Methods for Determining the Actual Contributions of Consumers to the Voltage Unbalance of a Three-Phase Network

The article addresses the division of responsibility for voltage unbalance between the supplier and consumers. Based on a review of existing methods, the superposition method was identified as the most established, though it requires well-defined impedance data. This study evaluates three alternative methods through comprehensive MATLAB/Simulink R2021a simulations (26 test cases) with an unbalanced voltage source and three consumers. The simulation results show that the consumer on/off switching method identified the dominant and secondary distortion sources in 25 out of 26 cases (96.2%) within the considered network topology. The method for establishing the relationship between distortion level and consumer load achieved a success rate of 92.3%. However, both methods are inherently qualitative and cannot quantify the actual contribution shares, which restricts their applicability as full-scale alternatives to the superposition method. The secondary power analysis method, despite its theoretical promise as a quantitative tool, proved to be the least effective: when analyzing only the active component of the secondary power, it identified the distortion sources in only 15 out of 26 cases (57.7%); when both active and reactive components were analyzed, the success rate dropped to 42.3%. This makes it unsuitable for systems with multiple unbalance sources. Thus, the superposition method remains the most suitable quantitative approach, provided that the required impedance data are available, while the consumer on/off switching method and the relationship-based method offer qualitative alternatives for source identification within the considered topology. Future work should focus on experimental validation and the development of a practical framework for allocating responsibility for voltage unbalance in practical distribution networks.