Output Voltage Tracking Research Articles

Operator-Based Triboelectric Nanogenerator Power Management and Output Voltage Control.

In this paper, an operator-based voltage control method for TENGs is investigated, achieving output voltage tracking without compensators and uncertainty suppression using robust right coprime factorization. Initially, a comprehensive simulation-capable circuit model for TENGs is developed, integrating their open-circuit voltage and variable capacitance characteristics. This model is implemented to simulate the behavior of TENGs with a rectifier bridge and capacitive load. To address the high-voltage, low-current pulsating nature of TENG outputs, a storage capacitor switching model is designed to effectively transfer the pulsating energy. This switching model is directly connected to a buck converter and operates under a unified control strategy. A complete TENG power management system was established based on this model, incorporating an operator theory-based control strategy. This strategy ensures steady output voltage under varying load conditions without using compensators, thereby reducing disturbances. Simulation results validate the feasibility of the proposed TENG system and the efficacy of the control strategy, providing a robust framework for optimizing TENG energy harvesting and management systems with significant potential for practical applications.

Design of a Switching Strategy for Output Voltage Tracking Control in a DC-DC Buck Power Converter

This work proposes the design of a commutation function to solve the output voltage trajectory tracking problem in the DC-DC Buck power electronic converter. Through a Lyapunov-type analysis, sufficient conditions are established, taking into account the discontinuous model, to ensure asymptotic convergence to the desired trajectories. Based on this analysis, a state-dependent switching function was designed to guarantee the closed-loop stability of the tracking error. To validate the control performance, circuit numerical simulations were carried out under abrupt disturbances in the source and load of the converter. The results demonstrate that the voltage tracking at the output of the converter is satisfactorily achieved.

Disturbance observer-based fixed time control for bidirectional DC-DC converter with input voltage and load uncertainty

The bidirectional DC-DC converter serves a vital role in the energy recovery system of new energy vehicles. However, external interference and parameter uncertainty can easily affect its dynamic performance. A disturbance observer-based fixed time control strategy for bidirectional DC-DC is proposed to address the impact of input voltage and load uncertainty on bidirectional converters. Firstly, the bidirectional converter model undergoes coordinate transformation, and disturbance observers are designed to compensate for input voltage and load disturbances. Secondly, based on the fixed time control theory, a fixed-time controller is devised for the bidirectional DC-DC converter to facilitate fast tracking and adjustment of output voltage without requiring measurement of input voltage and load current. Finally, simulation and experiment evaluations are conducted to assess the proposed scheme’s effectiveness in output voltage regulation.

A Compact and Efficient Boost Converter in a 28 nm CMOS with 90 mV Self-Startup and Maximum Output Voltage Tracking ZCS for Thermoelectric Energy Harvesting.

There are increasing demands for the Internet of Things (IoT), wearable electronics, and medical implants. Wearable devices provide various important daily applications by monitoring real-life human activities. They demand low-cost autonomous operation in a miniaturized form factor, which is challenging to realize using a rechargeable battery. One promising energy source is thermoelectric generators (TEGs), considered the only way to generate a small amount of electric power for the autonomous operation of wearable devices. In this work, we propose a compact and efficient converter system for energy harvesting from TEGs. The system consists of an 83.7% efficient boost converter and a 90 mV self-startup, sharing a single inductor. Innovated techniques are applied to adaptive maximum power point tracking (A-MPPT) and indirect zero current switching (I-ZCS) controllers for efficient operation. The startup circuit is realized using a gain-boosted tri-state buffer, which achieves 69.8% improved gain at the input VIN = 200 mV compared to the conventional approach. To extract the maximum power, we use an A-MPPT controller based on a simple capacitive divider, achieving 95.2% tracking efficiency. To address the challenge of realizing accurate voltage or current sensors, we propose an I-ZCS controller based on a new concept of maximum output voltage tracking (MOVT). The integrated circuit (IC) is fabricated using a 28 nm CMOS in a compact chip area of 0.03 mm2. The compact size, which has not been obtained with previous designs, is suitable for wearable device applications. Measured results show successful startup operation at an ultralow input, VIN = 90 mV. A peak conversion efficiency of 85.9% is achieved for the output of 1.07 mW.

Independent MPPT and voltage regulation of dual input DC - DC converter with a voltage multiplier cell

ABSTRACT A dual input boost DC–DC converter (DIBC) with combined voltage multiplier cell, the larger duty ratio (greater than 0.5), and the overlapping switching signal are required to obtain high voltage gain. This paper investigates the independent maximum power point tracking (MPPT) implementation on two solar photovoltaic (PV) energy sources along with the output voltage regulation of the DIBC during load and input voltage disturbances. For maximal power extraction, a single ended primary-inductance converter (SEPIC) is designed at each input, one with the perturb and observe (P and O) approach and the other with the incremental conductance algorithm. The small-signal transfer function model is used to design the voltage regulator. The MPPT algorithms for maximum power extraction as well as the inner current-loop and outer voltage-loop control approach have been implemented simultaneously. Duty ratio of the DIBC MOSFETs as a function of the converter output voltage and duty ratio of the SEPIC MOSFET as a function of MPPT are used to generate the switching signals. An experimental two 100W PV sources are developed using real-time solar simulator with the 200 W DIBC and controller is designed using XILINX SPARTAN-6 FPGA board. MATLAB simulation and experimental results ensure the active current sharing among the sources, reference output voltage (156.6 V) tracking, voltage regulation (below 5%) under different scenarios, and independent MPPT simultaneously.

Chatter-Free Non-Singular Fast Terminal Sliding Mode Control of Interleaved Boost Converter

In this brief, a global non-singular fast terminal sliding mode controller (NSFTSMC) is proposed to stabilize the output voltage of an interleaved boost converter which is affected by disturbances such as variations in supply voltage, load resistance, and system parameter uncertainties. First, the converter model is transformed into a simplified form to make the controller design process simple. Second, the two-time scale disturbance estimation technique is adopted to estimate the matched, unmatched disturbances, and un-modeled system dynamics. Then, a nonlinear controller based on the sliding mode algorithm is developed to achieve guaranteed large-signal stability. Unlike other controllers, the proposed one ensures global stability and features a fast dynamic response with accurate output voltage tracking ability over wide variations in operating range. Both simulations and experimentations verify the robustness and feasibility of the proposed controller.

Robust Non-Linear Controller Design for DC-DC Buck Converter via Modified Back-Stepping Methodology

This paper introduces two improved control algorithms for DC-DC converters. The first one is called “Non-Adaptive Modified Back-Stepping Control” (M-BSC) and the second one is called “Adaptive Modified Back-Stepping Control” (AM-BSC). Both the proposed control schemes allow one to increase the robustness to load and input voltage variations and make the DC-DC converter less sensitive to disturbances concerning the control algorithms available in the literature. The control aims to keep the output voltage at the desired value despite any changes that may occur during its operation. As a case study, the proposed control techniques have been applied to a DC-DC Buck converter. To validate the theoretical results and evaluate the performance of the proposed control algorithms, numerical simulations with four different scenarios have been analyzed: nominal operating conditions, load variations, output voltage tracking, and input voltage variations. The simulation results highlight the good performance of the proposed control algorithms compared to other classical algorithms, improving both the stationary error and the response time.

Design and analysis of robust backstepping controller for DC suppression of parallel UPS inverter system

AbstractHere, an improved control strategy is proposed, which adopts a non‐linear robust backstepping controller to eliminate DC circulating current in a parallel uninterruptible power supply (UPS) system. The traditional active and reactive power sharing control can ideally suppress the AC circulating current, but cannot effectively restrict the DC circulating current. Based on the traditional active power and reactive power sharing control (TAPRPSC) of the parallel UPS system, the proposed control strategy is used in each parallel inverter module to suppress the DC component disturbance in the inverter output voltage, which varies within a certain range. Hence the desirable steady‐state and dynamic performance of the system can be obtained. Moreover, the Lyapunov method is utilized to ensure the stability and robustness of the system. A parallel system of two UPS inverters with the proposed control strategy is built by Matlab/Simulink, and further experiments are carried out on the semi‐physical simulation platform of the Modelling Tech. Both the simulation and experimental results verify the effectiveness of the proposed control strategy for DC circulating current suppression and ideal output voltage tracking.

Design and Analysis of Zeta Converter for Power Factor Correction Using Cascade PSO-GSA-Tuned PI and Reduced-Order SMC

This paper presents the design and analysis of a single-phase power factor correction (PFC) scheme using a DC–DC Zeta converter operating in continuous conduction mode. The presented DC–DC converter exhibits non-linearity due to switching elements that degrades the performance of the converter. Therefore, this paper proposes a non-linear cascade control of particle swarm optimization-gravitational search algorithm (PSO-GSA) tuned proportional-integral (PI) and sliding mode controller (SMC) in outer and inner loop, respectively, to improve the performance of the converter. The robustness of the controller is analysed by applying the load and line variations to the converter. The simulation results showed that the steady state performance indices such as integral absolute error and integral square error, and transient performance indices like settling time and peak overshoot are significantly enhanced for the proposed cascade control scheme compared to the PSO and root locus method of tuning the outer PI with the inner SMC controller. The proposed control scheme gives better performance in terms of power factor improvement, percentage reduction in total harmonic distortion, and efficient tracking of output voltage for change in reference voltage compared to other techniques presented. Further, the performance of the proposed scheme is tested for battery charging application of the solar photovoltaic system. The demonstrated simulation results are validated by implementing the DC–DC Zeta converter in real-time hardware set-up.

Harmonic Voltage Control in Distributed Generation Systems Using Optimal Switching Vector Strategy

With increased penetration of renewable power and the nonlinear loads in the distributed generation (DG) systems, increased power quality concerns are exhibited in the active distribution networks, especially the challenges associated with the current and voltage harmonics in the system. Various conventional harmonic compensation techniques are developed for voltage-controlled DG inverters in past, majority involve either multiple proportional-integral (PI) or proportional-resonant (PR) controllers in eliminating grid current harmonics. The current-controlled inverters, on the other hand, are not preferred in industrial applications, accounting to their wide variations in the switching frequency. A novel and adaptive harmonic voltage control is developed here, for voltage-controlled DG inverters, which neither uses any PI regulators nor imposes stability issues associated with nonideal implementation of infinite gains of PR controllers. Interestingly, the developed control logic can be used for DG inverters, both in grid-connected and off-grid operational modes. Furthermore, this strategy allows a network operator to use this as an additional supplement that can be enabled/disabled as per the network requirement. The control logic exploits the property of an optimal-switching-vector controller, i.e., accurate output voltage tracking. Simulations results demonstrate the effectiveness of the controller, to suppress grid current harmonics and load voltage harmonics in grid-interfaced (GI) and off-grid modes, respectively, ultimately satisfying the mandatory IEEE standard-1547. Experimental results verify the viability of the controller for practical applications.

Improved Model Predictive Control for Three-Phase Dual-Active-Bridge Converters With a Hybrid Modulation

In this paper, an improved moving discretized control-set model predictive control (MDCS-MPC) with a hybrid modulation is proposed for 3p-DAB. The main objectives of this paper are to improve the efficiency in partial-load and to enhance dynamic performance for output voltage tracking. Firstly, the hybrid modulation, which consisted of triangular modulation, trapezoidal modulation as well as phase-shift modulation, can extend the soft-switching range and improve the efficiency for 3p-DAB, especially in light load conditions. Meanwhile, the closed-form of analytic expression of the hybrid modulation is derived and presented in the form of a simple table. Next, the designed hybrid modulation is incorporated into the proposed MDCS-MPC methodology to enhance the transition response for output voltage tracking. Furthermore, a proportional-integral observer is utilized to estimate the load current for the cost-saving of the current sensor. The main contribution of the proposed methodology relies on the fact that the dynamic response for output voltage tracking can be improved, the current stress can be reduced in light load, and the cost of the system can be saved. Finally, comparison experiments on a laboratory prototype are carried out to confirm the theoretical analysis and the performance improvement of the developed approach.

Dynamic prescribed performance sliding mode control for DC–DC buck converter system with mismatched time-varying disturbances

A generalized proportional integral observer (GPIO) based dynamic prescribed performance sliding mode control (DPPSMC) method for DC–DC buck converter with mismatched time-varying disturbance is proposed to achieve high output voltage tracking performance. Firstly, because extended state observer (ESO) could only estimate the constant interference, considering the mismatched time-varying interference, GPIO is designed to estimate the lumped disturbance so as to enhance the anti-disturbance performance. Then, for the sake of further improve the transient performance, the prescribed performance algorithm is introduced. However, the traditional prescribed performance adopts static performance function. The dynamic system tracking error is likely to exceed the boundaries set by performance functions due to external disturbance and uncertainty, leading to the failure of the algorithm. On account of this, a dynamic prescribed performance function (PPF) is put forward in this paper to keep the tracking error of the converter system always within the predefined error boundary and the algorithm failure problem is avoided. Finally, combined with disturbance estimation technology and dynamic PPF, DPPSMC method is designed to dispose mismatched time-varying interference and improve the transient performance. The Lyapunov stability theorem is applied to certify that the proposed control algorithm could stabilize the closed-loop system. Simulation and experimental result verify the meliority of the designed controller.

Single-phase Boost-type Active Tracking AC-AC Voltage Regulator with an Improved Hybrid Control Technique

This paper presents a switch-mode single-phase boost-type AC-AC voltage regulator. The topology of the regulator needs only reduced numbers of components. Unlike the similar studies in the literature, a new hybrid control technique with a closed-loop PID controller and a novel developed feedforward controller is applied to the regulator that enhances the active tracking of the reference output voltage to obtain a higher quality of the sine-wave output voltage, when the input AC voltage is an ideal pure sine or including different harmonics levels. The proposed regulator with the proposed control technique is tested both by simulation and experimentally. The experimental set-up for the regulator is designed for 0.75 kW output power, 0-100 Vp input voltage (50 Hz), and 0-200 Vp output voltage. The results have shown that the proposed switch-mode boost type regulator is capable of obtaining the desired AC voltage with harmonics lower than 5% THD (total harmonic distortion) for different input/output parameters and different load conditions.

Islanded microgrids with output distributed delay: Sampled-data based observer design

In this paper, two majors islanded microgrid issues are addressed: i) the voltage amplitude and frequency control and ii) the time delay introduced by the use of communication networks leading to instability. The studied system is composed of a distributed generator (DG), a voltage source inverter (VSI), an LC filter and local loads. After the system modeling, a voltage controller by means of the backstepping method is proposed. Then, the distributed time delay that comes in the VSI output current is dealt with supposing that it is the only measured signal and the measurements are available only in sampling periods. Two observers are designed to give online estimation of the state signals; the first one involves an intersample predictor and the second one uses a ZOH predictor. The predictors compensate the time delay and the sampling effects. The observers are designed on the base of the high gain principle to deal with the system nonlinearity. From simulations and formal analysis, the following results are assumed: the output voltage tracks its reference and it remains stable, the online estimated signals, given by both observers, converge exponentially to their real values with large time delay and sampling interval. It is worth noting that it is the first time that distributed time delay in islanded microgrids is addressed.

Analysis, control, and modeling of the three‐port converter without port voltage constraint for photovoltaic/battery system application

AbstractFor a photovoltaic (PV)/battery power system consisting of PV module, energy storage system, and local load, using a three‐port converter (TPC) instead of several single‐input converters is more desirable, such as simpler circuit, higher efficiency, lower cost, and centralized control without communication circuit. In this paper, a TPC is proposed and analyzed, which includes operating modes, steady‐state performance, and parameter design. Compared with other converters, the proposed TPC has a low cost, compact structure, and a more flexible voltage relationship among all ports. Moreover, energy management and control methods are further proposed for PV/battery systems based on the proposed converter, which can achieve maximum power point tracking (MPPT) of PV module and constant output voltage. In order to design the control loop and realize multivariable optimal control, a small‐signal model of the converter is obtained in each operation mode. Then a detailed decoupling design approach based on a small‐signal model is provided to allow a separate controller design for the proposed converter. Finally, the validity of the proposed converter and its energy management and control method are verified by experimental results.

Output-Voltage-Tracking Control for Buck Converters Using Variable Convergence Rate Mechanism Without Current Feedback

This article aims to accomplish the output voltage tracking task for buck converters without current feedback, diminishing the performance degradation from model-plant mismatches and load variations. The following contributions overcome these difficulties: a) the combination of Luenberger and disturbance observer (DOB) techniques for a parameter-independent voltage-derivative observer; b) the pole-zero cancellation control incorporating the DOB and active-damping injection techniques; and c) the exponential convergence guarantee to the target tracking system subject to the variable convergence rate mechanism. Convincing experimental evidence confirms the effectiveness of proposed tracking control using a prototype 3 kW buck converter control system.

Adaptive controllers for grid-connected DC microgrids

Droop technique is extensively adopted in dc microgrids, for both islanded and grid-connected modes of operation. However, voltage regulation and proper current sharing are considered as the major challenges in droop techniques. Moreover, changes in system parameters and wide load demand variations degrade the operational performance and the efficiency of the dc microgrid. In this paper, a finite-state-machine (FSM) based controller for the inner loop of microgrid converters is utilized. Although the FSM controller operates in voltage mode and requires no current sensors, the dynamic performance of the microgrid converters is limited. Thus, a distributed consensus output voltage tracking based on the performance recovery controller is presented which adopts nonlinear observers for the microgrid converters to account for model uncertainties and disturbances due to parameters variations. The dynamic performance and robustness of the FSM controller and performance recovery controller are assessed using PSCAD/EMTDC simulation. Moreover, a comparative study with the classical Proportional-Integral (PI) controller is presented, considering both rating-based and cost-based current sharing schemes of the dc microgrids.

A novel effective nonlinear state observer based robust nonlinear sliding mode controller for a 6 kW Proton Exchange Membrane Fuel Cell voltage regulation

This paper presents an effective strategy for controlling an Interleaved DC/DC Boost Converter (IBC) that is employed for reducing the current fluctuations in a 6 kW Proton Exchange Membrane Fuel Cell (PEMFC). The proposed design incorporates a new nonlinear control law combined with a nonlinear state observer, it aims at enhancing the durability of the Fuel Cells (FCs) and extending their lifetime. In this regard, a Nonlinear State Observer (NSO) is designed to simultaneously estimate current and voltage signals of the Fuel Cell Source (FCS) and a Nonlinear Sliding Mode Controller (NSMC) is constructed based on these estimates. The proposed sensorless control design is advantageous in avoiding current and voltage sensors redundancy to maintain low cost and complexity levels. Accurate output voltage tracking performance, tracking stability, and dynamic errors for a PEMFC-IBC are considered during changes of the internal model parameters in addition to effects of measurement uncertainties. A third advantage of this design is robustness and external disturbance rejection under large load variations. For these objectives, the observer and the controller parameters are optimally tuned using a recent Metaheuristic Particle Swarm Optimization Algorithm (MPSOA) inspired by the swarm intelligence for improving the dynamic performance of the controlled system. Furthermore, stability and tracking analysis properties of the closed-loop overall system are proved through Lyapunov theory for dynamic operating conditions. Finally, numerical simulations of a typical 6 kW PEMFC system validate the effectiveness of the proposed scheme with comparisons to contemporary approaches across the different cases.

The Power State Estimation Method for High Energy Ternary Lithium-ion Batteries Based on the Online Collaborative Equivalent Modeling and Adaptive Correction - Unscented Kalman Filter

Accurate power state estimation plays an important role in the real-time working state monitoring and safety control of high energy lithium-ion batteries. To solve the difficulty and low accuracy problems in its real-time power state estimation under various operating conditions, the working characteristics of the lithium cobalt oxide batteries are analyzed comprehensively under various operating conditions. An improved collaborative equivalent model is established to characterize its working characteristics and then the initial power state value is calibrated by using the experimental relationship between open circuit voltage and state of charge considering the importance of the precious estimation accuracy for the later iterate calculation and correction. And then, an adaptive correction - Unscented Kalman Filter algorithm is put forward and applied for the state of charge estimation and output voltage tracking so as to realize the real-time high-precision lithium-ion battery power state estimation. The experimental results show that the established model can predict the power state of high energy lithium-ion batteries conveniently with high convergency speed within 30 seconds, accurate output voltage tracking effect within 32 mV and high accuracy, the max estimation error of which is 3.87%, providing an effective working state monitoring and safety protection method in the cleaner production and power supply processes of the high energy lithium-ion batteries.

Time bound online uncertainty estimation based adaptive control design for DC–DC buck converters with experimental validation

In this paper, an adaptive controller is proposed for DC–DC buck converters featuring prescribed time bound estimation of unknown system uncertainties and exogenous disturbances followed by nominal output performance recovery. The objective of the proposed control is to attain a robust output voltage tracking in buck converter in presence of parametric, non-parametric, matched and mismatched perturbations across wide operating range. Different from neural network estimators and characterizing substantially low computational complexity, an online estimator is presented to reconstruct the incurred uncertainty. The estimated additive uncertainty is thereafter fed to the nominal backstepping controller for subsequent compensation in finite time. Exact recovery of nominal output voltage tracking is claimed in a piecewise sense owing to the accuracy and precise estimation of the unknown unparametrized lumped uncertainty manifested in the form of large sudden variations in load and input voltage. Rigorous performance and stability analysis of the online estimator, along with similar analysis of the overall tracking control system are undertaken. Extensive numerical study is carried out to investigate the performance of the proposed control scheme. Further, experimentation of the proposed controller on a dc–dc buck converter using control desk DS1103 with an embedded TMS320F240 processor has been performed. The obtained experimental results demonstrate a good agreement with the simulation findings.