Most residential homes operate on single-phase. The solar industry has made it very easy to install solar and battery backup for these single-phase services. What if you have a three-phase service? Is it possible to have single-phase backup paired with three-phase solar?
Solar PV Systems with Battery Backup
Solar array systems are great on their own. When paired with a battery backup system, they become more valuable and reliable during uncertain times. Most systems tend to stick to single-phase or three-phase, depending on the service provided.
Single-phase battery systems are the cheapest option, but can a single-phase backup system work with a three-phase solar system? This is a tricky question that has many different answers. Depending on how you plan to use your backup solar pv system will determine if this is possible. We will explore the different configurations and the benefits of each.
Existing Three-Phase Solar Inverter Connected To The Grid
The first configuration we will explore includes an existing three-phase solar inverter already connected to the grid. It would be possible to back up all three of these phases. However, this would require a three-phase battery inverter.
Using a single-phase battery inverter, we can AC couple to a single-phase. This would back up only one phase individually. It is possible to back up one, two, and three phases individually.
The downside to using this configuration is that each phase is backed up individually and cannot operate three-phase loads during a grid outage. Instead, the solar system would operate as three individual single-phase battery systems.
Backing Up Single-Phase of A Three-Phase System
If you plan on only backing up a single phase of your three-phase pv system, it is a good idea to connect 3 C T’s to each of the 3 phases. This will allow you to have the benefits of self-consumption across all three phases. If the battery inverter can monitor all phases, it can discharge the battery to the backed-up phase to allow solar power to be utilized across the additional phases.
Some residents with a 3-phase service might want to explore single-phase solar. This is also possible with a single-phase solar inverter and a single-phase battery inverter. However, only one phase will be able to benefit from the solar and battery system.
There are many different configurations possible when combining three-phase and single-phase backup systems. Depending on what you choose to use your battery system for can also play a large role in your system configuration.