivasan; Alexis Kwasinski. Control analysis of parallel DC-DC converters in a DC microgrid with constant power loads. International Journal of Electrical Power & Energy Systems 2020, 122, 106207 .
AMA StyleMahesh Srinivasan, Alexis Kwasinski. Control analysis of parallel DC-DC converters in a DC microgrid with constant power loads. International Journal of Electrical Power & Energy Systems. 2020; 122 ():106207.
Chicago/Turabian StyleMahesh Srinivasan; Alexis Kwasinski. 2020. "Control analysis of parallel DC-DC converters in a DC microgrid with constant power loads." International Journal of Electrical Power & Energy Systems 122, no. : 106207.
This paper develops an approach for two-day-ahead global horizontal irradiance (GHI) forecast using the naïve Bayes classifier (NB). Based on publicly available weather forecasting information about temperature, relative humidity, dew point, and sky coverage, they are used as a training set in NB classification with hourly resolution. To reduce having two times with the same GHI affecting the classification in the proposed model, two characteristics of the GHI under different weather conditions are considered: The daylight variation and diurnal cycle. More importantly, NB’s independence assumption-based on simple Bayes’ theorem makes the process speed faster and less constrained than other classification algorithms. The forecast performance is verified with several error criteria from established analytical practices using relevant statistics. Moreover, commonly used forecasting error criteria are discussed. This NB model shows improved results regarding error criteria and a good agreement for a clear day that satisfies the guideline for the evaluation of two-days-ahead forecast, when compared with other recent techniques.
Youngsung Kwon; Alexis Kwasinski; Andres Kwasinski. Solar Irradiance Forecast Using Naïve Bayes Classifier Based on Publicly Available Weather Forecasting Variables. Energies 2019, 12, 1529 .
AMA StyleYoungsung Kwon, Alexis Kwasinski, Andres Kwasinski. Solar Irradiance Forecast Using Naïve Bayes Classifier Based on Publicly Available Weather Forecasting Variables. Energies. 2019; 12 (8):1529.
Chicago/Turabian StyleYoungsung Kwon; Alexis Kwasinski; Andres Kwasinski. 2019. "Solar Irradiance Forecast Using Naïve Bayes Classifier Based on Publicly Available Weather Forecasting Variables." Energies 12, no. 8: 1529.
This paper presents a framework to systematically measure and assess power grids’ resilience with a focus on performance as perceived by customers at the power distribution level. The proposed framework considers an analogous measure of availability as a basic metric for resilience and defines other key resilience-related concepts and metrics, such as resistance and brittleness. This framework also provides a measurement for the degree of functional dependency of loads on power grids and demonstrates how the concepts of resilience and dependency are inherently related. It also discusses the implications of considering human-centered processes as fundamental constituting components of infrastructure systems. Thanks to its quantitative nature, the proposed resilience framework enables the creation of tools to evaluate power grids’ performance as a lifeline and to assess the effects of plans for optimal electrical power infrastructure deployment and operation. The discussion is supported by practical examples and empirical records from field damage assessments conducted after recent notable natural disasters.
Alexis Kwasinski. Quantitative Model and Metrics of Electrical Grids’ Resilience Evaluated at a Power Distribution Level. Energies 2016, 9, 93 .
AMA StyleAlexis Kwasinski. Quantitative Model and Metrics of Electrical Grids’ Resilience Evaluated at a Power Distribution Level. Energies. 2016; 9 (2):93.
Chicago/Turabian StyleAlexis Kwasinski. 2016. "Quantitative Model and Metrics of Electrical Grids’ Resilience Evaluated at a Power Distribution Level." Energies 9, no. 2: 93.
This review paper discusses power quality considerations for direct current (DC) electric power distribution systems, particularly DC microgrids. First, four selected sample DC architectures are discussed to provide motivation for the consideration of power quality in DC systems. Second, a brief overview of power quality challenges in conventional alternating current (AC) distribution systems is given to establish the field of power quality. Finally, a survey of literature addressing power quality issues in DC systems is presented, and necessary power quality considerations in DC distribution system design and operation are discussed.
Stephen Whaite; Brandon Grainger; Alexis Kwasinski. Power Quality in DC Power Distribution Systems and Microgrids. Energies 2015, 8, 4378 -4399.
AMA StyleStephen Whaite, Brandon Grainger, Alexis Kwasinski. Power Quality in DC Power Distribution Systems and Microgrids. Energies. 2015; 8 (5):4378-4399.
Chicago/Turabian StyleStephen Whaite; Brandon Grainger; Alexis Kwasinski. 2015. "Power Quality in DC Power Distribution Systems and Microgrids." Energies 8, no. 5: 4378-4399.