A Digital Control System for UPS Systems with Smart Grid Capability
Date
2019-08-12
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Abstract
Smart grids have recently become the center of attention for modernizing the grid system. In future smart-grids, energy storage systems are one of the key components, which can complement intermittent renewable energy sources and in turn increase reliability and efficiency of the grid system. Modern Uninterruptible Power Supply (UPS) systems can provide storage capacity for future smart grids since they usually include batteries. UPS systems can also provide instant electrical power to sensitive equipment and grid during various events such as brownout, power failures, spikes, voltage surges, EMI/RF noise, and frequency variations. Future UPS systems require to have much better dynamics in order to deal with transients. The control system of UPS systems mainly determines their dynamical performance and transient response. The existing state-of-the-art UPS control systems are based on linear PI controllers for the most part. Thus, current UPS systems usually show a sluggish transient response and they are not suited for future smart grid applications where instant power is required to maintain the system. In this thesis, new UPS systems with improved transient response are proposed. The proposed UPS system utilities a new controller that is able to improve the dynamic performance and allows for various smart grid functionalities. The proposed control system is based on the adaptive control theory, which adaptively changes the controller's parameters based on the UPS operating conditions. Furthermore, the proposed control system isolates the double-frequency ripple from the battery in the normal/charging mode as well as in the backup/discharging mode. Therefore, the new UPS system is well-suited for single-phase systems utilizing lithium-ion battery as storage. Mathematical analysis, simulation, and experimental results are presented to verify the performance of the proposed control system and demonstrate its superior performance.
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Keywords
Uninterruptible Power Supply, Power Electronics, Nonlinear Control
Citation
Mardani Boroujeni, F. (2019). A Digital Control System for UPS Systems with Smart Grid Capability (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.