How should a solar pump system with AC grid be designed?

yangh

Do we need to export the solar power to the grid when the water pump is not working?

Cactus1549

Let's introduce three solutions and their advantages and disadvantages

Cactus1549

Solution 1:

Connect RST of the VFD to AC grid, and connect +- to DC(solar).
Advantage: Simple and low cost.
Disadvantage: It cannot export the unnecessary electricity generated by solar to the grid.

Cactus1549

Solution 2:

The solar array connects to the AC grid through the PV inverter, the VFD also connects to the grid.
Advantage: It can export the unnecessary electricity generated by solar to the grid.
Disadvantage: If the AC grid outage, the PV inverter will not work, and even if the light is normal, the VFD and the water pump will not be able to obtain electricity.

Cactus1549

Solution 3:

In order to solve the problem in solution 2, we can add a connection from solar to the VFD. If the AC grid outage, we can disconnect the AC breaker QF1 and close the DC breaker QF2, so that the VFD and the water pump can directly obtain the electricity generated by solar.
Advantage: High reliability.
Disadvantage: High cost.