Solid-state transformer for mitigation of common mode insults
A high altitude electromagnetic pulse (HEMP) or other similar geomagnetic disturbance (GMD) has the potential to severely impact the operation of large-scale electric power grids by introducing low-frequency common-mode (CM) currents which deteriorate the performance of key grid components, such as large power transformers. A solid-state transformer (SST) can replace susceptible equipment and improve grid resiliency by safely redirecting, absorbing, and/or converting these CM insults.
1 . A solid-state transformer for mitigation of common mode insults, comprising:
a primary-side ac/dc converter on a grid side,
an intermediate dc/dc converter electrically connected in series to an output of the primary-side ac/dc converter which provides galvanic isolation of the grid side and a load side, thereby enabling large step-up/step-down ratios,
a secondary-side dc/ac converter electrically connected in series to an output of the intermediate dc/dc converter and configured to feed a downstream load,
an energy storage system electrically connected in parallel to the output of the primary-side ac/dc converter and configured to absorb common mode energy incident on the grid side of the primary-side ac/dc converter, and
a controller configured to divert the common mode energy to the energy storage system and output enough power from the primary-side ac/dc converter to ensure the secondary-side dc/ac converter outputs a constant current to a downstream load.
2 . The solid-state transformer of claim 1 , wherein the primary-side ac/dc converter comprises a four-leg ac/dc converter.
3 . The solid-state transformer of claim 1 , wherein the secondary-side dc/ac converter comprises a four-leg dc/ac converter.
4 . The solid-state transformer of claim 1 , wherein the intermediate dc/dc converter comprises a dual active bridge.
5 . The solid-state transformer of claim 1 , wherein the energy storage system comprises a battery, super capacitor, or flywheel.