Abstract: The assessment system for medium-high voltage multilevel UPQC topology is constructed based on R ²LC ² (reliability, redundancy, loss, cost, characteristic). After selecting some kinds of unified power quality conditioner (UPQC) topology structure, models are set up including loss model, fault model, simulation model, redundancy model and device model, to analyze and form assessment indexes including relationship between loss and topology, topology reliability, transient and steady-state characteristics, system stability, relationship between structure and cost respectively. Combining reciprocal affection among aforementioned five assessment indexes, hierarchy analysis model is established to quantitatively obtain weight coefficient of assessment indexes, construct pairwise comparison matrices, calculate sequence weight vector and completely analyze ensemble performance of many multilevel UPQC topology structure. Finally, the assessment system realizes comprehensive and accurate assessment of multilevel UPQC topology and provides selecting rules of multilevel UPQC topology types. A real application example uses cascade H bridge, modular multilevel converter (MMC) and alternate-arm multilevel converter (A ²MC) to confirm the practicability of the proposed assessment system.