Our Technology
We are currently developing three power conversion topologies and have more in our product pipeline.
The Hybrid Power Module
The HPM design incorporates multiple Maximum Power Point Tracking (MPPT) converters operating as parallel current sources to power a grid-frequency inverter. Novel controls allow the silicon (Si) and silicon carbide (SiC) devices to operate in parallel such that the majority of the power flows through the low cost, rugged Si switching at grid frequency and a smaller portion flows through the higher cost SiC switching at tens of kilohertz. The coordinated operation of all the devices (Si and SiC) in DC to AC conversion generates sinusoidal, three phase, low ripple AC current.
The circuit topology also eliminates the need for electrolytic capacitors, a common failure point in power electronics. High frequency switching of the SiC devices drastically reduces the size, weight, and cost of the inductor chokes on the AC or grid side of the circuit. Very low harmonics reduce filtering requirements which translates to lower material costs, lower weight, and lower volume for the same power output. Simulations indicate an overall system efficiency of 99%. All of these features provide a distinct competitive advantage over state of the art designs.
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Currently, we are building a prototype inverter based on this topology and preparing for lab testing. Current Technology Readiness Level is 3.
The Active Filter Topology
Typical inverter designs are 2-level or 3-level. Our approach adds a compact, Active Filter to a standard 2-level design to create what we call a 2.2-level inverter. Compared to today’s SiC inverters, our design shows a 10x reduction in switching losses, a 10x reduction in dv/dt noise, and 40% reduced SiC costs. This provides the following improvements over the state-of-the-art SiC solar inverters:
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50% reduction in total power loss compared to hard-switching SiC inverters, enabling higher current capacity alongside increased switching frequency.
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Cost savings by eliminating SiC diodes without any concern about body diode reverse recovery problem.
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Weight and cost savings in passive components (inductors and capacitors) with higher switching frequency.
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Reduced balance of system costs due to smaller heat sinks and elimination of liquid cooling.
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Reduced EMI for better noise immunity of sensors, gate drivers, and controllers.
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Higher overall efficiency.
This technology has been built and tested at NC State. As part of additional grant opportunities, we are currently optimizing a three phase prototype for energy storage applications.
The Paired Switch Half Bridge
This topology was developed to compete in the US DOE Silicon Carbide Packaging Prize which required entrants to design a power module using devices rated at 1.7kV or less but capable of converting power up to 5,000 volts at 1,500 Amps. Dr. Yu’s design minimizes commutation loop inductance, a key contributing factor to losses, through a specific arrangement of top cooled discrete packaged devices. Thermal management of tightly packed switches also requires a novel approach to cooling which we integrated into the design. This 5 MW module is only a few inches thick and 12” square. The next generation of this module could use 3.3kV or 6kV devices for increased performance and increase the power to nearly 20 MW. Applications include Medium Voltage Solid State Transformers, High Voltage DC Converters, drives for large industrial motors.
NCSI is actively seeking commercialization partners for all of our technologies.
