Methods of fuel cell operation with bi-directional inverters

A microgrid system, comprising:

• a first direct current (DC) power source electrically connected to a first DC electrical power bus;
• a second DC power source electrically connected to a second DC electrical power bus;
• a first uninterruptable power module electrically connected to the first DC electrical power bus and configured to be connected to an alternating current (AC) load via at least one load electrical power bus;
• a second uninterruptable power module electrically connected to the second DC electrical power bus and configured to be connected to the AC load via the at least one load electrical power bus;
• a first AC/DC inverter having a DC end and an AC end, wherein the first DC electrical power bus is connected to the DC end of the first AC/DC inverter;
• a second AC/DC inverter having a DC end and an AC end, wherein the second DC electrical power bus is connected to the DC end of the second AC/DC inverter;
• an automatic transfer switch (ATS) having a load terminal, an emergency terminal, and a normal terminal configured to be connected to an electrical power utility grid;
• a first AC electrical power bus electrically connected to the first and the second AC/DC inverters at their AC ends, and electrically connected to the load terminal of the ATS;
• and
• a second AC electrical power bus electrically connected to the emergency terminal of the ATS and to the at least one load electrical power bus.

A microgrid system, comprising:

• a first direct current (DC) power source electrically connected to a first DC electrical power bus;
• a second DC power source electrically connected to a second DC electrical power bus;
• a first uninterruptable power module electrically connected to the first DC electrical power bus and configured to be connected to an alternating current (AC) load;
• a second uninterruptable power module electrically connected to the second DC electrical power bus and configured to be connected to the AC load;
• a first bi-directional AC/DC inverter having a DC end and an AC end, wherein the first DC electrical power bus is connected to the DC end of the first bi-directional AC/DC inverter;
• a second bi-directional AC/DC inverter having a DC end and an AC end, wherein the second DC electrical power bus is connected to the DC end of the second bi-directional AC/DC inverter;
• an AC electrical power bus electrically connected to the first and the second bi-directional AC/DC inverters at their AC ends;
• a control device configured with control device executable code configured to cause the control device to execute operations comprising:
• determining if first DC electrical power output by the first DC power source to the first DC electrical power bus is less than, equal to or greater than a DC electrical power threshold to be provided to the first uninterruptable power module;
• and
• in response to determining that the first DC electrical power is less than the DC electrical power threshold:
• providing a portion of a DC electrical power output by the second DC power source to the second bi-directional inverter though the second DC electrical power bus;
• providing supplemental AC power from the second bi-directional AC/DC inverter to the AC electrical power bus;
• importing supplemental AC electrical power from the AC electrical power bus by the first bi-directional AC/DC inverter;
• and
• providing a second DC electrical power from the first bi-directional AC/DC inverter to the first DC electrical power bus, such that the first DC electrical power and the second DC electrical power are not less than the DC electrical power threshold.

A method of operating a microgrid system comprising:

• a first direct current (DC) power source electrically connected to a first DC electrical power bus;
• a second DC power source electrically connected to a second DC electrical power bus;
• a first uninterruptable power module electrically connected to the first DC electrical power bus and configured to be connected to an alternating current (AC) load;
• a second uninterruptable power module electrically connected to the second DC electrical power bus and configured to be connected to the AC load;
• a first bi-directional AC/DC inverter having a DC end and an AC end, wherein the first DC electrical power bus is connected to the DC end of the first bi-directional AC/DC inverter;
• a second bi-directional AC/DC inverter having a DC end and an AC end, wherein the second DC electrical power bus is connected to the DC end of the second bi-directional AC/DC inverter;
• and
• an AC electrical power bus electrically connected to the first and the second bi-directional AC/DC inverters at their AC ends,
• the method comprising:
• providing a same amount of AC electrical power to the AC load from the first and the second uninterruptable power modules;
• determining if a first DC electrical power output by the first DC power source to the first DC electrical power bus is less than, equal to or greater than a DC electrical power threshold to be provided to the first uninterruptable power module;
• and
• in response to determining that the first DC electrical power is less than the DC electrical power threshold, importing supplemental AC electrical power from the AC electrical power bus by the first bi-directional AC/DC inverter, and providing a second DC electrical power from the first bi-directional AC/DC inverter to the first DC electrical power bus, such that the first DC electrical power and the second DC electrical power are not less than the DC electrical power threshold.