Search Results (25)

In microgrids, battery chargers/dischargers are used to manage power flow between the battery and the DC bus and to regulate the DC bus voltage, ensuring safe operating conditions for sources and loads. These actions contribute to enhancing the sustainability of the microgrid by improving energy efficiency, extending battery life, and ensuring reliable operation. The classical converter adopted to implement the battery chargers/dischargers is the boost converter, which avoids high current harmonic injection into the battery because of its continuous input current. But due to the discontinuous output current, it introduces high current harmonics into the DC bus. This also occurs in Sepic, Zeta, or other DC/DC converters with discontinuous input or output currents. One exception is the Cuk converter, which has both continuous input and output currents. However, in the Cuk converter, the intermediate capacitor voltage is higher than the input and output voltages, thus imposing high stress on the semiconductors and requiring a costly capacitor with high energy storage. Therefore, this paper proposes the design of a battery charger/discharger based on a non-electrolytic capacitor boost converter. This topology provides continuous input and output currents, which reduces harmonic component injection, extends battery life, and increases operation efficiency. Moreover, it requires a lower intermediate capacitor voltage, thereby enhancing reliability. The design of this battery charger/discharger requires an adaptive sliding-mode controller to ensure global stability and accurate bus voltage regulation. A formal stability analysis and design equations are provided. The proposed solution is validated through detailed simulations, while the adaptive sliding-mode controller is specifically tested using a detailed software-in-the-loop approach. Full article

A fast terminal sliding mode control based on a fixed-time sliding surface is proposed for a permanent magnet arc motor (PMAM), effectively improving speed response, control accuracy, and disturbance rejection capability. Due to its piecewise structure and advanced logarithmic characteristics, a PMAM is subject to high-frequency disturbances. Additionally, it is also influenced by external disturbances. To address this, a sliding mode reaching law that combines terminal terms, linear terms, and switching terms is designed to reduce chattering and enhance robustness. Furthermore, to improve the convergence speed of the sliding mode and disturbance rejection ability, a novel fixed-time converging sliding surface based on a variable exponent terminal term is introduced. Numerical simulations verify the convergence and disturbance rejection capabilities of the proposed sliding surface. Stability based on the Lyapunov theorem is strictly proven. Experimental results validate the effectiveness and superiority of the proposed algorithm. Full article

Grid-forming (GFM) converters play a vital role in future power systems due to their ability to independently establish voltage and frequency. However, their interaction with AC circuits may give rise to synchronous oscillations, which pose a threat to system stability and dynamic performance. This paper investigates the issue of synchronous oscillations and proposes an ultra-local model predictive control strategy for their suppression. First, a small-signal power dynamic model is developed to analyze the mechanism behind these oscillations. It is revealed that this problem is related to the electromagnetic dynamics of power transfer and is strongly influenced by the line impedance characteristics. Then, a predictive control framework is formulated, which incorporates oscillation suppression into the control objective and enables the real-time optimization of the active power reference. To avoid reliance on detailed system models, an ultra-local modeling approach is introduced. In this framework, a fixed-time sliding mode observer is employed to estimate the system power dynamics in real time, enabling the prediction of future states without requiring grid-side parameters and facilitating the design of a model-free controller. Simulation results verify that the proposed method effectively mitigates synchronous oscillations while significantly enhancing system stability and robustness. Full article

This paper presents the development of a Three-phase Universal Programmable Electronic Load (UPEL) programmed as an unbalanced and distorted current source, highlighting its innovative control strategy and modulation approach. The core contribution is the implementation of Adaptive Sliding Pulse Width Modulation (ASPWM), a novel technique that combines Sliding Mode Control (SMC) with an Adaptive Hysteresis Band (AHB). This methodology eliminates the need for conventional Pulse Width Modulation (PWM), hybrid PI controllers, or cascade control structures, achieving superior robustness, faster response times, and a fixed switching frequency. The proposed ASPWM enhances energy quality by enabling precise control of active and reactive power, harmonic injection, and operation across multiple modes, including AC/DC rectification and DC/AC inversion. Simulation and experimental results validate the effectiveness of ASPWM in improving performance metrics, ensuring operational stability, and demonstrating adaptability for diverse scenarios. This study establishes ASPWM as a transformative control technique for advanced power electronics applications. Full article

Photovoltaic (PV) energy is gaining traction due to its direct conversion of sunlight to electricity without harming the environment. It is simple to install, adaptable in size, and has low operational costs. The power output of PV modules varies with solar radiation and cell temperature. To optimize system efficiency, it is crucial to track the PV array’s maximum power point. This paper presents a novel fixed-point FPGA design of a nonlinear maximum power point tracking (MPPT) controller based on synergetic control theory for driving autonomously standalone photovoltaic systems. The proposed solution addresses the chattering issue associated with the sliding mode controller by introducing a new strategy that generates a continuous control law rather than a switching term. Because it requires a lower sample rate when switching to the invariant manifold, its controlled switching frequency makes it better suited for digital applications. The suggested algorithm is first emulated to evaluate its performance, robustness, and efficacy under a standard benchmarked MPPT efficiency (${\eta }_{MPPT}$) calculation regime. FPGA has been used for its capability to handle high-speed control tasks more efficiently than traditional micro-controller-based systems. The high-speed response is critical for applications where rapid adaptation to changing conditions, such as fluctuating solar irradiance and temperature levels, is necessary. To validate the effectiveness of the implemented synergetic controller, the system responses under variant meteorological conditions have been analyzed. The results reveal that the synergetic control algorithm provides smooth and precise MPPT. Full article

An adaptive sliding mode controller (SMC) design with a reinforcement-learning parameter optimization method is proposed for variable-speed trajectory tracking control of underactuated vessels under scenarios involving model uncertainties and external environmental disturbances. First, considering the flexible control requirements of the vessel’s propulsion system, the desired navigation speed is designed to satisfy an S-curve acceleration and deceleration process. The rate of change of the trajectory parameters is derived. Second, to address the model uncertainties and external disturbances, an extended state observer (ESO) is designed to estimate the unknown bounded disturbances and to provide feedforward compensation. Moreover, an adaptive law is designed to estimate the upper bound of the unknown disturbances, ensuring system stability even in the presence of asymptotic observation errors. Finally, the Twin-Delayed Deep Deterministic Policy Gradient (TD3) algorithm is employed for real-time controller parameter tuning. Numerical simulation results demonstrate that the proposed method significantly improves the trajectory tracking accuracy and dynamic response speed of the underactuated vessel. Specifically, for a sinusoidal trajectory with an amplitude of 200 m and a frequency of 0.01, numerical results show that the proposed method achieves convergence of the longitudinal tracking error to zero, while the lateral tracking error remains stable within 1 m. For the circular trajectory with a radius of 300 m, the numerical results indicate that both the longitudinal and lateral tracking errors are stabilized within 1 m. Compared with the fixed-value sliding mode controller, the proposed method demonstrates superior trajectory tracking accuracy and smoother control performance. Full article

In recent years, there have been many studies focused on improving the performance of active materials; however, applying these materials to active machines still presents significant challenges. In this study, we introduce a light-powered self-translation system for an asymmetric friction slider using a liquid crystal elastomer (LCE) string oscillator. The self-translation system was composed of a hollow slide, two LCE fibers, and a mass ball. Through the evolution of photothermal-induced contraction, we derived the governing equations for the system. Numerical simulations revealed two distinct motion modes: the static mode and the self-translation mode. As the mass ball moved, the LCE fibers alternated between illuminated and non-illuminated states, allowing them to effectively harvest light energy to compensate for the energy dissipation within the system. Unlike traditional self-oscillating systems that oscillate around a fixed position, the asymmetric friction enabled the slider to advance continuously through the oscillator’s symmetric self-sustained oscillation. Furthermore, we explored the critical conditions necessary for initiating self-translation as well as key system parameters that influence the frequency and amplitude of the oscillator and average speed of the slider. This self-translation system, with its simple design and ease of control, holds promising potential for applications in various fields including soft robotics, energy harvesting, and active machinery. Full article

During the loading process, significant external position disturbances occur in the electro–hydraulic load simulation system. To address these position disturbances and effectively mitigate the impact of uncertainty on system performance, this paper first treats model parameter uncertainty and external disturbances as lumped disturbances. The various states of the servo valve and the pressures within the hydraulic cylinder chambers are then examined. Building on this foundation, the paper proposes a nonlinear multi-mode variable structure independent load port electro–hydraulic load simulation system that is tailored for specific loading conditions. Secondly, in light of the significant motion disturbances present, this paper proposes an integral sliding mode active disturbance rejection composite control strategy that is based on fixed-time convergence. Based on the structure of the active disturbance rejection control framework, the fixed-time integral sliding mode and active disturbance rejection control algorithms are integrated. An extended state observer is designed to accurately estimate the lumped disturbance, effectively compensating for it to achieve precise loading of the independent load port electro–hydraulic load simulation system. The stability of the designed controller is also demonstrated. The results of the simulation research indicate that when the command input is a step signal, the pressure control accuracy under the composite control strategy is 99.94%, 99.86%, and 99.76% for disturbance frequencies of 1 Hz, 3 Hz, and 5 Hz, respectively. Conversely, when the command input is a sinusoidal signal, the pressure control accuracy remains high, measuring 99.94%, 99.8%, and 99.6% under the same disturbance frequencies. Furthermore, the simulation demonstrates that the influence of sensor random noise on the system remains within acceptable limits, highlighting the effective filtering capabilities of the extended state observer. This research establishes a solid foundation for the collaborative control of load ports and the engineering application of the independent load port electro–hydraulic load simulation system. Full article

Aiming at the problems of speed overshoot, slow convergence and poor anti-interference in the control of permanent-magnet synchronous motors (PMSMs) without a position sensor, a pulse vibration high-frequency signal injection method for a permanent-magnet synchronous motor with an improved sliding mode control was designed. Firstly, the improved approach rate function is combined with the improved non-singular fast terminal sliding mode surface to design the non-singular fast terminal sliding mode controller (NFTSMC), which is used in the speed loop to improve the speed convergence ability and reduce its overshoot. Secondly, in order to eliminate the influence of the band-pass filter on the system bandwidth in the traditional high-frequency injection method, a pulse vibration high-frequency signal injection method that injects high-frequency voltage signals and synchronous current signals into the $\widehat{d}$ axis of the estimated two-phase rotation coordinate system $\widehat{d}\widehat{q}$ and the $\alpha \beta$ axis of the two-phase stationary coordinate system $\alpha \beta$ was designed to estimate the motor position and speed to achieve sensorless control. Finally, the above control strategy was compared with the speed loop PI and the traditional sliding mode controller (SMC) of the speed loop, respectively. The simulation and experimental results show that whether it is a no-load variable speed or fixed speed loading, the above control strategy can effectively reduce the speed overshoot, accelerate the speed convergence and improve the load capacity of the system. Full article

A zero-ripple input current is known to improve the lifetime of battery sets and fuel cells and to assure maximum power point tracking in PV panels. To perform current ripple elimination in a floating interleaved boost converter (FIBC), one of the typical linear inductors is substituted by a variable inductor, and phases of the converter have complementary duty cycles. This variable inductor is controlled using a switched current-source converter, which adjusts the input current ripple. An equivalent model for the variable inductor is presented, including uncertainties in the component description. To achieve current stabilization, a variable inductor controller was designed using the sliding modes approach via fixed frequency. An experimental prototype is implemented and tested with an output voltage controller to compare with the conventional FIBC. The results demonstrate that the input current ripple of the proposed converter is eliminated without significantly decreasing the efficiency. Full article

The main challenges of the input current control in synchronous DC-DC buck converters are the nonlinear model of the system, changes of the operating point in a wide range, and the need to use an input LC filter for current smoothing, which may result in the instability of the closed-loop system. In this paper, a step-by-step approach is developed for the design and improvement of a PI-feedforward closed-loop controller. It is shown that a linear PI controller cannot stabilize the closed-loop system properly during wide changes in model parameters, e.g., an equivalent series resistance of the input filter. To cope with the stability issues, a fixed-frequency sliding mode controller (SMC) has been developed in this paper for the implementation of an electro-mechanical actuator (EMA) emulator. Moreover, a systematic approach is proposed for controller tuning and the selection of the SMC’s gains. To achieve high power efficiency, high-frequency GaN switches are used for the practical implementation of the DC-DC converter. Despite large changes in the load current, the designed nonlinear controller can track the input current reference satisfactorily. Steady-state and dynamic responses of the proposed SMC are compared with conventional linear controllers. Considering the Lyapunov stability theorem, it is proved that the designed SMC can stabilize the closed-loop system in the entire utilizable domain. The proposed nonlinear SMC controller enjoys a very simple control law. Hence, despite having very high switching and sampling frequencies, it can be easily implemented. The experimental response of the designed synchronous DC-DC buck converter is evaluated experimentally by implementing the control strategy in a TMS320F28335PGFA DSP from Texas Instrument. Moreover, the comprehensive comparison of the proposed SMC controller and a PI-feedforward controller proved the superior performance of the developed closed-loop system, in terms of the transient time response, robustness, and stability of the EMA emulator. Full article

Resonant frequency tracking control of electromagnetic acoustic transducers (EMATs) remains a challenge in terms of drifting working frequency and reduced conversion efficiency caused by working environment changes. This paper presents a fixed-time nonsingular integral terminal sliding mode (FT-NITSM) control strategy for resonant frequency tracking of EMATs to realize precise and high robustness resonant frequency tracking performance. Specifically, a FT-NITSM control method with fast convergence feature is developed and a resonant frequency tracking controller for EMATs is further designed to improve the convergence speed and tracking accuracy. Fixed time stability of the proposed frequency tracking control system is proved through Lyapunov function analysis. Moreover, numerical simulations demonstrate that the FT-NITSM control strategy can ensure precise tracking of the system’s operating frequency to its natural resonant frequency in less than 3 s with a tracking error of less than 0.01 × 10⁴ Hz. With the maximum overshoot variation between −20 and 20 and error range in −5 and 5° at the steady state, the FT-NITSM control strategy can ensure the control system impedance angle $\theta$ being consistent and eventually bounded. This study provides a toolbox for the resonant frequency tracking control and performance improvement of EMATs. Full article

Conventional predictive control for permanent magnet synchronous motors (PMSMs) contains dual speed and current loops, and has a complex structure and multiple parameters to be tuned. Conventional predictive direct speed control (PDSC) exhibits an unsatisfactory steady-state performance. To tackle these issues, this paper presents a cascade-free modulated PDSC (MPDSC) scheme for PMSM drives. First, a speed predictive model is built, where a second-order sliding mode observer is employed to quickly and robustly estimate the load torque. Then, a dual objective cost function with speed and stator current tracking is designed, which improves the system’s steady-state performance. Furthermore, the analytical solution of the constrained optimal voltage vector is derived and it is synthesized by space vector modulation, resulting in a fixed switching frequency. Experimental results show that the proposed MPDSC has stronger robustness, and lower torque ripples and stator current harmonics compared to conventional PDSC. Full article

Due to the unknown disturbance caused by the harsh environment in deep water, the stability of Underwater Tracked Remotely Opreated Vehicle (UTROV) trajectory tracking control is affected; especially the resistance forces of random vibrations caused by non-differentiable random disturbance resistance, which has become one of the main problems in controller design. Considering engineering practice, a stochastic model and new dynamic damping-based terminal sliding mode event-triggered fault-tolerant controller were designed in this paper. Firstly, based on the random resistance pre-compensation theory for the first time, a stochastic model was designed for differential drive UTROV. Meanwhile, a new nonsingular terminal sliding mode and dynamic damping reaching law were designed to achieve global finite-time convergence and reduce chattering with better robust response speed. Furthermore, to deal with the wear and tear caused by actuator failure and fixed sampling rate transmission, a new dynamic event trigger mechanism was designed and the faults analyzed. On this basis, combined with the finite-time adaptive on-line estimation technology, it can not only better reduce the transmission frequency, but also the finite-time dynamic active fault-tolerant compensation. The control scheme has semi-globally finite-time stability in probability and is proved by theory, which is compliant with engineering requirements. Then, according to characteristics of innovation, the three groups of simulation of control methods are designed to compare the methods in this paper. Finally the advantages of the method are verified by simulation to achieve the design expectations. Full article

This paper considers the reference signal generation problem for the multi-functional operation of single-phase dynamic voltage restorers. For this purpose, a single-phase quasi type-1 phase-locked loop (QT1-PLL) is proposed. The pre-loop filter part of this PLL is composed of a frequency-fixed delayed signal cancellation method and a two-stage all-pass filter. Thanks to the frequency-fixed nature, the pre-loop filter is easy to implement and can provide rejection of any measurement offset. Moreover, this PLL benefits from the excellent harmonic robustness property of the conventional QT1-PLL. Small-signal modeling and gain tuning procedures are detailed in this paper. In order to track the reference voltage signals generated by the proposed PLL, a super-twisting sliding mode controller is also presented, which helps to achieve fast dynamic responses. Laboratory-scale prototype-based experimental studies were conducted to validate the developed reference generator and the controller. Experimental results show that the proposed method is fast in detecting and compensating any grid voltage anomalies to maintain constant load voltage despite voltage sag, swell, and harmonic distortions. Full article