Operation of the AC-AC Converter Based Dynamic Voltage Restorer in Weak Distribution Systems

Dynamic voltage restorer (DVR) is a series compensation device designed to compensate for voltage-related power quality (PQ) problems. In the weak distribution systems, the Thevenin impedance of the system is high. On the other hand, the AC-AC converter-based DVR takes the required compensation energy from the grid so that its current increases and extra voltage drop on the system impedance occurs worsening the situation. This paper investigates the operation challenges of the AC-AC converter-based DVR in weak distribution systems and determines the voltage sag compensation capability of the AC-AC converter-based DVR in such a condition. The detailed analysis of the voltage sag compensation capability of the DVR in weak grid is presented and the effect of different parameters such as the grid impedance, load current, and the load power factor are considered and analyzed. The analysis given in the paper are verified by simulation studies on a single-phase 220V DVR.