独立运行风光互补发电系统能量优化管理协调控制策略

针对系统运行工况复杂、供电稳定性和安全性要求高的特点,深入分析并给出独立运行风光互补发电系统能量流动及工作模式转换关系图,采用风电优先、光电次之、蓄电池辅助的电能分配原则与功率供需动态平衡的能量优化管理机制,提出包括能量管理与工作模式控制、风力发电控制、光伏发电控制和蓄电池充放电控制在内的功率协调控制策略。风力和光伏子系统控制均具有功率电压双闭环控制结构,功率外环采用基于梯度变步长MPPT算法或基于梯度信息LPTC算法产生最佳功率点电压,电压内环实现最佳功率点电压的自动、快速、无差跟踪,同时可实现MPPT和LPTC算法之间的平滑切换。仿真研究结果表明,本文所论能量优化管理协调控制策略能够根据风速、光照强度、负载的变化及蓄电池工况,协调风力发电、光伏发电子系统和蓄电池的工作状态,实现系统不同工作模式下自动运行及合理转换,保持能量供需动态平衡,实现系统的优化及可靠运行。     

非均衡负载独立光伏发电系统参数设计方法的研究

常规光伏系统设计多以获取最大电能为目标,而对于非均衡负载独立光伏系统,为满足各时间段负载正常供电不得不提高整体光伏发电系统的容量,而导致大量能量浪费。本文剖析了独立光伏发电系统内部各模块间的匹配关系,特别考虑非均衡负载对系统参数设计的影响,在此基础上构思独立光伏系统参数设计新方法,以提高光伏系统的可靠性和经济性的匹配。新算法能同时适应均衡负载和非均衡负载系统的参数设计。本文最后,利用该算法,对广州某一非均衡负载的独立光伏发电系统进行了参数设计,并做了分析和对比。     

光伏发电系统的防雷电结构设计研究

随着新能源的快速发展,太阳能发电应用范围越来越广泛。雷电作用在光伏组件上轻则会造成组件PN结间击穿和防倒流二极管击穿,重则会损坏控制器、逆变器或者是交、直流负载等设备及外围连接设备,为了确保太阳能光伏发电系统可靠和安全地工作,其防雷避雷问题必须解决。本文通过对雷电分析确定了其对光伏发电系统造成的影响及危害,重点阐述了结合不同的雷击形式优化设计光伏发电系统结构的避雷方案,并设计了一种新型的光伏发电系统用防雷器,更合理的保护光伏发电电源系统。     

太阳能光伏发电系统的系统分类

正太阳能光伏发电系统分为独立光伏发电系统、并网光伏发电系统及分布式光伏发电系统。a)独立光伏发电系统也叫离网光伏发电系统。主要由太阳能电池组件、控制器、蓄电池组成,若要为交流负载供电,还需要配置交流逆变器;b)并网光伏发电系统就是太阳能组件产生的直流电经过并网逆变器转换成符合市电电网要求的交流电之后直接接入公共电网。并网光伏发电系统有集中式大型并网光伏电站,一般都是国家级电站,主要特点是     

独立光伏混合储能发电自治系统配置优化

发电自治系统是指零排放不间断运行的系统。根据负载特性和太阳光照强度时间分布曲线,结合典型储能器件,包括蓄电池、燃料电池与电解制氢,用穷尽搜索法对独立光伏混合储能发电自治系统进行了优化配置。以年为运行周期,按照蓄电池、燃料电池与电解制氢的充放电顺序,得到实现不间断供电的配置方案。根据各器件的安装和运行维护成本,计算各配置方案的年运行成本。为实现独立光伏混合储能发电自治系统的配置优化提供设计依据。     

可逆流光伏与市电联合供电能量管理研究

针对光伏直流供电系统的能量变动性,提出了使用市电作为直流负载的能量补偿来源。系统由光伏电池、市电、移相全桥变换器、PWM整流器组成。在光伏发电能量大于负载所需时,将多余的能量馈送电网;在光伏发电能量不足时,由市网补充。系统的核心是实现光伏、市电、负载三者之间的能量管理。文章首先对整个供电系统进行了分析,然后讨论了系统的不同工作模式,最后提出了市电的能量补偿控制策略。仿真和实验表明所提的系统结构和控制策略能够实现市电与光伏供电系统的稳定联合供电。     

离网太阳能发电

离网太阳能发电：太阳能发电控制器（光伏控制器和风光互补控制器）对所发的电能进行调节和控制。一方面把调整后的能量送往直流负载或交流负载：另一方面把多余的能量送往蓄电池组储存,当所发的电不能满足负载需要时,控制器又把蓄电池的电能送往负载。     

基于新型混合储能结构的独立光伏发电系统

针对独立光伏发电系统特殊的工作情况,提出一种基于新型双向Buck变换器的有源式混合储能方案。建立系统模型,给出系统能量管理和控制策略。仿真和实验结果表明:所提出的混合储能方案能充分发挥超级电容器的优势,有效改善蓄电池的工作状态,延长其使用寿命,特别适合于负载功率脉动频繁的独立光伏发电系统。     

独立村落光伏电站系统运行及使用的调研与分析(3)——光伏系统用户情况及系统负载的调研与分析

本文为调研分析报告的第三部分,介绍了独立村落光伏发电系统用户用电情况及系统负载的调研分析结果,并提出了相关结论和建议。     

一种并网型风光互补发电系统的建模与仿真

分析了风光互补发电系统的技术优势,设计了基于固态变压器结构的并网型风光互补发电系统。分别建立了光伏系统,风力发电系统,超级电容和蓄电池的模型,并分析各环节的控制策略,提出了基于平均功率的储能设备容量配置方法。仿真结果表明,该系统能模拟风光互补系统在不同模式下的运行特性,可以有效降低功率波动和维持电压稳定,并能在低光照强度、低风速等情况下为系统提供短时能量支撑。     

Systematic procedures for sizing photovoltaic pumping system,using water tank storage

In this work, the performances of the photovoltaic pumping destined to supply drinking water in remote and scattered small villages have been studied. The methodology adopted proposes various procedures based on the water consumption profiles, total head, tank capacity and photovoltaic array peak power. A method of the load losses probability (LLP) has been used to optimize sizing of the photovoltaic pumping systems with a similarity between the storage energy in batteries and water in tanks. The results were carried out using measured meteorological data for four localities in Algeria: Algiers and Oran in the north, Bechar and Tamanrasset in the south. The results show that the performance of the photovoltaic pumping system depends deeply on the pumping total head and the peak power of the photovoltaic array. Also, for the southern localities, the LLP method shows that the size of the photovoltaic array varies versus LLP on a small scale. On the other hand, for the northern localities, the sizing of the photovoltaic array is situated on a large scale power. Because of the current high crud-oil price, the photovoltaic pumping still to be the best adopted energy resource to supply drinking water in remote and scattered villages.     

Model for energy conversion in renewable energy system with hydrogen storage

A dynamic model for a stand-alone renewable energy system with hydrogen storage (RESHS) is developed. In this system, surplus energy available from a photovoltaic array and a wind turbine generator is stored in the form of hydrogen, produced via an electrolyzer. When the energy production from the wind turbine and the photovoltaic array is not enough to meet the load demand, the stored hydrogen can then be converted by a fuel cell to produce electricity. In this system, batteries are used as energy buffers or for short time storage. To study the behavior of such a system, a complete model is developed by integrating individual sub-models of the fuel cell, the electrolyzer, the power conditioning units, the hydrogen storage system, and the batteries (used as an energy buffer). The sub-models are valid for transient and steady state analysis as a function of voltage, current, and temperature. A comparison between experimental measurements and simulation results is given. The model is useful for building effective algorithms for the management, control and optimization of stand-alone RESHSs.     

Analytical model for predicting the performance of photovoltaic array coupled with a wind turbine in a stand-alone renewable energy system based on hydrogen

We present the results of an analysis of the performance of a photovoltaic array that complement the power output of a wind turbine generator in a stand-alone renewable energy system based on hydrogen production for long-term energy storage. The procedure for estimating hourly solar radiation, for a clear sunny day, from the daily average solar insolation is also given. The photovoltaic array power output and its effective contribution to the load as well as to the energy storage have been determined by using the solar radiation usability concept. The excess and deficit of electrical energy produced from the renewable energy sources, with respect to the load, govern the effective energy management of the system and dictate the operation of an electrolyser and a fuel cell generator. This performance analysis is necessary to determine the effective contribution from the photovoltaic array and the wind turbine generator and their contribution to the load as well as for energy storage.     

Optimisation of a photovoltaic battery ultracapacitor hybrid energy storage system

Autonomous photovoltaic panels are intermittent sustainable energy sources which require energy storage to balance generation and demand, as photovoltaic generation is time and weather dependent. Traditionally batteries are the most common storage technology for photovoltaic systems. Photovoltaic batteries can encounter extended periods of low State of Charge (SOC), resulting in sulphation and stratification, reducing battery lifetime.Standalone photovoltaic systems are often used in remote areas away from the national grid for water irrigation system, requiring dc motor starting resulting in high inrush current, cathodic protection systems for oil and gas pipelines, emergency phones, warning signs, and telecommunication repeater stations, resulting in pulse discharging of the battery. A combination of depleted battery SOC and high burst current can result in premature loss of load due to stringent battery Low Voltage Disconnect (LVD) limits implemented by the battery management system.A combination of Valve Regulated Lead Acid (VRLA) batteries and ultracapacitors in a Hybrid Energy Storage System (HESS), which increases the power density of the overall system, is examined. Operating the ultracapacitor bank under high power conditions reduces the strain of large current extraction from the battery bank. The addition of the ultracapacitor bank presents the need for a methodology to optimise the photovoltaic system to prevent excess battery storage.This paper outlines the methodology utilised to optimise the combination of photovoltaic panels, batteries, and ultracapacitors for a given solar radiation and load profile employing Matlab software.     

Real-time simulation of photovoltaic modules

A photovoltaic (PV) array simulator, consisting of a computer controlled d.c. power supply producing up to 100 W and associated control software, was designed and developed to generate real-time current-voltage (I-V) output characteristic curves of photovoltaic cells under simulated conditions. The system is also capable of modelling radiation damage due to high energy particles. The system comprises a pre-regulator, a switch-mode regulator, a computer interface, and modelling and control software. The control software uses feedback of the output voltage and current to iteratively converge to the actual operating point for the connected load. Simulation results match the expected theoretical calculations well. The main advantage of the simulator is its ability to simulate different types and sizes of arrays under varying illumination and temperature using actual loads. The system can be used to study the short-term and long-term performances of PV modules and to predict end-of-life efficiency. The simulator is a far more cost effective and reliable replacement for actual field testing.     

Photovoltaic‐powered cold store and its performance

A photovoltaic‐powered cold store plant, the first of its kind, has been developed to store 10 tons of frozen fish at ?15°C. It consists of a photovoltaic array (4 kW peak), a battery bank (96 V DC, 180 A H), a vapour compression refrigeration system (1 ton), electronic controls for automatic operation of plant and an insulated cold chamber. Experiments were conducted on the system to evaluate its performance with no heat load (frozen fish at ?15°C) and with different heat loads. It is observed that the system can be operated with a maximum heat load of 2350 W to maintain the walk‐in‐cooler temperature below the freezing point of fish (?2°C). The performance studies conducted on these subsystems viz., photovoltaic array and battery bank showed that their output has deteriorated in 5 years. Copyright © 2001 John Wiley & Sons, Ltd.     

Partial shadowing of photovoltaic arrays with different system configurations: literature review and field test results

Partial shadowing has been identified as a main cause for reducing energy yield of grid-connected photovoltaic systems. The impact of the applied system configuration on the energy yield of partially shadowed arrays has been widely discussed. Nevertheless, there is still much confusion especially regarding the optimal grade of modularity for such systems. A 5-kWp photovoltaic system was installed at K.U. Leuven. The system consists of three independent subsystems: central inverter, string inverter, and a number of AC modules. Throughout the year, parts of the photovoltaic array are shadowed by vegetation and other surrounding obstacles. The dimensions of shadowing obstacles were recorded and the expectable shadowing losses were estimated by applying different approaches. Based on the results of almost 2 years of analytical monitoring, the photovoltaic system is assessed with regard to shadowing losses and their dependence on the chosen system configuration. The results indicate that with obstacles of irregular shape being close to the photovoltaic array, simulation estimates the shadowing losses rather imprecise. At array positions mainly suffering from a reduction of the visible horizon by obstacles far away from the photovoltaic array, a simulation returns good results. Significant differences regarding shadow tolerance of different inverter types or overproportional losses with long module strings could not be confirmed for the system under examination. The negative impact of partial shadowing on the array performance should not be underestimated, but it affects modular systems as well as central inverter systems.     

Low light conditions modelling for building integrated photovoltaic (BIPV) systems

The low irradiance efficiency of photovoltaic modules is important to the optimization of BIPV systems. When photovoltaic modules are integrated into a building, architectural design considerations compete with maximizing photovoltaic energy production. As a result, BIPV arrays are often not facing south and are frequently mounted vertically. Under these conditions, a greater portion of the total sunlight striking the array is diffuse or at high angles of incidence. In northern latitudes a significant amount of the total yearly energy is produced at low light levels.A grid-connected array of BIPV modules integrated into the BCIT Technology Centre building in Burnaby, B.C. was used for assessing the accuracy of an energy performance model developed for BIPV systems. The BIPV system uses AC modules and a computerized data acquisition system for monitoring the performance of modules and inverters. The performance model was developed from analysis of the open circuit voltage, maximum power point voltage and maximum power point current of the individual modules comprising the BIPV array.The algorithm for calculating power output of the photovoltaic array is derived from the ideal diode equation using the single diode model of a photovoltaic cell. An empirically derived parameter modifies the equation. Once the parameters for different module technologies are established, it is possible to compare their annual performance in a BIPV system.     

具有MPPT功能的智能户用光伏充电系统研究

光伏充电系统采用了恒流充电和du/dt恒压限流充电相结合的管理模式,在一定时间内以电压的变化量接近零,并使充电电流达到最小设定量作为判断蓄电池充电终止的条件,采用了电压自寻优算法实现了光伏电池的最大功率点跟踪.试验表明,系统除了具有智能化管理的特点外,光伏电池的最大功率点跟踪效果明显,且不用考虑日照强度和温度对光伏电池的影响,在一定程度上能够提高光伏电池的输出功率.     

A method for predicting long-term average performance of photovoltaic systems

A method for predicting the long-term average conventional energy displaced by a photovoltaic system comprising of a photovoltaic array, a storage battery, some power conditioning equipment with maximum power tracking capability and an auxiliary power facility, is described. System simulation is done over the average day of the month. Average hourly energy flows are estimated from a knowledge of array test parameters, monthly average hourly ambient temperature and monthly average daily hemispherical radiation. The monthly average diffuse component of radiation can be predicted from the hemispherical radiation by the use of an appropriate empirical correlation relating the monthly average diffuse fraction to monthly average clearness index. Hourly average radiation values are estimated from daily values using a statistical model. The condition that there should be no net battery energy gain during the average day enables the correct setting of the battery energy level at the beginning of the day. For a given hourly load profile, for example a constant 24 h-per-day load, a chart relating annual solar fraction with array and storage battery size, for a given location and set of array test parameters, can be plotted as a basis for design and economic optimisation of the system.