Research on the Novel Flexible On-Load Voltage Regulator Transformer and Voltage Stability Analysis

Voltage stability has always been a hot topic in power system research. Traditional On-Load Tap-Charger (OLTC) transformer is considered to play a very important role in the system voltage stability. However, in the heavy load of distribution network, the tap adjustment of OLTC transformer will lead to the shift of critical stable operating point, which bring the "negative voltage regulating effect" of voltage adjustment, and even cause the instability of system voltage. This paper presents a Flexible On-Load Voltage Regulation (OLVR) transformer based on power electronic technology. The Flexible On-Load Voltage Regulation (OLVR) transformer is a combination of Power Electronic Converter (PEC) and OLTC transformer, which can realize voltage step-less regulation and reactive power regulation. Meanwhile, the paper presents the equivalent models of distribution network with Flexible OLVR transformer and analyzes the critical operating point. Through the step-less voltage regulation control of the Flexible OLVR transformer, the negative voltage regulation effect of the transformer in on-load voltage regulation is avoided, and the voltage stability of the distribution network is improved.