Review of lithium-ion battery state of charge estimation

The technology deployed for lithium-ion battery state of charge (SOC) estimation is an important part of the design of electric vehicle battery management systems. Accurate SOC estimation can forestall excessive charging and discharging of lithium-ion batteries, thereby improving discharge efficiency and extending cycle life. In this study, the key lithium-ion battery SOC estimation technologies are summarized. First, the research status of lithium-ion battery modeling is introduced. Second, the main technologies and difficulties in model parameter identification for lithium-ion batteries are discussed. Third, the development status and advantages and disadvantages of SOC estimation methods are summarized. Finally, the current research problems and prospects for development trends are summarized.     

配电自动化终端配置的双层优化模型

针对现有配电终端配置模型的优化目标中多个指标量纲差异大且寻优效率低的问题,提出了一种配电终端配置双层优化方法。首先对配电终端类型和含配电终端的配电系统可靠性计算进行了分析。其次,建立了配电终端配置双层优化模型。上层优化模型以配电终端配置费用最小为目标,求解配电终端的安装位置。下层优化模型以系统停电损失费用最小为目标,求解配电终端的安装类型。然后,给出了双层优化模型求解方法,上层优化模型应用易实现的二进制粒子群算法求解,下层优化模型采用预设参数较少且寻优效率高的萤火虫算法求解。最后,通过IEEE RBTS BUS2算例系统验证了所提双层优化模型和求解方法的合理性和有效性。     

考虑输入变量相关性的输电网区间潮流分析

在仿射算法的基础上,考虑电力系统中部分输入变量之间的相关性对区间潮流算法进行改进。构建以平行四边形模型为基础的区间相关性体系,建立考虑区间相关性的电力系统不确定潮流模型。考虑区间包络不够准确对区间潮流计算准确性的影响,提出一种基于凸多边形模型的区间潮流计算方法。利用仿射算法将传统的区间潮流迭代转化成一组非线性优化问题,通过凸多边形模型将区间变量之间的相关关系转换成一组新的约束条件,并利用优化算法对该非线性优化问题进行求解,得到一系列更窄的区间潮流解。2个输电网算例表明,所提方法不仅能够反映不同相关性水平对计算结果的影响,还能定量刻画区间包络准确程度对区间潮流的影响。     

太阳能/热泵技术在木材干燥领域的应用

提出在家具行业领域,采用太阳能/热泵技术替代传统能源。介绍太阳能及热泵技术的基本原理及应用范围。通过太阳能/热泵技术在江西家具行业的应用,分析该技术的主要特点及注意事项。太阳能/热泵综合能源技术应用在家具行业可实现节能环保,具有推广价值。     

计及接地支路的直流潮流算法

在考虑无功注入和线路电阻的基础上,计入接地支路的影响并仍保持了直流潮流方程的线性形式,提出了适合于计算输电系统无功功率的直流潮流算法。该算法利用完整的节点导纳矩阵形成相应的并联元件导纳项,在不改变直流潮流方程线性形式的情况下计入接地支路中并联元件的影响。通过修正相角的回代求出所有PQ节点的电压幅值,结合复功率潮流方程可同时求得系统的有功功率和无功功率。IEEE-118节点算例结果表明:与不考虑接地支路的直流潮流算法相比,所提出的算法在保持现有直流潮流算法的有功潮流计算精度的前提下,提升了电压幅值和无功潮流的计算精度,使直流潮流算法适用于输电系统无功功率的计算。     

基于系统动力学的分布式可再生能源激励机制分析

国家和地方的清洁能源发展政策促进了清洁能源装机容量的井喷式增长,碳交易和绿色证书机制虽然都可以对清洁能源发展起到促进作用,但对于分布式和集中式的促进作用则显示出较大的不同。在分析证书价格传导过程的基础上,采用系统动力学方法从集中式可再生能源参与的批发市场和分布式可再生能源参与的零售市场两个层面进行建模,建立了碳排放权交易市场、绿色证书交易市场和电力市场三个宏观市场间的交互模型和包含分布式可再生能源的配电网模型。算例仿真了两种机制下集中式可再生能源、分布式可再生能源的发展轨迹,讨论了碳交易和绿色证书机制的价格设置对分布式可再生能源发展的影响,验证了提出的效益分享机制对分布式可再生能源的促进作用。     

电流差动保护在逆变型新能源场站送出线路中的适应性分析

新能源电源通过电力电子装置并网,其故障特性受控制策略影响而发生根本性变化,传统继电保护原理存在适应性问题。送出线路作为新能源场站电力外送的关键通道,其主保护电流差动保护能否正确动作对于新能源高效利用和系统安全运行十分重要。针对逆变型新能源场站,推导了逆变型新能源电源短路电流表达式,分析了各相短路电流之间的相位关系及其影响因素。在此基础上,分析了送出线路发生不对称短路时电流差动保护在并网系统为强、弱两种情形下的动作性能。研究结果表明,送出线路发生两相短路时,差动保护在并网系统为弱系统时存在拒动的风险、为强系统时灵敏性下降但不会拒动;送出线路发生接地故障时,零序电流的存在使得差动保护在并网系统为强、弱系统时均能可靠灵敏动作。实时数字仿真器(RTDS)试验验证了理论分析。研究结论为逆变型新能源场站送出线路主保护配置提供了参考。     

考虑扰动影响因子的多能融合微电网谐波责任区分

与传统大电网相比,多能融合微电网系统具有多样性、复杂性和随机性等特点,其直接测量所得的实时谐波数据存在随机波动性大、受扰动强等问题,无法准确反映关注谐波源的真实谐波责任。为此,在传统谐波责任模型中引入扰动影响因子,分析了扰动影响因子的建模依据及其对谐波责任区分精度的影响。为减弱扰动影响因子的影响,采用基于BP神经网络拟合的均衡谐波数据代替实时谐波数据,采用改进尺度参数的M估计稳健回归算法评估谐波责任。最后,利用基于Benchmark 0.4 kV标准低压电网仿真模型和宁波某工业园区的微电网实验工程实测数据,验证了该方法的有效性。     

Modelling of degradation and a soft failure moment during the operation of a supercapacitor applying selected diffusion processes

An important requirement imposed on storage batteries nowadays is to have sufficient capacity. At the same time a high level of availability, reliability and safety is required as well. Our intention is to determine a capacity degradation threshold and the moment the soft failure of a graphite supercapacitor (SC) occurs. If we do not take into account the idle state, the functioning of the supercapacitor might be expressed by charging and discharging processes under different operating conditions given by the allowed extent of SC design. When looking for the degradation threshold and the moment of soft failure occurrence we performed the experimental part of measuring in the climatic chamber. We performed and recorded the processes of SC charges and discharges at different temperatures: 40 °C, 25 °C and  −42 °C and at different charging and discharging currents: 2A, 4A, 6A and 8A. The experimental results were used to model mathematically the SC discharge process. Appropriate tools used for SC discharge are diffusion processes. In this case we apply a Wiener process with drift and an Itô process.     

Failure analysis of nozzle zone before valve of negative pressure chamber from main pipe coolant system in nuclear power plant

Nozzle zone before valve of negative pressure chamber from main pipe coolant system in the secondary circuit of reactor is made of F316 stainless as usual. The butt weld between nozzle and socket in main pipe is the weakest part. If the rupture occurs, it will directly lead to the leakage of main system. One nuclear power plant finds a local penetration crack in the weld of nozzle zone, and it leads to leakage in the inspection. The length of crack is 23.6 mm, nearly 41.7% of the perimeter. In this work, crack morphology observation, composition analysis, metallographic structure observation and hardness measurement are done for the leak part. Analysing with the service environment and force condition, the inner wall of nozzle has a greater stress concentration. It easily leads to fatigue cracking near the fusion line area with poor welding, and the crack extends from inner wall to outer wall. The fatigue crack evolves to corrosion fatigue crack during the crack propagation, and the further advices for use are provided.