Sliding mode control of boost and buck-boost power converters using method of stable system centre

Nonminimum phase tracking control is studied for boost and buck-boost power converters. The sliding mode controller is designed to track directly a causal voltage tracking profile given by an exogenous system. The nonminimum phase output tracking problem is reduced to a state tracking problem. Bounded state tracking profiles are generated by equations of stable system centre. Numerical examples demonstrate the effectiveness of the sliding mode control design.     

Galerkin‐based sliding mode tracking control of non‐minimum phase DC‐to‐DC power converters

Output voltage control of nonlinear DC‐to‐DC power converters is handicapped by the non‐minimum phase character exhibited by these systems. The problem has been usually solved with indirect control strategies that work through the input current. In this article, we report a robust control methodology that uses Galerkin‐based sliding manifolds, which use full state reference profiles and an estimate of the disturbed load parameter. The sliding surface incorporates a first‐order Galerkin approximation of the input current that provides robustness to piecewise constant load perturbations by dynamic compensation: it allows on‐line accommodation to the action of the load estimator. This results in high‐accuracy tracking of periodic references at the output resistance of boost and buck‐boost converters. Copyright © 2006 John Wiley & Sons, Ltd.     

An Adaptive Passivity‐Based Controller of a Buck‐Boost Converter with a Constant Power Load

This paper addresses the problem of regulating the output voltage of a DC‐DC buck‐boost converter feeding a constant power load, which is a problem of current practical interest. Designing a stabilising controller is theoretically challenging because its average model is a bilinear second order system that, due to the presence of the constant power load, is non‐minimum phase with respect to both states. Moreover, to design a high‐performance controller, the knowledge of the extracted load power, which is difficult to measure in industrial applications, is required. In this paper, an adaptive interconnection and damping assignment passivity‐based control—that incorporates the immersion and invariance parameter estimator for the load power—is proposed to solve the problem. Some detailed simulations are provided to validate the transient behaviour of the proposed controller and compare it with the performance of a classical PD scheme.     

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

This 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.     

Robust flat filtering DSP based control of the boost converter

The article deals with the design and implementation of a flat filter tracking digital controller for a boost dc-dc power converter. A highly perturbed switched boost converter circuit is shown to be efficiently controlled, in a trajectory tracking task for its non-minimum phase output, by means of a suitable linear filter, here addressed as a flat filter. Flat filtering is a natural robust version of generalized proportional integral control (GPIC) by which the effects of arbitrary time varying exogenous disturbances, unknown endogenous nonlinearities and un-modeled dynamics can be jointly attenuated in a conceptually similar fashion to observer-based active disturbance rejection control (ADRC) and algebraic identification based model free control (MFC) but: a) without using extended state observers and b) respecting the original system order in a time-varying simplified model while avoiding algebraic estimation techniques. The proposed control technique based on the TMS320F28335 digital signal processor chip is tested by means of realistic simulations and experimental setup.     

Closed-loop analysis and control of a non-inverting buck–boost converter

In this article, a cascade controller is designed and analysed for a non-inverting buck–boost converter. The fast inner current loop uses sliding mode control. The slow outer voltage loop uses the proportional–integral (PI) control. Stability analysis and selection of PI gains are based on the nonlinear closed-loop error dynamics incorporating both the inner and outer loop controllers. The closed-loop system is proven to have a nonminimum phase structure. The voltage transient due to step changes of input voltage or resistance is predictable. The operating range of the reference voltage is discussed. The controller is validated by a simulation circuit. The simulation results show that the reference output voltage is well-tracked under system uncertainties or disturbances, confirming the validity of the proposed controller.     

Fast terminal sliding‐mode finite‐time tracking control with differential evolution optimization algorithm using integral chain differentiator in uncertain nonlinear systems

This paper presents a fast terminal sliding‐mode tracking control for a class of uncertain nonlinear systems with unknown parameters and system states combined with time‐varying disturbances. Fast terminal sliding‐mode finite‐time tracking systems based on differential evolution algorithms incorporate an integral chain differentiator (ICD) to feedback systems for the estimation of the unknown system states. The differential evolution optimization algorithm using ICD is also applied to a tracking controller, which provides unknown parametric estimation in the limitation of unknown system states for trajectory tracking. The ICD in the tracking systems strengthens the tracking controller robustness for the disturbances by filtering noises. As a powerful finite‐time control effort, the fast terminal sliding‐mode tracking control guarantees that all tracking errors rapidly converge to the origin. The effectiveness of the proposed approach is verified via simulations, and the results exhibit high‐precision output tracking performance in uncertain nonlinear systems.     

An improved continuous sliding mode controller for flexible air‐breathing hypersonic vehicle

An improved continuous sliding mode control algorithm is proposed for a flexible air‐breathing hypersonic vehicle (FAHV), including nonsingular fast fixed‐time sliding surface (NFFS) and dual‐layer adaptive continuous twisting reaching law (DACTL). Firstly, the nonlinear control‐oriented model of FAHV is processed using input/output feedback linearization method with the significant flexible effects modeling as unknown matched disturbances. Secondly, a novel NFFS is improved from conventional fixed‐time sliding surface by adjusting power exponent to accelerate convergence rate. In the meanwhile, in order to avoid singularity aroused by fractional power term, an exponential convergent sliding surface is switched when tracking error approaches zero. Thirdly, a DACTL is proposed to realize finite‐time convergence of sliding mode variable with higher convergence precision and less chattering. Dual‐layer adaptive law is utilized to adjust the gain in DACTL based on equivalent control concept so as to enhance robustness automatically and avoid overestimation of control gain. Meanwhile, disturbances can be compensated without knowledge of Lipschitz constants. Ultimately, simulations on longitudinal control of FAHV demonstrate the control algorithm proposed is superior to conventional quasi‐continuous sliding mode controller in the aspect of convergence accuracy and chattering suppression.     

Design of Second Order Sliding Mode and Sliding Mode Algorithms: A Practical Insight to DC-DC Buck Converter

This paper presents a simple and systematic approach to design second order sliding mode controller for buck converters. The second order sliding mode control (SOSMC) based on twisting algorithm has been implemented to control buck switch mode converter. The idea behind this strategy is to suppress chattering and maintain robustness and finite time convergence properties of the output voltage error to the equilibrium point under the load variations and parametric uncertainties. In addition, the influence of the twisting algorithm on the performance of closed-loop system is investigated and compared with other algorithms of first order sliding mode control such as adaptive sliding mode control (ASMC), nonsingular terminal sliding mode control (NTSMC).In comparative evaluation, the transient response of the output voltage with the step change in the load and the start-up response of the output voltage with the step change in the input voltage of buck converter were compared. Experimental results were obtained from a hardware setup constructed in laboratory. Finally, for all of the surveyed control methods, the theoretical considerations, numerical simulations, and experimental measurements from a laboratory prototype are compared for different operating points. It is shown that the proposed twisting method presents an improvement in steady state error and settling time of output voltage during load changes.      

一种BUCK电路自适应的滑模控制算法

针对常见的BUCK电路滑模控制方案中存在的负载突变产生的干扰问题,设计一种新的自适应滑模控制器.通过观测BUCK电路中负载电阻的变化,自适应的修改控制参数以获得良好的动态性能和稳定性.通过实验仿真证明该方法在负载电阻变化时,能有效减小系统状态误差和提高系统稳定性.     

Experimental Implementation of New Sliding Mode Control Law applied To a DC–DC Boost Converter

The real implementation of sliding mode controllers (SMCs) to a DC–DC boost converter is a challenge due to the nonminimum phase behavior of these kinds of converters and the SMCs chattering problem. In this paper, new integral sliding mode control laws with linear and proposed nonlinear sliding surfaces are developed to overcome these problems. An experimental comparative study between these SMCs and the classical SMC applied for a DC–DC boost converter is presented.     

Decentralized adaptive neural network control of cascaded DC–DC converters with high voltage conversion ratio

Decentralized output voltage tracking of cascaded DC–DC converters is an interesting topic to obtain a high voltage conversion ratio. The control purpose is challenging due to the load resistance changes, renewable energy supply voltage variations and interaction of the individual converters. In this paper, four novel decentralized adaptive neural network controllers are designed on the cascaded DC–DC buck and boost converters under load and DC supply voltage uncertainties. In the beginning, individual buck and boost converter average models that can operate in both continuous and discontinuous conduction modes are derived. Then, the interconnected and decentralized state-space models of cascaded buck and boost converters are extracted. These models are highly nonlinear with unknown uncertainties which can be estimated by neural networks. Further, two decentralized adaptive backstepping neural network voltage controllers are proposed on cascaded buck converters to deal with uncertainties and interactions. However, these control strategies are not applicable to a boost converter due to its non-minimum phase nature. Then, two novel decentralized adaptive neural network with a conventional proportional–integral reference current generator are developed on the cascaded boost converters. Practical stability of the overall system is guaranteed for the proposed controllers using Lyapunov stability theorem. Finally, four control strategies provide good quality of output voltage in the presence of uncertainties and interactions. Comparative simulations are carried out on cascaded buck and boost converters to validate the effectiveness and performance of the designed methods.     

直流降压变换器的降阶扩张状态观测器与滑模控制设计与实现

本文针对直流降压变换器的负载电阻扰动和输入电压变化等系统不确定因素对输出电压的影响,提出了基于降阶扩张状态观测器的滑模控制方法(SMC+RESO).首先设计降阶扩张状态观测器对系统状态,负载电阻扰动和输入电压变化进行估计,然后基于估计值利用滑模控制技术设计控制器,实现对直流降压变换器系统给定电压跟踪的快速性和准确性.值得注意的是,不同于文[1]所提出的基于扩张状态观测器的滑模控制方法(SMC+ESO),本文所提出的方法采用降阶扩张状态观测器,实现简单,且无需电流传感器,减小了实际应用的成本.利用Lyapunov稳定性定理从理论上证明了所设计的控制器可以保证闭环系统的稳定性.仿真和实验结果表明,与已有的基于扩张状态观测器的滑模控制方法相比,所提出的控制方法更好地改善了系统的跟踪性能和对干扰和不确定性的鲁棒性能,且减少了成本,但是牺牲了系统稳态性能.     

Sliding mode learning control of non‐minimum phase nonlinear systems

In this paper, a novel robust sliding mode learning control scheme is developed for a class of non‐minimum phase nonlinear systems with uncertain dynamics. It is shown that the proposed sliding mode learning controller, designed based on the most recent information of the stability status of the closed‐loop system, is capable of adjusting the control signal to drive the sliding variable to reach the sliding surface in finite time and remain on it thereafter. The closed‐loop dynamics including both observable and non‐observable ones are then guaranteed to asymptotically converge to zero in the sliding mode. The developed learning control method possesses many appealing features including chattering‐free characteristic, strong robustness with respect to uncertainties. More importantly, the prior information of the bounds of uncertainties is no longer required in designing the controller. Numerical examples are presented in comparison with the conventional sliding mode control and backstepping control approaches to illustrate the effectiveness of the proposed control methodology. Copyright © 2015 John Wiley & Sons, Ltd.     

DC‐to‐AC power conversion on a ‘boost’ converter

In this article, we provide an approximate sliding mode control‐based solution to the DC–AC power conversion problem on a ‘boost’ converter. The approach uses the flatness property of the system as a pivot for generating a sequence of minimum phase output reference trajectory candidates. The generated candidates are obtained as differential parameterizations of the minimum phase inductor current variable in terms of the non‐minimum phase desired output capacitor voltage. The associated residual dynamics of the ideal sliding motions is shown to reasonably approximate the desired biased sinusoidal output capacitor voltage signal. Copyright © 2001 John Wiley & Sons, Ltd.     

High‐order sliding mode control design based on adaptive terminal sliding mode

High‐order sliding mode control techniques are proposed for uncertain nonlinear SISO systems with bounded uncertainties based on two different terminal sliding mode approaches. The tracking error of the output converges to zero in finite time by designing a terminal sliding mode controller. In addition, the adaptive control method is employed to identify bounded uncertainties for eliminating the requirement of boundaries needed in the conventional design. The controllers are derived using Lyapunov theory, so the stability of the closed‐loop system is guaranteed. In the first technique, the developed procedure removes the reaching phase of sliding mode and realizes global robustness. The proposed algorithms ensure establishment of high‐order sliding mode. An illustrative example of a car control demonstrates effectiveness of the presented designs. Copyright © 2011 John Wiley & Sons, Ltd.     

Output‐feedback tracking in causal nonminimum‐phase nonlinear systems using higher‐order sliding modes

Asymptotic output‐feedback tracking in a class of causal nonminimum phase uncertain nonlinear systems is addressed via sliding mode techniques. Sliding mode control is proposed for robust stabilization of the output tracking error in the presence of a bounded disturbance. The output reference profile and the unknown input/disturbance are supposed to be described by unknown linear exogenous systems of a given order. Local asymptotic stability of the output tracking error dynamics along with the boundedness of the internal states are proven. The unstable internal states are estimated asymptotically via the proposed multistage observer that is based on the method of extended system center. A higher‐order sliding mode observer/differentiator is used for the exact estimation of the input–output states in a finite time. The bounded disturbance is reconstructed asymptotically. A numerical example illustrates the efficiency of the proposed output‐feedback tracking approach developed for causal nonminimum phase nonlinear systems. Copyright © 2009 John Wiley & Sons, Ltd.     

Sliding mode controlled multiphase buck converter with interleaving and current equalization

This paper presents a sliding mode control design of a multiphase power converter. The use of multiphase converters and an appropriate phase shift result in chattering reduction to the desired level at a given switching frequency in the so called “ripple cancellation” or “harmonic cancellation”. Additionally, this strategy considers sliding mode as a suitable substitute for Pulse Width Modulation because of the benefits in sliding mode control, i.e. the possibility of achieving desired system responses regardless of parameter changes. A 4-phase buck converter prototype was built and the controller was programmed in an FPGA. Experimental results show that chattering reduction, robust output regulation and phase current equalization are achieved, thus validating the proposed approach.     

Finite‐Time Sliding Mode Trajectory Tracking Control of Uncertain Mechanical Systems

The problem of finite‐time tracking control is studied for uncertain nonlinear mechanical systems. To achieve finite‐time convergence of tracking errors, a simple linear sliding surface based on polynomial reference trajectory is proposed to enable the trajectory tracking errors to converge to zero in a finite time, which is assigned arbitrarily in advance. The sliding mode control technique is employed in the development of the finite‐time controller to guarantee the excellent robustness of the closed‐loop system. The proposed sliding mode scheme eliminates the reaching phase problem, so that the closed‐loop system always holds the invariance property to parametric uncertainties and external disturbances. Lyapunov stability analysis is performed to show the global finite‐time convergence of the tracking errors. A numerical example of a rigid spacecraft attitude tracking problem demonstrates the effectiveness of the proposed controller.     

Nonlinear output tracking in conventional and dynamic slidingmanifolds

Nonlinear output tracking in multi-input/multi-output (MIMO) systems with unmatched nonlinearities and disturbances is considered in sliding modes. The system is nonlinearly transformed to a form convenient for sliding mode synthesis. Both conventional and dynamic sliding mode controllers are designed to provide the desired nonlinear output tracking. In both cases, only the time-dependent part of the unmatched disturbance must be estimated. An example is provided to demonstrate the new design approach. Results show that both conventional and dynamic sliding mode control are insensitive to matched disturbances, but that dynamic sliding mode control accommodates to unmatched disturbances