The aim of this technical note is to provide a useful practical insight into some of the problems of using a variable electrical power source. It concentrates on single-phase Static Self-Commutating Inverters. While these are now quite common in the form of uninterruptable power supplies for computers, and as AC power sources in vehicles, their use in small stand-alone wind power systems poses particular difficulties which are discussed in detail, A brief section on Power Conditioning is also included as this may be desirable if power is supplied from a small wind or solar system, to reduce both slow voltage fluctuations and fast voltage transients, or to provide special supplies at different voltages.