Desenvolvimento de ferramentas computacionais para a análise de perdas em conversores estáticos: aplicação ao cálculo de rendimento de UPSs trifásicas de dupla conversão

Abstract

Double-conversion UPSs (Uninterruptible Power Supplies) are devices that provide safe and continuous supply to mission-critical systems, in which disturbances or interruptions in power supply can lead to losses or damages. This thesis aims to compare the energy efficiency performance of three-phase double-conversion UPS in two-level topologies, with silicon and silicon carbide (SiC) devices, and in three-level topologies in NPC1 (Neutral-Point Clamped) andNPC2 configurations, with silicon power modules. The adopted methodology is based on the comparison of 80 designs of double-conversion UPS, with several values of d.c. bus voltages,switching frequencies and rated power. In order to accomplish this goal, software tools with graphical interface were implemented in MATLAB, for semiconductor losses estimation and for inductor losses calculation in input and output LC and LCL filters. UPS simulations were performed in MATLAB/Simulink and include the inverter and rectifier control. For experimental validation of the theoretical results, a circuit of a 5.5 kW buck converter was built and power losses measurements were conducted with a digital wattmeter. Then, a simple and low cost indirect series calorimeter prototype was developed, in order to reduce the uncertainties in power losses measurement. Simulation results show that NPC1 topology exhibits the highest global efficiency among the silicon based UPSs, in most UPS designs. Furthermore, the SiC based UPSsmostly overcome the performance of silicon based UPSs, which shows the competiveness of SiC devices for UPS applications. Experimental results prove the agreement between theoretical and measured results using digital wattmeter. Preliminary tests with power resistors demonstrate the effectiveness of the indirect series calorimeter prototype. Lastly, the proposed techniques for losses evaluation could be extended for any power converter and could enhance equipment design regarding energy efficiency and power density.