变频钻机逆变器共用直流回路时的电容量研究

拖动逆变器共用直流回路绝大多数为深井变频电动钻机的标准配法,据此分析了其中直流电容在空载、电动、回馈时的工作过程以及计算最小电容量需要的相关要素,提出了在1个充放电周期中最长放电时间与调制频率的关系,给出了直流回路最小电容量计算式。以标配7 000 m变频钻机为例,计算了其电容量并以相应功率的西门子装置进行了验证。对设计安装空间有特殊要求的海上钻井平台系统和降低装置成本有实际的参考价值。

荧光灯用辉光启动器标准要点解析

针对GB20550/IEC60155荧光灯辉光启动器标准中对电容型镇流器串联电容器计算公式缺失的现状,介绍了在电感镇流器上串联电容器使之成为电容型镇流器的工作原理,并推导出对应的计算公式。针对我国目前在测量辉光启动器脉冲电压的普遍错误的方法,介绍了正确的测量方法。

EDLC charging performance for microgrid applications

In order to review storage performance of the electric double layer capacitor （EDLC） in microgrid applications, charging time and storage efficiency issues are mainly studied aiming at three different charging modes, including the constant voltage charging mode （CVCM）, the constant current charging mode （CCCM） and the constant power charging mode （CPCM）, based on the practical EDLC product. Numerical calculation methods are presented for different charging modes, and the charging efficiency is also reviewed with strict mathematical deductions, which is validated to be accurate enough and applicable through a simple case with the PV/EDLC system illustration. Finally, trade-off problems between charging time and energy loss are also studied. Research results show that the CPCM is more suitable for microgrid networks compared with the traditional constant-voltage and constant-current charging modes. The hybrid charging method is recommended to save energy and keep high efficiency relatively at the same time. However, how to manage the combination percentage of different charging modes in a reasonable way should be dealt with according to the practical requirements.

无功就地补偿节电技术的应用

无功功率的就地补偿这种方式,距电源最远,电阻R最大,无功经济当量最大。根据就地平衡的原则,无功在哪里产生就在哪里补偿,因此,就地补偿方式是有效合理的补偿方式。

An iterative computation method for interpreting and extending an analytical battery model

Battery models are of great importance to develop portable computing systems,for whether the design of low power hardware architecture or the design of battery-aware scheduling policies.In this paper,we present a physically justified iterative computing method to illustrate the discharge,recovery and charge process of Li/Li-ion batteries.The discharge and recovery processes correspond well to an existing accurate analytical battery model:R-V-W's analytical model,and thus interpret this model algorithmically.Our method can also extend R-V-W's model easily to accommodate the charge process.The work will help the system designers to grasp the characteristics of R-V-W's battery model and also,enable to predict the battery behavior in the charge process in a uniform way as the discharge process and the recovery process.Experiments are performed to show the ac-curacy of the extended model by comparing the predicted charge times with those derived from the DUALFOIL simulations.Various profiles with different combinations of battery modes were tested.The experimental results show that the extended battery model preserves high accuracy in predicting the charge behavior.

Optimized algorithm for balancing clusters in wireless sensor networks

Wireless sensor networks consist of hundreds or thousands of sensor nodes that involve numerous restrictions in-cluding computation capability and battery capacity.Topology control is an important issue for achieving a balanced placement of sensor nodes.The clustering scheme is a widely known and efficient means of topology control for transmitting information to the base station in two hops.The automatic routing scheme of the self-organizing technique is another critical element of wireless sensor networks.In this paper we propose an optimal algorithm with cluster balance taken into consideration,and compare it with three well known and widely used approaches,i.e.,LEACH,MEER,and VAP-E,in performance evaluation.Experimental results show that the proposed approach increases the overall network lifetime,indicating that the amount of energy required for com-munication to the base station will be reduced for locating an optimal cluster.

A durable P2-type layered oxide cathode with superior low-temperature performance for sodium-ion batteries

To power large-scale energy storage systems,sodium-ion batteries(SIBs)must have not only high-energy density but also high performance under a low-temperature(LT)environment.P2-type manganese oxides with high specific capacity are promising cathode candidates for SIBs,but their LT applications are limitedly explored.We proposed a P2-type Na_(0.67)Ni_(0.1)Co_(0.1)Mn_(0.8)O_(2) material with outstanding LT performance prepared through reasonable structure modulation.The material offers an excellent Na^(+) diffusion coefficient(approximately 10^(−9)-10^(−7.5) cm^(2) s^(−1))at−20℃,a superior LT discharge capacity of 147.4 mA h g^(−1) in the Na half-cell system,and outstanding LT full cell performance(energy density of 358.3 W h kg^(−1)).Various characterisations and density function theory calculations results show that the solid solution reaction and pseudocapacitive feature promote the diffusion and desolvation of Na+from the bulk electrode to interface,finally achieving superior electrochemical performance at LT.