一个多总线、多源可重新布局的斯特林放射性同位素电力系统测试平台的开发.doc

Development of a Multi-Bus, Multi-Source Reconfigurable Stirling Radioisotope Power System Test Bed

一个多总线、多源可重新布局的斯特林放射性同位素电力系统测试平台的开发

The National Aeronautics and Space Administration (NASA) has typically used Radioisotope Thermoelectric Generators (RTG) as their source of electric power for deep space missions. A more efficient and potentially more cost effective alternative to the RTG, the high efficiency 110 watt Stirling Radioisotope Generator 110 (SRG110) is being developed by the Department of Energy (DOE), Lockheed Martin (LM), Stirling Technology Company (STC) and NASA Glenn Research Center (GRC). The SRG110 consists of two Stirling convertors (Stirling Engine and Linear Alternator) in a dual-opposed configuration, and two General Purpose Heat Source (GPHS) modules. Although Stirling convertors have been successfully operated as a power source for the utility grid and as a stand-alone portable generator, demonstration of the technology required to interconnect two Stirling convertors for a spacecraft power system has not been attempted. NASA GRC is developing a Power System Test Bed (PSTB) to evaluate the performance of a Stirling convertor in an integrated electrical power system application. This paper will describe the status of the PSTB and on-going activities pertaining to the PSTB in the NASA Thermal-Energy Conversion Branch of the Power and On-Board Propulsion Technology Division.

国家航空航天局(NASA)过去通常用放射性同位素热电发电机(RTG)作为他们的深空探测任务的电力源。作为RTG的更加高效和成本效益更高的潜在替代品，高效的110瓦斯特林放射性同位素发电机(SRG110)已经由能源部(DOE)、洛克希德马丁公司(LM)、斯特林技术公司和NASA Glenn研究中心(GRC)共同开发。SRG110由两个双对布局的斯特林逆变器(斯特林发动机和线性交流发电机)和两个热源(GPHS)模块构成。尽管斯特林逆变器一直成功地用于电网的电源和便携式备份电源，还没有人尝试过证明把两个斯特林逆变器连接用于航天器的电力系统所需要的技术。NASA Glenn研究中心正在开发电力系统测试平台(PSTB)来评估在集成电力系统应用中的性能。本文将描述电力系统测试平台(PSTB)的状况和在NASA的电力热能转换分部和机载推进技术部正在进行的与PSTB有关的活动。

Nomenclature 术语

DAS Data Acquisition System
数据采集系统

DOE Department of Energy
能源部

FPGA Field Programmable Gate Array
场效应可编程门阵

GPHS General Purpose Heat Source
通用热源

GRC Glenn Research Center
Glenn研究中心

GPIB General Purpose Interface Bus
通用接口总线

I/O Input-Output
输入/输出

IP Internet Protocol
互联网协议

ISO / OSI International Standards Organization/Open Systems Interconnection
国际标准组织/开放系统互连

LMA Lockheed Martin Aeronautics
洛克希德马丁航空公司

Mpbs Mega-bits-per-second
每秒兆比特

NASA National Aeronautics and Space Administration
国家航空航天局

PMAD Power Management and Distribution
电力管理和配送

PSTB Power System Test Bed
电力系统测试平台

RISC Reduced Instruction Set Computer
减缩指令集电脑

RPC Remote Power Controller
远程电力控制

RTG Radioisotope Thermal-electric Generators
放射性同位素热电发电机

SEU Single Event Upset
单事件翻转

SRG110 Stirling Radioisotope Generator 110 Watt electric
110瓦斯特林放射性同位素发电机

STC Stirling Technology Company
斯特林技术公司

TDC Technology Demonstration Convertors
技术示范逆变器

UART Universal Asynchronous Receiver Transmitter
通用异步接收器发射器

TCP Transmission Control Program
传输控制程序

TCP/IP Transmission Control Program/Internet Protocol
传输控制程序/互联网协议

I. Background

Design of spacecraft electrical power distribution systems vary depending on the intended mission, duration, number and types of loads and electrical sources of energy. Typical power sources may be solar (photovoltaic), battery, or thermoelectric. The selection of energy source is driven by the mission objectives, orbits, and paths of travel in relationship to the sun. Missions extending great distances from the sun (typically beyond the orbit of Mars) require extended-life energy sources, which, depending on the mission requirements, generally eliminate photovoltaic and battery technologies from consideration. Radioisotope based power sources become the logical choice for this class of missions. As currently conceptualized, Stirling radioisotope power convertors show the potential for higher efficiency than radioisotope thermoelectric generators; thereby producing the same amount of electrical power while using a smaller quantity of the radioisotope heat source.

Ⅰ. 背景

航天飞机的电力配送系统设计随任务、持续时间、载荷的数量和类型的需要和电源的不同而不同。典型的电源是太阳能（光伏）、电池或热电。电源的选择由任务的目标、轨道和相对太阳的运行轨迹来决定。如果任务的范围，根据需要，超过了到太阳的距离（通常是超过火星的轨道）要求更长寿命的能源，基本上就排除了考虑选择光伏和电池的可能。对这类任务，放射性同位素电源是合理的选择。最近打样设计的斯特林放射性同位素电源逆变器展示了比放射性同位素热电发电机更高效率的潜能；因此可以用更少的放射性同位素热源产生同样的电力。

Design and development of a Power Management and Distribution (PMAD) system suitable for interconnection of one or more Stirling power convertors for spacecraft, satellite or rover applications have not previously been attempted. In order to fully evaluate the performance of Stirling power convertors in a variety of applications, a Power System Test Bed (PSTB) is being developed. The test bed will allow many aspects of Stirling power convertor system integration to be investigated. Some of the areas that will be investigated are as follows: interconnection of single and multiple Stirling power convertor sources, evaluation of the performance of Stirling power convertors while connected to a variety of different load types, evaluation of different Stirling controller types, reduction of risks and performance improvement through extensive fault testing and design improvement, and determination of stability margins.

设计和开发一个适用于连接几个用于航天飞机、卫星和探测器用途的斯特林逆变器的电力管理和配送(PMAD)系统是前所未有的。为了全面地评估斯特林逆变器在各种应用中的性能，我们开发了电力系统测试平台(PSTB)。这个测试平台将测试斯特林电力逆变器系统集成的很多方面性能。以下是一些待测领域： 一个和多个斯特林电力逆变器源的连接，斯特林逆变器与不同类型载荷连接的性能评估，不同类型斯特林控制器的性能评估，通过严格的故障检测和设计改进提高性能减少风险，以及确定稳定裕度。

In order to realize the final working PMAD system design, both power distribution system architectures and control system architectures were developed. Prior to initiation of the design of the power distribution system architecture a survey was conducted of prior interplanetary missions. The data, when available, were organized by mission, year launched, nominal and peak electrical power output, types and number of energy sources, and the types and quantities of connected loads. This data was used to characterize the types of loads that could be expected for future missions.

为了实现最终的实用PMAD系统设计，我们开发了电力配送系统布局和控制系统布局。在这个电力配送系统布局设计开始之前我们做了此前的星际任务调查。那些可获得的数据，按任务、发射年份、名义和峰值电力输出、能源的类型和数量以及所连接的负载的类型和数量来分类的。这些数据用来描述未来可能的任务的负载的类型。

The PSTB is designed to be highly flexible, allowing connection and management of multiple sources and loads. This will enable evaluation of the performance of different Stirling power convertors in a variety of configurations, rather than that of a single mission or application of Stirling power convertors. To protect the Stirling power convertors from excessive electrical loading, the Remote Power Controller (RPC) was developed. The RPC will provide precise control of load currents sensing and interruption of faults, without the latencies associated with conventional fuses.

我们把PSTB设计得具有高度的灵活性，允许连接和管理多种电源和负载。这使不同斯特林逆变器的多种布局，而不是斯特林电力逆变器的一个任务或应用，的性能评估成为可能。为了防止斯特林电力逆变器过载，我们开发了远程电力控制器(RPC)。RPC将提供精确的负载电流感应和故障干预控制，没有传统的熔丝带来的潜在问题。

The Technology Demonstration Convertor (TDC) is being developed by Stirling Technology Company (STC), previously under contract to Department of Energy (DOE), and currently under contract to Lockheed Martin Astronautics (LMA). There have been a total of 16 demonstrators built by STC to date. Glenn Research Center (GRC) has six of these in the Stirling Research Laboratory; four that were purchased for in-house testing and two that are being tested for LMA. Demonstrators #13 and #14 have been put on test for LMA at GRC in support of the SRG110 project (Fig. 1). These units are in operation around-the-clock and presently have been in operation in excess of 8200 hours.

技术示范逆变器(TDC)是由斯特林技术公司开发的，此前是按与能源部(DOE)的合同，现在是按与洛克希德马丁公司(LMA)的合同。目前斯特林技术公司共开发了16个示范逆变器。Glenn研究中心有六个在斯特林研究实验室；其中四个用于在室内测试，两个为LMA的试验件。#13 和 #14号示范逆变器在GRC承担LMA的试验用于验证SRG110项目（图1.）。这些单元都在夜以继日地运行，目前已经超额运行8200小时。

II. Three Phases of Power System Test Bed Design

The build-up of the PSTB will be performed in three phases. Phase I will have single power distribution bus architecture. Phase II will add a second power distribution bus, and additional Stirling convertor sources and loads. Phase III will add additional sources of power (battery and photovoltaic simulators) to the distribution system. Each phase will address different performance areas.

Ⅱ. 电力系统测试平台设计的三个阶段

PSTB的建造分为三个阶段。第一阶段为单一电力配送总线布局。第二阶段增加了第二个配送总线，还增加了斯特林逆变器和负载。第三阶段在配送系统中增加了电源（电池和光伏模拟器）。每个阶段都侧重不同的性能方面。

（图片缺失）

Figure 1. Technology Demonstrator Convertors #13 and #14 undergoing test at GRC.

图1. 在GRC进行试验的#13 和 #14技术示范逆变器。

A. Phase I

Phase I is a single bus power system architecture (Fig. 2) and will consist of a single bus connected to a pair of Stirling convertors. Different Stirling power convertors and controller combinations operated one at a time are connected to multiple loads. The input to the power distribution system will be the shunt regulated output of the Stirling controller. Electrical energy (AC) produced within the linear alternator is rectified and shunt regulated by the controller. Convertors are arranged as dual-opposing pairs. A benefit of arranging the convertors in this manner is dynamic balancing of the free pistons.

第一阶段是单一电力系统布局（图2.),由一条总线连接一对斯特林逆变器构成。不同的斯特林电力逆变器和控制器组合依次连接到多个负载上。电力配送系统的输入通过斯特林控制器输出调节来分流。线性交流发电机产生的电能（AC）由控制器调节整流和分流。逆变器双对布置。逆变器这样布置的好处是有利于无曲柄活塞的动态平衡。

Loads will be fixed and programmable in the PSTB by utilizing a programmable electronic load (NH Research S300) capable of constant current, constant voltage, constant resistance and constant power with a transient generator (40 microseconds – 1 second period and 10 microseconds – 1 second Rise/Fall time). The initial Stirling power convertors to be operated with the PSTB will be the STC TDC and Sunpower Incorporated EE-35 Stirling convertors. These Stirling power convertors are located in the Stirling Research Laboratory that was established to support a wide variety of tests related to the performance of Stirling power convertors. The PSTB will use Stirling convertors as the primary source of electrical power. The Stirling piston stroke and linear alternator power output of the TDC is controlled by a zener diode referenced, shunt regulated controller. Since the nominal output of the Stirling convertor pair is approximately 90 volts DC after the shunt regulator, and a nominal bus voltage of 28 volts DC is desired, DC/DC conversion will be used to reduce the output voltage. Other test configurations are planned, using a digital power controller with power factor correction.

负载可以是固定的和在PSTB上利用可编程电子负载(NH Research S300)，用瞬时发动机（40微妙--1秒周期和10微妙--1秒上升/稳态时间）输出恒定电流、恒定电阻、恒和恒定功率，实现可编程控制的。最先在PSTB上运行的斯特林电力逆变器是STC TDC和Sunpower公司的EE--35 斯特林逆变器。这些斯特林电力逆变器放在为做各种与斯特林电力逆变器性能有关的测试建立的斯特林研究实验室里。PSTB将以斯特林逆变器为主电源。TDC的斯特林活塞行程和线性交流发电机的输出由齐纳二极管参考，控制器分流调节控制。因为经过分流调节器的斯特林逆变器对的名义输出是90VDC，需要的名义总线电压是28VDC，因此要用DC/DC转变来减少输出电压。我们还规划了其它试验的布局，用有功率因数校正功能的数字电力控制器控制。

Output power of each TDC convertor is nominally 55 watts electric (We) or 110We for the pair. The convertors are designed to operate at nominal temperatures of 650 °C hot end and 80 °C cold end. The goals of this development phase include demonstration of performance, response to transients, and stability margin while operating a variety of connected loads. The PSTB design will be augmented as necessary in order to satisfy these goals. Stirling power convertor control schemes include zener diode controlled shunt regulated and advanced solid state controllers featuring active power factor correction.

每个TDC逆变器的名义输出功率为55瓦或一对输出110瓦（We:watts electric)。逆变器设计运行温度范围是 80 °C 到650 °C。这个开发阶段的目的包括驱动不同负载的示范性能、瞬态响应和稳定裕度。PSTB的设计将根据需要升级以满足这些目的。斯特林电力逆变器控制设计包括齐纳二极管控制的分流和先进的有主动功率因数校正功能的固态控制器。

Phase I development of the PSTB will encompass multiple areas of technology development and engineering design. The technology development areas are: Stirling power convertor analysis, PMAD system analysis, component testing, and subsystem integration. The engineering design areas involve: systems requirements definition, component selection, prototype development, performance testing, and control software and embedded firmware requirements definition, development and implementation.

PSTB开发的第一阶段涉及技术开发和工程设计的很多领域。技术开发领域包括：斯特林逆变器分析、PMAD系统分析、部件测试和子系统集成。工程设计领域包括：系统要求定义、部件选择、原型开发、性能测试和控制软件和嵌入式固件要求的定义、开发和实现。

In order to better understand the convertor performance with different configurations and loads, an analysis of both the PMAD and control system is being performed. Portions of the electrical power distribution system are being simulated using PSpice, and end-user power quality and system performance will be reviewed. The test results of the Stirling convertor configurations will then be compared to the analyses and predictions.

为了更好地理解不同布局和负载下逆变器的性能，我们分析了用于试验的PMAD和控制系统。我们用PSpice模拟了电力配送系统的一部分，终端客户的电力品质和系统性能将重新审视。斯特林逆变器布局的测试结果将与分析与预测结果比较。

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Figure 2. Power system architecture of Phase I.
图2. 第一阶段电力系统布局。

B. Phase II

The second phase of PSTB development will again incorporate multiple Stirling convertors to provide electrical power to the PSTB, this time with multiple primary power busses. The additional electrical busses add the capability to perform automated switching of critical loads to alternate power sources in the event of the loss of a primary electrical source. The design of the PSTB is such that it may be reconfigured electrically to allow the connection of multiple sources and loads to facilitate the evaluation of the Stirling power convertors under a variety of system configurations.

Loads designated as system critical may be fed from multiple busses, configured to select a second energized bus in the event of the loss of the primary bus. Multiple Stirling power convertors will be connected and power the separate busses.

B. 第二阶段

PSTB的第二阶段开发就再次组合多个斯特林逆变器来为PSTB提供电力，这次使用多个主电力总线。增加的电力总线增加了在主电力总线断路时把关键负载自动切换到备用电源的能力。PSTB的设计要实现电路重新布局以允许多个电源和负载连接来使在不同的系统布局下斯特林电力逆变器的性能评估更容易。

被指定的系统关键负载会用多个总线供电，按设计在主电源总线断路的情况下选择第二条供电总线。多个斯特林逆变器将连接和驱动不同的总线。

C. Phase III

Phase III will incorporate photovoltaic and battery simulators operating in conjunction with Stirling power convertors, simulating a spacecraft power bus. Control hardware representative of a flight system will be developed and integrated into the system, and loads representative of recent flight missions will be incorporated. For example, the RPC microcontroller will be integrated into a Single Event Upset (SEU) radiation-hardened Field P