Siting and capacity allocation for APFs based on optimal reactive power compensation and harmonic mitigation capacities of STATCOMs and MFGCIs

• A node classification method is proposed to determine the candidate nodes for installing APFs. • The two-layer K-means clustering algorithm verifies the adaptability of the proposed strategy in uncertain scenarios. • An optimal allocation model is constructed to optimise capacities of APFs, STATCOMs and MFGCIs. • The DAM-PSO algorithm is provided to solve the model and improve convergence. The high penetration of renewable energy and the application of power electronic equipment have exacerbated harmonic problems in new power systems, requiring effective mitigation strategy. In addition, static synchronous compensators (STATCOMs) and multifunctional grid-connected inverters (MFGCIs) with definite installation sites in distribution networks both have reactive power compensation and harmonic mitigation functions. These can assist active power filters (APFs) in harmonic mitigation. Therefore, an allocation strategy for APFs is proposed in this study to optimise the installation sites and capacities of APFs, as well as the capacities of STATCOMs and MFGCIs. Firstly, harmonic sensitivity is constructed to quantify the sensitivity of the total harmonic voltage distortion (THDv) at each node. Based on harmonic sensitivity, a node classification method is proposed to identify candidate nodes for APFs installation. Secondly, a two-layer K-means clustering algorithm is established to deal with uncertain operation scenarios. In the first-layer of clustering, typical days are clustered from the entire year and these typical days form representative operation scenarios in the second-layer of clustering. Then, an optimal allocation model with the objective of minimal total cost is constructed and solved with the dynamic adaptive mutation particle swarm optimisation (DAM-PSO) algorithm to optimise the capacities of APFs, STATCOMs, and MFGCIs. Finally, simulations on a modified IEEE 33 bus system verify that the proposed strategy achieved effective harmonic mitigation and reactive power compensation with economic advantage compared to the conventional strategy.