Benefits of Reducing Air Emissions: Replacing Conventional with Electric Passenger Vehicles

The study estimated the cost of local and global air emissions, and to compare the differences between electric passenger vehicles (EV) and conventional, internal combustion engine (ICE) vehicles. The air emissions were estimated for the year 2020, for Denmark, France and Israel, because of their significantly different fuel mixes to produce electricity—a high percentage of renewable energy, mainly nuclear energy and high fossil fuels, respectively. Air emissions from electricity production and conventional traffic were calculated for each country and then multiplied by the specific country’s cost of emissions. Subtracting the total cost of electricity production from the total cost of conventional transportation yields the total benefit for each of the economies studied. The environmental benefit, depending on EV penetration rates, was found to be in the range of 7.8 to 133 MEUR/year for Denmark, 94 to1948 MEUR/year for France and only 4 to 82 MEUR/year for Israel, whose energy mix is the most polluting. Our analysis also shows higher potential benefits when replacing passenger car fleets comprising a high percentage of diesel cars with EVs, as well as in highly populated areas. In addition, we quantified the differences between EVs with fixed batteries and the new switch able battery concept (EASYBAT), as part of the EU 7th Framework Program me. The additional electricity demands for the EASYBAT concept are negligible, and therefore, do not change the overall conclusion that the cleaner the electricity energy mix and the higher the penetration of EVs, the higher the environmental benefits achieved.

Power Quality Issues Concerning Photovoltaic Generation and Electrical Vehicle Loads in Distribution Grids

The high utilization level of renewable generation including residential photovoltaic (PV) systems together with the uncontrolled charging of electric vehicles (EVs) can have a significant impact on load characteristics in distribution networks. Harmonic content of PV generation, EV charging loads, and their influence on power quality indicators in residential distribution networks are discussed in this paper. For investigating likely power quality scenarios, PV generation and EV charging measurement results including current harmonic amplitude and phase angle values are used and compared with present load characteristics. Different modelling scenarios are analysed and a simplified model of harmonics in PVs and EVs is offered. The results of the study show moderate additional harmonic distortion in residential load current and voltage distortion at the substation’s busbar when PV generation and EV loading are added. The scenarios presented in this paper can be further used for modelling the actual harmonic loads of the PVs and EVs in distribution networks.

Analysis of Influence and Contribution on Distribution System under Widespread PVs and EVs

In recent years, against a background of an environmental problem and resource problem, the introduction of RES （renewable energy source） such as wind power generation and PV （photovoltaic generation）, EV （electric vehicle）, and PHEV （Plug-in hybrid electric vehicle） has been expanding. However, various problems have an ongoing discussion. When the production of electricity by RESs exceeds the power consumption, it is possible to cause a steep variation of point voltage and a deviation from a proper voltage range in a distribution system to which RESs are interconnected. When EVs and PHEVs have spread to the distribution system, a new peak power-demand and a steep voltage drop might occur in the midnight charging time zone in case the electricity charges are low. in this paper, the authors analyze the effects on the distribution system under widespread PVs, EVs, and PHEVs. In addition, the authors propose an improvement plan and analyze about the influence and contribution.

基于充电站调频能力的虚拟同步发电机控制策略

随着大量分布式电源的接入,微电网惯性水平显著降低,易导致频率失稳。而充电站(charging station,CS)内入网的电动汽车(electric vehicle,EV)可为电网提供辅助调频服务,基于此该文提出了一种基于CS调频能力的虚拟同步发电机(virtual synchronous generator,VSG)控制策略。首先,提出了基于CS调频功率的VSG控制架构,并基于用户充电需求,提出了反映EV调频能力的调频参与度因子计算方法;其次,提出了CS调频功率可控边界评估方法和基于EVs分类方法的功率响应模型;进一步,设计了自适应转动惯量、阻尼系数以及基于CS调频功率边界的频率-调频功率控制器;最后,在MATLAB/Simulink上搭建的CS VSG模型上进行仿真,验证了所提出的控制策略能减小频率的偏移量,提高系统的频率稳定性和动态调节能力,并基于CS调频能力和频率偏移量决定响应调频功率,实现其在CS内EVs间的合理分配。

Application of a simplified Grey Wolf optimization technique for adaptive fuzzy PID controller design for frequency regulation of a distributed power generation system

A Simplified Grey Wolf Optimizer(SGWO)is suggested for resolving optimization tasks.The simplification in the original Grey Wolf Optimizer(GWO)method is introduced by ignoring the worst category wolves while giving priority to the better wolves during the search process.The advantage of the presented SGWO over GWO is a better solution taking less execution time and is demonstrated by taking unimodal,multimodal,and fixed dimension test functions.The results are also contrasted to the Gravitational Search Algorithm,the Particle Swarm Optimization,and the Sine Cosine Algorithm and this shows the superiority of the proposed SGWO technique.Practical application in a Distributed Power Generation System(DPGS)with energy storage is then considered by designing an Adaptive Fuzzy PID(AFPID)controller using the suggested SGWO method for frequency control.The DPGS contains renewable generation such as photovoltaic,wind,and storage elements such as battery and flywheel,in addition to plug-in electric vehicles.It is demonstrated that the SGWO method is superior to the GWO method in the optimal controller design task.It is also seen that SGWO based AFPID controller is highly efficacious in regulating the frequency compared to the standard PID controller.A sensitivity study is also performed to examine the impact of the unpredictability in the parameters of the investigated system on system performance.Finally,the novelty of the paper is demonstrated by comparing with the existing publications in an extensively used two-area test system.

考虑电动汽车时空负荷的主动配电网重构策略

为了保证主动配电网在考虑电动汽车接入情况下的有效运行,提出了一种考虑电动汽车时空负荷的主动重构策略。将配电网根据功能划分为居民配电网、工业配电网、商业配电网,首先在考虑电动汽车时空转移特性的基础上,利用统计学方法构建了电动汽车在不同时间接入不同配电网的负荷,并获取了3个配电网24 h的负荷趋势曲线。其次构建了配电网最大供电能力的评估指标,可有效评估配电网当前运行状态的安全水平,并综合考虑线损及最大供电能力指标形成多层次的优化目标,利用二进制粒子群算法对优化问题进行求解,以得到配电网主动重构的策略,保证配电网全天候的安全经济运行;最后,以IEEE 33节点配电系统为例,结合实际数据验证了本文所提出主动重构策略的可行性和有效性,对于配电网实际运行起到了指导意义。

大倍率放电时电动汽车用锂离子电池的热性能

为保证锂离子动力电池安全、可靠和高效的运行,实验研究了其在大倍率放电时的热性能。实验中,对于一款商业电动车用3.2 V、50 Ah锂离子电池,用充放电测试仪和温湿度巡检仪,控制放电倍率为1C^3C(50~150 A)。结果表明:电池放电倍率越大,电池两端工作电压平台越低,电池放电量越小,电池表面的温升率越大。当放电倍率达到3C(150 A)时,电池表面温度超出其安全工作温度,因而,锂离子动力电池在大倍率放电时,需要为其增加散热设备。拟合了一组用于计算不同放电倍率下电池的瞬时产热量的经验公式。这些公式可用于锂离子动力电池的辅助散热设备的设计和选择。

电动汽车用永磁同步电动机功率特性及弱磁扩速能力研究(一)——恒转矩控制及弱磁控制时的功率特性

采用d、q坐标系下的相量分析方法 ,研究永磁同步电动机 (PMSM )、特别是电动汽车用PMSM 详细分析了不同弱磁率、不同凸极率对电机电压、电流相量变化轨迹的影响 ,及由此引起的电机的功率特性及弱磁扩速能力的差异 推导出以弱磁率和凸极率为变量的PMSM的弱磁扩速倍数表达式 ,由此得出提高PMSM弱磁扩速能力的根本途径 。

电动汽车用永磁同步电动机功率特性及弱磁扩速能力研究(二)——最大输入功率弱磁控制的功率特性及等效电流控制策略

采用永磁同步电动机d、q坐标系下的相量分析方法 ,分析了永磁同步电动机最大输入功率弱磁控制时的电压电流相量的变化轨迹及功率特性 ,提出最大输入功率弱磁控制的等效电流控制策略 推导出以弱磁率和凸极率为变量的PMSM的弱磁扩速倍数的数学表达式 ,提出提高PMSM弱磁扩速能力的根本措施 ,分析了损耗。

可发电电动车用无刷直流电动机换相信号检测方法

提出了一种检测可发电的电动车用无刷直流电动机无位置传感器换相信号的新方法,该方法通过检测无刷直流电动机三相平均线电压的六个过零点作为换相点。理论分析和实验结果表明提出的方法在较宽的工作范围内对电动和发电两种工作模式得到的换相信号都与霍尔位置传感器输出的换相信号相位一致,可使用与霍尔传感器配套的控制芯片。

考虑用户参与度的电动汽车能效电厂模型

为充分挖掘电动汽车集群的响应能力,探究补偿电价对用户参与度的影响,建立了考虑用户参与度的电动汽车能效电厂模型,该模型能够为能效电厂参与电力市场交易机制提供模型基础。构建了可综合考虑有功和无功响应能力的单体电动汽车的车网互动(V2G)模型;进而对电动汽车交通行为特性进行统计分析,根据不同类型电动汽车的响应特性,提出了考虑补偿电价的电动汽车用户参与度响应模型;在此基础上建立了考虑用户参与度的电动汽车能效电厂模型,定义了能效电厂有功和无功响应能力、储能能力、价格响应的成本函数,为能效电厂参与市场环境下电网的调度控制提供关键的模型参数。利用典型算例验证了考虑用户参与度的电动汽车能效电厂模型的有效性,仿真结果表明能效电厂的响应及储能能力具有时间分布特性,而能效电厂的价格响应特性受补偿电价的影响。

考虑电动汽车集群储能能力和风电接入的平抑控制策略

为促进风电在电网中的消纳吸收,提出了考虑电动汽车集群储能能力和风电接入的平抑控制策略。首先对单体电动汽车入网后的储能特性进行精细化建模,充分考虑储能容量对不同荷电状态(SOC)的电动汽车有功响应能力的约束,在此基础上构建了电动汽车集群储能能力评估模型;进而针对多个电动汽车集群的协同控制,提出了考虑集群储能能力差异性的联络线功率波动平抑控制策略。该策略根据SOC自适应算法,在考虑各电动汽车响应能力约束的基础上,根据自身SOC水平确定各电动汽车的目标功率值,从而充分利用电动汽车与电网交换功率的连续调节能力;同时,该策略提出2种不同的交换功率控制方法,并探究不同方法在减少放电过程方面的差异性。最后,算例中利用电动汽车集群储能能力平抑联络线的功率波动,仿真结果验证了所提出的电动汽车集群储能能力评估模型和平抑控制策略的有效性。

电动车用电池充电状态和功率强度估计

讨论了电动车 (EV)和混合电动车 (HEV )用电池电量模型和功率模型的建立 ,提出了一种新的电池剩余电量(SOC)和电池功率强度 (Powercapability)的综合估计方法。从电化学角度建立了一个电池参考模型 ,以安时计量为主并综合考虑影响电池SOC的多种因素进行SOC估计 ,功率强度估计主要基于电池等效内阻的估算。SOC估计和功率强度估计相结合 ,实现了在功率强度估计的同时对SOC估计提供自调整机制。该综合估计方法已经在我们自主开发的实验平台上实现 。

电动汽车虚拟电厂的多时间尺度响应能力评估模型

从电动汽车集群运营商的角度,对电动汽车虚拟电厂(EVPP)参与电力系统优化调度时的多时间尺度响应能力进行评估。首先,考虑包含荷电状态与充放电状态在内的电动汽车时序状态,建立了单一和连续时间断面单体电动汽车响应能力模型。在此基础上,提出了包含日前和日内修正的EVPP多时间尺度响应能力评估模型:在日前利用电动汽车状态预测数据对EVPP日前响应能力进行评估;在日内根据一种综合考虑响应时间裕度和荷电状态裕度指标的EVPP调控策略确定具体调控结果.进而对日前响应能力评估结果进行修正,在有效跟踪系统调控目标的同时实现EVPP响应能力动态更新。最后,以包含3种不同交通用途类型的电动汽车集群为例,验证了EVPP多时间尺度响应能力评估模型及调控策略的有效性。

具有功率因数校正能力的驱动充电一体化拓扑研究

针对目前电动汽车永磁同步电机牵引系统和锂电池组充电系统相互独立的问题,提出了一种电动汽车驱动充电一体化拓扑结构。驱动模式下的电机驱动系统等效为一个三相逆变器,在充电模式下将永磁同步电机驱动模块和电机重构成锂电池组充电系统中具有功率因数校正能力的升压/降压变换器,即PFC(power factor correction capability)变换器,其中IPM(interior permanent magnet)电机绕组充当滤波电感。分析一体化拓扑驱动和充电工作状态以及IPM电机绕组在不同充电模态的数学模型、IPM电机转子位置角与电机绕组电感值的关系。采用功率控制方式,根据输入功率设定值,控制输入功率跟随输入功率设定值,使功率因数达到1。仿真及实验结果表明:本文所提出的一体化拓扑结构及控制策略在充电过程中具有良好的功率因数校正能力。

基于同步采集和Lab VIEW的发电机并网监控装置设计

传统的同期并网装置存在庞大、操作复杂、移植性差等问题,低压移动电源装备一般不具备并网能力,这对其适用场景有较大局限。文中研制了一种基于同步采集卡和Lab VIEW软件平台的发电机组独立并网监控装置,重点对其系统设计方案进行分析论述。经应用测试验证,所设计装置不仅操作简易,通用性强,更能够搭配应急电源车实现低压并网功能,解决了供电保障现场电源点必须停电接入的问题。

Simulation Research on Combined Operation of Electric Vehicle Battery Swapping Station and Wind Farm

Towards the analysis of the developmental situation of wind power generation and electric vehicles,a novel idea for stabilizing the fl uctuation of wind farms’output by the use of battery swapping stations of electric vehicles is put forward in this paper,to effectively alleviate the impact of grid-connected operation of wind farms on the power system while promoting the fi eld operation of charging and battery swapping stations.A battery swapping station is treated as a capacity-variable energy storage power station,connected to the output terminal of a wind farm.A combined operation model for wind farm and battery swapping station is established based on the MATLAB/SIMULINK simulation platform and the control strategy is proposed for the operation of battery swapping stations.The simulation results show that the introduction of a battery swapping station can effectively stabilize the fl uctuation of wind farm output.

Integrated approach for optimal island partition and power dispatch

Operating in island mode when failure occurs in sure to maintain an uninterrupted power supply to significant loads. A two-stage approach that integrates optimal island partition and power dispatch is proposed in this paper, considering photovoltaics(PVs), batteries(BEs) and electric vehicles(EVs) as the power sources. In the first stage, energy indices are defined to describe the energy demand and the maximum energy that these distributed energy resources(DERs) can provide, and islands are partitioned based on an energy constraint. Considering the variability the loads and PVs, the energy constraint is a necessary but not sufficient condition for island operation,so in the second stage, a power dispatch model is proposed the active distribution network(ADN) is an effective mea-as a test for the island partition result. Sequential power flow is also simulated to guarantee a feasible and optimized island status. The situations when the tests are not passed are analyzed and classified, and corresponding modifications for the first stage model are provided. Multiple levels of constraints based on the energy index are established for the island partition model. The proposed approach has been validated through simulation using a modified IEEE 69-bus system which is divided into three districts with different load variability characteristics.

Load curve smoothing strategy based on unified state model of different demand side resources

Renewable energy based distributed generation(DG) has the potential to reach high penetration levels in the residential region. However, its integration at the demand side will cause rapid power fluctuations of the tieline in the residential region. The traditional generators are generally difficult to manage rapid power fluctuations due to their insufficient efficiency requirements and low responding speed. With an effective control strategy, the demand side resources(DSRs) including DGs, electric vehicles and thermostatically-controlled loads at thedemand side, are able to serve as the energy storage system to smooth the load fluctuations. However, it is a challenge to properly model different types of DSRs. To solve this problem, a unified state model is first developed to describe the characteristics of different DSRs. Then a load curve smoothing strategy is proposed to offset the load fluctuations of the tie-line of the residential region, where a control matrix deduced from the unified state model is introduced to manage the power outputs of different DSRs,considering the response order and the comfort levels.Finally, a residential region with households is used to validate the load curve smoothing strategy based on the unified state model, and the results show that the power fluctuation rate of the tie-line is significantly decreased.Meanwhile, comparative study results are shown to demonstrate the advantages of the unified state model based load curve smoothing strategy.

电动车辆磁悬浮飞轮储能双向变换器的死区补偿

电动车辆磁悬浮飞轮储能电池的充放电过渡态很快,其双向PWM变换器的死区会给飞轮电动机带来输入谐波、脉动转矩等负面作用,采用适宜的变换器死区补偿控制是实现飞轮高速稳定运行和能量有效转化的关键。在对车载磁浮飞轮装置的系统构成、功率匹配和死区机理的分析基础上,通过对其双向变换器的过渡时态、死区系数和补偿方法的研究,提出一种优化的动态对称死区补偿法。该方案基于变换器在旋转坐标系下的电流矢量方向判断,确定补偿方向并使指令PWM波形对称于开关周期的中心;得出基本电压矢量作用时间的算式并进行试验。研究结果表明:调整补偿深度可优化飞轮双向变换器的补偿效果;该方法解决了相电流波形的交越失真问题,抑制电动机的转矩脉动,有助于磁浮飞轮变换器实现可靠的能量转换。