61 research outputs found
Nonlinear constrained and saturated control of power electronics and electromechanical systems
Power electronic converters are extensively adopted for the solution of timely issues, such
as power quality improvement in industrial plants, energy management in hybrid electrical
systems, and control of electrical generators for renewables. Beside nonlinearity, this systems
are typically characterized by hard constraints on the control inputs, and sometimes
the state variables. In this respect, control laws able to handle input saturation are crucial
to formally characterize the systems stability and performance properties. From a practical
viewpoint, a proper saturation management allows to extend the systems transient
and steady-state operating ranges, improving their reliability and availability.
The main topic of this thesis concern saturated control methodologies, based on modern
approaches, applied to power electronics and electromechanical systems. The pursued
objective is to provide formal results under any saturation scenario, overcoming the
drawbacks of the classic solution commonly applied to cope with saturation of power converters,
and enhancing performance. For this purpose two main approaches are exploited
and extended to deal with power electronic applications: modern anti-windup strategies,
providing formal results and systematic design rules for the anti-windup compensator, devoted
to handle control saturation, and “one step” saturated feedback design techniques,
relying on a suitable characterization of the saturation nonlinearity and less conservative
extensions of standard absolute stability theory results.
The first part of the thesis is devoted to present and develop a novel general anti-windup
scheme, which is then specifically applied to a class of power converters adopted for power
quality enhancement in industrial plants. In the second part a polytopic differential inclusion
representation of saturation nonlinearity is presented and extended to deal with a
class of multiple input power converters, used to manage hybrid electrical energy sources.
The third part regards adaptive observers design for robust estimation of the parameters
required for high performance control of power systems
Analysis, Dimensioning and Robust Control of Shunt Active Filter for Harmonic Currents Compensation in Electrical Mains
In this chapter some results related to Shunt Active Filters (SAFs) and
obtained by the authors and some coauthors are reported. SAFs are complex power
electronics equipments adopted to compensate for cur-rent harmonic pollution in
electric mains, due to nonlinear loads. By using a proper "floating" capacitor
as energy reservoir, the SAF purpose is to inject in the line grid currents
canceling the polluting har-monics. Control algorithms play a key role for such
devices and, in general, in many power electronics applications. Moreover,
systems theory is crucial, since it is the mathematical tool that enables a
deep understanding of the involved dynamics of such systems, allowing a correct
dimensioning, beside an effective control. As a matter of facts, current
injection objective can be straightforwardly formulated as an output tracking
control problem. In this fashion, the structural and insidious
marginally-stable internal/zero dynamics of SAFs can be immediately highlighted
and characterized in terms of sizing and control issues. For what concerns the
control design strictly, time-scale separation among output and internal
dynamics can be effectively exploited to split the control design in different
stages that can be later aggregated, by using singular perturbation analysis.
In addition, for robust asymptotic output tracking the Internal Model Principle
is adopted.Comment: Paper presented at the AUTOMATICA_IT 2011 conference, Pisa, Italy,
September 201
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