Calculation of phase angle diversity for time-varying harmonic currents from grid measurement

Abstract

Phase angle diversity of harmonic currents emitted by different equipment, like electronic power supplies, modern lamps with electronic ballast, chargers for electrical cars or photovoltaic inverters, results in cancellation effects which represent an efficient way of managing harmonic levels in LV grids. Different methods have been presented in the last decades to quantify and evaluate the summation of harmonic currents based on grid measurements. There is not a general consensus about which method or index should be preferred, especially if time-variation of harmonic currents is considered. The paper discusses the impact of measurement accuracy and aggregation parameters on the calculation of the two main diversity indices, namely diversity factor and summation exponent. In case of time-varying harmonics an additional statistical post-processing is required which also depends on several parameters and calculation methods. Based on the results of the application of different methods to real grid measurement data, some guidance on suitability and limitations of the different methods are given.