Control Issues in Robust High-efficiency Energy Conversion with Application to Renewable Energy Systems

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Modern renewable energy systems (RES) face two main challenges in their evolution: (1) Fundamental sciences and technologies to produce reliable and economical energy sources; and (2) Energy processing technologies for reliable and optimal conversion of energy into usable forms. Although the electronics technology has been perfected in the past decades, it has to be redesigned and adapted to match new challenges. To this end, control, communication, and computing technologies, along with new power electronics converters and devices are expected to become increasingly important in modern RES. An area of particular importance is stable and robust control of intermittent power sources, loads, and energy storage devices. In particular, switching power converters are intrinsically nonlinear, subject to strict input/state constraints, and suffer from various uncertainties. Most existing control methods utilize linearized steady state models that neglect the above constraints or cannot be used to design robust controllers required by intermittent energy sources. Another common feature of RES energy converters is the existence of an optimal power operating point, which is dependable on the available input power and load conditions. To maximally utilize such converters, the power processing stage has to autonomously track the optimal point in a reliable and accurate manner. Furthermore, renewable energy systems often have inherently nonlinear characteristics with significant parametric and dynamic uncertainties. Hence, design methods based on linearization may fail to provide the full benefits of feedback systems due to neglecting nonlinear effects. ***To address the above challenges, the proposed research will investigate the following research topics: (a) Development of innovative extremum seeking algorithms to maximize energy harnessing efficiency through advanced controls; (b) Addressing dynamic stability issues in power electronics converters, including internal dynamics instability of boost converters and negative resistance instability due to constant and variable power loads; (c) Reduction of the number of sensors in power converters and fault tolerant control through advanced signal processing; and  (d) Experimental proof-of-concept validation of the research activities listed in parts (a)-(c) on laboratory scale setups to demonstrate the proposed solutions. This research program is motivated by pressing needs in modern energy conversion technology. As such, it would lead to innovative control design methods for power conversion by addressing some key technology barriers in RES such as stability, sensory requirement, and maximization of energy harnessing capability. The program will make new contributions to the RES literature, develop new expertise, and will further be utilized to initiate collaborative activities with relevant Canadian industries. **