Harmonic active power flow in low and medium voltage distribution systems

Abstract

This paper shows the principles of how the harmonic active power flow in radial low and medium voltage distribution systems varies due to the interaction between loads and the power system. The interaction is due to the change in source impedance caused by e.g. harmonic filters or capacitor banks and a mix of single and three phase nonlinear and linear loads. The active harmonic power flow in a certain point in a power system, with nonlinear loads, in most cases does not represent the actual flow to the loads in the downstream system. The harmonic active power is partly or completely included in the fundamental active power, depending on the mix of loads. Some basic examples are shown in addition with measurements from a low voltage system equipped with harmonic filters, feeding a nonlinear load.