Practical tables for tolerance assessment of adjustable speed drives under voltage sag

Abstract

The tolerance of adjustable speed drive (ASD) under voltage sag is important for users to select equipment and take mitigation methods. However, it is not easy for users to obtain the tolerance information of ASD. To address this issue, this paper proposes practical tables for tolerance assessment of ASD under voltage sag, providing a simpler and faster way for an approximate understanding of the tolerance of ASD. First, this paper proposes a calculation method for three trip characteristics to describe the tolerance of ASD. Second, this paper presents a voltage tolerance curve (VTC) assessment model based on the three trip characteristics, and the coordinate of the "knee point" of VTC can be assessed straightforwardly. Furthermore, the practical tables for tolerance assessment of ASD are formed based on the studies mentioned above. Users can obtain the tolerance of ASDs by looking up the table when they know several key parameters. Simulations tests verify the effectiveness of the calculation method and practical tables. INTRODUCTIONVoltage sag may lead to abnormal operation of sensitive equipment in the industrial process, bringing huge economic losses to industrial users [1-3]. Adjustable speed drive (ASD) is the indispensable but sensitive equipment in industrial processes, which may trip the process under voltage sags [4]. However, there is limited information about the tolerance of ASD from manufacturers [5]. Utilities and the users are interested in a simpler and faster method for an approximate understanding of the tolerance of ASD under voltage sag, when purchasing ASDs or mitigation equipment against voltage sag. The voltage tolerance curve (VTC) [6] is used to quantify the tolerance of ASD usually. There are two typical ways to obtain VTCs under voltage sags.The first way is the experimental test. IEEE Std. 1668-2017 [7] and IEC 61000-4-11 [8] recommend tolerance testing methods. The test results show that there are two major causes of ASD shutdown under voltage sag [9,10]: (i) the low DC voltage triggering the low-voltage protection (LVP) during the voltage sag, (ii) the inrush current triggering the overcurrent protection (OCP) at the ending of sag. DC voltage and current are affectedThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.