Supercapacitors for power control in a grid-connected photovoltaic system

并网光伏发电系统输出功率的波动性和随机性给并网后系统稳定性,光伏发电消纳以及光伏电站电能质量等方面带来了负面影响,制约了光伏发电的发展.针对这一问题,将超级电容器作为功率调节装置,控制光伏并网系统按指定值平滑,准确地输出功率,使光伏发电具有可调度性.在分析了超级电容特性,系统构成和双向DC/DC变换器状态空间平均小信号模型的基础上,提出功率,电流双闭环反馈滞环电流控制策略,控制超级电容器吸收或补充输出功率的波动成分.在PSCAD/EMTDC 电力系统仿真软件中构建仿真模型,对提出的系统和控制策略进行了仿真分析,良好的仿真结果验证了方法的可行性.     

独立光伏发电系统充放电控制策略

为了提高蓄电池的充电效率和延长蓄电池的使用寿命,提出了一种新的光伏发电系统充放电控制策略.该控制策略用双蓄电池代替以前的单一蓄电池,在充电过程中,蓄电池按照光伏系统提供的电流进行充电,根据蓄电池的充电电压特性和内部的温度特性来判别充电终止电压.同时,采用电压、温度微分模糊控制算法,既能防止光照强度、温度等外部环境发生变化而导致对蓄电池充电的提前切除,又可保护蓄电池的过充.仿真结果证明,该控制策略能显著提高蓄电池的充电效率和延长蓄电池的使用寿命.     

5 kW DC/DC converter for hydrogen generation from photovoltaic sources

This paper covers the design of a DC–DC power converter aimed for hydrogen production from photovoltaic sources. Power conditioning for such application is usually driven by different constraints: high step-down conversion ratio is required if the input voltage of such equipment has to be compatible with photovoltaic sources that are connected to grid-connected inverters; galvanic isolation; high efficiency and low mass. Taking into account those factors, this work proposes a push–pull DC/DC converter for power levels up to 5 kW. The operation and features of the converter are presented and analyzed. Design guidelines are suggested and experimental validation is also given.     

分布式光伏发电系统最大功率点跟踪技术比较研究

基于当前光伏阵列最大功率点跟踪技术的研究现状,介绍了适用于分布式光伏发电系统最大功率点跟踪的各种常用控制方法,阐述了每一种控制方法的技术原理,分析和比较了这些常用控制方法的特点,总结了各自的优点和缺点,最后对分布式光伏发电系统最大功率点跟踪方法的选择问题进行了探讨,并指出了具体选择方法时应综合考虑的各种因素。     

某15MW太阳能屋顶光伏发电工程的应用分析

在对太阳能屋顶光伏发电系统构成及发展意义阐述的基础上,通过对某15MW屋顶光伏发电工程大量实际数据的分析,表明太阳能屋顶光伏发电工程具有良好的社会、经济效益和广阔的发展前景。     

邮轮混合储能系统分段式下垂控制技术

针对脉冲负载频繁投切引起的邮轮混合储能系统频率、电压波动问题,提出一种改进的下垂控制策略。针对锂电池和超级电容混合储能系统建立仿真模型,为各储能单元配置独立的双向DC/DC变换器,仿真分析分段式下垂控制策略对功率分配和均流控制的效果。仿真结果表明：在负载突加或突卸工况下,分段式下垂控制策略可根据负载功率和直流母线电压变化自动控制储能系统功率流向,快速有效平抑电网的负载波动。     

Control strategies for a photovoltaic--Energy storage hybrid system

受光照,温度等自然条件影响,光伏电源输出有功功率具有较大的波动性.因此,本身既非恒压源又非恒流源的光伏电源并网运行时会产生一系列问题,如对电网冲击性大,需增加旋转备用容量,难以参与电网调度等.利用电池储能系统来控制有功功率输出,可以使平滑光伏电源功率波动成为可能.研究了光储联合发电系统的运行模式,提出了适用于光储联合发电系统的拓扑结构和控制策略,并对储能用功率转换系统(PCS)进行了分析和设计,最后基于某光伏电站的实际历史运行数据,对所提出的方案进行仿真研究,仿真结果验证了光储联合发电系统控制策略的有效性和可行性,为光储联合运行示范工程提供了一定的理论依据和有力借鉴.     

光伏发电的六象限法太阳自动跟踪系统

为了增加太阳能电池的输出功率,往往采用光伏板自动跟踪太阳的方法。文章在传统的四象限法跟踪基础上,设计了一种六象限法光电式太阳位置检测跟踪装置。采用STC12C5A60S2单片机作为控制芯片,以步进电机作为执行机构,通过单片机控制双步进电机,实现双轴太阳自动跟踪。实验表明,该系统不仅可以实现对太阳的自动跟踪,而且能提高对太阳跟踪的稳定性,具有较高的实用价值。     

Life cycle assessment and evaluation of energy payback time on high-concentration photovoltaic power generation system

In this study, the environmental load of photovoltaic power generation system (PV) during its life cycle and energy payback time (EPT) are evaluated by LCA scheme. Two hypothetical case studies in Toyohashi, Japan and Gobi dessert in China have been carried out to investigate the influence of installation location and PV type on environmental load and EPT. The environmental load and EPT of a high-concentration photovoltaic power generation system (hcpV) and a multi-crystalline silicon photovoltaic power generation system (mc-Si PV) are studied. The study shows for a PV of 100 MW size, the total impacts of the hcpV installed in Toyohashi is larger than that of the hcpV installed in Gobi desert by 5% without consideration of recycling stage. The EPT of the hcpV assumed to be installed in Gobi desert is shorter than EPT of the hcpV assumed to be installed in Toyohashi by 0.64 year. From these results, the superiority to install PV in Gobi desert is certificated. Comparing with hcpV and mc-Si PV, the ratio of the total impacts of mc-Si PV to that of hcpV is 0.34 without consideration of recycling stage. The EPT of hcpV is longer than EPT of mc-Si PV by 0.27 year. The amount of global solar radiation contributing to the amount of power generation of mc-Si PV is larger than the amount of direct solar radiation contributing to the amount of power generation of hcpV by about 188 kW h/(m² year) in Gobi desert. Consequently, it appears that using mc-Si PV in Gobi desert is the best option.     

光伏系统最大功率点跟踪方法

最大功率点跟踪是光伏发电系统中重要的问题.在对太阳电池特性曲线分析的基础之上,阐述了几种常用的光伏系统最大功率点的追踪方法.文章总结并分析了各种方案的优缺点.     

A maximum power point tracking control strategy with variable weather parameters for photovoltaic systems with DC bus

In photovoltaic (PV) system, the most commonly used DC/DC converter is the basic buck or boost circuit to implement the maximum point power tracking (MPPT) due to their simple structure and low cost while there are some MPPT constraint conditions. By contrast, the conventional buck/boost DC/DC converter without MPPT constraint condition is seldom used because of its high cost or poor performance. To keep the advantages of these three DC/DC converters while overcoming their shortcomings, in this paper, the constraint conditions of capturing the maximum power point (MPP) of PV systems with direct-current (DC) bus are found out. Then, on the basis of this work, a MPPT control strategy with variable weather parameters is proposed. In this strategy, a new buck/boost DC/DC converter is proposed, which not only avoids the MPPT constraint conditions of basic buck or boost DC/DC converter but also overcomes the shortcomings of conventional buck/boost DC/DC converter. Finally, lots of simulated experiments verify the accuracy of MPPT constraint conditions, test the feasibility and availability of proposed MPPT control strategy, analyze the MPPT performance of proposed PV system and compare the output transient-state performance with conventional perturb and observe (P&O) method.     

Implementation of photovoltaic water pumping system with MPPT controls

To increase the output efficiency of a photovoltaic (PV) system, it is important to apply an efficient maximum power point tracking (MPPT) technique. This paper describes the analysis, the design and the experimental implementation of the tracking methods for a stand-alone PV system, using two approaches. The first one is the constant voltage (CV) MPPT method based on the optimum voltage, which was deduced experimentally, and considered as a reference value to extract the optimum power. The second one is the increment conductance (Inc-Cond) MPPT method based on the calculation of the power derivative extracted by the installation. The output controller can adjust the duty ratio to the optimum value. This optimum duty ratio is the input of a DC/DC boost converter which feeds a set of Moto-pump via a DC/AC inverter. This paper presents the details of the two approaches implemented, based on the system performance characteristics. Contributions are made in several aspects of the system, including converter design, system simulation, controller programming, and experimental setup. The MPPT control algorithms implemented extract the maximum power point (MPP), with satisfactory performance and without steady-state oscillation. MATLAB/Simulink and dSpace DS1104 are used to conduct studies and implement algorithms. The two proposed methods have been validated by implementing the performance of the PV pumping systems installed on the roof of the research laboratory in INSAT Tunisia. Experimental results verify the feasibility and the improved functionality of the system.     

光伏电力混合储能系统的能量管理策略研究

文章提出了一种光伏电力混合储能系统的能量管理控制策略,主要应用于含有光伏电源(Photovoltaic,PV)、电池能量存储(Battery Energy Storage, BES)和交流负载的发电网络系统中。该策略能够充分利用电力系统中组合架构之间的连接关系,有效缓解了目前电网中BES系统存在的过充电、欠充电等问题,并将充放电电流控制在一个相对稳定的范围内,延长了电池的使用寿命。分别在含有传统铅酸和锂离子电池的混合能量系统中使用6 kVA电源转换器进行实验,结果证明了所提出的能量管理策略的正确性和有效性。     

基于改进遗传算法的风/光互补发电系统恒压控制

针对带有约束条件的风/光互补发电系统恒压控制这个多极值非线性组合优化问题,采用一种改进遗传算法,以系统发电成本最低为目标,根据拧制规则对一风/光互补发电系统的电压进行了优化.仿真结果表明.该算法能显著地提高收敛速度和计算精度,有效地提高了风/光互补发电系统的电压稳定性.     

A photovoltaic powered electrolysis converter system with maximum power point tracking control

One of the main problems for renewable and other innovative energy sources is the storage of energy for sustainability. This study focuses on two different scenarios to benefit from solar energy more efficiently. Photovoltaic (PV) energy is converted to the desired voltage level using a buck converter for generating hydrogen with electrolysis process. A maximum power point tracking (MPPT) algorithm is used to benefit from the photovoltaic sources more efficiently. The basic electrolysis load for hydrogen production needs low voltage and high current and controlled sensitively to supply these conditions. The photovoltaic powered buck converter for electrolysis load was simulated in MATLAB/Simulink software using a perturb and observe (P and O) MPPT algorithm and PI controller. The simulation results show that in normal, short circuit and open circuit working conditions the PV and load voltages are stabilized. The efficiency of the proposed system is reached more than 90% for high irradiance levels.     

Energy management of a hybrid photovoltaic system

This work describes a new control strategy for active energy flow in a hybrid photovoltaic (PV) system. The method introduces an online energy management by a hierarchical fuzzy controller between energy sources that consist of a photovoltaic panel (PVP), the battery and the load. The fuzzy logic controller has been developed for power splitting between PVP and battery, and it makes decision to choose the switching chain rules and corresponding controller. Simulation test results illustrate improvement in the operation's efficiency of online state of the switches and the battery's state of charge (SOC) has been maintained at a reasonable level. Copyright © 2010 John Wiley & Sons, Ltd.     

An integrated system for thermal power generation,electrical energy storage and CO2 capture

This work reports a newly proposed system for electrical energy storage. The new system combines a direct open nitrogen (cryogen) expansion cycle with a natural gas‐fuelled closed Brayton cycle and the CO₂ produced in the system is captured in the form of dry ice. Thermodynamic analyses are carried out on the system under the baseline conditions of 1 kg s^?1 natural gas, a combustor operating pressure of 8 bars and a cryogen topping pressure of 100 bars. The results show that the exergy efficiency of the proposed system is as high as 64% under the baseline conditions, whereas the corresponding electricity storage efficiency is about 54%. A sensitivity analysis has also been carried out on the main operating conditions. The results indicate that the baseline performance can be enhanced by increasing the gas turbine (GT) inlet temperature, decreasing the approach temperature of the heat exchange processes, operating the combustor at an optimal pressure of ～7 bars and operating the cryogen topping pressure at ～90 bars. Further enhancement can be achieved by increasing the isentropic efficiency of the GT and the liquefaction process. The results of this work also suggest that the power capacity installation of peak‐load units and fuel consumption could be reduced by as much as 50% by using the newly proposed system. Further work is suggested for an economic analysis of the system. Copyright © 2010 John Wiley & Sons, Ltd.     

储能技术在光伏并网发电系统中的应用分析

根据光伏并网发电系统的结构特点分析了不加储能装置的光伏并网发电系统对电网造成的不良影响,并分别从电网角度和用户角度提出了储能系统在光伏并网发电系统中的几种应用技术,最后提出了用于光伏并网发电系统的储能技术发展需求。     

Bidirectional energy storage photovoltaic grid-connected inverter application system

A novel topology of the bidirectional energy storage photovoltaic grid-connected inverter was proposed to reduce the negative impact of the photovoltaic grid-connected system on the grid caused by environmental instability. Using the proposed Inverter as a UPS power supply in case of a grid failure, storage electrical energy and regulating the energy delivered to the grid for reducing the pressure on the grid. A new artificial fish-swarm algorithm and variable step voltage perturbation method were presented to track the maximum power point of the solar panels. Analysis was done to reduce the output ripple of the inverter and sinusoidal pulse width modulation (SPWM) was selected to control the inverter. Model simulation was performed using PSpice software to obtain the volt-ampere characteristic curve of the solar panel output. The solar array simulator was used to verify the effect of maximum power point tracking at different light intensities. The study concludes that the maximum power point tracking (MPPT) efficiency of the bidirectional energy storage photovoltaic grid-connected inverter designed was as high as 99.9%. The distortion rate of the grid-connected current waveform was within 2% and the DC current component was less than 0.5%. The output voltage and power were in full compliance with the grid connection standard.     

Energy analysis of a CO2 recycling system

In this report, a CO₂ recycling system is proposed and designed for the purpose of CO₂ mitigation through utilization of natural energy (photovoltaic power generation). The materials for construction and unit requirements of this system are quantified and also an energy analysis is performed as one of life‐cycle analysis (LCA) of this system. Concrete required for the foundation of the facilities is the largest material requirement and accounts for 62 per cent of the total amount of materials for building this system. The energy consumption needed to build the photovoltaic (PV) power generation facilities represents the largest fraction of energy consumption and accounts for 82 per cent of the energy consumption needed for building of plants. The energy balance ratio of the system is approximately 1.85. It clearly reveals that this system would be an effective way to utilize natural energy. Copyright © 2000 John Wiley & Sons, Ltd.