A Hybrid Gallium-Nitride-Silicon Direct-Injection Universal Power Flow and Quality Control Circuit With Reduced Magnetics

This article presents a highly compact direct-injection power flow and quality (f/q) control topology that employs a novel hybrid switching scheme to eliminate the line transformers and discrete high-current inductors in the high-current series injection, which otherwise dominate size and cost. Moreover, the proposed design is especially suitable for the lower voltage levels from the distribution grid onward using the latest low-voltage high-current semiconductors, specifically fast-switching gallium-nitride transistors operating even with only clip-on magnetics, supported by silicon devices for sufficient over-load and fault tolerance. These floating modules are directly inserted in series with each phase and omit any ground connection, thereby only dealing with a small portion of the voltage difference, unlike series back-to-back converters that have to handle the full power. In consequence, by employing low-power components and omitting large line transformers and inductors, the circuit demonstrates remarkable compactness. This makes it highly suitable for installation in on-street utility boxes. Specifically, it occupies a mere 20% of the volume associated with transformer-injection circuits, 30% of that of series back-to-back converters, and 60% the volume of our previous purely silicon direct-injection configurations.