TT Electronics: Modular strategies for power conversion in UAS address SWaP concerns and increasing electrification


Modular Power Conversion Strategies in UAS Address SWaP Concerns and Increasing Electrification

Urban air mobility is poised to transform aviation: This industry overhaul is happening much faster with the support of the US Armed Forces. Once considered science fiction, the transport of people via small electric flying vehicles is a reality close to the future. Transporting people, medicine and supplies in urban applications proves the concept and value of electrified aircraft. This promise extends to troop transport, support and equipment resupply, search and rescue, securing base operations, moving goods, and more. – which means that unmanned aerial systems (UAS) can potentially reduce or replace manned helicopter missions in dangerous scenarios around the world.

DC power technologies are at the heart of many developing urban air mobility systems. These cells, powered by batteries storing DC power, eliminate the demand for AC-DC power conversion at the point of charge. This is a significant shift in power system design, allowing efficient high voltage DC distribution systems to be considered that are simultaneously compatible with energy storage (batteries) and charging requirements.

Addressing SWaP-C and DC Power Distribution Needs

While traditional aircraft incorporate gas turbines driving auxiliary power units that are naturally AC powered, the AC-DC conversion and distribution strategies required can inherently increase the number of power electronics on board. This design approach is in direct opposition to military design ideals of size, weight, power and cost (SWaP-C) – an issue made more complex by the ever-increasing amount of electrical power required aboard aircraft. planes. Power requirements are expected to expand the SWAP-C challenge, continually increasing at the rate of more sophisticated cockpit avionics and more electrically operated systems.

When power is distributed as DC, voltage conversion and conditioning of the power supply is still required, depending on how and where the power is to be used on board the aircraft . Should the design provide power, increasing it or decreasing it at the device level? Or is it smarter and more efficient to convert power levels before distribution to individual devices or applications? Both design strategies have value, and the ideal design choices should reflect the systems involved, aircraft type and purpose, reliability, robustness, scalability, life cycle, etc. Modular strategies demonstrate great potential in this type of power system design – capitalizing on proven designs and minimizing development time. It’s a competitive approach that protects SWaP-C ideals and keeps manufacturers focused on the next generation of aircraft design.

DC Power Distribution Strategies

Power requirements in a specific area of ​​an aircraft, for example the 28 volts commonly used in cockpit avionics, could be addressed only with power conditioning from a local battery source. Conversely, the required 28 VDC can be converted centrally and distributed as required by the systems. This design is best suited for smaller, less complex architectures, as cabling weight can increase when power is widely distributed to an array of on-board devices. A modern, flexible distribution architecture can also provide a layer of redundancy and gradual performance degradation to improve security and, in the context of military platforms, increase survivability.

A more strategic design might have increased voltage as a compromise to reduce wiring. By designing a primary distribution at 540 volts, backed up by a localized secondary distribution at 28 volts, stepping down is not necessary at each individual load; rather, the localized 28-volt network is designed to support multiple devices with a single conversion. Such a design is also beneficial for electronics operating in more isolated areas of the aircraft, such as a heater system or on-wing controls. Concerns about cabling weight increasing with cabling distances, resolved with a distributed power supply in a single higher voltage option, then scaled up to its required voltage locally beside the device. This design strategy becomes more complex with systems that require secondary loads that require multiple voltages, such as 28/5/3 volts.

Modular options increase flexibility

In response to these ever-changing power needs, as well as the demand for faster time to market, power solutions are more readily available as modular components that take into account both performance and scalability. Two distinct levels of modularity apply, the first of which includes the device itself. Parametric definition of design models eliminates the time and resources needed to develop from scratch, including a complete model and analysis of each design. These can be easily adapted and incorporated into custom designs for the full spectrum of secondary power needs, whether the application requires a 100 watt low power control unit or involves a heavier end load such as 6000 watts.

Custom design resources can be further reduced when a single device is developed to meet a superset of requirements. In this case, system developers should pay particular attention to the overall efficiency of the device; a family of building blocks can help alleviate efficiency issues, allowing interchangeability between different points in the design range. Each will offer its own defined performance window, which will require scaling up or down to achieve maximum efficiency. Performance thrives, time to market is fast, and proven engineering is repurposed for good.

The terminal unit itself defines the second level of modularity. Consider that a 2 kW converter can be designed for multiple uses, for example, applied to the power distribution strategy of a 4 kW or 6 kW application. This builds on proven technology in a modular design, responding to custom power levels and aligning with the power redundancy requirements of all-electric aircraft. Using this approach, the system design could have five individual but coordinated 2 kW converters to nominally supply 10 kW. Flexibility and redundancy are built into the design, along with automatic power routing, so the loss of a single converter does not affect overall system integrity. If an unlikely failure occurs, the remaining components compensate to keep the aircraft safe and operational – much like the multiple engines on board traditional aircraft. Such designs are also generally lighter than the traditional “A-lane/B-lane” duplication. Historically, power control systems have tended to operate in isolation, but today’s technical advancements highlight this as a significant shift and an ideal design path for aircraft power. electrical.

Increased electrification and agility in defense scenarios

Advances in massive global investment in energy storage technology – fuel cells and batteries – are transforming aviation. Military operations are inherently dangerous; however, air operations can be considered safer than ground transportation options exposed to improvised explosive devices (IEDs) or other ground attacks. More importantly, technological relationships add value to both sides of the equation. The defense industry benefits from commercial innovation, consistent with its long-standing goal of acquiring commercial technology of military value. At the same time, its own extensive resources such as flight safety testing and certification can help reduce risk and accelerate technology adoption, creating a global market for affordable urban air mobility technology. . Flexible distribution schemes and modular power electronics can be used to design very robust solutions with excellent survivability.

About the Author

Julian Thomas

Director of Engineering

TT Electronics working with Team Tempest, won a contract from BAE to design, develop and qualify a DC-DC converter for use in Tempest’s flight control system. The Tempest team is made up of industry partners, including BAE Systems, Rolls-Royce, Leonardo and MBDA, and is tasked with delivering world firsts in advanced technical capabilities. Together with the RAF’s Rapid Capabilities Office and the UK Ministry of Defence, this industry group is working to bring the Tempest fighter aircraft into service by 2035, replacing the existing Typhoon.

Connect with Julian at [email protected] or LinkedIn

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