Reduction of Total Harmonic Distortion and Effective Source Current in Circuits with Nonsinusoidal Waveforms

In linear resistor-inductor circuits, minimization of source rms current according to S. Fryze causes increase of total harmonic distortion (THD) and increase of source active powers resulting from higher harmonics of voltage and current. The authors of the present paper have proposed a method of the reduction of THD and rms value of the source current on the basis of the components of instantaneous power of the source. It has been demonstrated that the even component of that power secures a supply of the given active power from the source to the load. The odd component may be excluded from the instantaneous power of the source. Components of instantaneous power are the sums of the products of the even and odd components of source voltage and current. On the basis of these sums the voltage and current components have been determined, the compensation of which enables excluding the odd component of source instantaneous power, and in the same way- reduction of THD and rms value of the source current. The authors of the paper have presented the way of making use of the method in the situation when supply voltage is only odd or even function. It has been found out that it is possible to reduce THD of the source current several times in relation to THD of the source current while minimizing the source rms current according to Fryze, with negligible increase in the effective value of the source current in relation to the minimum value. Decrease of THD also causes significant decrease of active power of the source caused by higher harmonics of voltage and current.