Abstract
Power distribution systems nowadays are highly penetrated by renewable energy sources, and this explains the dominant role of power electronic converters in their operation. However, the presence of multiple power electronic conversion units gives rise to the so-called phenomenon of Constant Power Loads (CPLs), which poses a serious stability challenge in the overall operation of a DC micro-grid. This article addresses the problem of enhancing the stability margin of boost and buck-boost DC-DC converters employed in DC micro-grids under uncertain mixed load conditions. This is done with a recently proposed methodology that relies on a two-degree-of-freedom (2-DOF) controller, comprised by a voltage-mode Proportional Integral Derivative (PID) (Type-III) primary controller and a reference governor (RG) secondary controller. This complementary scheme adjusts the imposed voltage reference dynamically and is designed in an optimal fashion via the Model Predictive Control (MPC) methodology based on a specialized composite (current and power) estimator. The outcome is a robust linear MPC controller in an explicit form that is shown to possess interesting robustness properties in a wide operating range and under various disturbances and mixed load conditions. The robustness and performance of the proposed controller/observer pair under steady-state, line, and mixed load variations is validated through extensive Matlab/Simulink simulations.
Highlights
Modern DC micro-grids are preferred over conventional AC power grids, as they are better suited to the integration of energy storage devices together with renewable and alternative power sources, due to their inherent DC character
The integration of sources, loads, as well as energy storage devices requires the use of several different voltage levels, offered by multiple power electronic conversion units acting as interfaces between subsystems with different voltages
These architectures are not free of stability issues because they act as Constant Power Loads (CPLs), which exhibit a negative impedance behavior, unlike with typical resistive loads
Summary
Modern DC micro-grids are preferred over conventional AC power grids, as they are better suited to the integration of energy storage devices together with renewable and alternative power sources, due to their inherent DC character. In References [15,16], the authors deal with the robust voltage control problem of boost converters with nonlinear control methodologies, such as sliding mode [15] and passivity-based [16] control All these studies have considered only the trivial case of resistive loads, i.e., CVLs. More recent studies have proposed nonlinear control designs for addressing the CPL issue on a large-signal basis, see e.g., [17,18,19,20] and references therein.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
