Solis PV Inverter shutdown for Backup Generator
Backup generator do not like to be back fed or even too lightly loaded. For this reason you need to enable control of the solar inverter to either completely shut down the inverters to just reduce their generation with the state of the generator.
The following are multiple solutions for Solis inverters with Back Up generators:
Having a contactor that trips one of the phases to the inverters. This solution is the simplest but can be expensive. The solution is to have a power (rated to switch full rated power) on one (or more) of the phases going to the solar system. When an inverter sees low voltage on one of the phases it will stop generating.
To implement this in the simplest way is to have the coil for the contactor powered from the grid. This means that when the grid is there is will energise the magnet and close the contactor therefore giving the inverter(s) grid voltages. However if the grid is ever not there, the coil will be low voltage, de-energise and therefore opening the contactor and the voltage on the inverters will go low and stop all generation.
Pros: simple and reliable
Cons: can be expensive (full power contactors)
Demand Response Manager
On the Solis PV inverters there is a dry contact which is called Demand Response Manager (DRM). When the pins are closed (joint together with copper) the inverters will generate and conversely when the pins are opened (relay opened) the inverters will stop generating.
Will need a relay output on the GENSET or a site controller that has the logic to shut down the inverter. This can either be done as soon as the grid is lost or when the consumption is too low and generation is too high.
Pros: simple and cheap
Cons: will need a controller/genset (most generators of decent size have this already)
Grid frequency control
Solis inverters can be programmed to derate when the frequency of the voltage on the grid increases. This idea with the nature thing of generators to increase frequency when the loads become too light make for a great solution.
Setup the generator so it increases the frequency of voltage when the consumption becomes too low and generation becomes too high.
Pros: Saves the most diesel and eco-friendly
Cons: Complicated and have to have control over the generator
Have the Build Management System (BMS), control the inverters through MODBUS. The BMS can monitor the grid and generator to see when to turn ON/OFF the inverters. This can also be made advanced into controlling the inverters generation (see below how we do it with Solis EPM3-5G).
Pros: Cheap (except of price of engineering work to be done by BMS engineer), so powerful because it checks all parameters and controls everything
Cons: Engineering work is required
EPM failsafe Inverters
Having a low-power relay opening the communications between inverters and EPM. When Solis inverters are setup with a Solis EPM the inverters will always be monitoring the network to make sure the EPM is there; if the inverters ever detect a break in communications they will stop generating. You can setup a low power relay (controlled from a site controller/BMS) which breaks the communications only when you have the backup generator running.
Cons: complicated to setup and cause nuisance trips
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