Control of Grid Connected Photovoltaic Systems with Microinverters: New Theoretical Design and Numerical Evaluation

This paper addresses the problem of controlling grid connected photovoltaic (PV) systems that are driven with microinverters. The systems to be controlled consist of a solar panel, a boost dc–dc converter, a DC link capacitor, a single‐phase full‐bridge inverter, a filter inductor, and an isolation transformer. We seek controllers that are able to simultaneously achieve four control objectives, namely: (i) asymptotic stability of the closed loop control system; (ii) maximum power point tracking (MPPT) of the PV module; (iii) tight regulation of the DC bus voltage; and (iv) unity power factor (PF) in the grid. To achieve these objectives, a new multiloop nonlinear controller is designed using the backstepping design technique. A key feature of the control design is that it relies on an averaged nonlinear system model accounting, on the one hand, for the nonlinear dynamics of the underlying boost converter and inverter and, on the other, for the nonlinear characteristic of the PV panel. To achieve the MPPT objective, a power optimizer is designed that computes online the optimal PV panel voltage used as a reference signal by the PV voltage regulator. It is formally shown that the proposed controller meets all the objectives. This theoretical result is confirmed by numerical simulation tests.     

基于SG的Buck变换器自适应反步法控制

针对Buck变换器的非线性特性,考虑在电感电流连续导通模式下的数学模型,采用自适应反步法设计其闭环控制器,同时基于System Generator提出了数字控制器的实现方法,并分析了其负载扰动和电源扰动特性,将仿真结果与PI控制方式相比较,结果表明自适应反步控制的优越性和System Generator设计开发的有效性,为FPGA实现Buck变换器的数字控制器提供了新的设计流程,也为进一步研究其他DC-DC变换器的非线性控制提供了新思路.     

Passivity-based control for a DC/DC high-gain transformerless boost converter

In this work, an adaptive passivity-based controller for a DC-DC high-gain transformerlessdouble-inductor boost converter is fully detailed. The proposed current-mode control scheme results in two feedback loops, a current controller for tracking the inductor current considering damping injection and energy shaping, and a voltage loop composed by a proportional-integral action to guarantee output voltage regulation. Furthermore, a parametric uncertainty estimator using immersion-invariance approach is designed to improve the robustness of the current loop. As a result, a multi-loop adaptive nonlinear energy-based controller, which ensures regional asymptotic stability via Lyapunov analysis is accomplished. In addition, considering practical conditions, real-time numerical simulations, using a 1 kW case-study converter, are carried out in order to assess the effectiveness of the proposed control scheme. Results for output voltage regulation, current tracking, and parametric uncertainty estimation under input voltage and load step changes are shown.     

Climatic sensorless maximum power point tracking in PV generation systems

The problem of maximum power point tracking (MPPT) is addressed for photovoltaic (PV) arrays considered in a given panel position. The PV system includes a PV panel, a PWM boost power converter and a storing battery. Although the maximum power point (MPP) of PV generators varies with solar radiation and temperature, the MPPT is presently sought without resorting to solar radiation and temperature sensors in order to reduce the PV system cost. The proposed sensorless control solution is an adaptive nonlinear controller involving online estimation of uncertain parameters, i.e. those depending on radiation and temperature. The adaptive control problem at hand is not a standard one because parameter uncertainty affects, in addition to system dynamics, the output-reference trajectory (expressing the MPPT purpose). Therefore, the convergence of parameter estimates to their true values is necessary for MPPT achievement. It is formally shown, under mild assumptions, that the developed adaptive controller actually meets the MPPT objective.     

并联Boost变换器T-S建模与控制

在并联Boost变换器建模过程中,含有状态量的输入矩阵使得模型具有非线性特点,本文针对并联Boost变换器的这一特点,建立Boost变换器等价T-S模型,并根据建立的模型,利用Lyapunov函数方法和线性不等式方法,采用并行分配补偿(PDC)策略设计非线性T-S模糊控制器。仿真结果表明:本文所建立的并联Boost变换器的模型是准确的,设计的T-S模糊控制器是可靠的,系统工作稳定并且具有较强的抗扰动性能。     

Nonlinear control of a coupled PDE/ODE system modeling a switched power converter with a transmission line

We consider an infinite dimensional system modeling a boost converter connected to a load via a transmission line. The governing equations form a system coupling the telegraph partial differential equation with the ordinary differential equations modeling the converter. The coupling is given by the boundary conditions and the nonlinear controller we introduce. We design a nonlinear saturating control law using a Lyapunov function for the averaged model of the system. The main results give the well-posedness and stability properties of the obtained closed loop system.     

Cooperative modalities in robotic tele-rehabilitation using nonlinear bilateral impedance control

A nonlinear model reference adaptive bilateral impedance controller is proposed that can accommodate various cooperative tele-rehabilitation modes for patient–therapist interaction using a multi-DOF tele-robotic system. In this controller, two reference impedance models are implemented for the master and slave robots using new model reference adaptive control laws for the nonlinear bilateral teleoperation system. “Hand-over-hand” and “adjustable-flexibility” are two modes of patient–therapist cooperation that are realized using the proposed strategy. The Lyapunov-based stability proof guarantees the patient’s and the therapist’s safety during the cooperation and interaction with robots, even in the presence of modeling uncertainties of the multi-DOF teleoperation system. The performance of the proposed bilateral impedance controller is experimentally investigated for upper-limb tele-rehabilitation in the two mentioned cooperation modes.     

Development and analysis of adaptive fuzzy controllers for photovoltaic system under varying atmospheric and partial shading condition

Control of power electronics converters used in PV system is very much essential for the efficient operation of the solar system. In this paper, a modified incremental conduction maximum power point tracking (MPPT) algorithm in conjunction with an adaptive fuzzy controller is proposed to control the DC–DC boost converter in the PV system under rapidly varying atmospheric and partial shading conditions. An adaptive hysteresis current controller is proposed to control the inverter. The proposed current controller provides constant switching frequency with less harmonic content compared with fixed hysteresis current control algorithm and sinusoidal PWM controller. The modeling and simulation of PV system along with the proposed controllers are done using MATLAB/SIMSCAPE software. Simulation results show that the proposed MPPT algorithm is faster in transient state and presents smoother signal with less fluctuations in steady state. The hardware implementation of proposed MPPT algorithm and inverter current control algorithms using Xilinx spartran-3 FPGA is also presented. The experimental results show satisfactory performance of the proposed approaches.     

Output‐Feedback Nonlinear Adaptive Control of Single‐Phase Half‐Bridge Ups Systems

We consider the problem of controlling single‐phase half‐bridge power converters in UPS systems operating in the presence of changing load. The control objective is twofold: (i) ensuring a satisfactory power factor correction (PFC) at the grid–UPS connection; (ii) guaranteeing a tight regulation of the DC bus voltage and the half‐bridge inverter output voltage despite changes in load. The considered control problem entails several difficulties including: (i) the high dimension and strong nonlinearity of the system; (ii) the numerous state variables that are inaccessible to measurements; (iii) the uncertainty that prevails on some system parameters. The problem is dealt with using a multi‐loop nonlinear adaptive control system that makes use of the backstepping design technique. The inner loop ensures the PFC objective and involves an adaptive observer estimating the grid voltage and impedance parameters. The intermediary loop regulates the inverter output voltage to its reference, which is a sinusoidal wave, and it also contains an observer estimating the current in the inverter coil. The outer loop regulates the DC bus voltage up to small size ripples. The controller performances are formally analyzed using system averaging theory.     

Nonlinear robust adaptive Cartesian impedance control of UAVs equipped with a robot manipulator

In this paper, a new nonlinear robust adaptive impedance controller is addressed for Unmanned Aerial Vehicles (UAVs) equipped with a robot manipulator that physically interacts with environment. A UAV equipped with a robot manipulator is a novel system that can perform different tasks instead of human being in dangerous and/or inaccessible environments. The objective of the proposed robust adaptive controller is control of the UAV and its robotic manipulator’s end-effector impedance in Cartesian space in order to have a stable physical interaction with environment. The proposed controller is robust against parametric uncertainties in the nonlinear dynamics model of the UAV and the robot manipulator. Moreover, the controller has robustness against the bounded force sensor inaccuracies and bounded unstructured modeling (nonparametric) uncertainties and/or disturbances in the system. Tracking performance and stability of the system are proved via Lyapunov stability theorem. Using simulations on a quadrotor UAV equipped with a three-DOF robot manipulator, the effectiveness of the proposed robust adaptive impedance controller is investigated in the presence of the force sensor error, and parametric and non-parametric uncertainties.     

Boost变换器的T-S模糊建模与控制

针对Boost变换器的非线性特性,考虑变换器参数不同情况对系统模型的影响,分别建立了参数确定和参数不确定条件下Boost变换器的等价T-S模糊模型。基于建立的等价T-S模糊模型,利用Lyapunov函数方法和线性矩阵不等式方法,给出了Boost变换器并行分配补偿模糊控制器的参数化设计方法。仿真结果表明,所建立的Boost变换器T-S模糊模型是可靠的,所设计的模糊控制器与模糊PI相比具有较强的鲁棒性和抗扰性。     

DC/DC升压变换器非线性控制

设计一种基于电流模式的非线性控制器.控制器由电感电流的比例控制和电容电压的非线性比例积分控制两部分组成.对某DC/DC升压变换器的仿真结果表明,上述控制器是可行的.     

微电网的电流均衡/电压恢复自适应动态规划策略研究

含多类型分布式电源的微电网已经成为了未来电力系统的重要发展方向,其中风能和光能在降低化石能源消耗和二氧化碳排放等方面有着极大优势,考虑二者之间强互补性的协同调度已被广泛研究.但风/光协同调度的微电网多关注分钟级的调度或优化问题而非风/光波动下秒级的实时电流按容量比例精准分担,简称电流均衡,而精准电流均衡有助于可再生能源的高比例消纳.因此,本文提出了基于自适应动态规划的微电网电流均衡和电压恢复控制策略.首先,构建包含风电整流型电能变换器和光电升压型电能变换器的广义风光拓扑同胚升压变换器模型,其提供了后续控制器设计的模型基础.其次,本文将电流均衡和电压恢复问题转化为最优控制问题,基于此,每个能源主体的目标函数转化为获取最优控制变量和最小电压/电流控制偏差,进而转化为求解哈密顿?雅克比?贝尔曼(Hamilton-Jacobi-Bellman,HJB)方程问题.基于此,提出了基于贝尔曼准则的分布式自适应动态规划控制策略以求取HJB方程的数值解,最终实现电流均衡和电压恢复.最后仿真结果验证了所提分布式自适应动态规划控制策略的有效性.     

微电网的电流均衡/电压恢复自适应动态规划策略研究

含多类型分布式电源的微电网已经成为了未来电力系统的重要发展方向,其中风能和光能在降低化石能源消耗和二氧化碳排放等方面有着极大优势,考虑二者之间强互补性的协同调度已被广泛研究.但风/光协同调度的微电网多关注分钟级的调度或优化问题而非风/光波动下秒级的实时电流按容量比例精准分担,简称电流均衡,而精准电流均衡有助于可再生能源的高比例消纳.因此,本文提出了基于自适应动态规划的微电网电流均衡和电压恢复控制策略.首先,构建包含风电整流型电能变换器和光电升压型电能变换器的广义风光拓扑同胚升压变换器模型,其提供了后续控制器设计的模型基础.其次,本文将电流均衡和电压恢复问题转化为最优控制问题,基于此,每个能源主体的目标函数转化为获取最优控制变量和最小电压/电流控制偏差,进而转化为求解哈密顿?雅克比?贝尔曼(Hamilton-Jacobi-Bellman,HJB)方程问题.基于此,提出了基于贝尔曼准则的分布式自适应动态规划控制策略以求取HJB方程的数值解,最终实现电流均衡和电压恢复.最后仿真结果验证了所提分布式自适应动态规划控制策略的有效性.     

Self-tuning adaptive feedback linearizing output voltage control for AC/DC converter

This paper presents a cascade output voltage control law adopting the self-tuning adaptive inner and outer-loop controllers for a AC/DC converter modelled as a nonlinear system. The first contribution is to design the inner and outer-loop controllers updating their control gains to enhance the closed-loop performance, estimating unknown parameters. The second one is to show that the proposed inner-loop controller stabilizes not only current error dynamics but also output voltage dynamics viewed as internal dynamics. The effectiveness of proposed method is shown by performing experiments using a 3-kW AC/DC converter.     

嵌入式系统的自适应前照灯系统设计

为了改善驾驶员在夜间或能见度较低环境下的视野范围,提高行驶的安全性,介绍了一种基于嵌入式系统的汽车自适应前照灯系统的设计方案。此系统中的前照灯控制器采用FPGA来控制CAN总线控制器、数／模转换器和全桥电机驱动器等器件来实现接收方向盘转角信号,并使电机运行带动前照灯的转向。自适应前照灯系统控制中心使用的是ARM9处理器。该设计方案满足要求,已经在项目中获得了良好的应用效果。     

Nonlinear output feedback control of V2G single‐phase on‐board BEV charger

In this work, we consider the problem of controlling a single‐phase on‐board battery electric vehicle (BEV) charger with vehicle‐to‐grid (V2G) technology. The BEV charger consists of a bidirectional ac‐dc power converter connected to the single‐phase power grid, followed by a bidirectional dc‐dc power converter interfacing an EV battery pack. The main control objectives are fourfold: (i) Unitary Power Factor (UPF) in grid‐side; (ii) tight dc‐bus voltage regulation; (iii) safety battery charge and battery discharge during the grid‐to‐vehicle (G2V) mode and V2G mode, respectively; and (iv) asymptotic stability of the closed loop system. After an accurate system modelling, a nonlinear controller is designed using a backstepping design technique. The point is that the battery inner voltage is not accessible to measurement. Therefore, a nonlinear observer is invoked in order to estimate all non‐measured variables making the solution cheaper and noiseless. It is shown using a formal analysis and numerical simulations, that the proposed output feedback controller (combining a nonlinear controller and a nonlinear observer) meets all control objectives.     

高性能计算机总线变换器输出阻抗优化设计

针对中间母线架构分布式供电的高性能计算机电源稳定性问题,详细分析了三种不同控制方法总线变换器的输出阻抗特性,给出了负载点变换器输入阻抗低频值和总线变换器输出阻抗峰值的计算公式。建立了由一个总线变换器和两个负载点变换器组成的实验电路,对总线变换器输出阻抗进行了优化设计,并实际测量了输入和输出阻抗,验证了理论分析的正确性。实验和应用结果表明,输出阻抗优化设计可以有效解决高性能计算机电源稳定性问题。     

A new adaptive backstepping method for nonlinear control of turbine main steam valve

A new approach for nonlinear adaptive control of turbine main steam valve is developed. In comparison with the existing controller based on ＂classical＂ adaptive backstepping, this method does not follow the classical certaintyequivalence principle in the design of adaptive control law. We introduce this approach, for the first time, to power systems and present a novel parameter estimator and dynamic feedback controller for a single machine infinite bus （SMIB） system with steam valve control. This system contains unknown parameters such as reactance of transmission lines. Besides preserving useful nonlinearities and the real-time estimation of uncertain parameters, the proposed approach possesses better performances with respect to the response of the system and the speed of adaptation. The simulation results demonstrate that the proposed approach is better than the design based on ＂classical＂ adaptive backstepping in terms of properties of stability and parameter estimation, and recovers the performance of the ＂full-information＂ controller. Hence, the proposed method provides an alternative for engineers in applications.     

Maximum power tracking of a generic photovoltaic system via a fuzzy controller and a two-stage DC–DC converter

This study presents a new two-stage DC–DC converter for maximum power point tracking (MPPT) and a voltage boost of a generic photovoltaic (PV) system. An intelligent MPPT of PV system based on fuzzy logic control (FLC) is presented to adaptively design the proposed fuzzy controlled MPPT controller (FC-MPPTC) while a voltage boost controller (VBC) is used to fix the output voltage to a voltage level that is higher than the required operating voltage to the back-end grid impedance. Modeling and simulation on the PV system and the DC–DC converter circuit are achieved by state-space and the software Powersim. The PV string considered has the rated power around 600?VA under varied partial shadings. The FC-MPPTC and VBC are designed and realized by a DSP module (TMS320F2812) to adjust the duty cycle in the two-stage DC–DC converter. A special FLC algorithm is forged to render an MPPT faster and more accurate than conventional MPPT technique, perturb and observe (P&O). The simulations are intended to validate the performance of the proposed FC-MPPTC. Experiments are conducted and results show that MPPT can be achieved in a fast pace and the efficiency reaches over 90?%, even up to 96?%. It is also found that the optimized tracking speed of the proposed FC-MPPTC is in fact more stable and faster than the general P&O method with the boost voltage capable of offering a stable DC output.