Harmonic Source Localization in Distribution Systems Based on Subsystem Division

Addressing the challenges of harmonic source tracing caused by low micro-PMU (μPMU) coverage and multi-source coupling in distribution networks, this paper proposes a distributed harmonic source localization method based on subsystem partitioning and virtual current injection. Initially, to achieve high-precision extraction of target harmonic phasors from limited measurement data, an improved windowed interpolation Fast Fourier Transform (FFT) combined with a subspace projection denoising algorithm is utilized. Subsequently, a topology-based subsystem partitioning strategy is proposed to construct a “virtual harmonic current injection” model; by tentatively injecting virtual currents at nodes within the subsystem and calculating the deviation between the voltage response at terminal nodes and the measured values, a harmonic error vector is synthesized to identify local candidate nodes. Furthermore, a global screening algorithm based on a connection node correction strategy is designed to eliminate projection phantoms, thereby achieving precise identification of true harmonic sources across the entire network. Validation results based on an improved IEEE-33 bus system and an actual 10 kV distribution network in Jilin Province demonstrate that the localization accuracy remains above 97% even under severe operating conditions, such as 30% three-phase asymmetry and 50% line impedance drift; compared with the traditional power direction method, the proposed approach exhibits significant advantages in robustness and multi-source decoupling capability within complex noise environments.