A Novel Variable-Step Algorithm for DC-Side Voltage Stability Control Strategy in UPQC to Improve Power Quality

With the development of semiconductor technology, the increasing number of power electronic converters and nonlinear loads has further exacerbated power-quality issues in the grid. To address this, this paper presents an improved DC-side voltage control strategy for UPQC, aiming to enhance power quality under complex conditions. First, an adaptive filter is integrated into the linear active disturbance rejection control (LADRC) to address control accuracy issues caused by noise and parameter variations. To solve the voltage sag problem resulting from the filter, the effects of fixed-step and various variable-step algorithms within the filter are analyzed, and the optimal control strategy is identified. Simulation results demonstrate that the proposed arctangent function-based variable step-size algorithm (VAV-LADRC) strategy effectively improves the UPQC system’s performance in mitigating voltage sags, swells, and harmonics under dynamic load changes, enhancing the stability of the DC-side voltage. To further validate the generalizability of the method, a co-simulation of a photovoltaic power-generation system with the UPQC is conducted, simulating variations in solar irradiance. The results show that the proposed method maintains excellent control performance under complex conditions, providing a better practical solution for the efficient use of green energy.