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Demand response represents a significant but largely untapped resource that can greatly enhance the flexibility and reliability of power systems. This paper proposes a hierarchical control framework to facilitate the integrated coordination between distributed energy resources and demand response. The proposed framework consists of coordination and device layers. In the coordination layer, prior to each scheduling period, each coordinator receives the aggregated utility or cost functions as well as the power operating ranges from aggregators or device controllers. Then, various resources or their aggregations are optimally coordinated in a distributed manner to achieve the system-level objectives. The obtained regulation signals are sent back to aggregators or device controllers for real-time control. In the device layer, at the scheduling stage, the controller at each device reports to coordinators (directly or through aggregators) the required information for optimal coordination, and receives the regulation signals from its commander once the coordination is completed. During the real-time operation, individual resources are controlled to follow the optimal power dispatch signals. For practical applications, a method is presented to determine the utility functions of controllable loads by accounting for the real-time load dynamics and the preferences of individual customers. The effectiveness of the proposed framework is validated by detailed simulation studies.

Transactive energy is a control technique that uses market mechanisms to achieve desired control objectives. Several simulation studies and field demonstrations were carried out in recent years, but all focused on small scale systems and purpose-built simplified models which are not always capable of pointing out all the advantages and shortcomings of transactive energy methods. This work describes a co-simulation framework built on a hierarchical control architecture that allows for conducting studies on the impacts of a very large-scale deployment of transactive energy. The hierarchical transactive control architecture adopted in this work helps with alleviating computation and communication burden to facilitate a more effective large scale real-time market operation among device level resources and the system level operators. The co-simulation framework is evaluated using off-the-shelf simulators on an integrated power system model of unprecedented scale composed of the Western Electricity Coordination Council transmission system with tens of thousands of distribution systems deployed with flexible device-level distributed energy resources.

Udgivelsesdato: 2000-Oct-27 The low density lipoprotein (LDL) receptor is responsible for removing the majority of the LDL cholesterol from the plasma. Mutations in the LDL receptor gene cause the disease familial hypercholesterolemia (FH). Approximately 50% of the mutations in the LDL receptor gene in patients with FH lead to receptor proteins that are retained in the endoplasmic reticulum (ER). Misfolding of mutant LDL receptors is a probable cause of this ER retention, resulting in no functional LDL receptors at the cell surface. However, the specific factors and mechanisms responsible for retention of mutant LDL receptors are unknown. In the present study we show that the molecular chaperone Grp78/BiP co-immunoprecipitates with both the wild type and two different mutant (W556S and C646Y) LDL receptors in lysates obtained from human liver cells overexpressing wild type or mutant LDL receptors. A pulse-chase study shows that the interaction between the wild type LDL receptor and Grp78 is no longer detectable after 2(1/2) h, whereas it persists for more than 4 h with the mutant receptors. Furthermore, about five times more Grp78 is co-immunoprecipitated with the mutant receptors than with the wild type receptor suggesting that Grp78 is involved in retention of mutant LDL receptors in the ER. Overexpression of Grp78 causes no major alterations on the steady state level of active LDL receptors at the cell surface. However, overexpression of Grp78 decreases the processing rate of newly synthesized wild type LDL receptors. This indicates that the Grp78 interaction is a rate-limiting step in the maturation of the wild type LDL receptor and that Grp78 may be an important factor in the quality control of newly synthesized LDL receptors.