Battery for fault handling in bidirectional power conversion systems

A method comprising:

• providing a plurality of bidirectional power converters each operable (i) in a first mode to convert AC power received at AC terminals to DC power at DC terminals and (ii) in a second mode to convert DC power received at the DC terminals to AC power at the AC terminals, wherein the DC terminals of the plurality of bidirectional power converters are coupled to each other in series to form a converter stack, wherein ends of the converter stack define a DC power bus, and wherein each bidirectional power converter contributes a respective portion of a voltage of the DC power bus in the first mode;
• determining that a DC voltage across the DC terminals of a particular bidirectional power converter within the converter stack is below a threshold voltage;
• and
• based on the determination that the DC voltage is below the threshold voltage, (i) causing the particular bidirectional power converter to stop contributing a first portion of the voltage of the DC power bus and (ii) causing a battery to begin contributing the first portion of the voltage of the DC power bus.

A converter stack including a plurality of bidirectional power converters, a particular bidirectional power converter of the plurality comprises:

• AC terminals electrically coupled to an AC power system;
• DC terminals electrically coupled in series with DC terminals of one or more bidirectional power converters in the converter stack, wherein ends of the converter stack define a DC power bus, and wherein the DC terminals of the particular bidirectional power converter contribute a DC voltage to the DC power bus;
• a bidirectional conversion bridge configured to (i) convert AC power received at the AC terminals to DC power at the DC terminals and (ii) convert DC power received at the DC terminals to AC power at the AC terminals;
• and
• a battery configured to selectively couple to the DC terminals responsive to the DC voltage across the DC terminals being below a threshold voltage.