Hybrid Modeling Capability for Aircraft Electrical Propulsion Systems

PC Krause and Associates is partnering with Purdue University, EleQuant, and GridQuant to create a hybrid modeling capability. The combination of PCKA�s extensive dynamic modeling experience, Purdue�s work in electromechanical systems analysis, and GridQuant and Elequant�s development of the HELM algorithm uniquely positions the team to create this technology. HELM is a novel algorithm that solves the powerflow equations of electric power systems using a direct, constructive procedure. It was originally derived for terrestrial power grids and is now being applied to dc spacecraft power systems. The Phase I effort will focus on three technical objectives. The first is to provide a formal definition of the mathematical framework for the hybrid modeling capability. The second objective is to define a software architecture for its implementation. Lastly, the third objective is to demonstrate the capability on an aircraft electrical propulsion system. The test system is anticipated to be a variable-voltage/variable-frequency ac electrical propulsion system that PCKA is currently investigating with NASA as part of a Convergent Aeronautics Solutions (CAS) effort. Another alternative is the Hybrid Gas Electric Propulsion (HGEP) Project�s NASA Electric Aircraft Testbed (NEAT) system, which PCKA is also currently modeling. Some potential applications for this modeling technique include some of these applications include 1) efficient contingency analysis, 2) model-based control, 3) system identification and monitoring, and 4) analysis of pulsed loads.

The most immediate NASA applications for this technology are the NASA�s CAS and NEAT programs. While one will likely be selected as the testbed system for the Phase I, the other is similar in nature, and PCKA has existing models for both systems, which would ease transition of the modeling capability. The technique could also be applied to the Exploration Augmentation Module or International Space Station power systems, both of which are dc systems based on solar arrays with battery energy storage. These systems were modeled by PCKA under a prior NASA SBIR Phase II effort. In short, the proposed modeling technique is applicable to a wide range of electrical power systems and could be applied to virtually any NASA spacecraft or aircraft design. As the technology matures, its mathematical origin would allow it to be applied to other types of dynamic systems as well.

While the proposed effort is focused toward N+3 generation aircraft electric propulsion systems, other types of power systems can take advantage of the modeling architecture. The underlying mathematical formulation can be applied to essentially any type of power system. One example is instance terrestrial microgrid based systems that incorporate renewable energy sources (such as military operating bases or large office buildings). It should be noted that these systems can be either ac or dc in nature; however, the overall modeling environment and control structure can be largely the same. In fact, the initial focus on aircraft electrical propulsion systems (that combined ac and dc) will set the stage for this technology to be rapidly applied to other systems. Another application with large potential impact is traditional power grids. While load flow solvers such as HELM are used for daily planning and unit commitment, transient simulations are typically too computationally intense for short-term decision making. Analysis based on transient models is performed weeks or months in advance with estimated load profiles. The proposed hybrid modeling capability could provide a more efficient framework with which to incorporate transient modeling into short-term analysis of power grids.