Emerging Power Grid Integration in a Unified Simulation Environment

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With the emergence of distributed generation and increased online measurements and optimization, the traditional separation in the analysis and operation of the high-voltage transmission system and the lower voltages distribution systems is disappearing. In transmission, the requirement of 60 Hz synchronicity in maintaining angle and frequency stability across an extensive network of interconnections is "naturally" aided by the large inertia of the rotating masses of the large thermo and hydro generators. Wind and solar plants, on the other hand, require sophisticated control mechanisms, together with fast switching power electronic devices, to create a "synthetic" inertia that allows their coupling and join operation with the 60 Hz main grid.***     *The 60-Hz synchronicity of the new grid will require a close integration of the traditional grid with inertias in the order of the seconds, determined by the mechanical masses of the large hydro and thermo generators, working together with inertias in the order of the milliseconds, created by fast controllers in wind and solar farms driven by power electronic valves with time constants in the order of the microseconds. Three orders of time constants will be working together. In terms of solution techniques, electrical voltage and current phasor solutions in the main grid will have to "live together" with faster changing electrical voltages and currents in the wind and solar plants and with even faster changing voltages and currents in the power electronics converters.***     *The increased penetration of distributed non-dispatchable Variable Energy Resources (VER) will affect all aspects of the existing grid's design and operation, including technical aspects, economic and business models, and social and environmental impacts. With the new integrated grid, the optimization objectives of high voltage transmission will have to be integrated with the optimization objectives of distribution and customer levels. These three levels of objectives are not always in agreement with each other and individual optimums will have to be combined with global optimums. A fine granularity distributed control system, and a correspondingly extensive layer of ICT infrastructure, will be required to support the extended grid. The increased complexity will make the grid more sensitive to internal failures and more vulnerable to external cyber attacks.***     *Under this grant, we will advance the development of a unified comprehensive simulation environment that can integrate the complexity and multiplicity of objectives of the 21st century power system grid.