Model predictive control of grid-connected PV power generation system considering optimal MPPT control of PV modules

Because of system constraints caused by the external environment and grid faults, the conventional maximum power point tracking (MPPT) and inverter control methods of a PV power generation system cannot achieve optimal power output. They can also lead to misjudgments and poor dynamic performance. To address these issues, this paper proposes a new MPPT method of PV modules based on model predictive control (MPC) and a finite control set model predictive current control (FCS-MPCC) of an inverter. Using the identification model of PV arrays, the module-based MPC controller is designed, and maximum output power is achieved by coordinating the optimal combination of spectral wavelength and module temperature. An FCS-MPCC algorithm is then designed to predict the inverter current under different voltage vectors, the optimal voltage vector is selected according to the optimal value function, and the corresponding optimal switching state is applied to power semiconductor devices of the inverter. The MPPT performance of the MPC controller and the responses of the inverter under different constraints are verified, and the steady-state and dynamic control effects of the inverter using FCS-MPCC are compared with the traditional feedforward decoupling PI control in Matlab/Simulink. The results show that MPC has better tracking performance under constraints, and the system has faster and more accurate dynamic response and flexibility than conventional PI control.     

具有改进最大功率跟踪算法的光伏并网控制系统及其实现

光伏并网控制系统输送到电网的功率随着光照强度、环境温度以及光伏阵列输出电压的不同而变化,控制光伏阵列的工作点使其连续稳定地向电网输出最大功率非常必要。该文提出了基于同步旋转坐标变换实现光伏阵列最大功率跟踪与电流控制的电压源型逆变器相结合的三相光伏并网控制系统,该系统主要包括光伏阵列、直流母排电容、电压源型逆变器、滤波电感、数字信号控制器与电网。提出的改进最大功率跟踪方法,根据光伏阵列dP/dU-U的特性曲线,利用Newton-Raphson方法快速计算光伏阵列输出功率对电压的微分值,由此进一步形成光伏阵列工作在最大功率点的参考电压值。整个控制系统为双环控制,外环为电压控制环,利用一个PI调节器使光伏阵列输出电压工作在最大功率工作点;内环为电流控制环,利用2个PI调节器分别对d-q轴电流进行解耦控制,使逆变器输出电流与参考电流一致。根据所提出的控制算法,研制了一台三相光伏并网系统原理性样机,仿真与实验结果一致,系统具有良好的动稳态性能,说明了所提出的控制方案是非常有效的。     

光伏MPPT系统电压控制器的优化设计

分析了光伏MPPT系统构成及工作原理。使用基于变步长电压扰动法作为功率/电压寻优控制器。为实现快速稳定的光伏MPPT响应,重点对光伏输出电压控制器的电压环进行优化设计。设计了一种光伏MPPT电压复合控制器,采用电压顺馈+PI调节器的方法实现。通过对光伏输出电压控制器进行数学建模得到电压闭环传递函数。确定了最佳PI调节器参数以得到快速稳定的MPPT控制。仿真分析结果以及试验结果表明,此电压复合控制器能够快速、稳定地实现光伏MPPT响应。     

一种并网逆变器功率跟踪控制策略研究

分析了一种并网逆变器的功率跟踪控制方案.由于采用自抗扰控制器(ADRC),输出电流能够很好地跟踪电网电压,并能实现最大功率点跟踪(MPPT).通过对电流的闭环跟踪控制,实现了单位功率因数运行,并向电网馈送电能.实验表明,采用ADRC,稳定快速,输出电流超调小,能够有效地抑制各种扰动,且启动性能与稳定性能都要优于常规控制器.     

光伏并网系统参与电压调节的有功和无功协调控制策略研究

针对配电网线路阻抗大、分布式光伏并网系统无功调压能力有限,导致光伏电源在有功出力较大时并网点(PCC)电压越上限问题,在深入分析光伏系统PCC电压特性基础上,提出一种光伏逆变器有功和无功协调控制策略。在该控制策略下,光伏系统实时跟踪监测PCC电压变化,PCC电压不越限时,逆变器按最大功率点跟踪(MPPT)输出;PCC电压越上限时,优先利用逆变器剩余容量进行无功调压,若剩余容量不足,调节逆变器有功输出,并动态计算有功、无功最佳输出值,保证将PCC电压调节至满足要求的前提下,实现逆变器有功输出最大化、无功输出最佳化。算例结果验证了控制策略的有效性。     

Wavelet technique based islanding detection and improved repetitive current control for reliable operation of grid-connected PV systems

Recent years have witnessed a thrust towards the use of solar energy as the major renewable energy source for distributed power generation. The proposed system requires reliable detection technique and suitable current control strategy for proper operation. This paper focuses on plug-in repetitive current (RC) control strategy for grid connected inverter system and wavelet technique for electrical grid status identification. The performance of proposed current control technique employed for grid connected inverter system under distorted and unbalanced grid voltage is compared with the existing conventional methods like PI and PR controller. This controller uses the feedback control system for attenuating periodic disturbances, improving high quality sinusoidal output current and high power factor. The proposed scheme employs fourth order infinite impulse response (IIR) filter for maintaining its resonance frequency, output frequency matching with grid fundamental frequency and reduction of harmonics. The DC-DC boost converter implements incremental conductance based (INC) maximum power point tracker (MPPT) algorithm. The effects of LCL filter for improving disturbance rejection capability and dynamic performance of the proposed system is also demonstrated. Grid connected PV inverter employs wavelet technique for an islanding detection functionality in order to determine the status of the electrical grid. In order to show the effectiveness of the proposed algorithm, modeling and simulation for grid connected PV system is performed using MATLAB/SIMULINK and its PowerSim toolbox.     

单相非隔离型并网光伏逆变器研制

针对输入宽范围光伏电池电压,提出了一个采用准两级式主电路拓扑和双CPU控制的单相非隔离并网逆变器系统方案,并建立基于Simulink的光伏发电系统仿真模型。其中,为满足宽电压范围光伏电池的最大功率跟踪MPPT,系统的MPPT放在单相逆变桥级实现。仿真和实验结果表明,样机性能指标优良,系统采用的改进变步长扰动观察法可以减小MPPT时的振荡,采用基于电感安匝特性曲线插值求电感的方法,可以有效满足无差拍并网电流控制对输出滤波电感模型精度要求较高的特点,克服粉芯类磁芯电感随电流变化大的缺点。     

三相单级式光伏发电系统并网控制与仿真

基于三相单级式光伏并网发电系统的电路拓扑结构,提出了一种快速逼近插值算法实现光伏发电的最大功率跟踪,光伏并网采用电压外环和电流内环双闭环控制,通过同步旋转坐标变换结合逆变器的控制,利用比例积分控制实现无功功率与有功功率的独立解耦控制。MATLAB系统仿真结果表明,该方法能够快速稳定地实现单位功率因数最大功率并网,降低并网系统成本,提高光伏并网的电能质量。     

MPPT control design and performance improvements of a PV generator powered DC motor-pump system based on artificial neural networks

This paper presents the optimum photovoltaic (PV) water pumping system using maximum power point tracking technique (MPPT). The optimum is suspended to reference optimal power. This optimal technique is developed to assure the optimum chopping ratio of buck–boost converter. The presented MPPT technique is used in photovoltaic water pumping system in order to optimize its efficiency. An adaptive controller with emphasis on Nonlinear Autoregressive Moving Average (NARMA) based on artificial neural networks approach is applied in order to optimize the duty ratio for PV maximum power at any irradiation level. In this application, an indirect data-based technique is taken, where a model of the plant is identified on the basis of input–output data and then used in the model-based design of a neural network controller. The proposed controller has the advantages of fast response and good performance. The PV generator DC motor pump system with the proposed controller has been tested through a step change in irradiation level. Simulation results show that accurate MPPT tracking performance of the proposed system has been achieved. Further, the performance of the proposed artificial neural network (ANN) controller is compared with a PID controller through simulation studies. Obtained results demonstrate the effectiveness and superiority of the proposed approach.     

基于功率平衡原理的最大功率点算法实现

最大功率点跟踪(Maximum Power Point Tracking,简称MPPT)控制电路及控制方法是提高光伏器件利用效果的有效手段,但是检测光伏器件输出端电压、电流的传感器增加了硬件电路的成本和体积。从功率平衡角度对逆变器工作电流与光伏器件输出功率之间的关系进行分析,结果表明控制系统逆变器的输出电流可实现光伏器件的MPPT控制。由于该方法利用了逆变器并网工作所必需的检测信号,从而避免了对光伏器件输出信号的检测,降低了成本。实验结果验证了该方法的有效性。     

基于最优梯度MPPT控制的光伏水泵系统

为提高对光伏阵列的利用率,分析了一种基于最优梯度最大功率点跟踪(MPPT)控制的光伏水泵调速系统.根据光伏阵列的特性及最优梯度控制的方法,通过检测光伏阵列的输出电压、电流及单片机软件控制来实现MPPT.介绍了系统软件和硬件的设计,最后用给出的实验波形证明该方法能使系统稳定运行.     

三相光伏并网逆变器多目标优化模型预测控制

三相电压型并网逆变器广泛用于光伏发电领域。逆变控制方法用于提高并网系统效率和响应质量。模型预测控制策略使用离散时间模型预测下一个采样周期所有可能的输出值,根据评估函数选取最优电压向量。将模型预测控制用于三相电压型并网逆变器中。首先,建立三相光伏逆变器在d-q坐标系下的瞬时功率数学模型。其次,设计预测函数在线预测逆变并网参数。选择合适的目标函数控制逆变器下一采样周期的输出值。d-q坐标系下的跟踪精确迅速,所提出的控制策略计算量小,无需PWM调制,更容易实现。然后,对模型预测控制进行多目标优化。设计电流解耦控制减小系统输出有功功率,改变评估函数提高输出电流质量,修正交流侧电压参数提高预测的准确性。最后,仿真和实验结果证明提出的控制策略输出电流具有良好的动态性能和较低的谐波畸变率,可快速跟踪给定的参考值,具有无功补偿的功能。     

采用滑模变结构控制MPPT的三相光伏并网发电系统

光伏并网发电系统的传统外环控制通过最大功率点跟踪(MPPT)算法给出直流母排参考电压,利用PI调节器调节输出并网有功参考电流.鉴于滑模变结构控制的快速响应和强鲁棒性,提出了一种基于滑模变结构控制的直接电流MPPT算法.在建立系统稳态模型的基础上,由MPPT控制算法直接给定并网有功参考电流.电流内环为LCL滤波三相电压型...     

Nonlinear Adaptive Backstepping Controller Design for Three-Phase Grid-Connected Solar Photovoltaic Systems

A cascaded control structure is proposed in this paper for injecting active and reactive power in a three-phase grid-connected solar photovoltaic (PV) system by considering external disturbances. In the proposed cascaded control structure, there are two control loops—the outer loop voltage controller is used to ensure a continuous balance in power flow between the PV arrays and electrical power grid whereas the inner loop current controller controls the output current of the inverter. Moreover, the DC-DC boost converter is controlled to achieve a constant voltage at the input of the inverter. In order to obtain the power balance and extract maximum power, an incremental conductance (IC) based maximum power point tracking (MPPT) method is used in this paper. The current controller is designed using a nonlinear adaptive backstepping technique to regulate the active and reactive components of the grid current. The regulation of these currents towards desired values which in turn control the active and reactive power delivered into the grid. The overall stability analysis of the system is performed based on the formulation of control Lyapunov functions (CLFs). Finally, the performance of the designed controller is tested on three-phase grid-connected PV systems with single as well as multiple PV units under different environmental conditions and compared with an existing sliding mode controller. Simulation results confirm the effectiveness of the proposed adaptive backstepping control scheme and demonstrate the superior performance over the sliding mode controller.     

基于模糊神经网络的光伏发电系统功率控制方法

并网光伏发电系统的故障穿越是大规模新能源接入电网和灵活调控的技术难题,针对传统光伏发电系统在电网故障条件下穿越控制策略的不足,提出一种基于模糊神经网络的光伏发电系统功率控制方法。在电网电压突变和跌落情况下能够快速地调整光伏发电系统的工作模式,以适应光伏阵列最大输出功率和并网逆变器额定容量以及最大输出电流的限制,具有稳定性强、跟踪速度快等优点。给出了控制策略总体架构,详细阐述了电网故障控制器运行模式切换策略,建立了模糊神经网络算法的数学模型和实现流程。最后,在Matlab/Simulink平台下搭建了系统仿真模型,仿真结果验证了所提出控制策略的有效性。     

无差拍控制的非隔离型并网逆变器漏电流分析

为实现逆变系统高质量并网电流的输出,漏电流的消除对非隔离型光伏并网逆变器至关重要。分析了非隔离型单相并网逆变器漏电流的产生机理和流通回路,并基于无差拍电流控制原理,说明漏电流对逆变电流以及MPPT的影响。提出了一种基于无差拍电流控制的单相光伏并网逆变器漏电流补偿方法,并在Matlab/Simulink环境下进行仿真。通过仿真结果和实验测得值相比较表明,通过对逆变器占空比的补偿,可以有效地消除漏电流对逆变电流的影响,从而避免功率跟踪中出现误判或者找不到最大功率点的情况,实现逆变电流高质量输出和最大功率的正确跟踪。     

基于电导增量法的模型预测控制光伏MPPT算法

由于外界环境的多变性与随机性,光伏系统的全局最大功率点总是飘忽不定的。为使光伏系统在外界复杂环境下能够获得最大功率输出,提出了一种基于电导增量法的模型预测控制光伏MPPT算法。该算法将电导增量法与模型预测算法相结合,完成对光伏发电系统在外界复杂多变环境下的快速跟踪。通过建立系统性能指标函数,评价与估算出未来控制变量的动作,预测出P-U曲线的方向。最后通过simulink仿真表明了文章所提方法在外界光照强度发生突变时与单独使用电导增量法相比较可以同时提高系统的跟踪速度和控制精度。     

基于微分几何的微网Z源逆变器并网控制

针对应用于微网系统中的Z源逆变器及其并网控制研究,以光伏系统为例,根据Z源变换器本身具有的非线性特性,建立Z源逆变器直流链及逆变侧的仿射非线性模型,利用微分几何基本工具,构造恰当的坐标变换和预反馈,将原非线性系统精确线性化,然后对该系统进行线性最优控制器设计。该逆变器集最大功率点跟踪、升降压和并网发电等功能于一体。仿真...     

电压源型三相逆变器的模型预测控制策略

为了提高电压源型三相逆变器的控制性能,设计了一种新颖的模型预测控制(MPC)策略。新型MPC控制器使用三相逆变器系统的离散时间域模型来预测所有可能电压矢量生成的负载电流,并选择使所设计的成本函数最小的矢量作为最优矢量输出。成本函数中主要考虑的指标是下一个采样周期的电流误差。利用仿真软件和搭建的三相逆变器样机测试平台开展了与传统滞环控制和脉宽调制方案的对比仿真分析和实验。测试结果表明,新型MPC控制器可有效地控制负载电流并且表现出更优的动、静态性能。     

改进的光伏发电系统最大功率点跟踪方法

光伏发电系统可采用最大功率点跟踪控制技术来提高输出功率,但常规变步长扰动观察法存在功率-电压特性曲线的低压区变步长跟踪效果差、步长灵敏度受光照强度影响大等缺点。从变步长算法和控制系统结构两方面提出了改进措施,并在利用MATLAB/Simulink工具建立的最大功率点跟踪系统仿真平台上与常规变步长扰动观察法进行了对比试验。试验结果表明,跟踪时间和跟踪步数分别减少了50%和75%,同时PID控制环节使光照强度快速变化时的跟踪电压偏差从48.3%降低到13.8%,明显地提高了系统的动态性能。