Modular multilevel converters for battery energy storage
A battery energy storage system includes a plurality of battery cores. Each battery core of the battery energy storage system includes an array of battery cubes, and each battery core is configured to provide a first direct current power at a first voltage. The battery energy storage system further includes a plurality of direct-current-to-direct-current (DC-DC) converters. Each DC-DC converter of the battery energy storage system is configured to accept the first direct current power and each DC-DC converter is configured to provide a second direct current power at a second voltage. The battery energy storage system further includes a main modular multilevel converter (MMC). The MMC of the battery energy storage system is configured to accept the second direct current and to provide an alternating current at a third voltage.
1 . A battery energy storage system, comprising:
a plurality of battery cores, wherein each battery core of the plurality of battery cores includes an array of battery cubes each comprising a plurality of racks of battery cells, and is configured to provide a first direct current power at a first voltage;
multiple sets of direct-current-to-direct-current (DC-DC) converters wherein each set of the multiple sets of DC-DC converters includes a plurality of DC-DC converters connected in series, wherein each DC-DC converter of the plurality of DC-DC converters includes a dual-active bridge converter configured to provide galvanic isolation to the battery cores and wherein each first DC-DC converter of each set of the multiple sets of DC-DC converters is configured to accept the first direct current power and each last DC-DC converter of each set of the multiple sets of DC-DC converters is configured to provide a second direct current power at a second voltage; and
a main modular multilevel converter (MMC) connected in series with each last DC-DC converter of each set of the multiple sets of DC-DC converters, the main MMC configured to accept multiple inputs of the second direct current power and provide a first alternating current power at a third voltage.
2 . The battery energy storage system of claim 1 , wherein:
at least one DC-DC converter of each set of DC-DC converters comprises an isolated MMC, each isolated MMC connected in series to the main MMC.
3 . The battery energy storage system of claim 2 , wherein:
each isolated MMC is configured to offer bidirectional power flow.
4 . The battery energy storage system of claim 1 , wherein:
the first alternating current power is three-phase electric power.
5 . The battery energy storage system of claim 1 , wherein:
each last DC-DC converter of each set of DC-DC converters is configured to provide the second direct current power of the second voltage at a set voltage level.
6 . The battery energy storage system of claim 1 , wherein:
the first voltage of each battery core of the plurality of battery cores is a low voltage;
the second voltage of each set of DC-DC converters is a first high voltage of a greater value and different from the low voltage; and
the third voltage is a second high voltage different from the first high voltage.
7 . The battery energy storage system of claim 1 , wherein:
at least one DC-DC converter of each set of DC-DC converters is an isolated MMC and includes a plurality of sets of submodules, wherein at least two sets of submodules of the plurality of submodules is for the first direct current power and at least another two sets of submodules of the plurality of submodules is for the second direct current power.
8 . The battery energy storage system of claim 7 , wherein:
each set of submodules of the plurality of submodules of the isolated MMC comprises a half-bridge submodule.
9 . The battery energy storage system of claim 7 , wherein:
each set of submodules of the plurality of submodules comprises a full-bridge submodule.
10 . The battery energy storage system of claim 7 , wherein:
a first set of submodules of the plurality of sets of submodules is electrically coupled to a second set of submodules of the plurality of submodules;
the first set of submodules receives an incoming power at the first voltage, and provides an interstitial power at an interstitial voltage;
the second set of submodules receives the interstitial power, and provides an outgoing power at the second voltage; and
the interstitial voltage is greater than the first voltage and less than the second voltage.
11 . The battery energy storage system of claim 1 , further comprising:
a power controller, configured to adjust the second voltage provided by the plurality of DC-DC converters, at the array of battery cubes.
12 . The battery energy storage system of claim 1 , comprising:
a main DC-DC converter connected in series to the main MMC between the main MMC and the multiple sets of DC-DC converters.
13 . The battery energy storage system of claim 1 , wherein each set of DC-DC converters is connected in parallel with the multiple sets of DC-DC converters.
14 . The battery energy storage system of claim 1 , wherein the DC/DC converters and/or the main MMC is actively controlled via a storage dispatch unit.
15 . An energy provisioning system, comprising:
a plurality of power sources, wherein each power source of the plurality of power sources is configured to provide a first direct current power at a first voltage;
multiple sets of direct-current-to-direct-current (DC-DC) converters wherein each set of the multiple sets of DC-DC converters includes a plurality of DC-DC converters connected in series, wherein each DC-DC converter of the plurality of DC-DC converters includes a dual-active bridge converter configured to provide galvanic isolation to the power sources and wherein each first DC-DC converter of each set of the multiple sets of DC-DC converters is configured to accept the first direct current power and each last DC-DC converter of each set of the multiple sets of DC-DC converters is configured to provide a second direct current power at a second voltage; and
a main modular multilevel converter (MMC) connected in series with each last DC-DC converter of each set of the multiple sets of DC-DC converters, the main MMC configured to accept multiple inputs of the second direct current power and provide an alternating current power at a third voltage.
16 . The energy provisioning system of claim 15 , wherein:
at least one DC-DC converter of each set of DC-DC converters comprises an isolated MMC, each isolated MMC connected in series to the main MMC.
17 . The energy provisioning system of claim 16 , wherein:
each isolated MMC is configured to offer unidirectional power flow.
18 . The energy provisioning system of claim 15 , wherein:
the first alternating current power is three-phase electric power.
19 . The energy provisioning system of claim 15 , wherein:
Each last DC-DC converter of each set of DC-DC converters is configured to provide the second direct current power of the second voltage at a set voltage level.
20 . The energy provisioning system of claim 15 , wherein:
the first voltage of each power source is a low voltage;
the second voltage of each set of DC-DC converters is a first high voltage of a greater value and different from the low voltage; and
the third voltage is a second high voltage different from the first high voltage.
21 . The energy provisioning system of claim 15 , wherein:
at least one DC-DC converter of each set of DC-DC converters is an isolated MMC and includes a plurality of sets of submodules, wherein at least two sets of submodules of the plurality of submodules is for the first direct current power and at least another two sets of submodules of the plurality of submodules is for the second direct current power.