How do I condition power between a generator that does not produce a clean sine wave and a UPS to such a standard that the UPS will accept the power? I have tried running through a power conditioner, but I believe the problem is that the power conditioner does not stabilize or control the frequency of the power coming in which is probably all over the place. I believe the generator is also unlikely to put out a good frequency until it is under load and until the UPS accepts the power from the generator, no load is put on the generator. Is there a cheap way to do this other than buying a new generator?
All that needs to run on the generator is 1 desktop computer, 1 server, 1 router, 1 switch, 1 printer, and a few other small things. All told the load is under 500 watts as long as the server is not under a heavy processing load (which it almost never is). The UPS I am currently using is an APC Back-UPS. The generator puts out 800 watts, 900 peak.
Use a SmartUPS. The UPS use the power from the line to charge the battery while the output from the UPS is from the battery. APC call that way True Online. The line stay more isolated than like a backups where it's a on/off to go on battery in case of a powerloss.
Edited: The input range must be between 50 & 60hz, else it will fall on battery
Rather than adding a conditioner, get a generator that is meant for office/home loads. I'm guessing the generator you have now is meant for building sites & power tools with a specific type of electrical motor in them.
A domestic type generator will also be more quiet and efficient. And you can move it & use it for your fridge/freezer when needed.