Maximum Power Point Tracking Scheme for PV Systems Operating Under Partially Shaded Conditions

Current-voltage and power-voltage characteristics of large photovoltaic (PV) arrays under partially shaded conditions are characterized by multiple steps and peaks. This makes the tracking of the actual maximum power point (MPP) [global peak (GP)] a difficult task. In addition, most of the existing schemes are unable to extract maximum power from the PV array under these conditions. This paper proposes a novel algorithm to track the global power peak under partially shaded conditions. The formulation of the algorithm is based on several critical observations made out of an extensive study of the PV characteristics and the behavior of the global and local peaks under partially shaded conditions. The proposed algorithm works in conjunction with a DC-DC converter to track the GP. In order to accelerate the tracking speed, a feedforward control scheme for operating the DC-DC converter is also proposed, which uses the reference voltage information from the tracking algorithm to shift the operation toward the MPP. The tracking time with this controller is about one-tenth as compared to a conventional controller. All the observations and conclusions, including simulation and experimental results, are presented.     

基于电流单参量控制的MPPT系统的设计

针对现有太阳能最大功率点跟踪控制策略的不足,提出了一种新型的最大功率点跟踪控制策略,即基于电流单参量的最大功率点跟踪(MPPT)。首先阐述了该最大功率控制策略的基本原理与可行性,并重点描述了该最大功率点跟踪控制策略的系统设计与调试,其中侧重于系统核心设计:电流监控电路设计和基于纯CMOS数字电路硬件逻辑程序的步进PWM控制器设计,并且详细分析了其工作原理及元器件的选取。经调试与完善,该MPPT控制系统现已能实现最大功率点跟踪,同时显示出它区别于其他控制策略的优势。     

Dual-Module-Based Maximum Power Point Tracking Control of Photovoltaic Systems

The improved maximum power point tracking (MPPT) control method for small-scale dual-module photovoltaic (PV) systems is presented in this paper. With this method, the voltage and current information of each module are shared and utilized for the detection of the maximum-power point (MPP) without measuring power. This approach can be implemented in a simple structure, especially due to the elimination of memory and multiplication devices. The proposed method is verified by a hardware prototype of grid-connected dual-module PV systems with the proposed analog-implemented MPPT controller. In addition, practical issues of the proposed scheme are considered.     

Optimized Maximum Power Point Tracker for Fast-Changing Environmental Conditions

This paper presents a high-performance maximum power point tracker (MPPT) optimized for fast cloudy conditions, e.g., rapidly changing irradiation on the photovoltaic panels. The rapidly changing conditions are tracked by an optimized hill-climbing MPPT method called dP-P&O. This algorithm separates the effects of the irradiation change from the effect of the tracker's perturbation and uses this information to optimize the tracking according to the irradiation change. The knowledge of the direction of the irradiation change enables the MPPT to use different optimized tracking schemes for the different cases of increasing, decreasing, or steady irradiance. When the irradiance is changing rapidly this strategy leads to faster and better tracking, while in steady-state conditions it leads to lower oscillations around the MPP. The simulations and experimental results show that the proposed dP-P&O MPPT provides a quick and accurate tracking even in very fast changing environmental conditions.     

Individual Module Maximum Power Point Tracking for Thermoelectric Generator Systems

In a thermoelectric generator (TEG) system the DC/DC converter is under the control of a maximum power point tracker which ensures that the TEG system outputs the maximum possible power to the load. However, if the conditions, e.g., temperature, health, etc., of the TEG modules are different, each TEG module will not produce its maximum power. If each TEG module is controlled individually, each TEG module can be operated at its maximum power point and the TEG system output power will therefore be higher. In this work a power converter based on noninverting buck–boost converters capable of handling four TEG modules is presented. It is shown that, when each module in the TEG system is operated under individual maximum power point tracking, the system output power for this specific application can be increased by up to 8.4% relative to the situation when the modules are connected in series and 16.7% relative to the situation when the modules are connected in parallel.     

Dynamic Maximum Power Point Tracking of Photovoltaic Arrays Using Ripple Correlation Control

A dynamically rapid method used for tracking the maximum power point of photovoltaic arrays, known as ripple correlation control, is presented and verified against experiment. The technique takes advantage of the signal ripple, which is automatically present in power converters. The ripple is interpreted as a perturbation from which a gradient ascent optimization can be realized. The technique converges asymptotically at maximum speed to the maximum power point without the benefit of any array parameters or measurements. The technique has simple circuit implementations.     

动态频谱抗干扰系统在部分频带干扰下的性能

为了评估动态频谱抗干扰新体制在抗干扰通信中的性能,采用理论分析与仿真相结合的方法,研究了动态频谱抗干扰系统在部分频带干扰下的信道容量及比特误码率,并将其与常规跳频系统在部分频带干扰下的信道容量及比特误码率进行了比较.结果表明:在很宽的部分频带干扰因子取值范围内,动态频谱抗干扰系统的信道容量均大于常规跳频系统的信道容量,...     

Maximum Power Transmission in Mass-Limited Radio Systems

A simple fundamental relationship is derived between antenna gain and transmitter power which maximizes the effective radiated power in mass-limited satellite systems. In the most common case, maximum effective radiated power is achieved when the payload mass is divided equally between the antenna system and the power system. Although this may have been known intuitively to satellite designers, to the author's knowledge this relationship has never been published. Example calculations show that considerable increases in performance can be expected for satellites which employ high-gain multibeam antennas.     

On the necessity of joint adoption of both Distributed Maximum Power Point Tracking and Central Maximum Power Point Tracking in PV systems

In this paper, the main causes that are able to limit the efficiency of Distributed Maximum Power Point Tracking (DMPPT) are analyzed in detail. It will be shown that, to get full profit from DMPPT, it is necessary that the bulk inverter voltage belongs to an optimal range whose position and amplitude are functions of the following factors: the number of PV modules and dedicated DC/DC converters in a string, the atmospheric operating conditions characterizing each PV module (irradiance and temperature values), the voltage and current ratings of the physical devices the DC/DC converters are made of, and the adopted DC/DC converter topology. Moreover, it will be given proof of the necessity to couple the DMPPT function with a suitable centralized MPPT function carried out by the inverter through the proper control of its own DC input voltage. Copyright © 2012 John Wiley & Sons, Ltd.     

光伏发电中最大功率点跟踪控制方法综述

在光伏发电系统中,光伏电池输出特性具有明显的非线性特征,其输出功率受光照强度及环境温度影响很大。因此,为了提高光伏电池的利用效率,需要快速准确地对光伏电池的最大功率点进行跟踪控制。本文简要介绍了十多种常用的光伏电池最大功率点跟踪控制方法的原理,说明了各种控制方法的优缺点,指出了选择某一方法时需要综合考虑的因素,并展望了光伏发电系统最大功率点跟踪方法的发展方向。     

Investigation of Maximum Power Point Tracking for Thermoelectric Generators

In this paper, a thermoelectric generator (TEG) model is developed as a tool for investigating optimized maximum power point tracking (MPPT) algorithms for TEG systems within automotive exhaust heat energy recovery applications. The model comprises three main subsystems that make up the TEG system: the heat exchanger, thermoelectric material, and power conditioning unit (PCU). In this study, two MPPT algorithms known as the perturb and observe (P&O) algorithm and extremum seeking control (ESC) are investigated. A synchronous buck–boost converter is implemented as the preferred DC–DC converter topology, and together with the MPPT algorithm completes the PCU architecture. The process of developing the subsystems is discussed, and the advantage of using the MPPT controller is demonstrated. The simulation results demonstrate that the ESC algorithm implemented in combination with a synchronous buck–boost converter achieves favorable power outputs for TEG systems. The appropriateness is by virtue of greater responsiveness to changes in the system’s thermal conditions and hence the electrical potential difference generated in comparison with the P&O algorithm. The MATLAB/Simulink environment is used for simulation of the TEG system and comparison of the investigated control strategies.     

光伏并网系统中的最大功率点追踪控制

太阳能电池阵列输出特性具有强烈的非线性,为了提高系统的整体效率,一个重要的途径就是实时调整光伏电池的工作点,进行最大功率点跟踪(MPPT),使之始终工作在最大功率点附近。对并网系统的DC-DC电路原理和控制方法进行了研究,利用增量电导算法,通过脉宽调制的办法实现最大功率点的追踪,并用实验证实了其可行性和正确性。     

Maximum Power Point Tracking in a One-Cycle-Controlled Single-Stage Photovoltaic Inverter

In this paper, the design of the one-cycle controller of a single-stage inverter for photovoltaic applications is carried out by means of a multiobjective strategy to optimize inverter performance at both high and low insolation levels. Design constraints that account for different weather conditions are adopted. The optimization algorithm also provides useful information concerning the system sensitivity with respect to each of the controller parameters. This allows the design of a maximum power point tracking perturb and observe controller that significantly improves inverter performance. Experimental measurements confirm the predictions of theoretical and simulation results.     

Efficiency Study of a Commercial Thermoelectric Power Generator (TEG) Under Thermal Cycling

Thermoelectric generators (TEGs) make use of the Seebeck effect in semiconductors for the direct conversion of heat to electrical energy. The possible use of a device consisting of numerous TEG modules for waste heat recovery from an internal combustion (IC) engine could considerably help worldwide efforts towards energy saving. However, commercially available TEGs operate at temperatures much lower than the actual operating temperature range in the exhaust pipe of an automobile, which could cause structural failure of the thermoelectric elements. Furthermore, continuous thermal cycling could lead to reduced efficiency and lifetime of the TEG. In this work we investigate the long-term performance and stability of a commercially available TEG under temperature and power cycling. The module was subjected to sequential hot-side heating (at 200°C) and cooling for long times (3000 h) in order to measure changes in the TEG’s performance. A reduction in Seebeck coefficient and an increase in resistivity were observed. Alternating-current (AC) impedance measurements and scanning electron microscope (SEM) observations were performed on the module, and results are presented and discussed.     

最大功率跟踪控制在光伏系统中的应用

对最大功率跟踪控制中DC-DC变换器的原理和控制方法进行了实验研究,利用DC-DC转换电路和单片机控制系统实现最大功率点跟踪,使太阳电池始终保持最大功率输出;和普通的控制器相比增加输出功率5％～15％。     

光伏系统中最大功率点跟踪的研究

最大功率点跟踪是光伏发电研究的一个重要方向。本文介绍了光伏电池组件的特性以及光伏电池阵列最大功率点跟踪的原理,阐述了传统的跟踪光伏电池最大功率点的方法——扰动观察法,在此基础上提出了基于变换器输出电流控制的最大功率点跟踪法,该方法继承了扰动观察法的优点,并且降低了系统的成本,减轻了系统的运算负担。本研究在光伏系统的开发和应用中具有重要的科学研究意义和现实意义。     

光伏电池最大功率点跟踪控制研究

本文基于光伏电池数学模型,建立了光伏电池仿真模型.该模型能准确反映光伏电池的输出特性,而且参数调节方便.在不同的串联电阻和日照强度变化条件下,对光伏电池输出特性理论分析的基础上,建立实现最大功率跟踪(MPPT)的控制模型,仿真结果证明光伏电池的输出特性呈非线性,并随串联电阻和日照强度的变化而变化.为克服光伏电池输出功率...     

Hardware Implementation of Maximum Power Point Tracking for Thermoelectric Generators

This work describes the practical implementation of two maximum power point tracking (MPPT) algorithms, namely those of perturb and observe, and extremum seeking control. The proprietary dSPACE system is used to perform hardware in the loop (HIL) simulation whereby the two control algorithms are implemented using the MATLAB/Simulink (Mathworks, Natick, MA) software environment in order to control a synchronous buck–boost converter connected to two commercial thermoelectric modules. The process of performing HIL simulation using dSPACE is discussed, and a comparison between experimental and simulated results is highlighted. The experimental results demonstrate the validity of the two MPPT algorithms, and in conclusion the benefits and limitations of real-time implementation of MPPT controllers using dSPACE are discussed.     

太阳能最大功率点跟踪控制系统的研究与实现

针对太阳能本身的特点以及其功率特性,运用最大功率点跟踪的方法来实现对系统的控制,从而使太阳能的利用率得到大幅提高,造福人类。     

太阳能电池最大功率点跟踪技术探讨

介绍了光伏发电系统太阳能电池的输出特性及最大功率点跟踪技术的基本原理.分析了多种常用的跟踪方法的优缺点.重点研究了二次插值法的最大功率点跟踪技术.并设计了一个系统,应用常规实验方法及二次插值法寻找太阳能电池的最大输出功率,试验结果表明二次插值法能快速寻找太阳能电池的最大输出功率.