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1、发电厂直流电源改造分析孙国彬， 刘世杰（大唐淮北发电厂， 安徽 淮北 235000）摘 要：针对淮北发电厂一、二期直流电源系统运行中长期存在的问题，该文分析了直流电源系统改造的必要性，详细说明了高频开关电源的性能特点、高频开关电源模块工作原理及PWM工频变换技术，并介绍了淮北发电厂利用高频开关电源对原直流电源的典型改造方案。关键词：直流电源； 高频开关； 绝缘 中图分类号： 文献标识码：B Analysis of DC Power Supply Reform in Power Plant SUN Guo-bin, LIU Shi-jie （Huaibei Power Plant of Data
2、ng Power Group, Huaibei Anhui 235000）Abstract: In allusion to the problems in the operation of the DC power supply systems of the first-stage and second-stage projects at Huaibei Power Plant, which have existed for a long time. This paper analyzes the necessity of transform for the DC power supply s
3、ystems, elaborates the performance characteristics of the high frequency switching power supply, working principle of the high frequency switching power supply module and PWM power frequency conversion technology with the introduction of the typical transform scheme for the original DC power supplie
4、s by using the high frequency switching power supply at Huaibei Power Plant. Keywords: DC Power Supply; High Frequency Switch; Insulation 1 概述淮北发电厂近几年“上大压小”工程快速上马，原有发电机组相继关停（一期250MW 二期2125MW），只保留220V直流系统为220kV升压站、110kV升压站、35kV升压站所有出线线路开关保护及#1、#2、#3、#4主变保护提供操作、合闸电源。且220V直流电源主要来自可控硅整流系统，因全部为涉网设备，直流系统非
5、常重要。该厂原采用的直流电源设备是上世纪90年代可控硅整流设备，经过近二十年运行已存在较多问题，给日常生产、设备的安全运行构成了威胁。主要有：1.直流设备严重老化。2.故障频发，备品备件配置困难，维护量日益增加。3、直流电源系统稳定性差、效率低、纹波系数大，抗干扰能力差，监控系统不完善，不能满足系统自动化设备的要求。4、由于可控硅整流电源浮充电压易波动，会出现蓄电池脉动充放电现象，对免维护蓄电池损害极大，影响电池寿命。针对上述存在的诸多问题，我厂经过多方考察论证，决定先对二期220V直流电源进行改造，采用智能高频开关电源改进原可控硅整流装置。2 发电厂直流系统的重要性直流电源是电力系统的重要基
6、础设备，其作用主要是在发电厂正常运行时，对断路器的控制回路、信号设备、自动装置等设备供电；在一次系统故障时，给继电保护、信号设备、断路器的控制回路供电，以保证它们能可靠动作；在交流厂用电源中断时，给事故、直流油泵及交流不停电电源等负荷供电，以保证事故保安负荷的工作。如果直流系统不能正常工作，一次系统出现故障时，将会造成开关拒动或者死开关，甚至会发生越级跳闸，造成电网瓦解，这样将会给发电厂及电网的安全运行带来极大的风险。因此，直流电源在发电厂中十分重要，必须充分可靠，具有独立性。3 智能高频开关整流模块性能特点及工作原理3.1 高频开关技术性能高频开关频率结合脉宽调制（PWM）技术的研究和应用，
7、使开关电源迅速发展。目前，开关频率提高到75-500kHz左右，实现了电源设备小型化、轻量化、模块化。其性能指标比以往的可控硅整流器和磁饱和整流器等优越，其主要性能指标参数比较如表1。表1 高频开关整流装置与可控硅整流装置主要参数比较电源类型高频开关整流装置可控硅整流装置交流电源电压380V20%380V10%直流输出电压220V：198286V220V：193256V工作频率50Hz10%50Hz纹波系统0.5%2%稳压精度0.5%12%稳流精度0.5%12%动态响应200s100ms噪音4050dB5060dB效率91%6070%功率因数0.90.7输出电流5300A5300A从表中具体数
8、据表明，由高频开关整流模块组成的直流成套设备在各项技术指标上有明显的优势。3.2 智能高频开关系统主要特点l 采用模块化设计，灵活可靠。l 高频开关整流模块系列化，根据容量需求实现高性价比的配置。 l 采用软开关技术设计的高频开关整流模块，高效长寿命。l 充电模块N+1热备份，可带电插拔，在线维护，方便快捷。l 硬件低差自主均流技术，模块间输出电流最大不平衡度小。l 可选绝缘检测仪实时监测母线及各支路对地绝缘状况，确保系统和人身安全。l 监控模块采用大屏幕液晶显示，系统所有运行参数都可以通过监控模块设定，全中文界面，操作方便。l 提供包括RS-232/RS-485三遥接口，实现对电源系统的“遥
9、测、遥控、遥信”以及实现无人值守。l 蓄电池自动管理及保护，实时自动检测各蓄电池单体的端电压，总电压和温度，充、放电电流，并控制蓄电池的均充和浮充状态。3.3 智能高频开关整流模块工作原理高频开关整流模块在国内外各控制电源领域里已得到应用，在内部执行电路各有差异，但其工作原理及控制逻辑大经相同。其原理框图如图1所示。待添加的隐藏文字内容2图1 高频开关电源模块原理框图如图1，该系统由交流输入单元、AC/DC逆变单元、直流输出单元和控制监测单元等组成。交流输入单元由两路交流380V输入，经高压冲击的抑制尖峰电压设备和滤波阻容保护器等组成，三相全桥整流器输出电压经工频滤波后变成直流；经过DC/AC
10、高频逆变单元，在PWM脉宽调制电路作用下将直流变成交流高频脉冲电压；高频变压器将输入的高频交流脉冲电压降压处理，再经过LC滤波、EMI滤波后输出平稳直流。PWM脉宽调制电路及部分软开关谐振回路，根据电网和负载的变化，自动调节调频开关的脉冲宽度和移相角，使输出电流、电压在各种运行情况下保持稳定输出。高频开关模块中的高频变压器铁芯采用铁氧体或非晶体制成，有很好的高频传递特性，效率高、体积小、无噪音，变压器输出再经整流桥和滤波器等组成的直流输出单元后输出平稳直流。微机监控模块：是系统控制灵魂环节，微处理器CPU为核心构件，由液晶显示器或CRT显示。采集交流输入电源、直流母线、充电装置和蓄电池等信息，
11、实现以下功能：按蓄电池充放电程序自动控制充放电过程，实现预定充电程序控制运行；长期浮充电运行后，自动启动充电程序控制；交流失电恢复后，自动启动充电程序方式控制。显示直流系统的运行状态及故障和异常信号报警。设运行状态和报警信号的标准通讯接口RS485等，实现遥信、遥测、遥控、遥调和自检功能。实现直流系统的电压、电流监测、绝缘故障监测及蓄电池温度补偿和内电势测量等。微机监控模块满足蓄电池充放电程序功能及保证模块均流的功能是必要的，而直流母线绝缘监察和电压监视功能是否设置，目前有三种做法：充电装置具备全部功能，直流系统仍保留原专用装置。充电装置具备全部功能，直流系统不另设专用装置。充电装置不设直流母
12、线的绝缘、电压和电流测量及蓄电池温度补偿和内电势测量功能，由原专用装置完成。4 直流系统改造方案介绍我厂根据其配置的蓄电池容量和直流系统负荷的要求（直流系统设计电流容量为180A），采用双屏独立设计，互为备用；选用高频开关模块均为220V、20A；采用N+1备份方式，故充电、浮充电装置采用9个模块并联组成，自动均流措施。当其中有一个模块故障时，装置发出报警信号，这时负载由另外N个模块均流负担，不会影响正常供电；微机监控模块满足蓄电池充放电程序功能、保证模块均流的功能和电压监视功能；根据直流负荷分配情况，先进行二期直流系统改造，然后在进行一期直流系统改造，使之互为备用，可实现系统不停电改造。本次
13、二期直流系统改造拆除二期直流蓄电池组、二期浮充电装置、二期短冲装置，安装新的蓄电池组和两块直流负荷屏，启用老厂公用短冲装置，作为新的二期蓄电池组浮充装置使用；把原接入二期直流母线的所有负荷转移到新安装的两块直流负荷屏；改造完成后，一、二期直流系统母线经过刀闸切换实现互联，保证了网控直流系统安全、可靠运行。由图2所示，改造后的高频开关整流模块装置的直流系统框图可以看出，交流电源分别由两路引入，一投一备，互为备用，互为电气闭锁。直流输出由9个整流模块并列输出。蓄电池组与动力母线通过一只断路器接至直流输出口，控制母线通过自动调压后，保证控制母线电压在220V5%范围内。在正常运行情况下，由一路交流电
14、源提供整流模拟输入电源，另一路交流作为备用电源，当投入的交流电源故障时，故障的交流电源自动退出，备用交流电源自动投入，保证了交流供电的连续性。高频整流模块将交流电源经过高频脉宽调制整流，提供稳定可靠的直流电源，另一方面保证电池组的浮充电。当两路交流电源同时失电时，蓄电池组则作为备用电源提供220V操作电源，保证各控制、保护系统在交流电源故障时的操作电源和信号电源的供电连续性和可靠性。信息传输接口与NCS监控系统通信，采用标准的通信规约RS485。同时保留4点硬接线报警点。图2 高频开关整流装置直流系统框图5 小结采用智能高频开关整流装置后，结构布局合理，层次分明，监控系统更加完善，可实现在线参
15、数设置和查看故障信息报告；运行时性能稳定，效率高、可靠性高，大大减少了维护量。同时简化了220KV直流母线接线方式，使运行人员操作更加简便、快捷。也为升压站的安全奠定基础，保证了我厂其它机组的安全、稳定、经济运行。参考文献1 于长顺. 发电厂电气设备. 中国电力出版社,1991.2 深圳艾默生网络能源有限公司厂家资料.作者简介孙国彬（待以后补充）Editors note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, coverin
16、g severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio and through the crackling static from space hear the faint beeps of the worlds first satellite - Sputnik. I also missed watching Neil Armstro
17、ng step foot on the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I was fascinated with what goes on in the sky, and when NASA pulled the plug on the shuttle program I was heartbroken. Yet the privatized space race has renewed my childhood dr
18、eams to reach for the stars.As a meteorologist, Ive still seen many important weather and space events, but right now, if you were sitting next to me, youd hear my foot tapping rapidly under my desk. Im anxious for the next one: a space capsule hanging from a crane in the New Mexico desert.Its like
19、the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall from the edge of space - live.The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to the live stream of the Red
20、Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in a vertical straight line we would be go for launch.I feel this mission was created for me because I am also a journalist and a photographer, but abo
21、ve all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgartner, must have that same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a gust of swirling wind kicke
22、d up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thicker than a dry cleaning bag, scraped the ground I knew it was over.How claustrophobia almost grounded supersonic skydiverWith each twist, you could s
23、ee the wrinkles of disappointment on the face of the current record holder and capcom (capsule communications), Col. Joe Kittinger. He hung his head low in mission control as he told Baumgartner the disappointing news: Mission aborted.The supersonic descent could happen as early as Sunday.The weathe
24、r plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our d
25、ay-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause), he can exp
26、ect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, Fearless Felix will unclip. He will roll back the door.Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.Below, the Earth b
27、ecomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so despite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving into the shallow end.Skydiver preps for the big jumpWhen he jumps, he
28、 is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to stop him completely.If he goes too fast or spins out of control, he h
29、as a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy his 270-square-foot (25-square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).In order to deploy this chute successfully, he will have to slow to 172 m
30、ph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned, it wont. Baumgartner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaranteed to work higher than 25
31、,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
