Methods and systems for using solid state transformers to protect medium and low voltage electrical grids from extreme EMP transients

A system for suppressing an electrical surge induced by a transient electromagnetic energy disturbance comprising:

• embedded coordinated hybrid surge protection assemblies responding instantaneously to an overvoltage transient surge, induced by an electromagnetic pulse and exceeding a predetermined threshold level above a normal operating voltage of a solid-state transformer (SST), limiting the overvoltage transient surge to a magnitude of the predetermined threshold level and shunting overcurrent, the transient surge suppressing assemblies comprising at least one subcircuit network of bulk semiconductor components providing overcurrent shunting to solid ground with near-zero impedance without interfering with isolation between a medium voltage stage and a low voltage stage of the SST;
• embedded coordinated hybrid transient surge protection assemblies comprising a plurality of low voltage limiting, absorbing, switching, shunting, disconnecting, and reconnecting devices, comprising at least one subcircuit of nonlinear components and semiconductors, avalanche diodes and transistors, metal oxide varistors, gas discharge and glass gas discharge tubes, spark gap protectors, and ionization discharge devices, wide-bandgap compound semiconductor components installed at every converter cell of a plurality of converter cells of the SST, scalable for voltage, current, and energy handling capacity of a medium voltage stage converter cell;
• embedded transient surge suppressing assembly of blocking capacitors at an output of every direct to alternating current (DC/AC) switching module of each of the SST converter cells, connected to a primary winding of a high frequency transformer (HFT) of the SST, eliminating DC voltages from reaching the HFT, providing protection against extremely low frequency, quasi-DC voltages, induced in medium voltage electric power distribution lines from high altitude nuclear electromagnetic pulse and geomagnetic disturbance,
• the embedded transient surge suppressing assembly installed as a subcircuit of resonance network circuit of the converter cells with resonance subcircuit topology SST, limiting the propagation of transient surges across the high frequency transformer and enhancing surge protection of the SST, and, respectively, medium voltage electric power distribution grid and low voltage electric power distribution grid interfaced by the SST, wherein,
• electrically connected coordinated hybrid transient surge protection assemblies at an input of every converter cell at a medium voltage stage converter cell of the SST, comprise low voltage components transient surge suppressing assemblies, rated accordingly to an operational input voltage of the converter cells of the SST, having an operational voltage equal to medium voltage divided by a number of converter cells connected in series at the medium voltage stage of the SST, surge protection assemblies having mutually coordinated voltage limiting levels, scaled current capacity ratings, respectively limiting mutual operational degradation when limiting, absorbing, switching, and shunting overvoltage and overcurrent at the input of every converter cell at a medium voltage stage of the SST.

A system for suppressing an electrical surge induced by a transient electromagnetic energy disturbance on medium voltage and low voltage electric power grid line segments interfaced with a solid-state transformer (SST) comprising:

• embedded coordinated hybrid surge protection assemblies, responding instantaneously to an overvoltage induced by an electromagnetic pulse and exceeding a predetermined threshold level above a normal operating voltage of a solid-state transformer (SST), limiting overvoltage to a magnitude of the predetermined threshold level and shunting overcurrent, protecting the SST and grid segments interfaced by the SST without interfering with voltage isolation between an interfaced segment;
• embedded coordinated hybrid surge protection assemblies, comprising low voltage components installed on every converter cell of a modular multicell SST, interfacing and isolating a medium voltage electric power grid and a low voltage electric power grid, and installed on at least one converter cell of an SST with application specific topology, interfacing and isolating two low voltage electric power grid segments;
• an SST with embedded coordinated hybrid surge protection, connected in series with at least one additional SST with coordinated hybrid embedded surge protection, providing sequential coordinated voltage conversion with intermediate high voltage stage, enhancing robustness of surge protection and voltage isolation of medium voltage electric power grid segments and low voltage electric power grid segments;
• and
• an SST with embedded coordinated hybrid surge protection, connected in parallel with at least one additional SST with coordinated hybrid embedded surge protection and synchronized control, providing enhanced power conversion, redundancy of the surge protection, grid interfacing, and voltage isolation of the medium voltage electric power grid segments and the low voltage electric power grid segments, wherein,
• the SST with embedded coordinated hybrid surge protection, electrically connected in series or in parallel, interfacing medium and low voltage grid segments, provides resourceful protection against damaging effects of overvoltage and overcurrent surges, induced by a transient electromagnetic energy disturbance, responds instantaneously to limit the overvoltage and shunt the overcurrent, and provides EMP protection of the medium voltage electric power grid and the low voltage electric power grid.