Integrating Distributed or Renewable Resources

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    Impacts of Strategic Behavior and Consumer Requirements on the Promise of Demand Response
    ( 2018-01-03) Anwar, Muhammad Bashar ; O'Malley, Mark
    Demand response (DR) is envisaged to be of significance for enhancing the flexibility of power systems. The distributed nature of demand-side resources necessitates the need of an aggregator to represent the flexible demand in the electricity market. This paper presents a bilevel optimization model considering the optimal operation of a strategic aggregator in a day-ahead electricity market. Additionally, consumers’ requirements in terms of comfort satisfaction and cost reduction are considered by integrating detailed demand models and retail contract constraints. The results on the considered test system reveal that centralized optimization models would tend to over-estimate the capabilities of DR in an electricity market with strategic participants. Also, the flexibility value of DR for the power system and the profitability of the aggregator are significantly dependent on the retail contracts between the aggregator and the consumers, highlighting the need for careful contract design.
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    Real-time Voltage Regulation in Distribution Systems via Decentralized PV Inverter Control
    ( 2018-01-03) Lin, Weixuan ; Thomas, Robert ; Bitar, Eilyan
    We consider the decentralized reactive power control of photovoltaic (PV) inverters spread throughout a radial distribution network. Our objective is to minimize the expected voltage regulation error, while guaranteeing the robust satisfaction of distribution system voltage magnitude and PV inverter capacity constraints. Our approach entails the offline design and the online implementation of the decentralized controller. In the offline control design, we compute the decentralized controller through the solution of a robust convex program. Under the restriction that the decentralized controller have an affine disturbance feedback form, the optimal solution of the decentralized control design problem can be computed via the solution of a finite-dimensional conic program. In the online implementation, we provide a method to implement the decentralized controller at a time-scale that is fast enough to counteract the fluctuations in the system disturbance process. The resulting trajectories of PV inverter reactive power injections and nodal voltage magnitudes are guaranteed to be feasible for any realization of the system disturbance under the proposed controller. We demonstrate the ability of the proposed decentralized controller to effectively regulate voltage over a fast time-scale with a case study of the IEEE 123-node test feeder.
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    Coordination of DERs in Microgrids with Cybersecure Resilient Decentralized Secondary Frequency Control
    ( 2018-01-03) Liu, Hao Jan ; Backes, Matthew ; Macwan, Richard ; Valdes, Alfonso
    Microgrids are emerging as an important strategy to advance resiliency of modern electric power systems. In this paper, a robust decentralized secondary frequency control design for islanded microgrids is developed to enable resilient coordination and integration of distributed energy resources (DERs). We cast the control problem centrally under steady state and adopt the feedback-based Alternating Direction Method of Multipliers (ADMM) algorithm for solving the decentralized control updates. The ADMM algorithm uses measurements at various points in the system to solve for control signals. Measurements and control commands are sent over communication networks such as Ethernet-based local area networks in the IEC 61850 standard. To enhance the robustness to cyber intrusions, we modify the ADMM algorithm using the Round-Robin technique to detect malicious DERs. As a complementary defense, an agreement algorithm based on a fast computation of Kirchhoff law conditions is implemented for continuously detecting false measurements. The results are demonstrated through simulation for a representative microgrid topology.
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    An Adaptive Optimization-Based Load Shedding Scheme in Microgrids
    ( 2018-01-03) Gholami, Amin ; Shekari, Tohid ; Sun, Andy
    This paper proposes an adaptive optimization-based approach for under frequency load shedding (UFLS) in microgrids following an unintentional islanding. In the first step, the total amount of load curtailments is determined based on the system frequency response (SFR) model. Then, the proposed mixed-integer linear programming (MILP) model is executed to find the best location of load drops. The novel approach specifies the least cost load shedding scenario while satisfying network operational limitations. A look-up table is arranged according to the specified load shedding scenario to be implemented in the network if the islanding event occurs in the microgrid. To be adapted with system real-time conditions, the look-up table is updated periodically. The efficiency of the proposed framework is thoroughly evaluated in a test microgrid with a set of illustrative case studies.
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