Passivity-based Control Approach Research Articles

Port Controlled Hamiltonian Modeling and IDA-PBC Control of Dual Active Bridge Converters for DC Microgrids

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.

Trajectory Optimization of Robots With Regenerative Drive Systems: Numerical and Experimental Results

In this paper, we investigate energy-optimal control of robots with ultracapacitor-based regenerative drive systems. Based on a previously introduced framework, a fairly generic model is considered for the robot and the drive system. An optimal control problem is formulated to find point-to point trajectories maximizing the amount of energy regenerated and stored in the capacitor. The optimization problem, its numerical solution, and an experimental evaluation are demonstrated using a PUMA manipulator with custom regenerative drives. Power flows, stored regenerative energy, and efficiency are evaluated. Tracking of optimal trajectories is enforced on the robot using a standard robust passivity based control approach. Experimental results show that when following optimal trajectories, a reduction of about $\text{10}\text{--}\text{22}\%$ in energy consumption can be achieved for the conditions of the study, relative to the nonregenerative case.

Nonlinear adaptive observer for sensorless passive control of permanent magnet synchronous motor

This paper presents an adaptive nonlinear observer for sensorless passivity based control applied to permanent magnet synchronous motor. The passivity based control approach is applied to a complex and coupled nonlinear mathematical model of permanent magnet synchronous motor without any approximation or cancellation of nonlinearities.A nonlinear adaptive observer is proposed to estimate the mechanical speed and the unmeasured load torque (unknown disturbance) that has an effect on the control performance; therefore, those estimated states are then used to improve the performance of the passivity based control for permanent magnet synchronous motor.The performance of the proposed controller-observer have been tested using MATLAB/SIMULINK, where those Simulation results show a perfect tracking of the mechanical speed and load torque.

Adaptive control method for chaotic power systems based on finite-time stability theory and passivity-based control approach

Chaotic oscillation in a power system is considered the main cause of power blackouts in large-scale interconnected power grids. The chaotic oscillation mechanisms and the control methods for chaos oscillation of power systems need to be analyzed. This paper thus proposed an adaptive control method for chaotic power systems using finite-time stability theory and passivity-based control approach. The adaptive feedback controller is first constructed using the finite-time stability theory and the passive theory to make the chaotic power system equivalent to a closed-loop passive system. We then proved that the passive power system can stabilize the equilibrium points. We also extensively studied fourth-order power system. Results show that the controller based on the finite-time theory and the passivity-based control approach can effectively stabilize the chaotic behavior within finite time. The control strategy was also found to be robust to the different power system states.

A generalized passivity-based control approach for power compensation in distribution systems using electrical energy storage systems

This paper presents a generalized interconnection and damping assignment passivity-based control (IDA-PBC) for electric energy storage systems (EESS) such as: superconducting magnetic energy storage (SMES) and supercapacitor energy storage (SCES). A general framework is proposed to represent the dynamical behavior of EESS interconnected to the electrical distribution system through forced commutated power electronic converters. A voltage source converter (VSC) and a pulse-width modulated current source converter (PWM-CSC) are used to integrate SCES and SMES systems to the electrical power systems respectively. The proposed control strategy allows active and reactive power interchange between the EESS and electric distribution grids independently, guaranteeing globally asymptotically convergence in the sense of Lyapunov via Hamiltonian formulation. Simulation results show the effectiveness and robustness of the generalized IDA-PBC to operate EESS as active and reactive power compensator in order to improve operative conditions in power distribution grids under balanced and unbalanced conditions.

Flexible Structure Control of Unmatched Uncertain Nonlinear Systems via Passivity-based Sliding Mode Technique

This paper considers the problem of passivity-based sliding mode control of uncertain nonlinear systems. For this purpose, two cases are studied. In the first case, it is assumed that only the matched uncertainties exist in the system dynamics. In this case, the passivity-based control approach is used to design an appropriate sliding manifold with a flexible structure such that the asymptotic stability of the reduced-order model (i.e., the motion equations on the proposed sliding manifold) is guaranteed. In the second case, both matched and unmatched uncertainties are considered in the system dynamics and thus the reduced-order model has uncertain terms. In this case, the modified Lyapunov redesign technique is combined with the passivity-based control method for design of robust sliding manifold. The function that is basically used in the classical Lyapunov redesign method is the signum function, which is not differentiable. Since, for evaluating the derivative of the sliding manifold its equation must be differentiable, a new additional continuous control term is suggested. In addition, the robust practical stabilization of the motion equations is guaranteed without considering any limitation on the upper bound of the unmatched uncertainties. Finally, computer simulations are performed for a practical example (flexible spacecraft) and also a numerical example to demonstrate the ability of the proposed controller in robust stabilization of uncertain nonlinear dynamical systems.

Multi-purpose droop controllers incorporating a passivity-based stabilizer for unified control of electronically interfaced distributed generators including primary source dynamics

This paper presents multi-purpose droop controllers for electronically-interfaced distributed generators (EI-DGs). These controllers allow the micro-grids to operate in grid-connected mode, islanded mode and mode transition transients with a unique control configuration. The active and reactive-power sharing among EI-DGs are satisfied by the proposed droop controllers in islanded mode. On the other hand, in the grid-connected mode, the droop controllers adjust the output active and reactive-powers of EI-DGs at the pre-programmed constant levels. The provision of sufficient damping capability and maintenance of the transient stability in all operational modes of EI-DGs are warranted by the suggested stabilizer. This stabilizer, which is designed using the passivity-based control (PBC) approach, is incorporated in the droop controllers to dampen power-angle, frequency and voltage deviations during large transients using solely local information. The primary source dynamics of EI-DGs are also considered. It is analytically proven that the presence of the primary source dynamics leads to attenuation of the damping capability of EI-DGs in transients. To compensate the adverse effect of the primary source dynamics during transients a novel compensator is inserted in the frequency-droop loop. Finally, time-domain simulations are performed on a multi-resources MG to verify the analytical results compared to those obtained, based on a recently-developed strategy.

Adaptive control of fractional-order unified chaotic systems using a passivity-based control approach

Feedback passivity-based controller design for stabilization of fractional-order unified chaotic systems is proposed in this paper. Although feedback passivity-based control is a well-known method for integer-order systems, it has not been investigated for fractional-order systems due to a lack of suited mathematical results. In this paper, a recently established lemma for the Caputo fractional derivative of a quadratic function is utilized to facilitate the design. An adaptive mechanism is also employed such that the controller does not need to known the parameter of the systems. Moreover, based on a fractional-order extension of the Lyapunov direct method, the stability of the zero dynamics of the systems is also provided. Numerical simulations are performed to illustrate the effectiveness of the proposed design. The results show that the controller is able to effectively stabilize the chaotic behavior without the knowledge of the system parameter. In addition, it is also found that the transient dynamics of the controlled system and the control effort are markedly influenced by the fractional order of the system.

Hierarchical Robust Control of Oscillating Wave Energy Converters With Uncertain Dynamics

Energy-maximizing controllers for wave energy devices are normally based on linear hydrodynamic device models. Such models ignore nonlinear effects which typically manifest themselves for large device motion (typical in this application) and may also include other modeling errors. The effectiveness of a controller is, in general, determined by the match between the model the controller is based on and the actual system dynamics. This match becomes especially critical when the controller is highly tuned to the system. In this paper, we present a methodology for reducing this sensitivity to modeling errors and nonlinear effects by the use of a hierarchical robust controller, which shows small sensitivity to modeling errors, but allows good energy maximization to be recovered through a passivity-based control approach.

Passivity-based target manipulation inside a deformable object by a robotic system with noncollocated feedback

Target manipulation inside a deformable object by a robotic system is necessary in many medical and industrial applications. However, this is a challenging problem because of the difficulty of imposing the motion of the internal target point by a finite number actuation points located at the boundary of the deformable object. In this work, an optimal contact formulation and a control action are presented, in which a deformable object is externally manipulated with multiple robotic fingers such that an internal target point is positioned to a desired location. First, we formulate an optimization technique that minimizes the total force applied to the object to determine the location of actuation points to affect the desired motion. Then, a passivity-based control approach, based on energy monitoring and dissipation, is developed to improve stability of the whole system. The simulation results demonstrate the efficacy of the proposed method.

Passive internet-based crane teleoperation with haptic aids

Crane operation is a challenging task, due to the combined problem of obstacle avoidance and load swing suppression in underactuated conditions. This paper presents a human-machine interface that increases the operator’s perception of a gantry crane’s workspace. With this aim, a virtual environment resembling the workspace is connected with a haptic device. This allows the user to receive not only visual but also tactile feedback, thus increasing maneuvering safety. Additionally, this capability is integrated in a teleoperation setup, adopting a passivity-based control approach that guarantees overall stability. This includes also the design of controllers by means of the IDA-PBC method. Experimental results carried out with a laboratory crane show its feasibility for internet-based teleoperation and demonstrate the improvements on the system performance.

Application of interconnection and damping assignment to the stabilization of a synchronous generator with a controllable series capacitor

The modeling and control of a single machine infinite bus (SMIB) system using a controllable series capacitor (CSC) is presented here. The SMIB is modeled using two different models- the well-known second order swing equation and the third order flux-decay model. The actuator dynamics is incorporated as a first order system and the interconnection and damping assignment passivity-based control (IDA-PBC) approach is used for controller synthesis. The control objectives are to asymptotically stabilize a desired operating point and modify the transient response of the system. The two objectives are achieved by assigning a suitable energy function and modifying the interconnection structure between the electrical and mechanical subsystems, thereby improving the coupling between the two subsystems. Estimates of the domain of attraction of the operating point are also given.