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Anamika Dubey
The School of Electrical Engineering and Computer Science Washington State University Pullman Wasington USA

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Original research paper
Published: 28 March 2021 in IET Smart Grid
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Improving the reliability of power distribution systems is critically important for both utilities and customers. This calls for an efficient service restoration module within a distribution management system to support the implementation of self‐healing smart grid networks. Although the emerging smart grid technologies, including distributed generators (DGs) and remote‐controlled switches, enhance the self‐healing capability and allow faster recovery, they still pose additional complexity to the service restoration problem, especially under cold load pickup (CLPU) conditions. Herein, a novel two‐stage restoration framework is proposed to generate a restoration solutions with a sequence of control actions. The first stage generates a restoration plan that supports both the traditional service restoration using feeder reconfiguration and the grid‐forming DG‐assisted intentional islanding methods. The second stage generates an optimal sequence of switching operations to bring the outaged system quickly to the final restored configuration. The problem is formulated as a mixed‐integer linear program that incorporates system connectivity, operating constraints, and the CLPU models. It is demonstrated that on using a multi‐feeder test case, the proposed framework is effective in utilizing all available resources to quickly restore the service and generate an optimal sequence of switching actions to be used by the operator to reach the desired optimal configuration.

ACS Style

Shiva Poudel; Anamika Dubey. A two‐stage service restoration method for electric power distribution systems. IET Smart Grid 2021, 1 .

AMA Style

Shiva Poudel, Anamika Dubey. A two‐stage service restoration method for electric power distribution systems. IET Smart Grid. 2021; ():1.

Chicago/Turabian Style

Shiva Poudel; Anamika Dubey. 2021. "A two‐stage service restoration method for electric power distribution systems." IET Smart Grid , no. : 1.

Preprint
Published: 16 December 2019
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With the increased penetrations of distributed energy resources (DERs), the need for integrated transmission and distribution system analysis (T&D) is imperative. This paper presents an integrated unbalanced T&D analysis framework using an iteratively coupled co-simulation approach. The unbalanced T&D systems are solved separately using dedicated solvers. An iterative approach is developed for T&D interface coupling and to ensure convergence of the boundary variables. To do so, analytical expressions governing the T&D interface are obtained. First-order and second-order convergent methods using the Fixed-point iteration (FPI) method and Newton's method, respectively are proposed to solve the system of nonlinear T&D interface equations. The proposed framework is tested using an integrated T&D system model comprised of a 9-bus IEEE transmission test system integrated with a real-world 6000-bus distribution test system. The results show that the proposed framework can model the impacts of system unbalance and increased demand variability on integrated T&D systems and converges during stressed system conditions. As expected, Newton's method converges faster with a fewer number of iterations as compared to the FPI method and the improvements are more pronounced during high levels of system unbalance and high loading conditions.

ACS Style

Gayathri Krishnamoorthy; Anamika Dubey. Transmission-Distribution Co-Simulation: Analytical Methods for Iterative Coupling. 2019, 1 .

AMA Style

Gayathri Krishnamoorthy, Anamika Dubey. Transmission-Distribution Co-Simulation: Analytical Methods for Iterative Coupling. . 2019; ():1.

Chicago/Turabian Style

Gayathri Krishnamoorthy; Anamika Dubey. 2019. "Transmission-Distribution Co-Simulation: Analytical Methods for Iterative Coupling." , no. : 1.

Preprint
Published: 16 December 2019
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Battery energy storage systems (BESS) are proving to be an effective solution in providing frequency regulation services to the bulk grid. However, there are several concerns for the transmission/distribution system operators (TSO/DSO) with the frequent dispatching of the distribution-connected fast-responding storage systems. Unfortunately, the existing decoupled models for transmission and distribution (T&D) simulations are unable to capture the complex interactions between the two systems especially concerning frequency regulation problems due to rapidly varying distribution-connected distributed energy resources (DERs). In this paper, an iteratively coupled T&D hybrid co-simulation framework is developed to facilitate the planning studies for the system operators to help integrate distribution-connected BESS in providing frequency regulation services in response to highly variable DERs such as photovoltaic generation (PVs). Specifically, the proposed framework helps evaluate: (1) the effects of distribution-connected DERs/PVs on the response of the system's automatic generation control (AGC) response, and (2) highlights the use of BESS in providing frequency regulation services using integrated T&D model. The proposed framework is demonstrated using the IEEE 9-bus transmission system model (operating in dynamics mode) coupled with multiple EPRI Ckt-24 distribution system models (operating in quasi-static mode). It is shown that the proposed co-simulation framework helps better visualize the system AGC response and frequency regulation especially in the presence of high-levels of DER generation variability requiring frequent dispatch of BESS.

ACS Style

Gayathri Krishnamoorthy; Anamika Dubey. Hybrid Transmission Distribution Co-simulation: Frequency Regulation using Battery Energy Storage. 2019, 1 .

AMA Style

Gayathri Krishnamoorthy, Anamika Dubey. Hybrid Transmission Distribution Co-simulation: Frequency Regulation using Battery Energy Storage. . 2019; ():1.

Chicago/Turabian Style

Gayathri Krishnamoorthy; Anamika Dubey. 2019. "Hybrid Transmission Distribution Co-simulation: Frequency Regulation using Battery Energy Storage." , no. : 1.

Preprint
Published: 10 December 2019
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Extreme weather events have a significant impact on the aging and outdated power distribution infrastructures. These high-impact low-probability (HILP) events often result in extended outages and loss of critical services, thus, severely affecting customers' safety. This calls for the need to ensure resilience in distribution networks by quickly restoring the critical services during a disaster. This paper presents an advanced feeder restoration method to restore critical loads using distributed energy resources (DERs). A resilient restoration approach is proposed that jointly maximizes the amount of restored critical loads and optimizes the restoration times by optimally allocating grid's available DER resources. The restoration problem is modeled as a mixed-integer linear program with the objective of maximizing the resilience to post-restoration failures while simultaneously satisfying grid's critical connectivity and operational constraints and ensuring a radial operation for a given open-loop feeder configuration. Simulations are performed to demonstrate the effectiveness of the proposed approach using IEEE 123-node feeder with 5 DERs supplying 11 critical loads and IEEE 906-bus feeder with 3 DERs supplying 17 critical loads. The impacts of DER availability and fuel reserve on restored networks are assessed and it is shown that the proposed approach is successfully able to restore a maximum number of critical loads using available DERs.

ACS Style

Shiva Poudel; Anamika Dubey. Critical Load Restoration using Distributed Energy Resources for Resilient Power Distribution System. 2019, 1 .

AMA Style

Shiva Poudel, Anamika Dubey. Critical Load Restoration using Distributed Energy Resources for Resilient Power Distribution System. . 2019; ():1.

Chicago/Turabian Style

Shiva Poudel; Anamika Dubey. 2019. "Critical Load Restoration using Distributed Energy Resources for Resilient Power Distribution System." , no. : 1.

Preprint
Published: 08 December 2019
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Conservation voltage reduction(CVR) uses Volt-VAR optimization(VVO) methods to reduce customer power demand by controlling the feeders' voltage control devices. The objective of this paper is to present a VVO approach that controls the systems' legacy voltage control devices and coordinates their operation with smart inverter control. An optimal power flow (OPF) formulation is proposed by developing linear and nonlinear power flow approximations for a three-phase unbalanced electric power distribution system. A bi-level VVOapproach is proposed where Level-1 optimizes the control of legacy devices and smart inverters using a linear approximate three-phase power flow. In Level-2, the control parameters for smart inverters are adjusted to obtain an optimal and feasible solution by solving the approximate nonlinear OPF model. Level-1 is modeled as a Mixed Integer Linear Program(MILP) while level-2 as a Nonlinear Program(NLP) with a linear objective and quadratic constraints. The proposed approach is validated using 13-bus and 123-bus three-phase IEEE test feeders and a 329-bus three-phase PNNL taxonomy feeder. The results demonstrate the applicability of the framework in achieving the CVR objective. It is demonstrated that the proposed coordinated control approach help reduce feeders' power demand by reducing the bus voltages, the proposed approach maintains an average feeder voltage of 0.96 pu. A higher energy saving is reported during the minimum load conditions. The results and approximation steps are thoroughly validated using OpenDSS.

ACS Style

Rahul Ranjan Jha; Anamika Dubey; Chen-Ching Liu; Kevin P. Schneider. Bi-Level Volt-VAR Optimization to Coordinate Smart Inverters with Voltage Control Devices. 2019, 1 .

AMA Style

Rahul Ranjan Jha, Anamika Dubey, Chen-Ching Liu, Kevin P. Schneider. Bi-Level Volt-VAR Optimization to Coordinate Smart Inverters with Voltage Control Devices. . 2019; ():1.

Chicago/Turabian Style

Rahul Ranjan Jha; Anamika Dubey; Chen-Ching Liu; Kevin P. Schneider. 2019. "Bi-Level Volt-VAR Optimization to Coordinate Smart Inverters with Voltage Control Devices." , no. : 1.

Preprint
Published: 06 December 2019
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It is of growing concern to ensure the resilience in electricity infrastructure systems to extreme weather events with the help of appropriate hardening measures and new operational procedures. An effective mitigation strategy requires a quantitative metric for resilience that can not only model the impacts of the unseen catastrophic events for complex electric power distribution networks but also evaluate the potential improvements offered by different planning measures. In this paper, we propose probabilistic metrics to quantify the operational resilience of the electric power distribution systems to high-impact low-probability (HILP) events. Specifically, we define two risk-based measures: Value-at-Risk ($VaR_\alpha$) and Conditional Value-at-Risk ($CVaR_\alpha $) that measure resilience as the maximum loss of energy and conditional expectation of a loss of energy, respectively for the events beyond a prespecified risk threshold, $\alpha$. Next, we present a simulation-based framework to evaluate the proposed resilience metrics for different weather scenarios with the help of modified IEEE 37-bus and IEEE 123-bus system. The simulation approach is also extended to evaluate the impacts of different planning measures on the proposed resilience metrics.

ACS Style

Shiva Poudel; Anamika Dubey; Anjan Bose. Risk-based Probabilistic Quantification of Power Distribution System Operational Resilience. 2019, 1 .

AMA Style

Shiva Poudel, Anamika Dubey, Anjan Bose. Risk-based Probabilistic Quantification of Power Distribution System Operational Resilience. . 2019; ():1.

Chicago/Turabian Style

Shiva Poudel; Anamika Dubey; Anjan Bose. 2019. "Risk-based Probabilistic Quantification of Power Distribution System Operational Resilience." , no. : 1.

Preprint
Published: 04 July 2019
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An islanded microgrid supplied by multiple distributed energy resources (DERs) often employs droop-control mechanisms for power sharing. Because microgrids do not include inertial elements, and low pass filtering of noisy measurements introduces lags in control, droop-like controllers may pose significant stability concerns. This paper aims to understand the effects of droop-control on the small-signal stability and transient response of the microgrid. Towards this goal, we present a compendium of results on the small-signal stability of droop-controlled inverter-based microgrids with heterogeneous loads, which distinguishes: (1) lossless vs. lossy networks; (2) droop mechanisms with and without filters, and (3) mesh vs. radial network topologies. Small-signal and transient characteristics are also studied using multiple simulation studies on IEEE test systems

ACS Style

Abdullah Al Maruf; Mohammad Ostadijafari; Anamika Dubey; Sandip Roy. Small-Signal Stability Analysis for Droop-Controlled Inverter-based Microgrids with Losses and Filtering. 2019, 1 .

AMA Style

Abdullah Al Maruf, Mohammad Ostadijafari, Anamika Dubey, Sandip Roy. Small-Signal Stability Analysis for Droop-Controlled Inverter-based Microgrids with Losses and Filtering. . 2019; ():1.

Chicago/Turabian Style

Abdullah Al Maruf; Mohammad Ostadijafari; Anamika Dubey; Sandip Roy. 2019. "Small-Signal Stability Analysis for Droop-Controlled Inverter-based Microgrids with Losses and Filtering." , no. : 1.

Journal article
Published: 25 October 2017 in Inventions
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The widespread integration of photovoltaic (PV) units may result in a number of operational issues for the utility distribution system. The advances in smart-grid technologies with better communication and control capabilities may help to mitigate these challenges. The objective of this paper is to evaluate multiple voltage control methods and compare their effectiveness in mitigating the impacts of high levels of PV penetrations on distribution system voltages. A Monte Carlo based stochastic analysis framework is used to evaluate the impacts of PV integration, with and without voltage control. Both snapshot power flow and time-series analysis are conducted for the feeder with varying levels of PV penetrations. The methods are compared for their impacts on (1) the feeder’s PV hosting capacity; (2) the number of voltage violations and the magnitude of the largest bus voltage; (3) the net reactive power demand from the substation; and (4) the number of switching operations of feeder’s legacy voltage support devices i.e., capacitor banks and load tap changers (LTCs). The simulation results show that voltage control help in mitigating overvoltage concerns and increasing the feeder’s hosting capacity. Although, the legacy control solves the voltage concerns for primary feeders, a smart inverter control is required to mitigate both primary and secondary feeder voltage regulation issues. The smart inverter control, however, increases the feeder’s reactive power demand and the number of LTC and capacitor switching operations. For the 34.5-kV test circuit, it is observed that the reactive power demand increases from 0 to 6.8 MVAR on enabling Volt-VAR control for PV inverters. The total number of capacitor and LTC operations over a 1-year period also increases from 455 operations to 1991 operations with Volt-VAR control mode. It is also demonstrated that by simply changing the control mode of capacitor banks, a significant reduction in the unnecessary switching operations for the capacitor banks is observed.

ACS Style

Anamika Dubey. Impacts of Voltage Control Methods on Distribution Circuit’s Photovoltaic (PV) Integration Limits. Inventions 2017, 2, 28 .

AMA Style

Anamika Dubey. Impacts of Voltage Control Methods on Distribution Circuit’s Photovoltaic (PV) Integration Limits. Inventions. 2017; 2 (4):28.

Chicago/Turabian Style

Anamika Dubey. 2017. "Impacts of Voltage Control Methods on Distribution Circuit’s Photovoltaic (PV) Integration Limits." Inventions 2, no. 4: 28.

Journal article
Published: 28 March 2017 in Inventions
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This paper presents a planning framework for integrating energy storage (ES) systems into the distribution system. An ES system is deployed to simultaneously provide multiple benefits, also known as stacked-benefits, for the feeder. The primary and secondary application scenarios for the feeder are identified. The proposed ES deployment approach includes the following steps: (1) size the ES system for primary application; (2) identify optimal ES locations based on both primary and secondary application scenarios; (3) calculate the ES accommodation capacity for each potential location; and (4) develop control methods for ES units and conduct grid impact analysis to demonstrate ES applications. For the selected feeder, the primary application for ES deployment is to provide the N-1 contingency requirement. During normal operating conditions, ES is programmed for multiple secondary applications: voltage management and ancillary services by frequency regulation. A probabilistic approach is presented to obtain the optimal ES size for providing the N-1 contingency requirement. Optimal ES locations are obtained based on secondary application scenarios. Real and reactive power control methods are developed to demonstrate the viability of deploying an ES system for simultaneously providing multiple applications. The simulation results show that ES can successfully provide the stacked-benefits for the distribution circuit. The proposed framework is generic and can be employed for the ES integration analysis of any feeder, with different sets of primary and secondary applications.

ACS Style

Anamika Dubey; Pisitpol Chirapongsananurak; Surya Santoso. A Framework for Stacked-Benefit Analysis of Distribution-Level Energy Storage Deployment. Inventions 2017, 2, 6 .

AMA Style

Anamika Dubey, Pisitpol Chirapongsananurak, Surya Santoso. A Framework for Stacked-Benefit Analysis of Distribution-Level Energy Storage Deployment. Inventions. 2017; 2 (2):6.

Chicago/Turabian Style

Anamika Dubey; Pisitpol Chirapongsananurak; Surya Santoso. 2017. "A Framework for Stacked-Benefit Analysis of Distribution-Level Energy Storage Deployment." Inventions 2, no. 2: 6.

Journal article
Published: 27 June 2016 in Inventions
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Ensuring a high level of service reliability is of paramount importance in an all-electric ship. In the literature, shipboard power systems (SPS) have been designed for improved survivability and quality of service (QOS) requirements. This paper presents a two-level topology design approach and develops system-level architectures for SPS that ensure continuity of service and survivability in the event of outage or failure. A reliable SPS architecture is obtained by (1) the choice of topology, (2) optimally placing equipment loads within a topology, and (3) designing a reliable distribution circuit topology. First, a theoretical framework is developed to demonstrate the relationship between the reliability of a distribution circuit and the high-level topology of its connections. For the ship’s primary distribution system, a breaker-and-a-half (BAAH) topology was observed to be the most reliable. The reliability indices are further improved by optimally placing equipment loads within the BAAH topology. For zonal electric distribution (ZED) systems, an algorithm to design an optimal topology by minimizing the number of conductors while satisfying a required reliability measure is proposed. It is concluded that the reliability of a distribution circuit depends on: (1) the topology of its connections, and (2) the relative placement of equipment loads and generators.

ACS Style

Anamika Dubey; Surya Santoso. A Two-Level Topology Design Framework for Reliable Shipboard Power Systems. Inventions 2016, 1, 14 .

AMA Style

Anamika Dubey, Surya Santoso. A Two-Level Topology Design Framework for Reliable Shipboard Power Systems. Inventions. 2016; 1 (3):14.

Chicago/Turabian Style

Anamika Dubey; Surya Santoso. 2016. "A Two-Level Topology Design Framework for Reliable Shipboard Power Systems." Inventions 1, no. 3: 14.