Systems and methods for charging and discharging active power link modules in direct current power systems

A method of operating a modular power converter system including a plurality of active power link module (APLMs) directly coupled to each other, each APLM of the plurality of APLMs including a plurality of relays including a plurality of first relays and a plurality of second relays corresponding to a plurality of first-type ESDs, a plurality of switching devices coupled in electrical series and an antiparallel diode being coupled in electrical parallel with the plurality of switching devices, and at least one first-type energy storage device (ESD) of the plurality of first-type energy storage devices (ESDs) being coupled in electrical parallel with a series connection of the plurality of switching devices, the at least one first-type ESD configured to induce a first direct current (DC) voltage, wherein for each APLM, a first relay of the plurality of first relays is coupled to a first terminal of the at least one first-type ESD proximate a first switching device of the plurality of switching devices and a second relay of the plurality of second relays is coupled to a second terminal of the at least one first-type ESD proximate a second switching device of the plurality of switching devices, said method comprising:

• determining, with a sensor coupled to the plurality of switching devices, an operational status of at least one APLM of the plurality of APLMs, the operational status including a functional status and a non-functional status;
• establishing, with a switching controller coupled to the sensor and to the plurality of switching devices and to the plurality of relays, a plurality of switching states including switching states of the plurality of switching devices and switching states of the plurality of relays in response to the operational status;
• discharging, with a charge controller coupled to the switching controller and to a discharge circuit and the plurality of relays, the at least one first-type ESD of at least one respective APLM of the plurality of APLMs having the non-functional status to a voltage less than the first DC voltage by a predetermined amount the charge controller coupled to the at least one respective APLM via the first relay and the second relay;
• and
• replacing the at least one respective APLM having the non-functional status with at least one replacement APLM having the functional status.

A method of assembling a modular power converter system, said method comprising:

• directly coupling a plurality of active power link modules (APLMs) to each other, each APLM of the plurality of APLMs including a plurality of switching devices coupled in electrical series and an antiparallel diode being coupled in electrical parallel with the plurality of switching devices, a plurality of relays including a plurality of first relays and a plurality of second relays corresponding to a plurality of first-type ESDs, and at least one first-type energy storage device (ESD) of the plurality of first-type ESDs coupled in electrical parallel with a series connection of the plurality of switching devices, wherein for each APLM, a first relay of the plurality of first relays coupled to a first terminal of the at least one first-type ESD proximate a first switching device of the plurality of switching devices and a second relay of the plurality of second relays coupled to a second terminal of the at least one first-type ESD proximate a second switching device of the plurality of switching devices;
• coupling a charge controller to a switching controller, to the first relay and the second relay of the plurality of relays and to at least one of an electrical power source and a discharge circuit;
• coupling at least one second-type ESD in electrical parallel with the plurality of APLMs;
• and
• configuring the charge controller to alternately charge and discharge via at least one charge control signal received from the switching controller, the at least one first-type ESD in response to a plurality of switching states including switching states of the plurality of switching devices and switching states of the plurality of relays, wherein each APLM of the plurality of APLMs is configured to facilitate detachable electrical coupling to the modular power converter system.