Title :
Analysis of Parallel Operation of Uninterruptible Power Supplies Loaded Through Long Wiring Cables
Author :
Corradini, Luca ; Mattavelli, Paolo ; Corradin, Michele ; Polo, Filippo
Author_Institution :
Dept. of Electr., Univ. of Colorado, Boulder, CO, USA
fDate :
4/1/2010 12:00:00 AM
Abstract :
This paper discusses and analyses the parallel operation of uninterruptible power supplies (UPS) when loaded through long wiring cables having non-negligible inductance and resistance. This scenario is often encountered in practice, as the UPS power supplies are often located far from each other and from the load they are actually powering. The analysis demonstrates how long cable connections between the power supply system and the load deeply modify the behavior of the single UPS unit. It is shown how the cable inductance interacts with the UPS closed-loop output impedance modifying the control loop gain, ultimately generating resonance phenomena, which deteriorate or even compromise system stability and performances, if suitable provisions are not taken at the design stage. Experimental results carried out on two paralleled three phase, 40 kVA UPS units based on voltage-source inverters topologies confirm the validity of the theoretical discussion and the practical relevance of the phenomenon.
Keywords :
closed loop systems; invertors; power system stability; uninterruptible power supplies; UPS closed-loop output impedance; apparent power 40 kVA; control loop gain; long wiring cables; nonnegligible inductance; nonnegligible resistance; parallel operation; power supply system; system stability; uninterruptible power supplies; voltage-source inverters topologies; Digital control; modeling; uninterruptible power systems;
Journal_Title :
Power Electronics, IEEE Transactions on
DOI :
10.1109/TPEL.2009.2031178