Experimental study on the tolerance ability of adjustable speed drives to voltage sags

The process of energy transmitting is vulnerable to power quality problems. The adjustable speed drive (ASD) is one sensitive part of the process to voltage sags which will cause the interruption of the whole process if it trips due to sags. It is essential to analyze the voltage tolerance ability of ASDs and formulate a representative standard voltage tolerance curve (VTC) for it. Firstly, this paper analyzed basic influence principle of sags on ASDs and the influence of multiple factors on the voltage tolerance ability of ASDs, including sags types, load torque, motor speed, control strategy, pre-post sag voltage and harmonics. Then a test platform was established using the Chroma 61860 Regenerative Grid Simulator as the source of sag. 7 typical brands of ASDs with 2 kinds of rated power were selected to be tested. Later, sets of VTCs were obtained and further analyzed separately. The majority of the conclusions shows consistency to the theoretical analysis, but there are also some distinctions to the present conclusions. Finally, relatively universal VTCs for three of sags were proposed, which are of reference meaning to regulate the special standard curve for ASDs.