All the four ways of converting the parameters of electric energy: AC/AC, AC/DC, DC/DC, DC/AC may be regarded within the scope of direct frequency conversion, that is, as separate modes depending on the value of modulating frequency. In the total process conceived in this manner a zero value output frequency corresponds to the formation of different levels of the direct current, but in the inverter mode is modelled by forming the output voltage of the required frequency and value from the direct current level with the help of the modulating function. The approach to this process as a whole allows one to evolve new theoretical ideas concerning the generalisation of electric energy conversion and, consequently, on the basis of this generalisation, to create new conversion methods.