System memory effects in the sizing of stand‐alone PV systems

Models based on daily energy balance (or long‐term models) have been widely used as a tool in the stand‐alone photovoltaic (PV) system sizing, mainly with the purpose of obtaining analytical expressions of the relation between the generator size and the storage capacity of the battery. The system can then be designed to meet the reliability requirements of the specific case. However, such models represent the complex operation of a stand‐alone system in an oversimplified way. There is little research so far on the reliability and improvement of such models. Validation and possible modification of a long‐term system model requires comparison of the simulated state of charge (SOC) of the battery with that obtained from an experimental system. In this work, experimental data from a 6‐month operation of a basic stand‐alone PV system have been analysed and compared with modelling results. One obvious improvement that could be applied to the long‐term system model is to account for a charging efficiency of the battery, and this possibility is examined in the present work. However, comparison with the modelling results shows that the data cannot be fitted by simply taking into account battery inefficiency. A method to account for system memory effects in the increase of the battery SOC, imposed by the operation of the regulator, is necessary to accurately model the macroscopic diurnal charging/discharging process. Copyright © 2012 John Wiley & Sons, Ltd.     

Advanced Integrated Bidirectional AC/DC and DC/DC Converter for Plug-In Hybrid Electric Vehicles

Hybrid electric vehicle (HEV) technology provides an effective solution for achieving higher fuel economy, better performance, and lower emissions, compared with conventional vehicles. Plug-in HEVs (PHEVs) are HEVs with plug-in capabilities and provide a more all-electric range; hence, PHEVs improve fuel economy and reduce emissions even more. PHEVs have a battery pack of high energy density and can run solely on electric power for a given range. The battery pack can be recharged by a neighborhood outlet. In this paper, a novel integrated bidirectional AC/DC charger and DC/DC converter (henceforth, the integrated converter) for PHEVs and hybrid/plug-in-hybrid conversions is proposed. The integrated converter is able to function as an AC/DC battery charger and to transfer electrical energy between the battery pack and the high-voltage bus of the electric traction system. It is shown that the integrated converter has a reduced number of high-current inductors and current transducers and has provided fault-current tolerance in PHEV conversion.     

基于扩展卡尔曼滤波模型的电动汽车锂电池SOC估算研究

针对新能源电动汽车锂电池电荷状态SOC估算问题,在锂电池二阶RC等效电路模型基础上,引入扩展卡尔曼滤波方法,利用扩展卡尔曼滤波方法处理复杂非线性系统能力,建立了扩展卡尔曼滤波锂电池SOC估算模型,并通过MATLAB/Simulink对新建模型仿真分析。仿真结果显示,建立的扩展卡尔曼滤波锂电池SOC估算模型具有较高估算精度,整体误差小于±0.05%,满足新能源电动汽车对锂电池SOC估算要求。     

基于ARM电池检测管理系统的设计与实现

针对电池组进行充放电时,电池组内每个电池存在荷电状态(SOC)值不一致的问题,设计并实现了电池检测管理系统.提出了基于开路电压法、安时计量法以及卡尔曼滤波算法相结合的SOC值估计方法,通过飞渡电容实现每个电池之间能量的转移,最终使每个电池的SOC值趋向于一致.测试和实验结果表明,电池组进行充放电时,电池检测管理系统能够有效地解决每个电池SOC值不一致的问题,大大地提升了电池的使用寿命和使用效率.     

Predictive Reference Signal Generator for Hybrid Electric Vehicles

A novel model-based and predictive energy supervisory controller for hybrid electric vehicles (HEVs) is presented. Its objective is to minimize the fuel consumption (FC) of HEVs using only the information on the current state of charge (SoC) of the battery and data available from a standard onboard navigation system. This objective is achieved using a predictive reference signal generator (pRSG) in combination with a nonpredictive reference tracking controller for the battery SoC. The pRSG computes the desired battery SoC trajectory as a function of vehicle position such that the recuperated energy is maximized despite the constraints on the battery SoC. To compute the SoC reference trajectory, only the topographic profile of the future road segments and the corresponding average traveling speeds must be known. Simulation results of the proposed predictive strategy show substantial improvements in fuel economy in hilly driving profiles, compared with nonpredictive strategies. A parallel HEV is analyzed in this paper. However, the proposed method is independent of the powertrain topology. Therefore, the method is applicable to all types of HEVs.      

不同SOC区间及倍率下锂电池老化分析

选择合适的荷电状态(State of Charge,SOC)区间及放电倍率可有效减缓锂电池的老化.将可大倍率放电的钴酸锂电池作为研究对象,将其SOC划分为四个区间,结合三个不同的放电倍率进行双因素老化实验.结果表明,相同放电深度(Depth of Discharge,DOD)情况下,SOC区间越高电池老化越快;释放的容...     

SHORT COMMUNICATION: Does climate change affect the design of stand‐alone PV systems?

This paper investigates the effect of using sequences of past daily solar radiation data on PV system sizing for the case of Efford (UK). For a given system configuration that never sheds load, the lowest SOC reached by the battery is found by an energy balance model, and the energy deficit calculated for a given climatic cycle. Although the average irradiation changes little during the years 1958–1994, there is a substantial increase in the storage requirement, which seems to be related with an increase in the persistence of low solar radiation values. Copyright © 2005 John Wiley & Sons, Ltd.     

Design of a Reflex-Based Bidirectional Converter With the Energy Recovery Function

In this paper, a reflex charging strategy with the energy recovery function for a bidirectional converter (BC) is proposed to build a novel reflex-based BC (RBC) for increasing the battery charging efficiency in an uninterruptible power supply (UPS). The proposed RBC can provide a reflex charging current profile to charge the battery to obtain a high battery charging efficiency and prolong the battery life cycle. In particular, the negative pulse energy of the reflex charging current profile in the proposed RBC is recovered to reduce the battery charging dissipation. A soft transfer method is also developed in this paper to really erase the spike current in the RBC. A 400 W prototype is designed and implemented to verify the feasibility of the proposed RBC. Compared with a typical bidirectional converter, the battery charging efficiency, the battery charging speed, and the battery thermal deterioration effect are improved by about 10%, 8.8%, and 7%, respectively, with the proposed RBC.      

综合能源系统主动配电网常规负荷预测模型

为实现高精度、高效率的电力负荷预测,构建一种综合能源系统中主动配电网常规负荷预测模型.首先建立综合能源等效模型,分析不可控负荷、可控负荷、可调负荷的特性;采用主动式负荷特性分析方法与储能特征分析方法分析主动配电网的友好负荷与储能特性,在设计目标函数和约束条件的基础上实现对综合能源系统中主动配电网常规负荷预测模型的求解....     

混合储能在风光互补发电系统中的能量管理与控制策略

储能技术在风光互补发电技术中的应用使得风光互补发电技术得到了进一步完善,各个部分的控制更加合理、有效,系统更加稳定、安全,并且使用效率及寿命得到了提高。通过仿真验证了一种蓄电池与超级电容混合储能结构,在这种结构中通过控制DC/DC变换器将蓄电池的高能量密度及超级电容的高功率密度的特点相结合,并且运用滑动滤波器进行二者的能量分配,同时通过DC/DC变换器达到对各储能部分实时控制的目的,从而提高了混合储能系统的灵活性与实用性。     

Fuel cells for the long haul, batteries for the spurts [electricvehicles]

Until only a few years ago, when environmentalists, automakers, and other concerned parties spoke about low-emissions vehicles, they were almost always referring to electric vehicles (EVs)-cars, trucks, and buses powered by batteries of one kind or another. Today, having so far failed in their quest for a battery that could make EVs practical, they are looking more and more to hybrid electric vehicles (HEVs), which automakers had hitherto rejected as merely an interim solution. But hybrids based on a combination of electric motors and internal combustion engines are attractive for two main reasons: they require no technology breakthroughs and no new infrastructure. They work with existing batteries since they do not rely on them for primary energy storage; rather, they can obtain fuel at any service station. An alternative to HEVs is fuel cell powered vehicles. The principles of this technology and the associated hydrogen storage issues are discussed. Other alternative fuels are briefly outlined     

Trip-Based Optimal Power Management of Plug-in Hybrid Electric Vehicles

Hybrid electric vehicles (HEVs) have demonstrated the capability to improve fuel economy and emissions. The plug-in HEV (PHEV), utilizing more battery power, has become a more attractive upgrade of the HEV. The charge-depletion mode is more appropriate for the power management of PHEVs, i.e., the state of charge (SOC) is expected to drop to a low threshold when the vehicle reaches the trip destination. Trip information has so far been considered as future information for vehicle operation and is thus not available a priori. This situation can be changed by the recent advancement in intelligent transportation systems (ITSs) based on the use of on-board global positioning systems (GPSs), geographical information systems (GISs), and advanced traffic flow modeling techniques. In this paper, a new approach to optimal power management of PHEVs in the charge-depletion mode is proposed with driving cycle modeling based on the historic traffic information. A dynamic programming (DP) algorithm is applied to reinforce the charge-depletion control such that the SOC drops to a specific terminal value at the end of the driving cycle. The vehicle model was based on a hybrid electric sport utility vehicle (SUV). Only fuel consumption is considered for the current stage of the study. A simulation study was conducted for several standard driving cycles and two trip models using the proposed method, and the results showed significant improvement in fuel economy compared with a rule-based control and a depletion sustenance control for most cases. Furthermore, the results showed much better consistency in fuel economy compared with rule-based and depletion sustenance control.      

面向蓄电池的多输入源低功耗充电电路设计

针对蓄电池的储能问题,提出了一种多输入源且可扩充的高效充电电路和相应的控制算法。该充电电路主要由数字控制单元（DCU）、比较器、基于Dickson电荷泵结构的时钟倍压器（CVD）以及模拟开关组成,可以对多个独立能量采集器（EH）进行电能收集。该系统支持通过热插拔方式扩充任意数量的EH。提出的控制算法可以将从各个EH采集到的能量传递到能量储存装置而不会互相干扰。采用0.18 μm CMOS工艺对提出电路进行了具体实现。实验结果显示,相比类似的蓄电池充电系统,该充电电路的功耗最低,只需1.72μW的功耗,能够为三个输入源提供高达96.1%的最大充电效率。     

Investigation of the Energy Regeneration of Active Suspension System in Hybrid Electric Vehicles

This paper investigates the idea of the energy regeneration of active suspension (AS) system in hybrid electric vehicles (HEVs). For this purpose, extensive simulation and control methods are utilized to develop a simultaneous simulation in which both HEV powertrain and AS systems are simulated in a unified medium. In addition, a hybrid energy storage system (ESS) comprising electrochemical batteries and ultracapacitors (UCs) is proposed for this application. Simulation results reveal that the regeneration of the AS energy results in an improved fuel economy. Moreover, by using the hybrid ESS, AS load fluctuations are transferred from the batteries to the UCs, which, in turn, will improve the efficiency of the batteries and increase their life.      

ADVISOR-based model of a battery and an ultra-capacitor energy source for hybrid electric vehicles

An energy source is the heart of a hybrid electric vehicle. If it is capable of supplying enough power at all times, then it is an adequate source. Major problems presently facing the industry include the size, cost, and efficiency of the energy source. The primary energy source presently used in automotive systems is a battery. In order to reduce the cost of the battery, the current needs to be decreased and stabilized so it is not very erratic. The purpose of this paper is to introduce and justify the use of a new model for an energy source: a battery in parallel with an ultra-capacitor. The ultra-capacitor can supply a large burst of current, but cannot store much energy. Conversely, the battery can store mass amounts of energy; however, without expensive and inefficient units, a battery cannot provide the current that the ultra-capacitor can. By combining the two energy sources in parallel, the storage and peak current characteristics desired can be achieved. The standards of the vehicle are not degraded, allowing this to be a promising technique to incorporate into hybrid electric vehicles to reduce their cost and increase the efficiency of their energy-source system.     

小功率智能型太阳能控制器的设计

主要针对小功率太阳能光伏系统中铅酸蓄电池使用寿命短、充电效率低、功能单一等问题,在对常规充电方法的分析对比基础上,提出了采用快速PWM动态恒压充电法。很大程度上满足了小功率光伏系统对控制器的特殊要求。并根据这一理论设计了一种充电效率高、工作可靠、智能化的太阳能控制器,显著地延长了蓄电池的使用寿命,扩大了系统的控制功能。     

Modellierung der parallelen Antriebsstränge für ein Hybrid-Elektrofahrzeug vom Typ „Hybrid Through The Road“

Hybrid electric vehicles (HEV) are equipped with an internal combustion engine (ICE) and an electric drive (ED). They are devided into serial and parallel HEVs, depending on the power flow. The ED needs to be controlled. This allows reduction of emissions and the amount of gas. In regenerative braking, the braking energy is converted into electrical energy and fed into a battery. The fuel efficiency of the ICE in the driving state is increased by loading or uploading through ED. Cut off the ICE while standstill reduces the waste of gas. A simulation tool in MATLAB/SIMULINK calculates the amount of gas for an HEV of parallel type for a given driving cycle. The drives are considered as efficiency maps from measured data. The fuel economy of the HEV depends on the driving cycle, the vehicle mass and the engine speed while shift of gears. For a vehicle of Minivan class, the saving is between 17% up to 25% compared to a vehicle driven by an ICE only.     

An advanced permanent magnet motor drive system for battery-poweredelectric vehicles

Availability of high-energy neodymium-iron-boron (Nd-Fe-B) permanent magnet (PM) material has focused attention on the use of the PM synchronous motor (PMSM) drive for electric vehicles (EVs). A new Nd-Fe-B PMSM is proposed for the drive system, which possesses high power density and high efficiency, resulting in greater energy and space savings. The design and optimization of the motor employs finite element analysis and computer graphics. Increasingly, a new PWM inverter algorithm is developed for the drive system, which can handle the nonconstant battery voltage source. An efficiency optimizing control is adopted to further improve the energy utilization of the drive system. Both the control strategy and the PWM generation are implemented in a single-chip microcontroller. As a result, the motor drive achieves high power density, high efficiency, and compactness. A prototype of the 3.2 kW battery-powered drive system has been designed and built for an experimental mini-EV     

The state of the art of electric and hybrid vehicles

In a world where environment protection and energy conservation are growing concerns, the development of electric vehicles (EV) and hybrid electric vehicles (HEV) has taken on an accelerated pace. The dream of having commercially viable EVs and HEVs is becoming a reality. EVs and HEVs are gradually available in the market. This paper will provide an overview of the present status of electric and hybrid vehicles worldwide and their state of the art, with emphasis on the engineering philosophy and key technologies. The importance of the integration of technologies of automobile, electric motor drive, electronics, energy storage, and controls and also the importance of the integration of society strength from government, industry, research institutions, electric power utilities, and transportation authorities are addressed. The challenge of EV commercialization is discussed     

Influence of Battery/Ultracapacitor Energy-Storage Sizing on Battery Lifetime in a Fuel Cell Hybrid Electric Vehicle

Combining high-energy-density batteries and high-power-density ultracapacitors in fuel cell hybrid electric vehicles (FCHEVs) results in a high-performance, highly efficient, low-size, and light system. Often, the battery is rated with respect to its energy requirement to reduce its volume and mass. This does not prevent deep discharges of the battery, which are critical to the lifetime of the battery. In this paper, the ratings of the battery and ultracapacitors are investigated. Comparisons of the system volume, the system mass, and the lifetime of the battery due to the rating of the energy storage devices are presented. It is concluded that not only should the energy storage devices of a FCHEV be sized by their power and energy requirements, but the battery lifetime should also be considered. Two energy-management strategies, which sufficiently divide the load power between the fuel cell stack, the battery, and the ultracapacitors, are proposed. A charging strategy, which charges the energy-storage devices due to the conditions of the FCHEV, is also proposed. The analysis provides recommendations on the design of the battery and the ultracapacitor energy-storage systems for FCHEVs.