Solar Plant in a Remote location

[D!NNy]

Hello,

Question 1: Can someone help me to understand why and what size of reliable power generation in parallel to solar plant is needed for operating in isolated grid area (where there is no existing grid)? I was told that the DC to AC converters require reliable operating reference voltage and frequency to generate the electricity from the solar farm. If this is the case, a 10MW solar plant requires how much of reliable source of power. example 500kW diesel generation or 1MW diesel generation? how to size this generation unit??

Question 2: How to provide the KVAR support from the inverters in the solar plant to the loads in a completely isolated system? can i add bunch of capacitor banks to match the reactive loads in different locations??

Thanks for the help in advance.
Dinesh

 

[GoldDigger]

1. The problem is not just the reliability and stability of the reference voltage source.
An ordinary grid interactive inverter is designed to sink excess power into the grid (reference source) if the PV is producing more power than the local loads are demanding.
To do what you want to do will require a grid interactive inverter that is actually designed for off-grid use with generator support. These units will be able to produce power even if the generator fails and more important will sense any reverse power flow (or flow below a minimum amperage) back into the generator and will shut the system down or reduce the PV output accordingly.

It is possible to build a system which combines hybrid inverters having a generator support option and carefully controlled grid tie inverters (such systems are specifically produced using the right combination of their products by SMA and other manufacturers, but the off-grid inverters require a battery bank for their own stability.)

It is also possible to design an entire system using just grid tied inverters and generators with an elaborate custom control system, but that would be a job for a PE with specific expertise in that area. The size of the generator would be the least of the problems involved.
2. By their nature, grid tied inverters do not care about the KVAR of the load within fairly broad limits. Just as a full grid can adapt within limits to low PF loads.
But there are also GTIs which are designed specifically for PF compensation and actively sense the PF of the load rather than just looking at the voltage present at their interface terminals.
Again, a very specialized area found in commercial/utility grade products. SMA has some white papers on this too.