Bi-Directional DC-DC Optimizer Reduces Cost of DC-Coupled Solar + StorageJuly 10, 2019 by Scott McMahan
Alencon Systems LLC introduced the Bi-Directional Optimizer for Storage Systems called the BOSS. The Alencon BOSS is a novel solution for both improving and bringing down the cost of dc-coupled solar + storage deployments while extending the useful life of the batteries and improving battery rack utilization.
The BOSS controls the charge and discharge of individual battery racks in both dc- and ac-coupled deployments, and it supports the integration of energy storage with 600V, 1000V, or 1500V PV strings.
The BOSS leverages Alencon's patented Galvanically Isolated dc-dc conversion topology, a unique architecture that offers a number of benefits not available from other non-isolated dc-dc converters. These benefits include the ability to pair high voltage 1500V PV with lower voltage battery chemistries as well as the ability to incorporate grounded PV systems with floating batteries on the same dc-bus.
Additionally, because the BOSS is a rack-level dc-dc converter it ensures the optimal utilization of each battery rack within the cabinet. By addressing each battery rack individually, the BOSS also enhances system safety by limiting the fault currents in the event of a sudden short to ground, potentially reducing system cost by eliminating the need for additional safety devices.
Also, the BOSS makes battery rack augmentation over the life of a storage project much easier and more cost-effective by allowing the installation of battery racks with different charge-discharge voltages onto the same dc-bus.
Alencon says one very unique feature of the BOSS is that it makes it easy to deploy DC-coupled Solar + Storage projects with string inverters.
"As a leader in the field of DC-coupling for Solar + Storage, our customers looked to us to help them to continue to find more cost-effective solutions for deploying DC-Coupled Solar + Storage projects, which lead us to develop the BOSS" says Alencon Systems President Hanan Fishman. "DC-coupling of Solar + Storage is growing rapidly in popularity. The Alencon BOSS applies our unique galvanically isolated technology to address a number of needs that storage developers are facing."
"The BOSS addresses a number of heretofore unmet needs by DC-DC converters in the DC coupled Solar + Storage space, including the ability to incorporate transformerless string inverters into these projects, the ability to resolve grounding challenges on the same DC-bus, the ability to optimize battery charge at the rack level as well as offer a more intuitive approach to battery rack augmentation over the life of a project."
The BOSS is available in a number of form factors including:
- A 19-inch rack-mounted unit allows easy integration into a battery cabinet.
- An outdoor-rated, rail or wall-mounted form factor can be installed either inside a battery cabinet or outside of it.
- An indoor cabinet of stacked, rack-mounted units
- An outdoor, cement pad-mounted version enclosing a number of rack-mounted units
According to Alencon, any number of BOSS units can be installed in parallel and can be easily packaged into a single cabinet if desired. The devices have novel mechanical packaging with forced air cooling.
Figure 2: The Alencon BOSS can be packaged in several form factors, including single rack-mounted or rail-mounted units or indoor or outdoor cabinets.