NOVEL CONTROL APPROACHES TO IMPROVE SINGLE AND MODULAR DC-DC CONVERTERS DYNAMICS IN DATA CENTERS
Creators: Borzooy, Amir
Publisher: name: University of Alberta Library
Year: 2023

<p>In many modern power electronics applications such as data centers, there are specific requirements such as fast load dynamics and sensitive power, voltage or current sharing. Therefore, power converters need to provide and maintain ultra fast responses to achieve a certain control objective. For example, for voltage regulators connected to the points of the load in data centers, very fast load step changes pose an extra challenge on the design of the power converter such that conventionally, excessive passive components are used to regulate the output voltage. On the other hand, in higher power applications such as data centers or electric vehicles, modular power converters are used to guarantee perfect power sharing and optimum system dynamics and voltage/current regulations for fast load transients. Recently,<br>
researchers are trying to tackle these challenges through advanced control systems without over-designing the hardware and passive components, to reduce the cost,<br>
and increase lifetime of power converters. This research addresses advanced control methods to improve converter performances for both single and modular DC-DC converters.<br>
This research first proposes a new controller to achieve fast load transient responses in the load-connected DC-DC converters of power management systems in data centers. The controller is designed to achieve identical dynamics for all state variables in the converter and is able to provide load transient responses with recovery times of less than one switching cycle and low overshoot/undershoot levels. A systematic design approach is introduced for the controller, for both continuous and discontinuous conduction modes of operation.<br>
Moreover, for DC-DC converters used in the intermediate stage of the power management system in a data center, a controller is proposed to compensate for low system damping levels in high load currents, or equivalently, low load resistance values. The controller is based on decoupling system dynamics from the load resistance value, once the controller is applied to the system. The proposed approach improves the load transient response of the converter in large load steps, while achieving a converter with small energy storage requirements. At the same time, the controller enables converter dynamics enhancements without auxiliary circuits, to reduce the<br>
cost, volume, and complexity of the system.<br>
Finally, a controller is proposed to improve steady-state and dynamical performances of modular DC-DC converters. This controller can achieve very fast power sharing among the modules, while obtaining an accurate voltage/current<br>
regulation for fast load dynamics. The introduced approach is applicable to all converter topologies and is robust against parameter uncertainties and parameter mismatches among the modules. The proposed distributed control system is formulated for Input-Series Output-Parallel (ISOP), Input-Parallel Output-Series (IPOS), and Input-Series Output-Series (ISOS) DC-DC converters. For all the controllers proposed in this thesis, a proof of stability is provided. Also, the appropriate performances of the controllers are verified through simulation and experimental results.</p>