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SiC-Based High Voltage Capacitor Charging Innovations



TECHNOLOGY AREA(S): Electronics, Ground/Sea Vehicles, Weapons

ACQUISITION PROGRAM: ONR 331 POM-15 Multi-Function Energy Storage FNC, ONR 35 Electromagnetic Railgun INP

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 5.4.c.(8) of the solicitation. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Develop an advanced, modular and scalable capacitor charging converter that takes advantage of the unique characteristics of wide bandgap semiconductor devices. This converter will be capable of charging one or more 325kJ capacitor(s) to 6.5-10kVDC in 5 seconds at a repetition rate of up to 10 charges per minute. This duty cycle will be continuous without pause, and indefinite. The charger will be able to vary energy level and charge duration as needed to meet mission requirements, and present a manageable and reasonably continuous and level load to reduce effects on the power system.

DESCRIPTION: Future electric weapons, such as Electromagnetic Railguns, will require high-voltage supplies to provide power to their pulse-forming-networks (PFNs). While high-output-voltage power converters have been successfully applied in other applications, existing units have inadequate power densities to be deployed in volumetrically constrained shipboard applications. Additionally, most existing high-output-voltage converters do not accept input voltages in the range of projected Navy power systems. In commercial and other military applications, wide-bandgap semiconductor materials such as silicon carbide and gallium nitride have enabled substantially smaller switching devices with greater thermal capabilities, higher breakdown voltages, and much faster switching frequencies. This technology can enable the development of more compact, better-performing, and more efficient high-voltage power converters.

The Navy capacitor charging application is very different from commercial capacitor chargers in that the power levels are higher (i.e. a greater amount of capacitance is being charged), the per-kW size is smaller to fit within the constrained space on ships, and the charging converters are operated continuously at high repetition rates. In addition, the Navy converters must be compatible with the shipboard environment with its unique shock, vibration, and other environmental requirements. For this reason, it is necessary to develop application-specific converters for this application rather than applying a commercial-off-the-shelf solution.

This topic pursues innovative means of charging capacitors from zero to 6.5-10 kVDC, in a rapid, repetitive manner, with a range of input voltages. The proposed charging converter to be produced shall have the following characteristics:


-Be able to draw power from a battery or rectifier source with input voltages of 650-1100 VDC. Different add-on front ends can be used to accommodate higher input electric distribution voltages of 6.5 kVDC, and/or 4160 VAC, with one of these selected for demonstration.


-Be able to charge 325kJ of capacitance (or integer multiples of this value to enhance power density) in 5 seconds and have a repetition rate of 10 charges per minute, continuously with no maximum number of charges.


-To minimize peak power demands on the source, the charging converter shall have a peak-to-average power ratio of no more than 1.1 over the charge cycle.


-Proposed concepts shall incorporate liquid cooling since they will ultimately reject their heat to water provided by the ship. Coolant will be 0-35°C Seawater and/or 5-40°Coolant (50/50 Propylene Glycol/Water)


-To fit within the shipboard environment, the charging converters should have a power density, using average not peak power, of 3 MW/m3 or greater, not including additional add-on modules proposed for interfacing with higher voltages. Dimensions will be tailored to best facilitate serviceability, changeout, and appropriate bussing within a group of charger units. The longest single dimension will not exceed 72”.


-The outputs of the converters should be galvanically isolated from the input voltage.


-Parameters of the charging profile (i.e. the ramp rate of power at the beginning and end of the charge cycle) should be adjustable in order to be compatible with a variety of power sources. Load behavior will not include any large (>25%) drops or other behaviors that are unsupportable by prime movers or power system dynamic requirements.


-In order to be compatible with the shipboard environment, the final design should meet the following requirements: Shock MIL-S-901D, Vibration MIL-STD-167-1A, and Transportability MIL-STD-810G (design to but not test to these requirements under phase I/II).


-Suitable to be multiplexed to a single power converter or source. The controls for operation should allow multiple units to start charging simultaneously or with a variable delay.


-A desirable but not required attribute would allow the device to operate bidirectional, potentially enabling other uses in power conversion between 6.5-10kVDC and a lower feed voltage (650-1100 VDC).


-The small business may use any switching devices, power electronic topologies, and control strategies that meet the requirements above and herein as defined for the phases of execution.

PHASE I: Demonstrate the feasibility of an advanced, scalable, modular converter charger for 325 KJ capacitor(s) using wide bandgap switching devices. As applicable, demonstrate the effectiveness of the solution with hardware, modeling and simulation, and applicable engineering analysis. A Simulink simulation will be created under the base phase and delivered to the Navy. Hardware-based demonstration will support validation of the model, and a validated version will be provided to the Navy under the option phase, if awarded, as a Simulink file, capable of operating under the Opal-RT real-time HIL environment. Establish performance goals and provide a Phase II developmental approach and schedule that contains discrete milestones for product development.

PHASE II: Develop, demonstrate and fabricate a prototype with characteristics identified in Phase I. In a laboratory environment, demonstrate that the prototype meets the performance goals established in Phase I, as related to charging performance and continuous operations. Conduct performance, integration, and risk assessments. Update simulations according to the as-built design attributes. Testing during this phase should demonstrate the ability to charge a capacitor(s) with the required charge time with rep rate capability. Thermal management will be sufficiently characterized to ensure that steady-state is reached. The unit, as built, will be assessed by simulation and implemented design practices for suitability to meet shock, vibration and environmental characteristics. The performer will then develop a cost benefit analysis and cost estimate for a naval shipboard unit. Provide a Phase III installation, testing, and validation plan, including shock, vibration and environmental requirements, which includes spare test units.

PHASE III DUAL USE APPLICATIONS: Working with the Navy and Industry, as applicable, design and construct a fully functional high voltage charging converter meeting all requirements listed in the Description section. The company will support the Navy for test and validation to certify and qualify the system for Navy use. The converter will be tested at full power and maximum rep rate during this phase in an in indicative manner at the vendor as a Factory Acceptance Test (FAT), and then at a Navy test facility where appropriate high voltage equipment can be demonstrated with it. The company shall explore the potential to transfer the technology during this SBIR effort to other military and commercial systems. Market research and analysis shall identify the most promising technology areas and the company shall develop manufacturing plans to facilitate a smooth transition to the Navy. Private Sector Commercial Potential: Technologies developed in this program are applicable utility and industrial applications requiring high density dc power conversion, especially those involving the charging of large banks of capacitors. Examples include fusion research facilities such as the National Ignition Facility (NIF) which use 100’s of megajoules of stored energy. Technologies would also be applicable to more general medium voltage power electronics applications such as High-Voltage DC transmission (HVDC) systems, medium-voltage motor drives, and systems designed to interface alternative energy supplies to the medium voltage distribution grid.


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  • MIL-S-901D:
  • MIL-STD-167-1A:
  • MIL-STD-810G:

KEYWORDS: Electromagnetic; capacitors; pulsed-power; converter; power electronics; pulse-forming; wide bandgap; silicon carbide; railgun; gallium nitride

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