
Building industry opens up new world of entrepreneurial struggle to build a three provinces of regional central cities--in the Communist x counties the six plenary session members and comrades: today, I was commissioned by the County party Committee Standing Committee, reports to the General Assembly. Consideration of all members and alternates, and comrades attending advice. A, and this year yilai of work recalled this year yilai, in municipal of right led Xia, County solidarity led County people, to science development views for guide, to good activities for mainline, according to "a city four modernizations three more" of development thought, concentrated poly force, work hard, political, and economic, and culture, and social and party of construction are made has new progress, County rendering out wind fresh are, and career prosperity, and social settled, and people mind into of good situation. (A) facilitating the construction of the project. Firmly establish the "scratch project is
economic, grasping development project is to hold" philosophy, to extraordinary efforts to promoting the construction of key projects. Plot 108 key projects for the year, with a total investment of 29.3 billion yuan, iron plate, Josh stone cement waste heat power generation and 13 projects completed, worship of 1.2 million tons of pellets, Hua Yu 80,000 sets of grandparent chicken farming, 47 projects under construction, completed investment of 3.95 billion yuan, annual plan of 69.3%. The first half of the County's gross domestic product is expected to reached 8.5 billion yuan, and total revenue of 943 million Yuan. (B) structural adjustment achieved remarkable results. Actively transforming the pattern of economic development, industrial ecology, and agricultural modernization and industrialization of services. High x-County • Tin iron circular economy demonstration area, and further expand economic development zone Jing Dian recycle economy ecology industry Park, Park,
circular economy and rapid economic development. Focus more on the dialectical relationship between development and environmental protection, energy saving and emission reduction projects play an important role. Vigorously developing agriculture, ecological agriculture, agriculture, modern agricultural clearing along the River Promenade begins to take shape. Key tourism projects is going well, WA Palace area was named "top ten most influential cultural relics in Hebei province landscape". Develop new services, and services with new developments. (C) urban-rural integration process. Promoting "three-year difference" campaign, battle of two large demolition completed 32 days of 530,000 square meters, exceeded the annual Task 7 months in advance. General big building jiangjun road, bridge and highway bridges, the green heart of the city and other urban construction projects, and focus on building new countryside and new housing model villages, urban and rural areas improve.
Highway opened to traffic, Liu Zhang, Qing LAN high-speed x-County section completed by the end of August. Urban and rural
短期启动为脱硝氨区系统因故停运24小时以上72小时以内的重新启动。在短期启动前,有液位容器的处于连续运行状态,其他机械设备处于停用状态。
development work steadily in the pilot counties, to build peace neighborhood offices approved, "change", urban and rural communities (Center), immigrant communities, pilot projects such as integrated management of urban and rural sanitation in order. (D) maintain social harmony and stability. In the case of tight financial situation, continue to increase the input of people, happy people battle. Urban central heating and upgrade rural power grids, rural reconstruction of shabby housing ten major projects being delivered, has been overfulfilled ahead. Strengthening of social programs, college entrance examination to record heights; new rural insurance coverage rate of the city's first, launched in new rural cooperative medical clinic co-ordination; ... Perfect Park catering, accommodation, education, recreation and other tertiary industries supporting, improving socialization service level, for industries, businesses and create a good environment for development. 3, flexible investment, enhance
the industry. Construction of industrial parks, just set up a platform for the development of only attract more projects into the district, to form agglomeration advantages. A innovation project. To be purposeful, targeted investment, will have a basis of the County's industrial packaged bundles, overall publicity and promotion. Initiative going, please come in and carry out all-round, multi-level and wide-range of investment activities. The Township industrial projects, in principle, to put to the West industrial parks. What town project, is that the output value of the Township. Second, we must grasp the standards selected items. Full account of extend the industry chain and the integration of factors of production, not only efforts to introduce a number of scientific and technological content and high added value, growth and strong driving force of large projects and large enterprises, but also on domestic-funded enterprises and in accordance with the direction of industrial development of
small and medium projects, project man, small project overwhelming. Meet the area of the County's new industrial projects and city back into rural enterprises, in principle, all stationed in industrial parks. Meanwhile, strict control of excess capacity and high energy consumption, high emission enterprises to enter. Thirdly, increased incentives on the project. Investment of the whole society, the Township and County units go out and draft project. To establish investment incentives for successful introduction of significant project gives awards to units and individuals, the introduction of tax for the implementation of the project, to introduce organization into rewards. 4, preferential policies, and security industries. In terms of project examination and approval, by area Administrative Committee in conjunction with the development, planning, land, industry and commerce, quality control and other departments, "one-stop reception, one-stop service", the simplified procedures, the time limit
originally. In the management of EIA in accordance with the
制零电压开关(PS PWM ZVS,Phase Shift Pulse Width Modulation Zero Voltage Switch)(零电
流)谐振变换器,这种电路克服了 PWM 方式硬开关造成的较大的开关损耗的缺点,又实
现了恒频工作,克服了准谐振和多谐振变换器工作频率变化及电压、电流幅度大的缺点。采
用这种工作原理,大大减小了开关管的损耗,不但提高了效率也提高了工作频率,减小了体
积,更重要的是降低了变换电路对分布参数的敏感性,拓宽了开关器件的安全工作区,在一
定程度上降低了对器件的要求,从而显著提高了开关电源的可靠性。
目前,美国、挪威、新西兰、英国、法国等不少国家已经采用 VMOS, IGBT 研制出工
作频率为 1MHz,效率达 93%,可靠性显著提高的 DC/DC 变换器用于通信电源。在发达国
家中,目前通信电源都实现了集中监控。监控由监控模块(置于电源机架内)的 RS232 接
口—PC 计算机和相应的软件完成。监控模块可实时监测电源各部分的电压、电流等参数,PC
计算机可定时巡检各台电源的运行参数,并能执行开关和控制,实现了遥测、遥控、遥信、
遥调四遥功能,使程控机房实现了无人值守。
1.2 国内开关电源的发展现状
国内开关电源技术的发展,基本上起源于 20 世纪 70 年代末和 80 年代初。当时引进的
开关电源技术在一些高等院校和科研院所停留在试验开发和教学阶段。20 世纪 80 年代中期
开关电源产品开始推广和应用,该时期开关电源的特点是采用 20KHz,PWM 调制技术,效
率可达 65%~70%。
经过 20 多年的不断发展,开关电源技术有了重大进步和突破。新型功率器件的开发促
进了开关电源的高频化,功率 MOSFET 和 IGBT 可使中小型开关电源工作频率达到 400KHz,
(AC/DC)或 1MHz(DC/DC);软开关技术使高频开关电源的实现有了可能,不仅减少了电
源的体积和重量,而且提高了电源的效率,国产 6kW 通信开关电源,采用软开关技术,效
率可达 93%;控制技术的发展以及专用控制芯片的生产,不仅使电源电路大幅简化,而且使
开关电源的动态性能和可靠性大大提高;有源功率因数校正技术(APFC)的开发,提高了
AC/DC 开关电源的功率因数,既治理了电网的谐波污染,同时又提高了开关电源的整体效率。
最近几年来,为了提高开关电源的可靠性,进一步提高转换效率,提高工作频率,减小
体积,并降低电磁干扰,在吸收国外最新进展的基础上,开始了准谐振、多谐振开关变换器
和相移脉宽调制零电压(零电流)谐振变换器的研究实验工作。尤其是由于后者具有较多的
优点,受到了大家的重视,投入了较多的研究力量,取得了一些进展,提高了效率、可靠性,
降低了电磁干扰,并已有少量应用,但总的来说仍处于研究探索阶段。在远程集中监控方面,
有些地方已采取乡支局电源监控模块(含单片机)— 调制解调器(Modem)—电话线—调
制解调器—县电信局 PC 计算机的方案实现了支局电源的远程集中监控和乡支局机房的无人
值守。从整体性能看,我国通信电源设备与国外同类产品相比存在一定的差距。主要差距在
工作的可靠性、稳定性和技术性能等方面。因此,组织力量研制开发具有自主知识产权、技
术含量高的新一代通信电源,对振兴民族工业,提高产品的质量和市场竞争力,提高开发队
伍的研究水平都具有重要意义,同时,也会带来显著经济和社会效益。
2、研究内容及方案的确定
鉴于开关电源在现代社会中的广泛应用,尤其是大功率开关电源在通信系统中的重要地
位,本小组根据课程设计要求,通过查阅资料以及对相关内容的分析,确定 48V/62.5A 大功
率通信开关电源的实现方案和各个部分电路的具体设计如下所述。
2.1 总体思路及实现方案
通常输入的市电为 220V 交流电压,而我们需要得到的是 48V 的直流输出,因此需要先
将输入的交流电整流成幅值较高的直流电。然后把得到的直流电经过全桥式功率变换器,变
换器在 PWM 控制电路的控制下将直流电转换成高频交流方波,经高频变压器隔离并传输到
次级,然后通过高频整流滤波电路将交流方波转换成直流,再经输出滤波电路滤波后得到所
需电压稳定的直流电。而在本设计中由于给出的已为 530V 直流输入,所以我们的设计电路
中不需要再考虑整流的情况,直接将直流输入电压经过高频全桥逆变电路,具体原理框图如
下图 1 所示。