Day-ahead optimal charging/dischargingscheduling for electric vehicles inmicrogrids

Microgrid as an important part of smart grid comprises distributed generators (DGs), adjustable loads, energy storage systems (ESSs) and control units. It can be operated either connected with the external system or islanded with the support of ESSs. While the daily output of DGs strongly depends on the temporal distribution of natural resources such as wind and solar, unregulated electric vehicle (EV) charging demand will deteriorate the unbalance between the daily load curve and generation curve. In this paper, a statistic model is presented to describe daily EV charging/discharging behaviors considering the randomness of the initial state of charge (SOC) of EV batteries. The optimization problem is proposed to obtain the economic operation for the microgrid based on this model. In dayahead scheduling, with the estimated power generation and load demand, the optimal charging/discharging scheduling of EVs during 24 h is achieved by serial quadratic programming. With the optimal charging/discharging scheduling of EVs, the daily load curve can better track the generation curve. The network loss in grid-connected operation mode and required ESS capacity in islanded operation mode are both decreased.     

Study on Power Fluctuation Dispatch and Capacity Design of Short Period Power Fluctuation Compensation System in Consideration of Power Loss

Since the output of photovoltaic (PV) generation includes power fluctuations caused by natural conditions, the installation of PV on a large scale is expected to affect load frequency control of the power grid. One method of compensating power fluctuations is the use of energy storage (ES), such as batteries and capacitors. A power fluctuation compensation system composed of an electrical double layer capacitor energy storage system (ESS) and a Li‐ion battery energy storage system is considered. The power loss characteristics of both ESSs during power fluctuation compensation are modeled by equivalent circuits based on ES impedance spectra. The models are validated by experiments simulating power fluctuation compensation. Using these ES models, simulations were carried out to determine the power fluctuation dispatch method between the two ESSs and the capacity of the ESSs in consideration of power loss minimization.     

兼顾可靠性与经济性的孤岛型光储微电网容量配置方法

可靠性和经济性是孤岛型光储微电网容量配置的2个重要参照,但不能同时最优.为协调二者矛盾,提出了一种兼顾可靠性与经济性的孤岛型光储微电网容量配置方法.该方法针对概率类、频率及持续时间类指标,从容量及功率角度进行了可靠性评估与经济性分析,对比研究了不同负荷点接入光储微电网的配置方案.结果表明:一定储能配置方案下,光伏容量的增加可优化概率类指标,但频率及持续时间类指标变化并非单调;合理的储能配置能进一步优化概率类指标,降低或平抑系统平均停电次数指标对微电网的冲击;在负荷水平较低处安装微电网可实现可靠性与总成本的最优折中.     

Expert survey on Energy Storage Systems: Regulation and policy from an Indian power sector perspective

A survey of Indian power-sector stakeholders on the subject of Energy Storage System (ESS) policy and regulatory issues is presented. The survey is divided into four sub-themes: the need for ESSs; ESSs in a network context; ESSs in the market; and ESSs in innovation. Respondents support the need for dedicated ESS regulation, including a definition of ESSs. In terms of networks, respondents support unrestricted ownership, and the development of dedicated grid connection standards and the provision of ancillary services for the network by ESSs; this would allow their participation in wholesale energy markets. However, opinions diverge on the level of ESS regulatory oversight needed for grid investment deferral. As far as power markets are concerned, respondents agree on the need for updating bidding formats, special treatment for ESSs regarding grid access charges to eliminate market entry barriers and to incentivise the operational versatility of ESSs. However, opinions diverge on the appropriate compensation mechanism to be applied for services provided by ESSs. There is an agreement on supporting innovative ideas such as P-to-everything (P2X) conversion and the use of regulatory sandboxes for enabling ESS.     

Optimal Placement of Intermittent Renewable Energy Resources and Energy Storage System in Smart Power Distribution Networks

This paper presents an efficient strategy to optimally allocate renewable energy sources (RES), primarily wind and solar photovoltaic (PV), and energy storage system (ESS) in electrical distribution networks with a goal of minimizing costs and active power losses. The proposed planning strategy is used to determine the number of possible and optimal locations for the hybrid RES–ESS system. This paper further presents a control scheme to optimally dispatch the output of ESS, which increases the effective utilization of RES by reducing their day-ahead forecast errors in order to minimize the deviation between forecasted and actual values. In our proposed strategy, the location that produces the least overall power losses complying with the system constraints is considered as the optimal one. In order to evaluate the effectiveness of the proposed method, this paper considers a case study of a 16-bus test system that comprises of several loads, wind farm, PV, and ESS. The test results demonstrate that by determining the optimal bus location for the RES–ESS system, overall power losses as well as peak load can be significantly reduced.     

风-光电站中储能系统混合最优配置及其经济性研究

储能是解决大规模可再生能源并网问题的重要手段,然而,储能系统的投资成本高、运维损耗大,且不同类型储能系统的技术经济参数存在差异。因此,研究不同类型储能系统的混合优化配置及其经济性具有十分重要的意义。提出风光电站内容量型和功率型储能系统混合配置优化方法,以储能系统全生命周期净收益最大为目标,采用遗传算法进行求解;以张家口地区风光电站实际运行数据和当前3种主流储能电池实际参数为例,分析不同敏感性因素对储能系统选型及容量配置的影响。算例结果表明：容量型储能系统的经济性对电池价格变化更为敏感;液流电池及超级电容混合配置的经济性最佳。     

风-光电站中储能系统混合最优配置及其经济性研究

储能是解决大规模可再生能源并网问题的重要手段,然而,储能系统的投资成本高、运维损耗大,且不同类型储能系统的技术经济参数存在差异。因此,研究不同类型储能系统的混合优化配置及其经济性具有十分重要的意义。提出风光电站内容量型和功率型储能系统混合配置优化方法,以储能系统全生命周期净收益最大为目标,采用遗传算法进行求解;以张家口地区风光电站实际运行数据和当前3种主流储能电池实际参数为例,分析不同敏感性因素对储能系统选型及容量配置的影响。算例结果表明：容量型储能系统的经济性对电池价格变化更为敏感;液流电池及超级电容混合配置的经济性最佳。     

微电网储能系统控制及其经济调度方法

储能系统对微电网的安全稳定运行和经济效益有重要影响。分析微电网中分布式储能系统的离网和并网控制方法;针对传统下垂控制中,线路阻抗引起的微电网系统稳定性问题,提出改进的下垂控制策略和控制结构,以减少微电网功率波动和提高运行稳定性。为实现对负荷的削峰填谷和提高储能设备运行经济性,根据分时电价,建立分布式储能系统的经济调度数学模型,在此基础上提出一种考虑分时电价的经济调度方法。结合算例验证该调度方法的经济性和实用性。     

考虑多重分时电价和效益潜力的电力储能系统调度策略

电力储能系统接入电网在保证电力系统安全稳定运行方面具有诸多优势,执行储能系统调度策略能够实现削峰填谷,并从中获得经济效益.在不同的分时电价下,储能系统调度策略获得的经济效益往往具有差异性,因此定量研究不同分时电价下储能系统调度策略的效益潜力,对提高电力系统的整体经济效益具有重要意义.建立了考虑多重分时电价的储能系统调度策略效益潜力评估模型,量化储能系统调度策略在多重分时电价下的经济效益.以2018年某地的实际负荷数据为分析对象,采用改进粒子群优化算法验证所提储能系统调度策略的有效性,分析结果表明,所提储能系统调度策略效益潜力评估模型对提高电力系统的经济效益具有实用价值.     

用于削减工业园区用电功率峰值的蓄冷空调系统的规划建模与优化

针对工业园区综合能源系统的削峰问题,建立将蓄冷空调系统用于削峰的优化规划模型,提出采用临界运行电价和经济平衡电价分别作为蓄冷空调系统运行经济性与规划经济性的度量。进而根据经济平衡电价确定规划时的最优蓄冷容量,进一步确定相关的设备容量。然后对冰蓄冷系统和水蓄冷系统进行经济性对比与分析,为决策者提供选择蓄冷类型的经济依据。最后以某工业企业的空调系统改造为水蓄冷空调系统作为算例,计算相应的经济平衡电价、最优蓄冷容量和相关设备容量,并验证最优蓄冷容量的正确性。     

风电与储能系统互补下的火电机组组合

针对具有风电和火电机组的电力系统,在储能系统配置给定的前提下,提出通过储能尽量消除风电不确定性并部分以备用形态出现的研究思路,建立了火电机组组合2层优化决策模型。上层问题以火电机组组合成本最小为目标,下层问题以储能系统对电网中电能时空平移和提供备用所得收益最大为目标,以储能系统消除不确定性程度为满足对象,其中计及了自动发电控制(AGC)机组和非AGC机组的特性,以及系统频率调节效应的作用。基于分解协调的原理,通过上、下层问题的交替迭代对该模型予以求解,决策储能系统充/放电功率、调控范围及机组启停方案。该方法可在减少火电机组备用容量的同时,提升系统应对不确定性的能力,通过10机组系统验证了模型和方法的有效性。     

Optimal siting and sizing of demand response in a transmission constrained system with high wind penetration

This paper describes algorithms that use demand-side management to address large-scale integration of wind power. In particular, demand response (DR) is used to manage wind power intermittency by shifting the time that electrical power system loads occur in response to real-time prices and wind availability. An economic dispatch with transmission, DR capacity and operational constraints is used to model the operation of a transmission constrained system with a high penetration of wind power. This optimization model is used to determine the optimal sizing and distribution of DR given a fixed budget for customer incentives and the installation of enabling technology. We demonstrate the effectiveness of the operational model based on a simple PJM 5-bus system and an IEEE 118-bus system. Simulation results show that transmission constraints have a greater effect on sizing of DR capacity than the location of wind power, which means that buses electrically close to congested lines tend to have higher incentives to deploy DR resources than other buses. The second part of the work examines optimal siting of technology that enables DR based on the frequency of DR based load changes, which are generally a function of the network location.     

电力需求侧规模储能容量优化和经济性分析

储能系统由于具备对功率和能量的时间迁移能力,是实施电力需求侧管理、控制负荷变动的一种有效手段。分析并建立由储能系统初始投资成本、运行维护成本、设备更换成本和资金收益构成的储能系统净现值目标函数,为准确估算储能在频繁不规则循环下的寿命周期,提出了一种基于等效寿命损耗的电池寿命计算模型;为确定储能充放电起止时刻,提出了一种改进的储能充放电策略。在容量优化计算中,采用量子编码结合自适应遗传算法,并引入灾变思想以提高计算速度达到全局最优。最后基于某电力需求侧一典型日的数据,分别对锂离子、钠硫、铅酸储能系统容量进行优化,通过基于净现值的经济性分析,对比三种储能应用于电力需求侧的经济性,结果表明,基于文中设置的边界条件,钠硫储能较另外两种储能更具经济性。     

Cycle analysis using exhaust heat of SOFC and turbine combined cycle by absorption chiller

The power generating efficiency of solid oxide fuel cell (SOFC) and gas turbine combined cycle is fairly high. However, the exhaust gas temperature of the combined cycle is still high, about 300^°C. Thus, it should be recovered for energy saving, for example, by absorption chiller. The energy demand for refrigeration cooling is recently increasing year by year in Japan. We propose here a cogeneration system by series connection of SOFC, gas turbine and LiBr absorption chiller to convert the exhaust heat to the cooling heat. As a result of cycle analysis of the combined system with 500‐kW‐class SOFC, the bottoming single‐effect absorption chiller can produce a refrigerating capacity of about 120 kW, and the double‐effect absorption chiller can produce a little higher refrigerating capacity of about 130 kW without any additional fuel. But the double‐effect absorption chiller became more expensive and complex than the single‐effect chiller. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(1): 49– 55, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20578     

Cost benefit of a cooling energy storage system

Since the air conditioner (A/C) load contributes 30% of the peak demand of Taiwan Power Company (Taipower) system during the summer season, load management by A/C load clipping has become one of the most important topics in the Taipower system. Since the eutectic salt is a complete inorganic compound with a freezing point of 47°F and latent heat of 41 Btu/lb, it is a good medium for an energy storage system. An A/C system with an 1800 RT-HR eutectic salt energy storage tank was built on the campus of the National Sun Yat-Sen University (NSYSU) for demonstrating the cooling energy storage (CES) system. By computer simulation, it is found that 41.1% of the electric peak demand has been reduced and 56% of the energy consumption has been shifted from peak hours to off-peak hours by the CES-system. In this paper, the mathematical model of the eutectic salt CES-system has been developed for computer simulation of the energy storage system. It is found that the optimal capacity of the storage tank is determined by the off-peak time period and the largest annual electricity charge saving could be obtained by applying the smallest nominal chiller size under the optimal operating conditions     

风储联合发电系统电池荷电状态和功率偏差控制策略

提出了一种新型的基于风电功率预测偏差和电池荷电状态(SOC)反馈的储能系统控制策略,通过预测结果计算风电功率的变化偏差,得出完全补偿波动所需的储能系统充放电功率,引入补偿系数联合求解获得储能系统的充放电控制指令。同时,建立了补偿系数的动态优化模型,包括长时间尺度下基于输出功率波动和电池容量变化指标的基准补偿系数寻优模型,短时间尺度下基于电池SOC指标和充放电状态的补偿系数快速修正模型。算法采用的最优求解和SOC指标具有广泛的适应性,便于推广不同容量储能系统在风电功率平滑中的应用,可以兼顾储能电池的寿命和输出功率的平滑性。算例结合风电场的功率实测数据,进行储能系统配置仿真,验证了该控制策略能够最大程度发挥储能系统能力,在维持电池能量稳定前提下,平抑风电场输出功率的波动。     

Analysis of the demand charge in DC railway systems and reduction of its economic impact with Energy Storage Systems

In addition to energy consumption, DC railway operators must also pay for the demand charge. This term of the electricity bill has not been studied in detail in the literature and penalizes power peaks. The big fluctuations on the power demand which characterize railway systems make the demand charge important for railway operators. This paper studies the impact of the demand charge on DC railway systems and proposes a solution based on Energy Storage Systems (ESSs) to reduce it. An analysis of the main parameters of the ESS regarding the reduction of the demand charge is provided, as well as an explanation of the effects of different control strategies on the system performance. Most of the savings obtained with the installation of ESSs come from the reduction in the energy consumption; nevertheless, the savings coming from the reduction in the demand charge are significant and contribute to the economic viability of the investment.     

主动配电网电池储能系统优化配置方法

旨在确定全钒液流电池(VRB)储能系统(ESS)的最佳配置,以应对主动配电网(ADN)中风力发电的集成.相应地,提出了一种考虑储能的动态效率和寿命的电池储能系统优化配置方法.与以前的研究不同,所提出的储能优化配置方法中考虑了VRB的动态效率和寿命.此外,该方法综合考虑了风电消纳、减少负荷中断、减少温室气体排放、网损、V...     

基于动态无功电压灵敏度的有源配电网移动式储能优化调度

随着城市负荷尖峰以及分布式电源渗透率的持续攀升,有源配电网存在负荷峰谷差进一步增大以及电压越限的风险。移动式电池储能系统(MBESS)具备时间-空间灵活性和四象限输出能力,考虑其有功出力参与削峰填谷、无功出力参与电压调节,提出了一种基于电压灵敏度分析的有源配电网MBESS的优化调度方法。首先,针对MBESS出力与接入位置之间的耦合影响,推导定有功功率条件下满足仿射关系的无功电压修正灵敏度;其次,考虑不同网络结构下不同节点电压的调整需求,提出一种动态无功电压修正灵敏度的计算方法,旨在确定MBESS的时序最优接入方案;然后,构建充分考虑运行经济性与可靠性的MBESS双层优化调度模型;最后,以IEEE 33节点配电系统为例,采用增强烟花算法对所提模型进行求解,结果表明所提方法能够在保证MBESS具备较好经济效益的同时,有效减小负荷峰谷差以及提升配电系统的整体电压水平。     

A study of the merits of a battery combined photovoltaic generation system for a residential house

In this paper we examine the merits that a practical photovoltaic system combining photovoltaic generation with storage batteries would provide if used in ordinary residences. Various configurations and operation methods could be envisaged for such a system. In this research we examined the optimal battery capacity, operation methods, and economic effects for a system emphasizing an economical merit for the user. We first calculated the hourly amount of photovoltaic generated electricity each month, and used data on average load patterns from actual measurements to calculate battery capacity. Next, taking battery capacity and photovoltaic module capacity/price as parameters, we calculated and evaluated the economic merit for ordinary residences. The result showed that the optimal battery capacity for combination with 3‐ or 5‐kW photovoltaic generation is around 10 kWh, and that a combined system provides a merit even though it entails higher photovoltaic module costs than the use of photovoltaic generation alone. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(4): 20–31, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10302