Practical Analytical Model of Adjustable Speed Drive for Tolerance Ability Evaluation of Transient Low Voltage Disturbance

The failure of adjustable speed drive (ASD), which is sensitive to transient low voltage disturbance such as voltage sag and short duration interruption, will bring considerable loss to industrial users. Evaluating the disturbance tolerance ability of adjustable speed drives is the key to improve its tolerance. The voltage tolerance curve (VTC) is a tool to quantify the tolerance of voltage sag sensitive equipment including adjustable speed drives. However, the traditional test strategy for obtaining this curve is time-consuming and may introduce errors caused by the performance deterioration of the tested equipment. This paper proposes an analytical model of adjustable speed drive based on its response mechanism analysis to voltage sags. The model constructs a group of practical formulas for calculating the knee point of the voltage tolerance curve. The knee point can be used to quickly estimate the contour of the curve. This model can help engineers to conduct a first-cut assessment of the sag tolerance for drives to select equipment or design planning. Experimental tests are carried out to verify the effectiveness of the proposed method. Moreover, an application of the results is presented to improve the traditional test strategy.