Do you just want a fixed frequency source? Are you using a dedicated IC for this function?, because there is usually a voltage feedback which you can just fix. If you do this, you will not get regulation, it will be free-running..
A PLL is a good way of making a frequency ultra-stable, but I don't think it is necessary in an inverter application. PLLs are used at high frequencies where stability is important because of matching transmitters and recievers...
Steve