Measurement-Based Control and Its Applications

Abstract

In the present proposal, we describe the use of a measurement based approach to one important broad area of control engineering and to two important application areas. The control engineering is Robust control and the application areas are the methods of searching for maximum power of photovoltaic (PV) arrays and the design of droop control strategies for microgrids.Robustness is important in closed-loop control systems, since they must function despite perturbations in the parameters from those assumed in the design process. In this proposal, we describe an approach for designing robust controllers based on frequency response measurements. The preliminary results show how classical stability margin based designs can be upgraded to a computer aided approach showing achievable designs, through the analytic determination of design surfaces that qualitatively and quantitatively display design trade offs. This approach to design will be extended to other criteria such as control signal constraints and parameter uncertainty. The design of photovoltaic arrays presents an important practical problem where automatic determination of maximum power is desired under different environmental conditions. The technical challenge is made more difficult by the fact that PV cells have nonlinear V-I characteristics that change unpredictably with the solar incidence. We outline an approach based on pointwise Thévenin equivalents of the nonlinear PV cell, that can be determined from measurements. This approach can lead to an online measurement based algorithm to extract the maximum power from the PV arrays.The design of droop control strategies for power sharing in microgrids presents several challenges as the utility grid changes according to the occurrence of events such as connection/disconnection of the grid and sources. We outline an approach to the problem of power sharing based on measurements.We propose to develop these two design approaches, which will be evaluated in an experimental test bed. (AU)