Online estimation of passive elements in a double conversion UPS system with no additional sensors

Uninterruptible Power Supplies (UPS) represent the main technology used to supply a wide range of critical applications in which information, communication and technology (ICT) facilities such as high-tier datacenters are widely included. Beyond power converters, UPS systems require passive elements not only for proper current/voltage filtering but also to create an internal DC bus. Since these elements are typically subjected to a high amount of stress, deviations of their value can occur over time. With these deviations the overall UPS performance typically decreases and if an element reaches its end-of-life, the protection of the critical loads can even be highly compromised. Hence, the estimation of UPS passive elements is of extreme importance. In this paper, two real-time strategies based on the Adaptive Linear Neuron (ADALINE) approach are proposed to estimate the inductance and capacitance of UPS filters as well as DC bus capacitors capacitance. By using the proposed technique, only sensors required for UPS controllers are used with no additional hardware being required. Simulation results are presented to demonstrate the effectiveness of the proposed estimation methods.

I. Introduction

Uninterruptible Power Supplies have proven to be the key technology to supply a wide range of important and sensitive applications including critical Information, Communication and Technology (ICT) systems. These systems typically go from small domestic networks to large ICT systems usually found in medical and military facilities such as high-tier datacenters, large telecommunication infrastructures and other large critical networks that must be permanently supplied under strict power quality requirements. In highly sensitive ICT applications even small grid phenomena such as sags, surges and spikes can lead to hardware failure, system malfunctions and data corruption. Hence, in these type of applications, double conversion UPS systems are adopted. The double conversion or online UPS system represents the topology that provides the highest level of protection to the critical load since the load is fully isolated from the power grid. Thus, it is the studied UPS configuration in this work.