Microsatellite combined attitude/energy systems

We have constructed a high-temperature super conductor-magnet momentum wheel for microsatellites and propose a micro high-temperature superconductor energy storage and attitude control system for nano/pico satellites. The momentum wheel for micro satellites has a mass of 1.1 kg with an angular momentum capacity of 3.5 J sec. It occupies a volume of 12.7 cm in diameter and 5 cm in height. It operates within the restricted power budget of a microsatellite with a total power supply of only 10 watts. It consumes less than 1 watt for sustenance. The micro high-temperature superconductor flywheel for nano/pico satellites has an angular momentum capacity of 0.083 Js and stores 2.32 kJ at 530 krpm. Its energy storage capacity is approximately 45 Wh/kg with an energy density of around 370 kJ/L. The HTS systems can perform the dual function of a power/attitude control system and are ideally suited for low Earth orbit energy storage, power generation, and attitude control of spacecraft.     

Performance characteristics of lithium-ion cells for NASA's Mars2001 Lander application

NASA requires lightweight rechargeable batteries for future missions to Mars and the outer planets that are capable of operating over a wide range of temperatures, with high specific energy and energy densities. Due to the attractive performance characteristics, lithium-ion batteries have been identified as the battery chemistry of choice for a number of future applications, including Mars rovers and landers. The Mars 2001 Lander (Mars Surveyor Program MSP 01) will be one of the first missions which will utilize lithium-ion technology. This application will require two lithium-ion batteries, each being 28 V (eight cells), 25 Ah and 8 kg. In addition to the requirement of being able to supply at least 200 cycles and 90 days of operation on the surface of Mars, the battery must be capable of operation (both charge and discharge) at temperatures as low as -20°C. To assess the viability of lithium-ion cells for these applications, a number of performance characterization tests have been performed, including: assessing the room temperature cycle life, low temperature cycle life (-20°C), rate capability as a function of temperature, pulse capability, self-discharge and storage characteristics, as well as mission profile capability. This paper describes the Mars 2001 Lander mission battery requirements and contains results of the cell testing conducted to-date in support of the mission,     

基于等效时间的混合储能系统高功率密度优化配置

越来越多的电力电子装置应用到多电飞机（MEA）电力系统中,导致MEA用电负荷功率呈现脉动特性,采用混合储能系统（HESS）平抑负荷功率脉动。为减少HESS重量,提出了一种高功率密度的优化配置方法。为建立负荷功率与储能介质之间的关系,提出了等效时间（ET）的概念,比较两者的ET常数作为储能系统类型选取的依据。进一步提出空间矢量法,采用能量型储能介质矢量和功率型储能介质矢量合成负荷功率,确定最优单体和截止频率,实现了HESS高功率密度配置。同时,从能量约束和功率约束两个方面进行HESS的容量的计算。最后,通过算例配置和仿真分析验证了本文所提方法的可行性和正确性。     

Bipolar nickel-metal hydride batteries for aerospace applications

Electro Energy Inc. (EEI) is developing high power, long life, bipolar nickel-metal hydride batteries for aerospace applications. Bipolar nickel-metal hydride designs allow for high energy and high power designs with a 25 percent reduction in both weight and volume as compared to prismatic and/or cylindrical Ni-MH designs. Utilizing a sealed wafer cell design EEI has demonstrated a 1.2 kW/kg power capability. Prototype designs have achieved 70 Wh/kg. Designs studies show 80 Wh/kg are achievable with EEI's state-of-the-art technology. The sealed wafer cell is the building block for EEI's high power and high voltage bipolar batteries making the assembly easy and significantly lower in cost. Satellite and aircraft batteries are being developed which provide high power and long life. Sealed cells now show excellent rate capability and life. Cells tested in a low earth orbit (LEO) cycle have reached 9000 cycles and continue on test. High power, bipolar battery designs are ideal in applications where using conventional aerospace battery technology would require excessive capacity; weight and volume, thereby reducing usable payload on the vehicle     

Parallel operation of shunt active power filters with capacitylimitation control

This paper presents a capacity-limitation technique to enlarge the power capacity that can be handled by the shunt active power filters (APFs). The capacity limited includes the reactive power as well as the amplitude of the distortion current supplied by the APFs. Under capacity-limitation control m+1 APFs supply the load reactive power with m APFs supplying their rated power and one APF supplying a fraction of its rated value. Similarly, n+1 APFs supply the load current harmonic with n APFs supplying the distortion current limited in amplitude and one APF supplying a fraction of its limited amplitude. Advantages of the proposed approach include high flexibility for extending system capacity, high reliability due to no control interconnection, reducing power capacity demand of APF, high modularity due to identical APFs, stable reactive power and harmonic current sharing and its performance is insensitive to parameters mismatch of APFs, cost-effective due to modularization, and so on. Three single-phase 1 KVA APFs are designed and implemented. The effectiveness is demonstrated by some experimental results     

Hubble Space Telescope at twelve years of age

The Hubble Space Telescope was deployed from the Space Shuttle Discovery into a 380-mile high Earth orbit on April 25, 1990. It subsequently made outstanding astronomical discoveries with its 8-foot (2.4-meter) telescope and other scientific instruments. Critical to the successful observations was continuous availability of power from its solar arrays during sunlit periods, and from nickel-hydrogen batteries when the satellite was in the Earth's shadow. The adopted nickel-hydrogen batteries were carefully selected and tested to confirm their depth-of-discharge and operating temperature that delivered the longest life in charge/discharge cycling service. These batteries had a design life of 7 years. At 12 years after launch the Hubble batteries have delivered more charge/discharge cycles than any other batteries in low-Earth orbit. However, the Hubble batteries have been subjected to many unexpected stresses, and peculiar reductions in battery capacity have been observed. Battery replacement requires a costly trip to the Hubble Space Telescope by astronauts, so the remaining useful life of the batteries must be predicted. Already in four servicing missions, astronauts have replaced or modified optics, solar arrays, a power control unit, and various science packages. A fifth servicing mission is scheduled in 2004. This paper discusses battery charging hardware and software controls, history of battery events in Hubble, cell performance model and spare battery tests, and capacity walkdown.     

Spacecraft energy storage systems

Flywheel Energy Storage Systems represent an exciting alternative to traditional battery storage systems used to power satellites during periods of eclipse. The increasing demand for reliable communication and data access is driving explosive growth in the number of satellite systems being developed as well as their performance requirements. Power-on orbit is the key to this performance, and batteries are becoming increasingly unattractive as an energy storage media. Flywheel systems offer very attractive characteristics for both energy storage, in terms of energy density and the number of charge/discharge cycles, and the important side benefit of spacecraft attitude control     

Residual stress indentation model based on material equivalence

A novel residual stress indentation model for conical indentation loading is proposed to describe the relationship between the residual stress, material constitutive parameters, load, and displacement for materials with a uniaxial constitutive relationship that obeys Hollomon’s power law (H-law). The novel model was established based on the principle that the equivalent material without residual stress corresponds to the original material with residual stress, conical indentation theoretical model based on energy density equivalence, and an assumed power-law relationship between the dimensionless residual stress and relative difference of the yield stresses of the equivalent material and original material. Sixty imaginary H-law materials with ten equibiaxial and ten uniaxial residual stresses were investigated by Finite Element Analysis (FEA). The residual stresses predicted by the novel model from the indentation load–displacement curves simulated for the imaginary materials are in close agreement with those applied by the FEA. Finally, indentation tests for Cr12MoV steel, 45 steel, and 6061-T6511 aluminum alloy were carried out on their specimens without residual stress and their bending specimens with equibiaxial and uniaxial residual stresses. The residual stresses predicted by the novel model according to the indentation load–displacement test curves are in good agreement with those applied by the tests.     

某型训练指挥台电源系统的优化设计

电源系统是为某型训练指挥台内部各设备提供能源支持的基础单元。通过对电源系统的组成结构和功能的系统分析,针对电源系统存在的 3个方面不足,包括:启动冲击电流过大、电源开关存安全隐患以及风扇组交流负载消耗不合理,提出相应的优化措施,即:应用软启动电源降低启动冲击电流、利用低压控制高压提高安全性、使用直流风扇替换交流风扇降低交流负载消耗。实际应用表明,在采用上述优化措施后系统的可靠性和安全性均得 到了明显提高,达到了优化的目的。     

电流滞环控制的三相馈能式电子负载仿真研究

论述了一种用于航空发电机测试用的三相馈能式电子负载功率拓扑方案及其电流控制策略。首次将三相馈能式拓扑方案应用于航空发电机测试负载，这种馈能式电子负载采用电流滞环PWM技术，可实现功率因数无级调节，既可模拟阻性、容性、感性等各种航空发电机负载形式，又能通过三相逆变器将发电机发出的电能以功率因数1回馈给电网，这样降低了设备的功耗，缩小了设备的体积。建立了系统d-q模型。对系统方案进行了理论论证。并给出了Matlab仿真结果。     

电能回馈型航空发电机测试用电子负载的研制

论述了一种用于航空发电机测试的电能回馈型电子负载的实现方案。这种电能回馈型电子负载采用电流滞环PWM技术,可实现功率因数无级调节,可模拟阻性、容性、感性等各种航空发电机负载形式,并通过三相逆变器将发电机发出的电能以功率因数1回馈给电网,降低了设备功耗,缩小了设备体积。采用Matlab进行了系统仿真,仿真结果验证了该方案的可行性。     

Development of a long cycle life sealed nickel-zinc battery forhigh energy-density applications

Nickel-zinc battery technology is being developed for commercial applications requiring high energy density and high power capability. Development cells have demonstrated the ability to deliver over 60 Watt-hours per kilogram at the one hour rate. Cycle life has been improved to more than 600 cycles at 80% depth of discharge by using a patented, reduced solubility zinc electrode and an improved sealed cell design. More than 8000 charge/discharge cycles at 10% depth-of-discharge have been completed. Large quantities of sealed prismatic cells have been manufactured, including a 140 cell, 220 V battery for a hybrid electric vehicle (HEV)     

多电飞机高压直流并联供电系统发展现状与关键技术

多电飞机（MEA）逐步实现机载二次能源的统一,可有效提升飞机能源利用率。高压直流（HVDC）供电系统（EPS）从原理上更容易实现电源的并联运行,利于多发动机/多发电机布局下供电容量的扩展,并实现不中断供电,进一步提升系统的供电品质和鲁棒性。分析了高压直流供电系统的特点与优势,系统总结了高压直流并联供电系统的研究现状,在此基础上阐述了并联供电系统的关键技术和问题。提出并构建基于新型双凸极无刷直流发电机的双通道高压直流并联供电系统,实现了系统均流控制,完成高压直流并联供电时突加突卸负载、投入并联、退出并联等动态过程的实验验证。研究结果表明高压直流并联供电系统具有良好的稳态精度与动态性能,在多电乃至全电飞机（AEA）上有重要研究价值和应用潜力,其动态行为、建模方法和控制保护逻辑等问题值得进一步深入研究与实践。     

Stepped Sinewave Inverter

A stepped sinewave dc/ac inverter was analyzed for an inductive load with respect to load current and voltage, harmonics, power factor, and efficiency. This special inverter of high efficiency and low harmonic content is constructed by synthesizing the sinusoidal output by discrete voltage sources, such as storage batteries, solar cell, etc., with electronic switching of the sources at specific time intervals. The switching times are determined for the condition of minimum distortion of the synthesized wave. A 50 W inverter was built and tested to demonstrate this approach.     

机载计算机开关电源的并联均流技术

简单的介绍了机载计算机开关电源的工作原理,机载计算机开关电源在并联时,严重地存在着负载电流不能被各个机载计算机开关电源均匀分担的问题,经过理论分析,简单说明了并联对机载计算机开关电源的影响,以及机载计算机开关电源的并联均流方式,同时介绍了负载均衡控制器UC3907实现机载计算机开关电源并联均流技术的原理.     

Hybrid power sources for pulsed current applications

A battery-capacitor hybrid power source was discharged under pulsed current conditions and various ambient temperatures. Significant improvements in voltage drop and run time were obtained with the hybrid device over the battery alone. An equivalent circuit was established to evaluate the voltage behavior of the hybrid device. It was found that at the peak discharge current, as much as 50% of the total energy supplied was provided by a capacitor with only about one-third of the battery's volume     

低含气率影响下圆柱动静压轴承特性分析

为研究低含气率条件下,温度和气泡含量对润滑油黏度的影响,采用涡轮油和氮气制备油气两相流,在不同温度下采集含气率和动力黏度,拟合得到两相流的黏度计算模型.针对带有深浅腔的圆柱动静压轴承,基于拟合的黏度模型,结合有限元法和有限差分法联立求解油膜Reynolds方程、能量方程及两相流等效密度模型,分析了不同偏心率下承载力、摩...     

一种机载无线电连接器的设计与试验

目前,无线技术发展相对成熟,对于飞机系统有巨大的应用前景,能有效避免有线传输方式带来的重量大、布线难和连接器易故障等问题。文中提出一种无线连接器,基于无线通信技术和无线传能技术,完成信息和能量的无线传输,并完成样机开发和功能与应用场景测试实验。试验结果表明,该无线连接器在10 mm内具备15 W的负载供电能力,且通讯传输波特率可达115 200 bps,可以有效避免有线电连接器对外界因素敏感易失效等问题,为机载系统连接器的设计提供新的解决方案。     

超声速氩气流磁流体发电初步实验研究(英文)

利用激波风洞,采用氦气驱动氩气,在平衡接触面运行方式下得到高温气体,通过在低压段注入电离种子K2CO3粉末,实现高温条件下导电流体的产生,开展了超声速氩气流磁流体功率提取初步实验研究。在喷管入口总压0.32MPa、总温6504K,磁场强度约0.5T、喷管出口气流速度1959m/s的条件下,对分段磁流体功率提取通道电极的感应电压和短路电流进行了测量,实验测量结果与理论计算相吻合,并由电压电流计算得出了平均电导率约20S/m左右,在负载系数为0.5的情况下,磁流体功率提取通道最大的功率密度可达4.7971MW/m3,最大焓提取率为0.34%。最后分析并给出了气体状态参数T1,M1,T2,M2的测试原理与方法。