Abstract: Resonant parts can be used in current controllers to suppress harmonics. However, they may cause destabilization of poorly damped grid and/or input-filter resonances, particularly for a nonnegligible converter time delay. This letter presents a design method whereby destabilization is prevented by making the converter's input admittance passive.

Abstract: This paper describes a detailed design procedure for passivity-based controllers developed using the Brayton–Moser (BM) framework. Several passivity-based feedback designs are presented for the voltage-source converter, specifically for the H-bridge converter, since nowadays it is one of the preferred solutions to connect direct current (dc) loads or distributed sources to the alternating current (ac) grid. Independent of the operating mode, namely, the rectifier and regenerative operating mode, the achieved control aims are: high power factor correction in the ac-side and optimal dc voltage regulation capability in the dc-side. The proposed controllers can use series or parallel damping-based solutions for the error dynamics, naturally providing the conditions for stability and tuning of control parameters. In addition, the BM structure facilitates the addition of virtual resistance-inductance-capacitance (RLC) filter circuits to the control design for the rejection of low frequency harmonics. The effectiveness of series/parallel damping is investigated in case of abrupt changes in the load, using conductance estimators. Simulation and experimental results validate the analysis.

Abstract: Passivity indices are used to measure the excess or shortage of passivity. While most of the work in the literature focuses on stability conditions for interconnected systems using passivity indices, here we focus on passivity and passivation of the feedback interconnection of two input feed-forward output-feedback (IF-OF) passive systems. The conditions are given to determine passivity indices in feedback interconnected systems. The results can be viewed as the extension of the well-known compositional property of passivity. We also consider the passivation problem which can be used to render a non-passive plant passive using a feedback interconnected passive controller. The passivity indices of the passivated system are also determined. The results derived do not require linearity of the systems as it is commonly assumed in the literature.

Abstract: This paper studies the problem of frequency regulation in inverter-based microgrids with time-varying voltages, described by a third-order model. Building upon our previous result on optimal frequency regulation in an ordinary power grid [1], we propose the design of internal-model-based controllers and analyze it within an incremental passivity framework. We believe that this framework is general enough to allow for more complex control scenarios in future extensions.

Abstract: The origin of passivity, as viewed from the Point Defect Model, is presented in terms of the phase space analysis of the rate law for the growth of passive films It is shown that passivity is due to the formation of a metastable oxide and hence, the occurrence of passivity is a kinetic phenomenon, in which the rate of film growth of the oxide at the metal/barrier layer interface into the metal at zero barrier layer thickness must exceed the rate of barrier layer dissolution at the barrier layer/solution (bl/s) interface, in order for the barrier layer to exist If this relationship does not hold, the barrier layer disappears and the surface becomes depassivated Depassivation is illustrated with respect to transpassive dissolution, acid depassivation, pitting corrosion, flow assisted corrosion, impingement attack, resistive depassivation and other phenomena The theory also leads to the development of Kinetic Stability Diagrams (KSDs), in which the potential for depassivation is plotted against p

Abstract: A passivity framework for hydraulic actuators is developed by considering the compressibility energy function for a fluid with a pressure-dependent bulk modulus. It is shown that the typical actuator's mechanical and pressure dynamics model can be obtained from the Euler-Lagrange equations for this energy function and that the actuator is passive with respect to a hydraulic supply rate which contains, in addition to the flow work (PQ), the compressibility energy also, which has often been ignored. A storage function for the pressure error is then proposed and the pressure error dynamics are shown to be a passive two-port subsystem. Trajectory tracking control laws are then derived using the storage function. A case study is presented to compare the new passivity-based approach and the traditional backstepping approach using a quadratic pressure error term. In this example, the proposed approach has one fewer parameter to tune, is less sensitive to velocity measurement error, and requires lower feedback gains than the traditional approach.

Abstract: The main contribution of this paper is the generalization of well-known energy-based control techniques (i.e., energy-balancing passivity-based control, passivity-based control with state-modulated source, and interconnection and damping assignment passivity-based control) to the case in which the plant is a port-Hamiltonian system in implicit form. A typical situation is when (part of) the system is obtained from the spatial discretization of an infinite dimensional port-Hamiltonian system: in this case, the dynamics is not given in standard input-state-output form but as a set of DAEs. Consequently, the most popular control by energy-shaping techniques have to be extended to deal with dynamical systems with constraints, and geometrical conditions for the existence of the regulator based on the properties of Dirac and resistive structures of the plant are also necessary. The methodological results are discussed with the help of simple but illustrative examples in which the port-Hamiltonian systems in imp...

Abstract: Human controllers as pilots or drivers can be described by linear time invariant systems cascaded with time delay. Inspired by this, we ‘generalize’ the denition of passivity index to irrational transfer functions and use the passivity index to examine passivity of some existing human models. The results show that the human model is non-passive due to the time delay which represents inherent human limitations. We then propose a passication scheme when a human operator is in the loop. By this scheme, the closed-loop system with human in the loop as a controller can have desired positive passivity indices to address the control tasks of interest.

Abstract: In this paper, a new criterion for passivity of haptic devices is obtained. This criterion creates a relationship between Coulomb friction coefficient, viscous friction coefficient, sampling rate, and the maximum simulated stiffness. The process of derivation of the passivity criterion is described in detail. This criterion is improved compared with other existing criteria and predicts passivity in haptic rendering more accurately. In particular, for speeds of less than 5 cm/s, the new passivity criterion should replace the previous criteria to avoid unwanted vibrations of stiff virtual walls. Analytical and numerical investigations are presented to validate the new criterion. A specific trajectory is designed and the movement of the haptic robot is investigated on this trajectory to validate and compare this passivity criterion with the previous criteria.

Abstract: In this paper, we present a tutorial on passivity based attitude control that has been investigated over the past two decades. Both regulation control and adaptive tracking control for the attitude motion of rigid bodies are discussed under a unified passivity framework. Our attention is mainly confined to the attitude control schemes that are based on the passivity notion. Output feedback attitude control, attitude synchronization, and some open problems are also discussed.

Abstract: This paper proposes a new complex dynamical network model, in which the state, input, and output variables are varied with the time and space variables. By utilizing the Lyapunov functional method combined with the inequality techniques, several criteria for passivity and global exponential stability are established. Finally, numerical simulations are given to illustrate the effectiveness of the obtained results.

Abstract: Telepresence combines different sensorial modalities, including vision and touch, to produce a feeling of being present in a remote location. The key element to successfully implement a telepresence system and thus to allow telemanipulation of a remote environment is force feedback. In a telemanipulation, mechanical energy is conveyed from the human operator to the manipulated object found in the remote environment. In general, energy is a property of all physical objects, fundamental to their mutual interactions in which the energy can be transferred among the objects and can change form but cannot be created or destroyed. In this thesis, we exploit this fundamental principle to derive a novel bilateral control mechanism that allows to design stable teleoperation systems with any conceivable communication architecture. The rationale starts from the fact that the mechanical energy injected by a human operator into the system must be conveyed to the remote environment and vice versa. As will be seen, setting energy as a control variable allows a more general treatment of the system than the more conventional setting of specific system variables, as can be position, velocity or force. Through the Time Delay Power Network (TDPN) concept, the issue of defining the energy flows involved in a teleoperation system is solved with independence of the communication architecture. In particular, communication time delays are found to be a source of virtual energy. This fact is observed with delays starting from 1 millisecond. Since this energy is intrinsically added, the resulting teleoperation system can be non-passive and thus become unstable. The Time Delay Power Networks are found to be carriers of the desired exchanged energy but also generators of virtual energy due to the time delay. Once these networks are identified, the Time Domain Passivity Control approach for TDPNs is proposed as a control mechanism to ensure system passivity and therefore, system stability. The proposed method is based on the simple fact that this intrinsically added energy due to the communication must be transformed into dissipation. Then the system becomes closer to the desired one, where only the energy injected from one side of the system is conveyed to the other one. The resulting system presents two qualities: On one hand, system stability is guaranteed through passivity, independently from the chosen control architecture and communication channel; on the other, performance is maximized in terms of energy transfer fidelity. The proposed methods are sustained with a set of experimental implementations using different control architectures and communication delays ranging from 2 to 900 milliseconds. An experiment that includes a communication Space link based on the geostationary satellite ASTRA concludes this thesis.

Abstract: To deal with the nonlinear model of the three-phase shunt hybrid active power filter( SHAPF), a control strategy is proposed with the passivity-based control method. An averaged Euler-Lagrange system model of the three-phase SHAPF was presented firstly. Then according to the passivity of the SHAPF,a nonlinear control strategy was proposed by using the energy shaping and damping injection design methodology. The global asymptotic stability of the close-loop system was ensured by the proposed control strategy. Finally,simulation results illustrate good harmonic suppression and DC-bus capacitor voltage regulation can be both achieved with the proposed strategy,and better harmonic elimination performance and robustness are shown compared with the linear quadratic regulator method.

Abstract: This paper studies the passivity-based consensus analysis and synthesis problems for a class of stochastic multi-agent systems with switching topologies. Based on Lyapunov methods, stochastic theory, and graph theory, new different storage Lyapunov functions are proposed to derive sufficient conditions on mean-square exponential consensus and stochastic passivity for multi-agent systems under two different switching cases, respectively. By designing passive time-varying consensus protocols, the solvability conditions for the passivity-based consensus protocol synthesis problem, i.e., passification, are derived based on linearization techniques. Numerical simulations are provided to illustrate the effectiveness of the proposed methods.

Abstract: Noisy behaviour of time domain passivity control (TDPC) at low velocity is a well known problem for delayed teleoperation systems. This paper presents a novel adaptive model-based passive controller to alleviate some of the noise problems associated with delayed teleoperation system using the TDPC approach. By composing an online estimation of phantom human tissue model and passivity observer on the master side, a high transparency of teleoperation can be achieved while the system passivity is maintained by modifying the damping of the master. The performance of the developed approach was validated using one-degree-of-freedom master–slave robot system with constant time delay. Results show that the phantom tissue parameters can be accurately estimated. In addition, the passivity of the system is observed by the passivity observer using the output of the identified tissue model. Results demonstrate that stable teleoperation with time delay can be achieved and the environment force can be accurately reflect...

Abstract: The invention discloses a modular multi-level current converter passivity modeling and control method which mainly comprises the following steps: step 1, a modular multi-level current converter passivity mathematic model is established, and an equalization state-space equation within a switching period is obtained; step 2, a modular multi-level current converter energy forming method algorithm model based on the equalization state-space equation is established, and a passive system from an input state variable Xi to an output state variable X is defined; step 3, a current converter damping injection algorithm model is established; step 4, a current converter control model based on all module switching functions is established. The modular multi-level current converter passivity modeling and control method has the advantages that stabilized and balanced control over capacitance and voltages on the direct current sides of upper bridge arms and lower bridges arms and quick tracking control over currents on the alternating current sides of all the bridges arms can be realized rapidly, the defects of a traditional modular multi-level current converter control strategy are overcome, and a feasible means is provided for the design of a control strategy of a flexible direct current transmission system.

Abstract: A nonlinear current-mode proportional-integral (PI) controller is proposed for the challenging problem of regulating the output voltage of a dc/dc boost power converter. For the analysis, the accurate average nonlinear model of the boost converter is used, while a new advanced passivity-based nonlinear stability analysis is applied. Particularly, it is firstly proven that the closed-loop system is passive and a unique equilibrium exists. A new sequential method is proposed for constructing a suitable Lyapunov storage function for the entire closed-loop system, which is capable to prove the input- to-state stability of the system. All these properties are eventually used to prove convergence to the desired equilibrium. Finally, the effectiveness of the proposed PI controller is evaluated through simulation and experimental results for cases where step changes on the voltage reference value occur.

Abstract: The paper investigates the stability and passivity analysis problems for a class of uncertain neural networks with time-delay via delta operator approach. Both the parameter uncertainty and the generalized activation functions are considered in this paper. By constructing an appropriate Lyapunov-Krasovskii functional, some new stability and passivity conditions are obtained in terms of linear matrix inequalities (LMIs). The main characteristic of this paper is to obtain novel stability and passivity analysis criteria for uncertain neural networks with time-delay in the delta operator system framework. A numerical example is presented to demonstrate the effectiveness of the proposed results.

Abstract: This paper tackles the problem of power regulation for wind turbines operating in the top region by an adaptive passivity based individual pitch control strategy An adaptive nonlinear controller that ensures passivity of the mapping aerodynamic torque-regulation error is proposed, where the inclusion of gradient based adaptation laws allows for the on-line compensation of variations in the aerodynamic torque The closed-loop equilibrium point of the regulation error dynamics is shown to be UGAS (uniformly globally asymptotically stable) Numerical simulations show that the proposed control strategy succeeds in regulating the power output of the wind turbine despite fluctuations of the wind field due to wake and turbulence, without overloading the pitch actuators

Abstract: The time delay in the current control loop of a grid-connected voltage-source converter (VSC) may cause instability if the VSC is equipped with an inductive-capacitive-inductive (LCL) input filter. However, instability is prevented if the input admittance of the VSC can be made passive. This paper presents a systematic method for gaining passivity. Thereby, stability is obtained for any LCL-filter resonance and for any passive grid impedance. The method is equally applicable to single-phase and three-phase systems.