Fabio Ronchi

Robust nonlinear control of shunt active filters for harmonic current compensation

An advanced control strategy of shunt active filters (SAF) aiming to compensate for harmonic current in the electric supply grid is proposed. The SAF considered here is suitable for three-phase three-wire current harmonic compensation and is based on AC/DC three-phase boost converter topology. Robust control of the active-reactive current/power delivered by the SAF is designed exploiting the internal model principle. The stabilization of the DC-link voltage dynamics is addressed along with the fulfillment of the harmonics compensation objective. The two-time scale behavior of the SAF is exploited to apply the averaging theory in the control design. Experiments are provided to show the effectiveness of the proposed solution.

Control of a camless engine electromechanical actuator: position reconstruction and dynamic performance analysis

Camless internal combustion engines offer major improvements over traditional engines in terms of efficiency, maximum torque and power, and pollutant emissions. Electromechanical valve actuators are very promising in this context, but they present significant control problems. Further, to keep system cost at an acceptable level, a control system without a valve position sensor needs to be adopted. Low valve seating velocity, small transition time for valve opening and closing, and unavailability of position sensor are conflicting objectives that need to be jointly considered. In this paper, a control system architecture is presented, capable of dealing with all these issues. It is shown that a position tracking controller is needed: a key point is the design of the reference trajectory to be tracked. Actuator physical limitations strongly influence the feasible trajectory when low valve seating velocity is required, thus affecting valve transition time. Owing to the same limitations, valve electromagnets have to be energized for a significant part of the trajectory, thus allowing valve position reconstruction starting from electrical measurements only. A method for position reconstruction is presented, which makes use of auxiliary coils to reconstruct electromagnets fluxes; it is shown via sensitivity analysis that the functional characteristics of position reconstruction and its accuracy are compatible with the required applications. The trajectory design is then addressed as an optimization problem that explicitly considers the tradeoff between fast dynamic performance and system robustness. The solution of this optimization problem enlightens the limitations on achievable dynamic performance, which are presented and discussed.

Sensing device for camless engine electromagnetic actuators

A position reconstruction method for camless engine electromagnetic valve actuators control without direct position measurement is proposed. The method makes use of flux signals, obtained through integration of a secondary coil voltage added at each electromagnet. By this solution, both fluxes and position signals are available for the design of the feedback position controller. The paper discusses the accuracy that can be obtained for position reconstruction, linking it to the system parameters tolerances. Experimental results are reported to show the validity of the proposed solution.

Shunt active filters: selective compensation of current harmonics via state observer

This paper deals with partial current harmonics compensation by means of shunt active filter. A novel observer-based scheme is proposed to estimate load harmonics. This task is performed in d-q reference frame where active and reactive current components are enlightened. Positive and negative sequences are distinguished for selective compensation. Predictive action can be generated using the proposed observer to improve current tracking performances. Experimental results are presented to show the effectiveness of this technique.

Robust control of shunt active filter based on the internal model principle

In this paper an advanced control strategy is proposed for shunt active filter (SAF) used in electric current harmonic compensation. Internal model principle is exploited to achieve asymptotic cancellation of harmonics generated by a nonlinear load connected to a three-phase electric main. Robustness with respect to electrical parameters uncertainties of the shunt active filter is achieved. A preliminary theoretical discussion about the stabilization of the internal voltage dynamics of the SAF is provided. The properties of the proposed solution are tested by simulations.

Robust perfect compensation of load harmonics in shunt active filters

In this paper an advanced control strategy is proposed for shunt active filter (SAF) used in three-phases three-wires current harmonic compensation. The SAF considered are based on AC/DC three-phase boost converter topology. The robust solution presented by the authors previously is used as a starting point to develop the stabilizing controller of the DC-MA voltage dynamics. SAF resistive power losses cause the instability of this voltage dynamics when perfect harmonics compensation is achieved. An integrator with a suitably designed deadzone is placed in the voltage controller to guarantee DC-link voltage dynamics stabilization without perturbing the current harmonics compensation. Two time-scale behavior of the SAF is exploited to apply the averaging technique and input to state stability arguments in the control design.

Trajectory generation for camless internal combustion engine valve control

Camless internal combustion engines offer major improvements over traditional engines in terms of efficiency, maximum torque and power, pollutant emissions. Electromechanical valve actuators are very promising in this context, but still present significant control problems. Low valve seating velocity, small transition time for valve opening and closing, unavailability of position sensor are the main objectives to be considered in the design of the valve control system. Actuator physical limitations strongly influence the feasible trajectory when low valve seating velocity is required, thus affecting valve transition time. One key point for the control is the design of the reference trajectory to be tracked by the closed loop controller. In this paper, the trajectory design is addressed, solving an optimization parametric problem that explicitly considers the physical constraints and the trade-off between fast dynamic performance and system robustness.

Four-wires shunt active filters: optimized design methodology

This paper deals with the design of a four-wire shunt active filter (SAF) based on a AC/DC converter. Different methodologies in choosing suitable values of the components, both inductor and capacitor, are presented for different objectives. The first two present a procedure to design the inductor limiting the current ripple of the filter. The others deal with the capacitor design: the first solution is based on the knowledge of the load spectrum, while the second one regards the worst load case for a given maximum current of the inverter switches. Both the algorithms are based on a model inversion and are control-oriented.

Stabilization of the voltage internal dynamics of a shunt active filter

Abstract This paper is mainly focused on the stabilization of the DC-link voltage dynamics of three-phases, three-wires Shunt Active Filters (SAF) based on AC/DC boost topology. This relevant issue is usually neglected in SAF control development. The robust solution presented by the authors in (L. Marconi, 2003) is used as a starting point to develop the internal voltage stabilization controller. A non-trivial definition of the stabilization objective is proposed and the two timescale behavior of the SAF is exploited to apply the Averaging technique and Input to State Stability arguments in the control design.

Performance Evaluation of a Hydraulic Clutch Control System

Abstract A hydraulic actuated clutch control system for commercial cars is analyzed. A physical model of the system is firstly derived: this model is then used both to define a closed loop controller, through derivation of a simplified model, and to asses the dependencies of the closed loop system performances on some plant and controller key parameters. Trade-off curves are derived that link the required performances, namely response speed and tracking error, to this key parameters. It is shown how this curves can be used to fix the specifications for both plant configuration and electronic control unit in an optimized way, in order to achieve guaranteed performances at minimum system cost.