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Nowadays, the use of photovoltaic energy-based systems as distributed generation facilities in the operation of microgrids has been increasing considerably. This entails some issues that must be considered when maintaining the microgrid parameters within suitable values owing to the inherent intermittency and variability of the solar energy throughout the day. Hence, a well-selected and designed control strategy allows the improvement of the dynamic performance by accomplishing the control tasks and maintaining the voltage and frequency within suitable levels, as well as reducing power losses, where it is also important to consider proper power sharing among the grid-feedings by covering the needs of the connected load. In this paper, an optimization method is employed in a Hierarchical Control Structure to optimally distribute the power supplied by photovoltaic energy-based grid-feedings, which allows obtaining the minimal generation cost. A passivity-based control strategy is developed at the primary control level, and the black start procedure for microgrid performance in simulation is obtained. As part of the validation method, the models used in the simulation results consider all the system dynamics to show the detailed response with the operation scenarios.

This paper presents a generalized controller design to regulate the output voltage of second-order DC-DC converters feeding an unknown constant power load (CPL). Passivity-based control plus damping injection theory is employed to design a generalized action control to stabilize DC-DC converters. Furthermore, starting from the immersion and invariance (I&I) method, a generalized observer for second-order DC-DC converters is implemented to estimate the CPL value. By mixing the proposed controller with the I&I method, an adaptive generalized control approach is presented, which guarantees the locally asymptotic stability of the closed-loop for each converter. The main advantage of the nonlinear adaptive control design is its nonparametric dependence on the capacitance and inductance values, which makes it robust against parametric uncertainties. Phase portrait and sensitivity analyses are performed, and simulation and experimental results are examined to evaluate the performance of the proposed approach, which is also compared against feedback linearization and sliding mode control. Simulation and experimental results show the robustness and effectiveness of the adaptive proposed control approach.

While the unified power quality conditioner based on modular multilevel converter (MMC-UPQC) can be used for recovering power quality of voltage and current in high voltage grids, it is difficult to manage the power quality when the grid voltage imbalance is large. In this paper, a passivity-based control (PBC) combined with sliding mode control (SMC) is proposed for MMC-UPQC to improve the power quality under the unbalance of grid voltage in power systems. First, according to the structure of MMC-UPQC, the equivalent mathematical model is presented for unbalanced power grids. Second, the detection quantity is separated without phase-locked loop using a method of positive and negative sequence separation. Furthermore, a passive sliding mode control (PSMC) strategy is designed and applied to a multi-level and high voltage power quality compensation system. The proposed controller can improve the control accuracy of system parameters, response speed, and compensation effectiveness. Finally, the MATLAB/Simulink simulation and the real time laboratory (RT-LAB) based hardware-in-the-loop (HIL) experimental results show that the proposed PSMC strategy can compensate voltage and current rapidly and accurately, and the controller has strong robustness against system parameter changes.

This article presents a nonlinear passivity-based control for a grid-connected cascaded H-bridge (CHB) photovoltaic (PV) system. The proposed control system is based on a port-controlled Hamiltonian model extracted from the synchronous reference frame system. Grid current dynamics is included in this model. Compared to existing solutions, the proposed control method has a robust performance and enhances the stability of the CHB-based PV system in the case of disturbances such as unequal irradiance over distinct PV arrays or a sudden sag or swell in the grid voltage. This controller also provides the independent control of each dc-link voltage. Therefore, the individual maximum power point tracking algorithms can be realized in each PV array, and the harvested energy can be maximized. Finally, simulation results and experimental investigations are conducted to verify the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

To cope with future goal of efficiency, next generation of more electrical aircraft is likely to embed reconfigurable microgrid for the primary electrical distribution. The stability analysis of such time-varying structure is challenging. Conventional linear and nonlinear approaches failed to produce proper answers from a practical point of view. Under conditions, passivity property of each equipment is sufficient to ensure stability of the overall microgrid. But with improper passivity-based control (PBC) design, the passivity property may not be propagated. The main contribution of this article is to propose a modified IDA-PBC procedure that will ensure the passivity properties of the system regarding its electrical inputs and outputs involved in the interconnection. Thus, for electrical microgrids resulting from the interconnection of controllable equipment, input/output filters, and electrical lines, if all the equipment embed the proposed control, the whole microgrid have passive properties and the global stability of the system is ensured. Moreover, this article will also present how to achieve the proposed control with high transient and robust performances thanks to nonlinear parameters’ estimator preserving the passivity proper. Experimental validation of the proposed control in representative electrical conditions is provided. [ABSTRACT FROM AUTHOR]

Voltage and frequency control in an islanded ac microgrid (ImG) amounts to stabilizing an a priori unknown ImG equilibrium induced by loads and changes in topology. This article puts forth a unified control framework, which, while guaranteeing such stability, allows for modular ImGs interconnecting multiple subsystems, that is, dynamic $RLC$ lines, nonlinear constant impedance, current, power (ZIP) and exponential (EXP) loads, and inverter-based distributed generation units (DGUs) controlled with different types of primary controllers. The underlying idea of the framework is based on the equilibrium-independent passivity (EIP) of the ImG subsystems, which enables stability certificates of ImG equilibria without explicit knowledge of these equilibria. In order to render DGUs EIP, we propose a decentralized controller synthesis algorithm based on port-Hamiltonian systems (PHSs). We also show that EIP, being the key to stability, provides a general framework, which can embrace other solutions available in the literature. Furthermore, we provide a novel argument based on LaSalle’s theorem for proving asymptotic voltage and frequency stability. Finally, we analyze the impact of actuator saturation on the stability results by exploiting the inherent EIP properties of the PHS DGU model. Theoretical findings are backed up by realistic simulations based on the medium-voltage CIGRE benchmark network. [ABSTRACT FROM AUTHOR]

In this paper, a new passivity-based control approach is designed to improve the robustness and stability of autonomous vehicles in performing path-tracking tasks. A port-Hamiltonian model is a special geometric structure and provides a systematic and insightful framework to describe many physical systems from an energy perspective. The passivity-based control establishes a new and simple structure to achieve the path-tracking task by the port-Hamiltonian structure. Firstly, the path-tracking error system is transformed into a port-Hamiltonian system with the perturbation. The energy-shaping method is utilized to ensure the asymptotic stability, and the stability proof of the closed-loop, path-tracking error system is given. The proposed real-time, passivity-based controller is directly dependent on the passive outputs, which is robust to parameter uncertainties caused by load changes. Moreover, the control performance of steering control will be degraded when the steering angle is saturated. The yaw-moment control is introduced to enhance the driving safety. In the wheel torque distribution, an optimization-based control allocation is designed to minimize the sum of tire loads and to make them more evenly distributed to each tire. Finally, simulations are implemented in MATLAB/Simulink and CarSim co-simulation to demonstrate the effectiveness of the designed strategy under different driving conditions. [ABSTRACT FROM AUTHOR]

We propose a control approach for fully actuated mechanical systems using interval arithmetic, which guarantees global uniform ultimate boundedness of the tracking error and robust performance despite model uncertainties and input disturbances. Existing robust control methods often require computationally expensive or empirical estimations of bounds of state-dependent, nonlinear perturbations, arising from model mismatches. Our robust feedback control approach is different and removes these difficulties by using interval arithmetic to determine online the worst case perturbation acting on the error dynamics. We present two interval-arithmetic-based robust controllers by robustifying inverse-dynamics and passivity-based nominal control schemes. The effectiveness of our approach is demonstrated on a real robot manipulator with uncertain dynamics. [ABSTRACT FROM AUTHOR]

This article presents a robust passivity-based control (PBC) strategy to mitigate the instability effect of the dc–dc boost power converter supplying a constant power load and a constant voltage load in dc microgrid systems. The control robustness of the PBC against both line and load variation is significantly improved by adding the nonlinear disturbance observer (NDO). Using the disturbance estimation technique, this observer works in parallel with the PBC strategy to compensate the disturbances of the system through a feed-forward compensation channel. Based on the dissipation property, the PBC strategy ensures the system stability, whereas the NDO guarantees global trajectory tracking to the reference voltage during disturbances. This control strategy not only ensures large-signal stability of the system, but also provides a fastest recovery performance during disturbances of the system as compared with other PBC strategies. The hardware-in-loop and real-hardware experimental results are provided to verify the control robustness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

The port-Hamiltonian form (PHF) of nuclear reactor dynamics is first given with the corresponding Hamiltonian function determined by the shifted-ectropies of neutron kinetics and reactor thermal-hydraulics. Then, a passivity-based control (PBC) is proposed by adding extra damping injections to the PHF, and it is shown by theoretical analysis that satisfactory closed-loop stability can be guaranteed. The newly designed control law is applied to a nuclear heating reactor, and the simulation results not only verify the theoretical analysis but also show the satisfactory reactor power-level control performance. [ABSTRACT FROM AUTHOR]

Dynamic wireless charging (DWC) is one of the most promising and economical power supply solutions for electric vehicles (EVs), which can address range anxiety and downsize the volume of onboard batteries. To solve the null power phenomenon and transfer power pulsation phenomenon in DWC scheme, this paper proposes a new magnetic coupler array to implement continuous charging and reduce the output power variation. The transmitters are placed with a proper interval to eliminate the adjacent coupling and enlarge the coil array’s effective length. ANSYS Maxwell is utilized to demonstrate the finite element analysis (FEA) of the DWC system. A larger receiver coil is designed to significantly mitigate power pulsation and increase the magnetic coupling as the receiver moves along the array. With the well-designed receiver coil, the output power pulsation is $\pm$ 1.52 $\%$. For the high-power capacity scenario, a multilevel connected DC-DC converter is designed on the receiver side to regulate the transfer power. Besides, a passivity-based control (PBC) is developed for the receiving DC-DC converter based on the Euler-Lagrange (EL) model, and a current sharing compensator is employed to balance each phase inductor current. Finally, a 500- $\text{W}$ prototype is constructed, and experimental results are represented to validate the proposed optimized coil array and the proposed PBC method. [ABSTRACT FROM AUTHOR]

This article contains a new passivity-based control design approach for dc microgrids. The design is purely based on experimental data—bypassing the requirement of the network modeling. This approach permits the control of dc microgrids and preserve stability, despite of further interconnection of new passive loads and new passivity-based-controlled converters. This model-free approach generates control laws in a pure numerical way; bypassing the requirement of dealing with a high number of variables and equations that naturally appear in an increasingly complex dc microgrid. Experimental results are presented to corroborate the advantages of our approach. [ABSTRACT FROM AUTHOR]

The majority of marine current conversion technologies are based on permanent magnet synchronous generators (PMSG) due to its numerous advantages such as high-power density, low cost, and favorable electricity production. However, nonlinear properties of the generator and parameter uncertainties, makes the controller design more than a simple challenge. This paper proposes a new adaptive passivity-based (PB) modified super twisting algorithm (PBSTA) for control performance improvement (low tracing errors, fast convergence response, robustness) of a PMSG based marine current energy conversion system under swell effect and parameter uncertainties. The proposed approach combines a new PB current control (PBCC) with a new adaptive modified super twisting algorithm through a fuzzy logic supervisor. A new adaptive fractional order PID (FO-PID) controller is introduced to design the desired dynamics of the system. The main contributions and motivation of this work include the extraction of maximum power from the tidal current, integrating it to the grid and making the closed loop system passive. This is possible by reshaping system energy and introducing a damping term that compensates the nonlinear terms by a damped way and not by cancellation. Two steps are needed to design the proposed controller: the first step includes the derivation of reference current based on the reference torque using adaptive FO-PID. In the second step, the overall control law is computed by the proposed PBSTA. The exponential stability and error convergence of the proposed controller are analytically proven. The developed controller is tested under parameter variations and it is compared to benchmark nonlinear control methods such as sliding mode. Extensive investigation under MATLAB/Simulink, demonstrates clearly that the proposed technique provides higher efficiency and robustness over the benchmark nonlinear control methods.

A passivity-based control (PBC) strategy with improved robustness for single-phase three-level rectifiers feeding resistive and constant power loads (CPLs) is proposed. It is shown that the control of the rectifier can be achieved if the damping injection is applied to the grid current only. In this case, the knowledge of load resistance is required in the computation of reference grid current amplitude. Since the output voltage and load current are dc quantities, the load resistance can be estimated easily. Then, the amplitude of the reference grid current is calculated from the power balance equation of the rectifier. The transfer function from reference grid current to actual grid current is derived. The derived transfer function is analyzed under variations in the filter inductance. The results reveal that the proposed PBC offers strong robustness to variations in the filter inductance when a suitable damping gain is selected. The performances of the proposed PBC strategy under undistorted and distorted grid voltage as well as, variations in inductor are investigated via experimental studies during steady-state and transients caused by the resistive load and CPL changes. In all cases, the output voltage is regulated at the desired value, and grid current tracks its reference.

The multilevel connected dc–dc converters system is considered a practical technology to increase the capacity and reduce voltage and current stresses on the power devices. In practice, mismatched parameters are inevitable, which increase the challenge of output voltage regulation and current sharing control. In order to conquer these difficulties, this article investigates the current sharing based on incremental passivity control for multilevel connected dc–dc converters. Combined with passivity-based control, a finite-time estimator is given to improve the robustness against the load variations. The proposed method results in a linear control law despite the bilinear nature of this system. Moreover, analysis exhibits that stability and current sharing are independent of inductor parameters. Furthermore, stability of the closed-loop system has been proved that the proposed approach is valid both for a linear and nonlinear load. After introducing the proposed control scheme, simulation and experiments are offered to validate its fast transit response and antidisturbance performance. [ABSTRACT FROM AUTHOR]

The dynamic wireless charging for electric vehicles (EVs) is considered an efficient and practical choice to extend the driving range and reduce battery pack size. However, the coupling coefficient between transmitter coils and receiver coil varies rapidly on a large scale during the EVs moving, so it deteriorates the charging performance of dynamic wireless power transfer in EVs, such as the discontinuous charging for the lithium-ion batteries in EVs. Moreover, the charging power and efficiency of the system can also be affected. To solve these issues, a dc–dc converter is added to cascade on the receiver side to improve the output power and efficiency of the system. Furthermore, the passivity-based proportional-integral control is designed for the dc–dc on the receiver side of dynamic wireless charging system to improve the performance against the rapidly changing coupling coefficient. Finally, compared with the conventional proportional-integral-derivative controller, simulation and experimental results are given to show the performance and robustness of dynamic wireless charging system by the proposed method. [ABSTRACT FROM AUTHOR]

Electric multiple units (EMUs) have been the cause of low frequency oscillation (LFO) incidents in high-speed railway (HSR) network train systems (NTSs). In this paper a norm criterion with the advantages of simpler calculation while being less conservative than other norm criteria is introduced to analyze the stability of the NTS. A control strategy of EMU four-quadrant converters (4QCs) consisting of ac current passivity-based control (PBC) and dc voltage sliding mode variable structure (SMS) control, i.e. PBC-SMS, is proposed for LFO suppression. The NTS stability analysis with PBC-SMS results in superior critical LFO condition. A single EMU simulation validates the improved steady-state and dynamic performance of the PBC-SMS compared to other conventional methods; NTS simulations based on field tested network parameters verify the superior LFO suppression capability of the proposed method. Finally, guidelines for LFO suppression are recommended based on a comprehensive sensitivity analysis of the traction network, 4QC circuit and controller parameters of an NTS.

We consider a small helicopter structure that is maneuvered through the control of moving masses. It is referred to as a swash mass helicopter (SMH). This paper addresses the trajectory tracking control problem for the SMH, with a specific focus on the decoupling change of coordinates of both rotational and translational dynamics. We propose a control scheme in which position tracking is the primary objective, while the attitude tracking task is considered as a secondary objective. The intermediate control signals related to the attitude dynamics exploit the structural properties of the SMH and are enhanced with terms that grant a more accurate tracking of the target trajectory. The closed-loop system stability under the trajectory tracking objective is obtained following the Interconnection and Damping Assignment Passivity-Based Control (IDA-PBC) approach. In addition, the presence of external disturbances can diminish the trajectory tracking performance. For this reason, a nonlinear outer loop controller is added to the IDA-PBC to compensate the disturbances. Finally, the results of several simulations are reported to evaluate the performance of the control strategy.

In this paper, a practical passivity-based control (PBC) with active disturbance rejection control (ADRC) is proposed to improve performance of the Vienna rectifier under unbalanced grid conditions. In general, the traditional double-loop control based on positive and negative sequence transformation is used in Vienna rectifier under unbalanced grid conditions. However, it could not fundamentally solve the additional time delay caused by the second harmonic filter and loss of performance caused by a linear weighted sum of proportional integral (PI) controller. What's more, the complexity of the controller is high for the positive and negative sequence currents need to be controlled separately. The PBC is a nonlinear controller based on energy dissipation and it has strong robustness to interference. Further, the line voltage based PBC in inner current loop can deal with the voltage unbalance effectively and easily without negative sequence transformation. To improve the disturbance rejection ability, the ADRC is applied in outer voltage loop, which could overcome PI's drawbacks of step overshoot and slow response. Under unbalanced grid conditions, the proposed control strategy has good performance, easy implementation and less consuming time with PBC control in inner current loop, and it has strong robustness and fast track performance with ADRC control in outer voltage loop. The detailed mathematical model, control principle and controller design of the Vienna rectifier are thoroughly analyzed. In addition, simulation results based on SIMULINK are also given in the paper. Finally, a downsize 5kW Vienna rectifier prototype is built to validate the correctness and effectiveness of the proposed strategy.

Nowadays, the Passivity-Based Control (PBC) has been successfully applied to digitally controlled Grid-Connected Inverter (GCI) with LCL filter. As a nonlinear method, the PBC controller has strong robustness against the parameter drift of the LCL filter and the grid impedance, where the parameters of the PBC controller still need to be designed carefully to achieve a good control performance. The existing design methods are based on separating the PBC controller into three control loops. Therefore, the design process is cumbersome, especially for inexperienced engineers, due to the complex structure of the PBC controller. In this article, an intelligent Particle Swarm Optimization (PSO) algorithm is utilized to simplify the parameters design of the PBC controller, where the difficulty of manual calculations is avoided and the parameters can be more easily and efficiently obtained using MATLAB in offline mode. Furthermore, a Kalman filter observer is adopted to estimate the state variables in the PBC controller, where only the grid-injected current needs to be sampled in the overall GCI system. Simulations and experiments are provided to verify the correctness and effectiveness of the proposed PBC controller design method.

This paper deals with the problem of passivity analysis and passivity-based synthesis for continuous-time stochastic hybrid singular systems (SHSSs). First, a set of linear matrix inequalities for the stochastic admissibility and passivity, which is also known as the positive real lemma, is obtained for continuous-time SHSSs. The proposed condition successfully holds a necessary and sufficient condition for the positive realness of SHSSs, whereas the existing papers in the literature have been handled only sufficient conditions. Next, the passivity-based control synthesis problem is also considered based on the new positive real lemma. The passivity-based stabilization criterion for the closed-loop system with its mode-dependent state-feedback control is expressed in terms of matrix inequality. Thus, by introducing an additional slack matrix to the non-convex conditions, the feasible conditions for the control gain are obtained in terms of linear matrix inequalities. Finally, a numerical example is provided to show the effectiveness of the result.

This article presents a systematic robust current control design approach for three-phase voltage-source converters. Robustness is guaranteed by combining intrinsic passive properties of the impedance uncertainty at the point of common coupling together with stability results from a passivity-based control theory. This approach ensures stability against typical uncertainty sources at mid and high frequencies, such as cable resonances or other converters interaction, with significant less conservative performances than the obtained with the traditional robust control theory. The approach uses multiobjective controller synthesis formulation that allows us to logically combine robustness requirements with performance objectives avoiding heuristic iteration over the control structure and parameters. The controller synthesis is performed by means of a nonsmooth $\mathcal {H}_{\infty }$ optimization technique that tunes all free parameters of a vector-based controller function, which constraints its structure. This results in a synthesized controller with lower order than those obtained with convex optimization definitions of the $\mathcal {H}_{\infty }$ control problem. The design methodology is validated in time and frequency domain by means of theoretical analysis and experimental results with three usual grid filters: L, LCL, and LLCL. [ABSTRACT FROM AUTHOR]

In this article, a novel damping control scheme for V/I droop-controlled direct current (dc) microgrids is proposed to attenuate the oscillatory components in the power and current. At first, the model of the dc microgrid is introduced providing stability analysis. Then, the damping controller is designed using the interconnection and damping assignment passivity-based control (IDA-PBC) methodology. In addition, the gain selection technique for the IDA-PBC is developed. The proposed control scheme ensures that the oscillations of the output power and current are effectively attenuated. The validity of the proposed control algorithm has been verified by the results from both hardware-in-the-loop simulation and proto-type experiments. [ABSTRACT FROM AUTHOR]

Finite control set model predictive control (FCS-MPC) of three-level neutral point clamped inverter-fed induction motor has received wide concern recently, thanks to its low switching frequency and fast dynamics. However, the performance largely depends on the accurate measurement and parameters which determine the feedback and control loops, respectively. Besides, FCS-MPC demands a large number of resources to perform the exhaustive search, which indicates that the computation burden increases exponentially with the increasing switching states. Aiming at improving the robustness under the condition of unavoidable measuring noises and parameter variation as well as reducing the computational burden, a passivity-based model predictive control (PB-MPC) scheme is presented in this article. For an ideal system, the PB-MPC has a similar character as that of the FCS-MPC. In real applications, where noises and disturbances impact the system more or less, PB-MPC outperforms FCS-MPC due to the power shaping and damping injection inherited from passivity-based control which ensures the asymptotic stability. A Lyapunov function is designed to prove the stability of the proposed scheme. The stability and efficiency are verified by both simulation and experimental results. [ABSTRACT FROM AUTHOR]

This letter proposes a passivity-based current control (CC) scheme for voltage-source converters, featuring a virtual-flux-based damper and a passive output admittance with a wide range of time delay involved in the CC loop. The admittance modeling and experimental tests validate the effectiveness of the approach. [ABSTRACT FROM AUTHOR]

This paper presents a passivity-based control for the DC/DC Buck-Boost converter-inverter-DC motor system. Such control exploits the energy structure associated with the system error dynamics. This in order to solve the trajectory tracking task for both the converter voltage and motor bidirectional angular velocity, without using electromechanical sensors. The successful experimental validation of the proposed control is performed in a built prototype of the system, using Matlab-Simulink and a DS1104 board.

Owing to the strong robustness against system parameter changes and external perturbations, the passivity-based control (PBC) has been widely adopted in grid-tied inverter (GTI). However, for a PBC-based GTI with LCL-filter, there are three damping gains and two interactively coupled-feedforward terms in the control loop, resulting in the controller design challenge for engineers. In order to help electrical engineers to well design the PBC controller for LCL-filtered GTI, a new design of the damping gains is proposed, by limiting the inherent steady-state error of grid-injected current. Furthermore, the state observer is also adopted to reduce the number of sensors. The robustness against the parameters shift and wide grid impedance variation is also addressed. The effectiveness of the proposed control design strategy will be verified through experimental results on a 3 kW/3-phase/110 V experimental lab setup. [ABSTRACT FROM AUTHOR]

This paper proposes an interconnection and damping assignment passivity-based control (IDA-PBC) for multimachine power systems including hydro-turbine governing systems (HTGS) with surge tank. The main objective is to stabilize the rotor speed and regulate the terminal voltage of each synchronous machine in a power system. The proposed control is decentralized, thus avoiding challenges of communication between generators. Passivity theory is used since the open-loop of the HTGS presents a port-Hamiltonian structure. IDA-PBC allows a control law that maintains the passive structure in closed-loop, guaranteeing its asymptotic stability using Lyapunov's theory. The dynamics of each HTGS are described by an eleventh-order model, which can be reduced to a tenth-order. The proposed control is tested in a 12-bus test system and compared to a standard control, which considers a voltage regulator and exciter based on the IEEE type ST1A excitation system model and power system stabilizer IEEE-PSS1A. The governing system based on a PID control with static and transient droop is also employed. Additionally, the proposed controller is compared to a sliding mode controller. Time-domain simulations demonstrate the robustness and appropriate performance of the proposed decentralized control under different large disturbances. [ABSTRACT FROM AUTHOR]

Because of the non-linear load increase in the electrical grid, the use of active power filter has gone increasing, this last is to improve the power quality. In the study of control applied to the active power filter, cascade control is the most used; this control scheme consists of two control loops: one external dc voltage control loop and one internal current control loop. For this work, in the external loop, a proportional-integral (PI) control is used, whereas in the inner loop a passivity-based controller (PBC) is used. The main objective of this work is to present a proposal for tuning of PI and PBC controllers. This tuning methodology allows computing the gain k of the traditional PBC based on switching frequency, taking into a count the error dynamics. From step response analysis, the PI parameters are obtained. This tuning proposal is simple and has shown to be consistent for different switching frequency values. Through the measurement of the active power filter performance, the tuning proposal has been corroborated. Simulation and experimental results are presented. [ABSTRACT FROM AUTHOR]

In this paper, we develop a cooperative control algorithm for a group of multirotor unmanned aerial vehicles (UAVs) transporting a suspended payload of unknown mass. In addition, the vehicles are subjected to unknown environmental disturbances in the form of wind. The control structure is analyzed using Lyapunov theory, and both numerical simulations and results from experimental field trials on an outdoor multirotor platform further validate the proposed control algorithm. [ABSTRACT FROM AUTHOR]

This article proposes a passivity-based approach for simulating satellite dynamics on a position-controlled robot equipped with a force–torque sensor. Time delays intrinsic in the computational loop and discrete-time integration degrade the behavior of the satellite dynamics reproduced by the robot. These factors can generate an energy-inconsistent simulation and can even render the system unstable. In this article, time delay and discrete-time integration effects are analyzed from an energetic perspective and compensated through a passivity-based control strategy to ensure a faithful and stable dynamic simulation with position-controlled robots. The benefit of the proposed strategy is validated by simulations and experiments on the On-Orbit Servicing Simulator (OOS-SIM), a robotic facility used for simulating free-floating dynamics. [ABSTRACT FROM AUTHOR]

In the more electric aircraft context, dc distribution systems have a time-varying structure due to the flexible distributed loads and complex operation conditions. This feature poses challenges for system stability and increases the difficulty of the stability analysis. Besides, the risk of instability may be increased under constant power load condition due to the negative incremental impedance characteristic. To this end, this article proposes an improved interconnection and damping assignment passivity-based control scheme. Particularly, an adaptive interconnection matrix is developed to establish the internal links in port-controlled Hamiltonian models and to generate the unique control law. The damping assignment technique is addressed to tune the dynamic characteristic. In order to meet the load requirements of different voltage levels, the design procedures were given for determining the control law in both boost converter and buck converter cases. The simulation and experimental results are performed to demonstrate the validity of the proposed control approach. [ABSTRACT FROM AUTHOR]

This article presents an integrated scheme for supplementary damping control of unified power flow controllers (UPFCs) in order to mitigate low-frequency oscillations in power systems. The entire control system consists of the primary control and the supplementary control. In the primary control, the passivity-based control is considered in the current control loop of two converters for achieving more prompt and accurate dynamical responses. In the supplementary control, the transient energy function (TEF) approach will be explored first for designing the damping control of UPFCs. This control action can be considered as an extension of droop control used in the synchronous generator. In order to further cope with unmodeled dynamics of power systems and provide the online dynamic adaptation ability, neural networks approximated control actions are designated for online weight adjustments of the TEF-based supplementary control. Numerical simulations on three benchmark systems have been performed to validate the proposed control method for providing the extra damping and suppressing power swings even under severe operating conditions. [ABSTRACT FROM AUTHOR]

Power electronics-based medium-voltage direct current (MVdc) microgrids consist of several interconnected feedback-controlled switching converters. Such systems experience bus voltage stability challenges owing to the negative incremental resistance of constant power loads and converter control loop interactions. To tackle the stability challenges, this paper presents the application of the interconnection and damping assignment passivity-based control (IDA-PBC) approach to the port-controlled Hamiltonian model of dual active bridge (DAB) source-side converters in an MVdc microgrid. For the DABs, a fundamental average model approach considering phase shift modulation is provided and used for deriving the corresponding IDA-PBC control law. We analyze the effectiveness of the controller on large signal scenarios considering disturbances such as load step up, and DAB disconnection. Hardware-in-the-Loop experiments using Opal-RT and Labview field programmable gate arrays (FPGAs), as well as, low power prototype tests are carried out to demonstrate the validity and feasibility of the proposed approach. [ABSTRACT FROM AUTHOR]

Passivity-based control (PBC) relies on an accurate mathematical model and thus its performance will be degraded by the weak robustness against parameters uncertainties, modeling error, and external disturbances. Moreover, it cannot achieve zero tracking error of the steady-state current under parameter uncertainties and modeling error. This paper proposes a novel disturbance-observer- (DO) based PBC (DO-PBC) for static synchronous compensator (STATCOM) to achieve better stability and dynamic performances against disturbances. A DO that has been introduced into the PBC current loop is used to compensate system disturbances, which can improve the robustness of the control system and eliminate the steady-state tracking error. Moreover, the proposed DO-PBC provides faster responses in handling various kinds of disturbances. Then, the detail design process, stability and robustness analysis, and parameters tuning method are investigated and presented. Also, the proposed method is simple to be implemented by the separation principle. The performance comparisons among the proportional integral, the conventional PBC, and the proposed DO-PBC are carried out to show the effectiveness of the proposed method against disturbances and the precise current tracking, via simulation tests and experimental tests based on a down-scale laboratory prototype experiment of 380 V STATCOM. [ABSTRACT FROM AUTHOR]

Recently, low-frequency oscillation (LFO) occurs in electrified railways, which exhibits a synchronous periodic oscillation of about 2–7 Hz in the traction network and electric multiple units (EMUs). To suppress the LFO, an improved model predictive control (MPC) combining with extended state observer (ESO) is proposed. First, for the design of ESO, the changes of system parameters and the unmodeled item in vehicle mathematical model are extended to a new variable and then estimated to compensate the calculated control voltage in real time. Second, the observer stability is analyzed by obtaining the transfer function, and the appropriate gains of observer are chosen through the pole assignment technique. At last, by the combination of the predictive currents, the optimal control voltages can be obtained. The control performance among MPC, dq decoupling control, passivity-based control, and the proposed method is compared. In addition, the system robustness when system parameters change is discussed. At last, to further verify the effectiveness of the proposed method for suppressing LFO, an integrated dSPACE semi-physical experimental platform including eight simulated EMUs and an equivalent traction network is constructed. Simulation and experimental results show that the proposed method not only effectively suppresses LFO but also accelerates the response speed of traction line-side converter, reduces the distortion of grid-side and vehicle-side currents, and overcomes the disadvantages of MPC and dq decoupling control under the mismatching of system parameters. [ABSTRACT FROM AUTHOR]

This paper presents an admittance controller based on the passivity theory for a powered upper-limb exoskeleton robot, which is governed by the nonlinear equation of motion. Passivity allows us to include a human operator and environmental interaction in the control loop. The robot interacts with the human operator via force/torque (F/T) sensor and interacts with the environment mainly via end-effectors. Although the environmental interaction cannot be detected by any sensors (hence unknown), passivity allows us to have natural interaction. An analysis shows that the behavior of the actual system mimics that of a nominal model as the control gain goes to infinity, which implies that the proposed approach is an admittance controller. However, because the control gain cannot grow infinitely in practice, the performance limitation according to the achievable control gain is also analyzed. The result of this analysis indicates that the performance in the sense of infinite norm increases linearly with the control gain. In the experiments, the proposed properties were verified using 1-DoF testbench, and an actual powered upper-limb exoskeleton was used to lift and maneuver the unknown payload. [ABSTRACT FROM AUTHOR]

This paper presents a new procedure to design a control law using the classical interconnection and damping assignment technique within the passivity-based port-Hamiltonian framework. The sought goal is to reduce the complexity of solving the so-called matching equations. The proposed approach is applied to two case studies of planar rolling nonprehensile manipulation, namely, the ball-and-beam and the eccentric disk-on-disk. The performance of the resulting controllers is illustrated through both simulations and experimental results, showing the applicability of the design in a real setup. [ABSTRACT FROM AUTHOR]

In this paper, a decentralized switched current control is presented for dc microgrids. The dc microgrid is modeled considering dc–dc converters as controlled current sources instead of traditional voltage sources in droop control schemes. The proposed current control consists of switching between two current reference signals while keeping the voltage level at the loads and with proper current distribution. It is shown that the closed-loop system is stable through passivity analysis. Experimental tests are performed to illustrate the effectiveness of the proposed control strategy using a laboratory microgrid. [ABSTRACT FROM AUTHOR]

In this brief, we develop a mathematical model of a flexible spacecraft system composed of a hub and two symmetrical beams using the port-Hamiltonian framework. This class of system has favorable properties, such as passivity for controller synthesis and stability analysis, where the global Hamiltonian plays the role of a Lyapunov function candidate. The spacecraft model is viewed as a power-conserving interconnection between an infinite (beam) and finite (hub) dimensional system. We show that the interconnection result has a port-Hamiltonian structure and is passive. The introduction of a nonlinear feedback term, which takes into account the beam’s flexibility, is developed using the control by an interconnection approach. The closed-loop stability is proven; then, through explicitly solving the partial differential equations of the system, asymptotic stability is obtained. Finally, the experimental results are carried out to assess the validity of the proposed design methodology. [ABSTRACT FROM AUTHOR]

Asymmetric voltage sags often occur at the point of common coupling, which connects industrial active distribution networks to the utility grid. Distributed generations face the challenges of riding through and supporting the voltage under the grid faults. In order to tackle these challenges, a hybrid control strategy, combined with the frequency droop with passivity-based switch function, is proposed. By adopting the proposed strategy, the positive/negative sequence active/reactive power is injected to recover the voltage. The novel PBSF is enhanced by including both control components of inverter's output current and output voltage based on the Euler–Lagrange model. The novel frequency droop is applied to achieve the positive/negative sequence active/reactive power injection with a satisfied sharing accuracy among the coordinated operation of parallel connected multiple inverters. Extensive simulation and experimental results have validated the effectiveness of the proposed strategy with an effective dynamic response performance and stability. [ABSTRACT FROM AUTHOR]

This paper proposes a new nonlinear stability analysis for the acceleration-based robust position control of robot manipulators by using disturbance observer (DOb). It is shown that if the nominal inertia matrix is properly tuned in the design of a DOb, then the position error asymptotically goes to zero in regulation control and is uniformly ultimately bounded in trajectory-tracking control. As the bandwidth of a DOb and the nominal inertia matrix are increased, the bound of error shrinks, i.e., the robust stability and performance of the position control system are improved. However, neither the bandwidth of the DOb nor the nominal inertia matrix can be freely increased due to practical design constraints, e.g., the robust position controller becomes more noise-sensitive when they are increased. The proposed stability analysis provides insights into the dynamic behavior of DOb-based robust motion control systems. It is theoretically and experimentally proved that nondiagonal elements of the nominal inertia matrix are useful in improving the stability and in adjusting the tradeoff between robustness and noise sensitivity. The validity of the proposal is verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]