Quantitative system compatibility and characteristics analysis of two-level and three-level low voltage industrial drives

Even though low-voltage (LV) two-level adjustable-speed drives (ASDs) have become the primary choice for most motor control applications, their shortcomings in power quality and motor side characteristics do exist. Three-level neutral point clamped (NPC) ASDs are popular in medium-voltage (MV) applications with higher performances, but they are rarely adopted in LV industry due to their higher initial investment. Very little has been published in the complete quantitative comparisons between LV two-level and three-level ASDs. This paper is devoted to analyze the characteristics and system compatibility indices such as induction machine (IM) voltage and current total harmonic distortion (THD), inverter losses and efficiency, common mode voltage (CMV) and differential mode voltage (DMV) vs. long cable effects, for practical two-level and three-level ASD systems as pulse width modulation (PWM) methods, load, as well as switching frequency change. Analytical and simulation results are verified experimentally at a two-level and a three-level 40hp (30kW), 460V platforms coupled with a four-quadrant driven dynamometer system.