A Novel Transformer-Less Dynamic Voltage Restorer Based on Modified ANPC for Low-Voltage Distribution Network

Dynamic voltage restorer (DVR) is an effective solution for mitigating voltage sags and swells, but conventional DVRs employ bulky and expensive line-frequency transformers, which significantly increase the overall cost of the device and hinder widespread adoption in low-voltage distribution systems. To satisfy the demand for high economic viability of DVRs, this article analyzes the three-level active neutral-point clamped (ANPC) converter from a novel series-shunt perspective and proposes a transformer-less DVR based on a modified ANPC (MANPC-TDVR). Compared to other DVRs, the proposed topology eliminates the transformer by sharing the shunt part and expanding the series parts, which leads to a lower total cost. The series parts provide voltage compensation, while the shunt part maintains the energy balance. The MANPC-TDVR features a dual-port structure, connecting the grid and load separately. To resolve the switching signal conflicts caused by the shared shunt part, a decoupling modulation strategy is introduced. Furthermore, operation principles and control strategies of the MANPC-TDVR are elaborated. Simulation results from a 250-kVA model and experimental validation on a scaled-down 3-kVA prototype confirm the feasibility and effectiveness of MANPC-TDVR.