Buck Converter System Research Articles

Design and Stability Analysis of a Discrete-time Sliding Mode Control for a Synchronous DC-DC Buck Converter

This paper presents the design, analysis, and verification of a new scheme of digital sliding mode control (DSMC) for output voltage control of synchronous dc-dc buck converter to achieve fast transient response and high robustness under wide parameters variations. In this article, two different control laws are proposed for controlling the switches. First, a control law, without considering the disturbance item in the dynamic equation of the synchronous buck converter system, is obtained in the state space model and its stability analysis is presented. Then, in order to improve the dynamic performance of the buck converter, in the case of load and line changes, another control law, with considering the disturbance item is obtained and analyzed. In fact, we designed a control law that closed-loop system has strong robustness against matched or unmatched uncertainties as it reduced chattering, steady state error, overshoot and undershoot of output voltage. Its implementation only needs output error voltage measurement and doesn’t need current measurement. The simulation results are obtained using the MAT-LAB/SIMULINK software. Simulation results show that the proposed DSMC in the presence of a disturbances model is superior to proposed DSMC without disturbances consideration during immediate load and line voltage variations. In other words, it exhibits considerable reduction in terms of the overshoot and undershoot of output voltage response through an optimal control law during load changes. The proposed method almost overcomes the steady-state error and reduces the chattering to about 0.8%. Also, the overshoot and undershoot values are 4.8% and 3.9%, respectively.

Current Sharing Control for Parallel DC–DC Buck Converters Based on Finite-Time Control Technique

The problem of current sharing controller for parallel dc–dc buck converter system is investigated in this paper. Specifically, to achieve the goal of sharing control and improve the systems dynamic performance, a new finite-time current sharing control algorithm is designed and employed. Under the proposed control algorithm, rigorous proofs show that not only the output voltage of the converter system can reach the desired reference voltage in a finite time, but also the objective of current sharing can be achieved within almost the same time. In addition, when the external load is time-varying and unknown, a finite-time load estimator is given to handle the load variation, and an adaptive finite-time current sharing control algorithm is subsequently developed. Experimental results are presented to verify the effectiveness of the proposed method, and to show its advantages over some traditional control algorithms. It is shown that a faster convergence rate and a better load disturbance rejection performance can be yielded by the present algorithm. Finally, it is shown that the main results can be extended to the case of $n$ parallel dc–dc buck converters.

GPI observer‐based composite current‐constrained control approach for DC–DC buck converters

In this study, overcurrent protection technique is investigated for the voltage regulation problem of the DC–DC buck converter system with time-varying disturbances and uncertainties. Normally, fast dynamics during the start-up phase generates large transient current. The overlarge transient current may lead to risks of hardware damage. By selecting conservative control parameters, the current constrained performance can be realised. However, the transient performance and disturbance rejection ability are sacrificed. It is of significant importance to design a controller which keeps a good balance between dynamic performance and overcurrent protection. Moreover, the control accuracy is inevitable affected by the time-varying disturbances effects, including load variations, input voltage fluctuations and circuit parameter perturbations. In this paper, the control design is divided into two parts. Firstly, by inserting a dynamic penalty term into the state feedback controller, a baseline current-constrained scheme is developed. Rigorous stability analysis and current constraint performance are given under the presented baseline controller. Secondly, taking the time-varying disturbances into account, a novel GPI observer-based composite current-constrained controller can be developed by combining disturbance estimations and the baseline controller. Experimental results are provide to demonstrate the effectiveness of the presented control strategy.

A Simple Control Approach for Buck Converters With Current-Constrained Technique

The output voltage tracking problem with overcurrent protection for a pulse width modulation-based dc–dc buck converter is investigated in this brief. On the one hand, large transient current during the start-up phase is required for fast dynamics. On the other hand, overlarge transient current may lead to a risk of hardware damage. Conventionally, this problem is solved by choosing conservative control parameters, while the dynamic performance is sacrificed to a certain extent. Besides, the load uncertainty is inevitable in practical applications. Hence, a control design that keeps a good balance between dynamic performance, overcurrent protection, and robustness is desired. To this end, a novel and simple current-constrained controller is constructed. Both dynamic performance and current constraint are taken into account. The low complexity of the proposed current-constrained controller yields a higher reliability of dc–dc buck converter control system, and reduces cost of hardware. Moreover, it shows a nice property of robustness against load uncertainty. Control action is penalized by adjusting controller gains automatically when inductor current tends to the barrier bound. Rigorous stability analysis is given under the presented controller. Comparative simulation and experimental results between the proposed control scheme and the classic proportion–integration–differentiation control scheme on the buck converter system are illustrated to verify the feasibility and effectiveness of the proposed control scheme.

Overcurrent Protection Control Design for DC-DC Buck Converter With Disturbances

This paper deals with the output voltage regulation problem for dc-dc buck converters. Overcurrent protection and disturbances are both taken into consideration. The main challenge of control design is how to ensure that the current constraints are not violated at any time in the presence of disturbances. At first, a high-gain disturbance observer is utilized to estimate the disturbances. Then, a novel punishment mechanism for the inductor current is designed in the control scheme. Finally, based on the novel current-constrained technique and the high-gain disturbance observer, a composite control approach is proposed. The new control method not only guarantees the current within the required range but also has a nice ability on the disturbance rejection. In the meantime, rigorous stability proof is also presented. The theoretical analysis also explains how disturbances affect the satisfaction of the current constraints. The experimental results on a buck converter system are illustrated to verify the feasibility and effectiveness of the proposed control scheme.

Optimized Digital Controllers for Switching-Mode DC-DC Step-Down Converter

In this paper, a nonlinear least squares optimization method is employed to optimize the performance of pole-zero-cancellation (PZC)-based digital controllers applied to a switching converter. An extensively used step-down converter operating at 1000 kHz is considered as a plant. In the PZC technique, the adverse effect of the (unwanted) poles of the buck converter power stage is diminished by the complex or real zeros of the compensator. Various combinations of the placement of the compensator zeros and poles can be considered. The compensator zeros and poles are nominally/roughly placed while attempting to cancel the converter poles. Although PZC techniques exhibit satisfactory performance to some extent, there is still room for improvement of the controller performance by readjusting its poles and zeros. The (nominal) digital controller coefficients thus obtained through PZC techniques are retuned intelligently through a nonlinear least squares (NLS) method using the Levenberg-Marquardt (LM) algorithm to ameliorate the static and dynamic performance while minimizing the sum of squares of the error in a quicker way. Effects of nonlinear components such as delay, ADC/DAC quantization error, and so forth contained in the digital control loop on performance and loop stability are also investigated. In order to validate the effectiveness of the optimized PZC techniques and show their supremacy over the traditional PZC techniques and the ones optimized by genetic algorithms (GAs), simulation results based on a MATLAB/Simulink environment are provided. For experimental validation, rapid hardware-in-the-loop (HiL) implementation of the compensated buck converter system is also performed.

Continuous Finite‐Time Sliding Mode Control for Uncertain Nonlinear Systems with Applications to DC‐DC Buck Converters

AbstractThis paper investigates the continuous finite‐time control problem of high‐order uncertain nonlinear systems with mismatched disturbances through the terminal sliding mode control method. By constructing a novel dynamic terminal sliding manifold based on the disturbance estimations of high‐order sliding mode observers, a continuous finite‐time terminal sliding mode control method is developed to counteract mismatched disturbances. To avoid discontinuous control action, the switching terms of a dynamic terminal sliding manifold are designed to appear only in the derivative term of the control variable. To validate its effectiveness, the proposed control method is applied to a DC‐DC buck converter system. The experimental results show the proposed method exhibits better control performance than a chattering free controller, such as mismatched disturbances rejection and smaller steady‐state fluctuations.

Modified Elman Neural-PID Controller Design for DC-DC Buck Converter System Based on Dolphin Echolocation Optimization

This paper describes a new proposed structure of the Proportional Integral Derivative (PID) controller based on modified Elman neural network for the DC-DC buck converter system which is used in battery operation of the portable devices. The Dolphin Echolocation Optimization (DEO) algorithm is considered as a perfect on-line tuning technique therefore, it was used for tuning and obtaining the parameters of the modified Elman neural-PID controller to avoid the local minimum problem during learning the proposed controller. Simulation results show that the best weight parameters of the proposed controller, which are taken from the DEO, lead to find the best action and unsaturated state that will stabilize the Buck converter system performance and achieve the desired output. In addition, there is a minimization for the tracking voltage error to zero value of the Buck converter output, especially when changing a load resistance by 10%.

Modified Elman Neural-PID Controller Design for DC-DC Buck Converter System Based on Dolphin Echolocation Optimization

This paper describes a new proposed structure of the Proportional Integral Derivative (PID) controller based on modified Elman neural network for the DC-DC buck converter system which is used in battery operation of the portable devices. The Dolphin Echolocation Optimization (DEO) algorithm is considered as a perfect on-line tuning technique therefore, it was used for tuning and obtaining the parameters of the modified Elman neural-PID controller to avoid the local minimum problem during learning the proposed controller. Simulation results show that the best weight parameters of the proposed controller, which are taken from the DEO, lead to find the best action and unsaturated state that will stabilize the Buck converter system performance and achieve the desired output. In addition, there is a minimization for the tracking voltage error to zero value of the Buck converter output, especially when changing a load resistance by 10%.

Modified Elman Neural-PID Controller Design for DC-DC Buck Converter System Based on Dolphin Echolocation Optimization

This paper describes a new proposed structure of the Proportional Integral Derivative (PID) controller based on modified Elman neural network for the DC-DC buck converter system which is used in battery operation of the portable devices. The Dolphin Echolocation Optimization (DEO) algorithm is considered as a perfect on-line tuning technique therefore, it was used for tuning and obtaining the parameters of the modified Elman neural-PID controller to avoid the local minimum problem during learning the proposed controller. Simulation results show that the best weight parameters of the proposed controller, which are taken from the DEO, lead to find the best action and unsaturated state that will stabilize the Buck converter system performance and achieve the desired output. In addition, there is a minimization for the tracking voltage error to zero value of the Buck converter output, especially when changing a load resistance by 10%.

Simulasi dan Analisa Performansi Buck Converter Dengan Pengendali Dua Derajat Kebebasan

DC power supply are commonly used to convert DC voltage level to another level. One type of DC power supply is a buck converter that is used to lower a voltage level. In order to have a proper feedback of voltage output in buck converter system, it will be controlled by a Two Degrees of Freedom PID Controller. This research aim to analyze the performance of the buck converter that have a Two Degrees of Freedom PID Controller. Two Degrees of Freedom Controller has proportional, integral and derivative control parameters. The simulation of the system is made with the help of software MATLAB. The first simulation and analysis is buck converter system without controller. From the analysis, the desired criteria is obtained . Then a buck converter system was designed. It is controlled using a parallel type of Two Degrees of Freedom PID Controller as well as feedforward, feedback, and filter. From all these types of controllers, it showed that the first order of Proportional Differential Filter (PDF) feedforward type with the value of Kp = 171, Kd = 0.00545, Tf = 4.88e-07 and the first order of PDF feedback type with the value of Kp = 171, Kd = 0.00545, Tf = 4.88e-07 was considered as the proper controller that matched with the characteristic. Therefore, it could be concluded that the buck converter controlling system with Two Degrees of Freedom PID Controller could produce a buck converter system with a good performance compared to buck converter without any controllers. Keywords: Buck converter, Two Degrees of Freedom PID Controller, control system, time domain performance .

Robust Stability Analysis of a DC/DC Buck Converter Under Multiple Parametric Uncertainties

Stability studies are a crucial part of the design of power electronic systems, especially for safety critical applications. Standard methods can guarantee stability under nominal conditions but do not take into account the multiple uncertainties that are inherent in the physical system or in the system model. These uncertainties, if unaccounted for, may lead to highly optimistic or even erroneous stability margins. The structured singular value-based $\mu$ method justifiably takes into account all possible uncertainties in the system. However, the application of the $\mu$ method to power electronic systems with multiple uncertainties is not widely discussed in the literature. This paper presents practical approaches to applying the $\mu$ method in the robust stability analysis of such uncertain systems. Further, it reveals the significant impact of various types of parametric uncertainties on the reliability of stability assessments of power electronic systems. This is achieved by examining the robust stability margin of the dc/dc buck converter system, when it is subject to variations in system load, line resistance, operating temperature, and uncertainties in the system model. The $\mu$ predictions are supported by time-domain simulation and experimental results.

The Resistance Comparison Method Using Integral Controller for Photovoltaic Emulator

<span>A Photovoltaic (PV) emulator is a device that produces a similar output as the PV module and it is useful for testing the PV generation system. This paper present a new and simple control strategy for the PV emulator using the combination of the Resistance Comparison Method with the Integral Controller. The closed-loop buck converter system with the current-mode controlled and the single diode model are used for the PV emulator. The results obtained from the proposed PV emulator are compared with the conventional PV emulator using the Direct Referencing Method as the control strategy. The proposed PV emulator produces a more accurate output, 74 % faster transient response, and a lower output voltage ripple compared to the conventional PV emulator.</span>

A Bond Graph Approach for the Modeling and Simulation of a Buck Converter

This paper deals with the modeling of bond graph buck converter systems. The bond graph formalism, which represents a heterogeneous formalism for physical modeling, is used to design a sub-model of a power MOSFET and PiN diode switchers. These bond graph models are based on the device’s electrical elements. The application of these models to a bond graph buck converter permit us to obtain an invariant causal structure when the switch devices change state. This paper shows the usefulness of the bond graph device’s modeling to simulate an implicit bond graph buck converter.

Robust Output Voltage Regulation for DC–DC Buck Converters Under Load Variations via Sampled-Data Sensorless Control

The global robust output voltage regulation problem for dc–dc buck converter systems is investigated by means of designing a sampled-data almost disturbance decoupling (ADD) control methodology. Aiming to effectively restrain the output fluctuation caused by load variations, a physically realizable robust controller is proposed by employing a linear discrete-time observer to generate reliable state-reconstructed information under the conception of sensorless control. By virtue of output feedback domination approach, the proposed control strategy is able to achieve ADD, i.e., the output voltage interference can be arbitrarily attenuated in the $L_{2}$ gain sense. To ensure the theoretical rationality of the proposed approach, rigorous stability analysis for the hybrid closed-loop system is provided. Moreover, both simulation and experimental results demonstrate the effectiveness of the proposed controller, and the regulating principle and robustness analysis of involved parameter selection are studied. The direct-designed digital compensator will facilitate the practical implementation in power electronic systems.

A novel photovoltaic emulator based on current-resistor model using binary search computation

The Photovoltaic (PV) emulator is a nonlinear power supply that produces a similar Current-Voltage characteristic of the PV module. This equipment simplifies the testing phase when developing the PV generation system such as the Maximum Power Point Tracking (MPPT) converter and PV inverter. However, the conventional control strategy used in the PV emulator, the Direct Referencing Method, is highly dependable on the parameters of the power converter circuit and the Proportional-Integral (PI) controller. As a result, the output voltage oscillates and becomes inaccurate at certain load conditions. In this paper, a new control strategy based on the Current-Resistance (I-R) PV model combined with the Binary Search Method is introduced. The I-R PV model is derived based on the single diode model. The closed-loop buck converter system with the current-mode controlled and the PI controller are used in the PV emulator system. The load of the PV emulator consists of the resistive load and the MPPT converter. The results obtained from the proposed control strategy are compared with the conventional Direct Referencing Method. The results show the proposed control strategy produces a more reliable operating point, a higher accuracy, and a faster transient response compared to the conventional Direct Referencing Method.

Robust Double‐integral T‐S Fuzzy Output Regulation for Nonlinear Systems

AbstractThis paper proposes a robust double‐integral T‐S fuzzy output regulator design for affine nonlinear systems in the presence of parametric uncertainty and external disturbance. First, we adopt double integrators (an error integrator and an input integrator) to obtain an augmented T‐S fuzzy model representation which has a common input matrix of fuzzy rules. This property yields less stability conditions. Next, by introducing a set of virtual desired variables (VDVs), a double‐integral VDV‐based fuzzy regulator is proposed to cope with unknown bias and to achieve asymptotical output regulation. Afterward, the controller is simplified to avoid VDV calculation and enhance robustness to uncertainty and external disturbance. In contrast to traditional regulation design, the double‐integral non‐VDV fuzzy regulator design reduces the number of fuzzy controller rules and stability LMIs. Moreover, the error coordinate transformation is removed and the uncertainty is allowed in this paper. Finally, a DC/DC buck converter system is taken as the example to demonstrate the expected performance.

Finite‐time disturbance observer based non‐singular terminal sliding‐mode control for pulse width modulation based DC–DC buck converters with mismatched load disturbances

This study investigates a finite-time disturbance observer (FTDO) based non-singular terminal sliding-mode control (NTSMC) approach for pulse width modulation based DC–DC buck converters subject to matched/mismatched resistance load disturbances. Considering the mismatched resistance load disturbance which does not act in the same channel as the control input, a novel non-singular terminal sliding-mode manifold incorporating with a disturbance estimation technique is designed. A FTDO-based NTSMC method is introduced for DC–DC buck converter systems. A rigorous finite-time stability analysis is also presented. As compared with the nominal NTSMC and existed SMC+ extended stated observer (ESO) method, the proposed method obtains a better disturbance rejection ability no matter the disturbances satisfy the so-called matching condition or not. Simulation and experimental comparison results are implemented to verify the effectiveness of the proposed control method.

Design of a Prediction-Accuracy-Enhanced Continuous-Time MPC for Disturbed Systems via a Disturbance Observer

This paper addresses the prediction accuracy enhancement problem in the context of continuous-time model predictive control (MPC) by using a disturbance observer. The disturbance estimation is introduced in the output prediction to correct the errors caused by disturbances and uncertainties, which eventually leads to the desired offset-free tracking performance. Due to such a different design philosophy, the computational burden of the proposed method will be significantly reduced as compared with the existing offset-free MPCs for disturbed systems. Another promising feature of the proposed method lies in its nominal performance recovery property. The workability of the proposed method is validated by its application to a dc–dc buck converter system.

Multiphase Current-Controlled Buck Converter With Energy Recycling Output Impedance Correction Circuit (OICC)

This study is related to the improvement of the output impedance of a multiphase buck converter with peak current mode control (PCMC) by means of introducing an additional power path, which virtually increases the output capacitance during transients. Various solutions that can be employed to improve the dynamic behavior of the converter system exist, but nearly all solutions are developed for a single-phase buck converter with voltage mode control, while in the voltage regulation module applications, due to the high currents and dynamic specifications, the system is usually implemented as a multiphase buck converter with current mode control to ensure current sharing. The proposed circuit, output impedance correction circuit (OICC), is used to inject or extract a current n – 1 times larger than the output capacitor current, thus virtually increasing n times the value of the output capacitance during the transients. Furthermore, the OICC concept is extended to a multiphase buck converter system and the proposed solution is compared with the system that has n times bigger output capacitor in terms of dynamic behavior and static and dynamic efficiency. The OICC is implemented as a synchronous buck converter with PCMC, thus reducing its penalty on the system efficiency.