Passivity Theory Research Articles

Distributed control and passivity‐based stability analysis for time‐delayed DC microgrids

AbstractFor cooperation among distributed generations in a DC microgrid (MG), distributed control is widely applied. However, the delay in distributed communication will result in steady‐state bias and the risk of instability. This paper proposes a novel distributed control for time‐delayed DC MGs to achieve accurate current proportional sharing and weighted average voltage regulation. Firstly, by utilizing an advanced observer based on the PI consensus algorithm, the steady‐state bias problem is addressed. Then, using the passivity theory, stability analysis is conducted to reveal the principle of system instability caused by communication delay. On this basis, to offset the adverse effects of communication delay on the system stability, scattering transformation is introduced in the observer‐based distributed control. Moreover, considering the potential delay from the measurement stage in real‐life scenarios, the sufficient condition of the system stability is concluded by constructing the Lyapunov–Krasovskii functional. Finally, the performance of the proposed control and conclusions of stability analysis are verified by hardware‐in‐loop tests.

Robust hybrid control strategy for active power management in Kabertene wind farm within Algeria’s PIAT grid

The paper introduces a hybrid control strategy for optimised active power management in Algeria's Kabertene wind farm, crucial for the pole insalah-adrar-timimoune (PIAT) grid's stability. This strategy merges simultaneous interconnection and damping assignment (SIDA) passivity theory, passivity-based control (PBC), and multivariable proportional-integral-derivative (PID) controllers. This combined approach ensures frequency and voltage stability within the PIAT grid, which encompasses various elements like wind farms, solar plants, gas turbines, and dynamic impedance (Z), current (I), and active power (P) (D-ZIP), load model. By tailoring controllers for doubly fed induction generators (DFIGs) using SIDA-PBC principles and optimising internal parameters, the strategy achieves precise control of active power output. Additionally, particle swarm optimisation (PSO) refines power scheduling, which is especially beneficial for intermittent renewable sources like DFIGs. This comprehensive strategy offers numerous advantages: improved network stability, minimized voltage deviations, reduced frequency fluctuations, and enhanced integration of renewable energy sources. The paper emphasises practical implementation considerations, providing valuable guidance for efficient Kabertene wind farm operation and integration. This research contributes significantly to fostering cleaner and more reliable energy systems, facilitating the PIAT grid's transition towards sustainable energy generation.

Tuning chemical short-range order for stainless behavior at reduced chromium concentrations in multi-principal element alloys

Single-phase multi-principal element alloys hold promise for improved mechanical properties as a result of multiple operative deformation modes. However, the use of many of these alloys in structural applications is limited as a consequence of their poor aqueous corrosion resistance. Here we introduce a new approach for significantly improving the passivation behavior of alloys by tuning the chemical short-range order parameter. We show that the addition of only 0.03 to 0.06 mole fraction of Al to a (FeCoNi)0.9Cr0.1 alloy changed both the magnitude and sign of the Cr-Cr order parameter resulting in passivation behavior similar to 304L stainless steel containing twice the amount of Cr. Our analysis is based on comparing electrochemical measures of the kinetics of passive film formation with chemical short-range order characterizations using time-of-flight neutron scattering, cluster expansion methods, density functional theory and Monte Carlo techniques. Our findings are interpreted within the framework of a recently proposed percolation theory of passivation that examines how selective dissolution of the non-passivating alloy components and short-range order results in excellent passive films at reduced levels of the passivating component.

자평명리학의 운명가능론과 그의 변천

This article examines how Seo Ja-pyeong's theory of possible fate, which founded the study of Japyeong Myeongri in the early North Song Dynasty, is inherited and changed during the major successors after the Southern Song Dynasty. Seo Ja-pyeong was wary of luxury and emphasized on the doing one's bestand waiting Heaven's decree and took the theory of possible fate that if he blocked it with his accumulation of virtuous deeds, he would return in a bad way. Jin So-am emphasized accumulation of virtuous deeds and the immutability of misdeed, arguing that good deeds and evil deeds, as well as life expectancy, could increase or decrease just by thinking about them. Jin So-am recognized accumulation of virtuous deeds as a higher concept than nasolabial folds in terms of the influence that determines the life, and presented an example of successful 改命 through accumulation of virtuous deeds. Lim Cheol-cho emphasized the practice of virtue and listened to the donation of property as a way of good deeds, but donating to a religious organization has no effect and should be shared with poor relatives He argued that there was an effect of changing Heaven's decree. In addition, it was said that if you cultivate virtue, you can receive rewards and make up for people's work, and the purposeful good deeds of changing Heaven's decree were also considered to be effective. In addition, it was considered that the virtue of parents or ancestors influenced the name of a child. In addition, it was considered that the person's name was a combination of not only the nasolabial folds but also the ancestors' graves and ancestors' virtues based on feng shui. Seo Ja-pyeong, Jinso-am, and Im Cheol-cho saw that they can change Heaven's decree through accumulation of virtuous deeds in common. However, if Seo Ja-pyeong's theory of naming is a passive theory of possible fate, Jin So-am and Im Cheol-cho's theory of naming can be said to be a positive theory of possible fate, and among them, Jin So-am is the most active.

Reconfigured passivity‐based control strategy of LCL‐type grid‐connected inverter under complex grid conditions

SummaryLCL‐type grid‐connected inverters have seen extensive use of the passivity‐based control (PBC) system. However, traditional PBC systems rarely take time delay into account while designing the system or doing a stability study. Therefore, utilizing Lyapunov's criterion to conclude that the system is stable is not accurate. The analysis revealed that the differential terms of PBC loops with the Euler–Lagrange (EL) mathematical model could induce instability considered control delay for LCL‐type grid‐connected inverter system. Compared with traditional EL‐PBC method, this paper proposed a reconstructed EL‐PBC scheme by properly optimizing the noise term. Then, the equivalent output impedance of the grid‐connected inverter system with proposed controller is analyzed with frequency domain passivity theory. The controller parameters are also optimized to ensure both the internal stability of LCL‐type grid‐connected inverter and the risk of interactive resonance in complex weak and nonideal grid. Results from simulation and experimentation support the modified control structure's efficacy and performance.

Research on modular multi-level converter control based on passivity theory

All In view of the poor dynamic performance of the conventional PI control method in modular multilevel converter (MMC) systems, an up-to-date control strategy using passive theory is proposed. First, the topology of the system and its mathematical model are presented, then its Euler-Lagrange (EL) model is developed and its passivity is proved. Next, the dq-axis component of the current is chosen as the state variable to derive the passivity-based control (PBC) law and from this, the current passivity controller is designed. Simulation shows that compared with conventional PI control, the PBC in this paper can respond quickly to the change of current or power under different operating conditions, with good harmonic characteristics and better dynamic characteristics.

Monotone One-Port Circuits

Maximal monotonicity is explored as a generalization of the linear theory of passivity, aiming at an algorithmic input/output analysis of physical models. The theory is developed for maximal monotone one-port circuits, formed by the series and parallel interconnection of basic elements. These circuits generalize passive LTI transfer functions. Periodic input signals are shown to be mapped to periodic output signals, and these input-output behaviors can be efficiently computed using a maximal monotone splitting algorithm, which decomposes the computation according to the circuit topology. A new splitting algorithm is presented, which applies to any monotone one-port circuit defined as a port interconnection of monotone elements.

Finite-Time Passivity and Synchronization for a Class of Fuzzy Inertial Complex-Valued Neural Networks with Time-Varying Delays

This article investigates finite-time passivity for fuzzy inertial complex-valued neural networks (FICVNNs) with time-varying delays. First, by using the existing passivity theory, several related definitions of finite-time passivity are illustrated. Consequently, by adopting a reduced-order method and dividing complex-valued parameters into real and imaginary parts, the proposed FICVNNs are turned into first-order real-valued neural network systems. Moreover, appropriate controllers and the Lyapunov functional method are established to obtain the finite-time passivity of FICVNNs with time delays. Furthermore, some essential conditions are established to ensure finite-time synchronization for finite-time passive FICVNNs. In the end, corresponding simulations certify the feasibility of the proposed theoretical outcomes.

Energy, Passivity, and Morphological Capacities

The morphology of a system may be exploited to reduce the controller workload or to perform specific tasks, e.g., locomotion processes. However, understanding and characterizing these capacities in terms of physical quantities remains an open problem. In this paper, we pose the question: are energy and dissipation useful physical quantities to characterize morphological capacities? First, to illustrate the relevance of this question, we present some basic concepts of passivity theory that are useful for carrying out an energy-based analysis of the behavior of dynamical systems. Then, we analyze the behavior of a mechanical system, and we show how its morphology affects its energy. Finally, we present a detailed analysis of a passive walker and explain how its locomotion capacities can be interpreted in terms of energy.

Network Identification for Diffusively Coupled Networks With Minimal Time Complexity

The theory of network identification, namely identifying the (weighted) interaction topology among a known number of agents, has been widely developed for linear agents. However, the theory for nonlinear agents using probing inputs is far less developed, relying on dynamics linearization, and thus cannot be applied to networks with non-smooth or discontinuous dynamics. We use global convergence properties of the network, which can be assured using passivity theory, to present a network identification method for nonlinear agents. We do so by linearizing the steady-state equations rather than the dynamics, achieving a sub-cubic time algorithm for network identification. We also study the problem of network identification from a complexity theory standpoint, showing that the presented algorithms are optimal in terms of time complexity. We demonstrate the presented algorithm in two case studies with discontinuous dynamics.

Passivity-Oriented Impedance Shaping for LCL-Filtered Grid-Connected Inverters

The passivity theory provides an effective way to tackle the instability due to the inverter-grid interaction, which tells that the system stability can be guaranteed if the grid impedance and the inverter output impedance are both passive. Since the grid impedance is generally passive, the system stability can be immune to the grid impedance variation if the inverter output impedance is also passive. This paper develops a series and parallel impedance shaping method to ensure that the output impedance of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -filtered grid-connected inverter is dissipative up to the Nyquist frequency. Since the inverter output impedance can be decomposed into two passive elements and one active element, its non-dissipative property results from the latter, and thus the virtual series impedance shaping is introduced to cancel out the active element. Unfortunately, it poses impact on the low-frequency loop gain and system phase margin in the meantime. To alleviate this impact, a high-pass filter is inserted in the series impedance shaping function. Subsequently, a virtual parallel impedance is introduced to enhance the passivity robustness, such as against filter parameter variations. Moreover, the proposed method does not require any additional sensors. Experiments from a 6-kW prototype confirm the effectiveness of the proposed method.

Nash Equilibrium Seeking for General Linear Systems With Disturbance Rejection.

This article explores aggregative games in a network of general linear systems subject to external disturbances. To deal with external disturbances, distributed strategy-updating rules based on the internal model are proposed for the case with perfect and imperfect information, respectively. Different from the existing algorithms based on gradient dynamics, by introducing the integral of the gradient of cost functions on the basis of the passivity theory, the rules are proposed to force the strategies of all agents to evolve to the Nash equilibrium, regardless of the effect of disturbances. The convergence of the two strategy-updating rules is analyzed via the Lyapunov stability theory, passivity theory, and singular perturbation theory. Simulations are performed to illustrate the effectiveness of the proposed methods.

Robust Sampling-Based Control of Mobile Manipulators for Interaction With Articulated Objects

In this article, we investigate and deploy sampling-based control techniques for the challenging task of the mobile manipulation of articulated objects. By their nature, manipulation tasks necessitate environment interactions, which require the handling of nondifferentiable switching contact dynamics. These dynamics represent a strong limitation for traditional gradient-based optimization methods, such as model-predictive control and differential dynamic programming, which often rely on heuristics for trajectory generation. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sampling-based</i> techniques alleviate these constraints but do not ensure robots' stability and input/state constraints either. On the other hand, real-world applications in human environments require safety and robustness to unexpected events. For this reason, we propose a novel framework for safe robotic manipulation of movable articulated objects. The framework combines sampling-based control together with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">control barrier functions</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">passivity theory</i> that, thanks to formal stability guarantees, enhance the safety and robustness of the method. We also provide the practical insights that enable robust deployment of stochastic control using a conventional central processing unit. We deploy the algorithm on a ten-degree-of-freedom mobile manipulator robot. Finally, we open source our generic and multithreaded implementation.

Passive Fuzzy Controller Design for the Parameter-Dependent Polynomial Fuzzy Model

This paper discusses a passive control issue for Nonlinear Time-Varying (NTV) systems subject to stability and attenuation performance. Based on the modeling approaches of Takagi-Sugeno (T-S) fuzzy model and Linear Parameter-Varying (LPV) model, a Parameter-Dependent Polynomial Fuzzy (PDPF) model is constructed to represent NTV systems. According to the Parallel Distributed Compensation (PDC) concept, a parameter-dependent polynomial fuzzy controller is built to achieve robust stability and passivity of the PDPF model. Furthermore, the passive theory is applied to achieve performance, constraining the disturbance effect on the PDPF systems. To develop the stability criteria, by introducing a parameter-dependent polynomial Lyapunov function, one can derive some stability conditions, which belong to the term of Sum-Of-Squares (SOS) form. Based on the Lyapunov function, two stability criteria are proposed to design the corresponding PDPF controller, such that the NTV system is robustly stable and passive. Finally, two examples are applied to demonstrate the effectiveness of the proposed stability criterion.

On-Chip Self-Sensing Piezoelectric Micro-Lens Actuator With Feedback Control

High-speed micro-lens actuators are required for fast auto-focusing in miniaturized cameras. The speed can be enhanced by adding damping at the resonance frequency through feedback control. Previous approaches to implement the feedback control were based on expensive off-chip bulky laser sensors that are not suitable for miniaturized cameras. In this paper, using an on-chip self-sensing piezoelectric sensor with a novel readout circuit, a passive resonant controller is designed, implemented, and tested. The stability of the closed-loop micro-lens actuator is guaranteed through the use of mixed negative-imaginary and passivity theory in the controller design. The performance of the controller with the on-chip self-sensing piezoelectric sensor and readout circuit is compared to that off-chip laser sensor, and results show comparable performance. The closed-loop micro-lens actuator with the on-chip piezoelectric sensor damps the fundamental resonance mode by 20.6 dB, which is similar to the 21.9 dB reduction obtained using the off-chip laser sensor. The settling time for the closed-loop actuator using the on-chip self-sensing piezoelectric sensor is less than 10 ms, which is also comparable to the 8 ms obtained with the off-chip laser sensor. The signal-to-noise ratios for the on-chip self-sensing piezoelectric sensor and off-chip laser sensor are 108 dB and 118 dB, respectively. These results show that the piezoelectric micro-lens actuator using the on-chip self-sensing piezoelectric sensor can replace the bulky and expensive off-chip laser sensor without sacrificing performance, making it more appealing for portable micro-optics devices.

Using an extended ICAP-based coding guide as a framework for the analysis of classroom observations

A coding guide based on the Interactive, Constructive, Active, Passive (ICAP) theory was developed and used to analyze the transcripts from filmed classroom observations. The analysis focused on the lesson tasks used by the 20 participating teachers to promote student cognitive engagement and the links between these tasks and student learning. The results showed that a) only 30% of the lesson tasks were assigned the Constructive and Interactive codes, and b) there were important teacher differences. About half of the teachers provided no or very few opportunities for Constructive or Interactive student cognitive engagement in their lessons.

Command smoothing-proxy sliding mode control of hydraulic servo system considering structural flexibility

In this study, a command smoothing-disturbance observer-based proxy sliding mode control (CS-DPSMC) method is proposed for a class of hydraulic servo systems with structural flexibility. First, to alleviate the influence of residual vibration due to structural flexibility, command smoothing method (CS) is used to modify the desired trajectory; Then, a nonlinear disturbance observer-based proxy sliding mode controller (DPSMC) is developed so as to make the hydraulic actuator track the desired trajectory. Besides, the control signal is continuous because the discontinuous sign function is theoretically canceled. Therefore, high-frequency unmodeled dynamics of flexible structures will not be excited. According to the passivity theory and Lyapunov theory, the stability of the control system is proven. The effectiveness of the proposed algorithm is verified by comparative numerical analysis.

Passivity-based adaptive robust super-twisting nonlinear control for electro-hydraulic system with uncertainties and disturbances

In this paper, a passive-based adaptive robust super-twisting nonlinear controller (PBARSNC) is proposed for high accuracy torque tracking control of the novel electro-hydraulic loading system with disturbances and uncertainties. The construction of the stability of this electro-hydraulic control system is given using passivity theory that results in a passivity-based controller (PBC). Considering parameter uncertainties and constant or slowly varying disturbances, adaptive law is adopted in the passivity-based controller. Furthermore, super-twisting second-order sliding mode control is used to reject modeling uncertainties and matched disturbances. Passivity theory, adaptive method and super-twisting algorithm are synthesized via the recursive design method. The proposed passive-based adaptive robust super-twisting nonlinear control can guarantee the torque tracking performance in the presence of various uncertainties, which is very important for high-accuracy tracking control of hydraulic servo systems. Extensive simulations are carried out to verify the high-accuracy tracking performance of the proposed control strategy.

A Novel Protection Method to Enhance the Grid-Connected Capability of DFIG based on Wind Turbines

This paper proposes a robust protection technology to enhance the grid-connected capability of the doubly fed induction generator (DFIG) based on wind turbines (WTs) under low voltage ride through (LVRT) conditions. The proposed method to control the rotor side converter (RSC) and grid side converter (GSC) uses proportional–integral (PI) controllers. The protection devices are the static compensator (STATCOM), crowbar, series dynamic resistor (SDR), and DC-chopper, with the proposed method to control STATCOM using proportional–integral (PI) controllers and the proposed method to control the rest of the protection devices based on the allowable threshold values of rotor current and DC-link voltage. The protection coordination strategy between them is proposed to avoid the disconnection between the rotor circuit and grid, maintain the DC-link at constant voltage, enhance the dynamic response of WT, and improve the voltage response at the point of common coupling (PCC) of WT. The DFIG-WT of 2 MW-575 V connecting to the 34-bus IEEE network is carried out to verify the effectiveness of the proposed method under the conditions of symmetrical and asymmetrical faults, and the LVRT requirements of the Spanish grid code are considered. The obtained simulation results using the PSCAD/EMTDC software show that the rotor current, DC-link voltage, voltage PCC, and power oscillation damping are significantly improved compared to not using it or applying the conventional method based on passivity theory. Therefore, the LVRT capability of the proposed DFIG-WT system is significantly enhanced, and it has enough ability to continue to provide electrical energy to the power network. Abbreviation DFIG, Doubly Fed Induction Generator; DVR, Dynamic Voltage Restorer; FACTS, Flexible AC Transmission System; FRT, Fault Ride Through; FS-WT, Fixed-Speed Wind Turbine; GSC, Grid Side Converter; LVRT, Low Voltage Ride Through; PCC, Point of Common Coupling; PI, Proportional–Integral; PMSG, Permanent Magnet Synchronous Generator; PWM, Pulse Width Modulated; RSC, Rotor Side Converter; SDR, Series Dynamic Resistor; STATCOM, Static Compensator; SVC, Static Var Compensator; UPFC, Unified Power Flow Controller; VS-WT, Variable-Speed Wind Turbine; SLG, Single Line-to-Ground; LL, Line-to-Line; LLG, Double Line-to-Ground; WT, Wind Turbine

Spectral Energy Model-Driven Inversion of XCO2 in IPDA Lidar Remote Sensing

Carbon observation satellites based on passive theory (e.g., OCO-2/3, GOSAT-1/2, and TanSat) have relatively high carbon dioxide column concentration (XCO2) accuracy when the observation conditions are met. Passive satellites have data bias and coverage deficiencies due to cloud cover, low albedo, low-light conditions, and aerosol scattering, resulting in carbon observation satellites based on passive theory that cannot meet the demand for high-precision, all-day, all-weather XCO2 monitoring. Active detection satellites are urgently needed to support global carbon sources, sinks, and carbon neutrality. China intends to launch a sensor satellite with active detection of XCO2 in the coming years. In this work, based on the satellite’s scaled-down airborne experiments, a spectral energy model was developed to optimize the conventional inversion algorithm and achieve a more accurate XCO2 inversion. The 1.572- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> integrated path differential absorption (IPDA) lidar column length is used indirectly to evaluate the accuracy of the spectral energy model for signal extraction. Also, the experimental results show that the accuracy of the signal extracted by the 1.572- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> IPDA lidar column length is 0.74 and 6.20 m at sea and on land based on the indirect evaluation of the length of the 1.572- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> IPDA lidar column length. The optimized XCO2 was evaluated (standard deviation as an evaluation metric) and its XCO2 standard deviation reduced by 31%, 63%, and 66% in the ocean, plains, and mountains, respectively. Our algorithm can obtain the XCO2 with a consistent trend by using XCO2 from the OCO-2 satellite as a reference. The calculated XCO2 is more accurate in areas dominated by anthropogenic factors (plains), due to the accuracy of the IPDA detection mechanism. This algorithm improves the accuracy and robustness of XCO2 inversion and has important reference significance for the IPDA lidar carried by China’s satellites to be launched in this year.