Connecting Grid Tie Inverters to a 5kw Sine Wave Inverter: Safe or Risky?

[Silentkitty2]

As I am well aware you CAN'T connect inverters in parallel due to the Frequency's and wave forms not matching BUT. What if you build a small unit using a 5kw sine wave inverter pure sine wave clean and reliable and connect several small 500w grid tie inverters to this as a grid tie inverter is designed to match the wave forum of the grid its connected to would this work safely or will it raise or just simply substitute the power from the 5kw inverter and lighten the load.

Any thoughts?

 

[Bobbywhy]

Silentkitty2, It's difficult for me to understand just what you're asking/proposing. Will you please ask again, trying to be more clear? Sorry for my lack of understanding.

Power inverters have been connected in parallel to "share the load" for many years. Obviously their phases must be synchronized and, to avoid current unbalances, each inverter's output voltage needs to be identical to the others. Simple control/interconnect circuits exist for controlling this. Then each converter then supplies equal current (power) to the load.

In 1979 I installed, tested, and supplied a critical load with 5 each 450 KVA three-phase power converters connected in parallel as an Uninterruptible Power Supply. The total maximum available to the load was 2.25 MVA.

Bobbywhy

 

[Silentkitty2]

im wanting to basically connect inverters in parallel to boost the wattage output without buying a expensive large inverter.just simply connecting inverters together won't work as the feqenceys won't path without syncing them I am looking for the cheapest and essayist way. would using 1 5kw sine wave inverter connecting a multi switch to it and connecting multiple grid tie inverters being 500w each or so and connect them to the muti switch to boost the wattage of the 5kw inverter.

 

[Bobbywhy]

Silentkitty2,

Unfortunately I’m unable to give any advice or suggestions for your project. You have not made clear exactly what you have now or what you desire. I’ve never heard of a “multi switch” used in power distribution. A multi-switch is used to divide Radio Frequency signals (very low power) from an antenna for distribution to multiple receivers. Circuit breakers or solid-state SCR switches are normally used to connect and disconnect power inverters. Grid tie inverters convert DC to AC for connection to the power grid. They either pass energy to the grid (for sale) or allow energy to flow from the grid to the load. Maybe they would function in a parallel configuration, but I’m not sure how (or if).

Is the load being powered by the grid now? Is it single or multi-phase? Is there any DC source involved? Even if you posted here on Physics Forums a block diagram of your existing system, and another one of your planned system as you visualize it and included every detail of the input power and the load characteristics I would still hesitate to attempt any recommendations. One minor mistake during the complex process of engineering evaluation, recommended action, equipment acquisition, installation and connection, and power-up process exposes your equipment to great risk. One mistake with a power inverter system can result in maximum smoke and fire. I know that’s true from personal experience!

The “cheapest and easiest way” that you’ve indicated is often not the best choice. A more prudent approach would be to find a competent engineering firm to advise you.

http://en.wikipedia.org/wiki/Multiswitch
http://en.wikipedia.org/wiki/Grid-tie_inverter

Bobbywhy

 

[RocketSci5KN]

Honestly, your best option in all respects is to just pay for the 5KW commercial unit. Look on ebay for deals - there is a lot of cheap Chinese made units.