UPS 系统与发电机组的兼容性文档格式.docx

1、 不间断电源系统的制造商和用户很早就已经注意到发电机组和UPS之间的配合问题，特别是由整流器产生的电流谐波。电流谐波对供电系统产生的不良影响是非常明显的：包括发电机组的电压调节器，UPS的同步电路。因此，UPS系统工程师们设计了输入滤波器并把其应用到UPS中，成功地在UPS应用中控制了电流谐波。这些滤波器对UPS与发电机组的兼容性起到了关键作用。Virtually all input filters use capacitors and inductors configured to trap the most destructive current harmonics at the modu

2、le input terminals. The configurations are narrowly prescribed by the design of module power elements and the desired maximum percentage of total harmonic distortion in full load module current. An added benefit of most filter designs is the input power factor improvement they produce in loaded modu

3、les. One of the consequences of input filter application, however, is the small but significant reduction in overall module power efficiency. Most input filters consume between ?and 1% of the real power passed through the module. Input filter design has always been a balancing act between desired an

4、d undesired characteristics. 事实上所有的输入滤波器都使用电容器和电感用以吸收UPS输入端的最具破坏性的电流谐波。该设计考虑到了UPS电路固有的和在满载情况下的最大可能的全部谐波畸变的百分比。大多数滤波器的另一个益处是提高带载UPS的输入功率因数。然而输入滤波器的应用带来的另一个后果是使UPS整体效率的降低。绝大多数滤波器消耗1%左右的UPS功率。输入滤波器的设计一直在有利和不利的因素之间寻求平衡。UPS engineers, in an effort to improve UPS system power efficiency, have recently mad

5、e some advancements in input filter power consumption. Filter efficiency improvement, to a great extent, was made in conjunction with the introduction of Isolated Gate Bipolar Transistor （IGBT） technology into the module design. The higher efficiency of the IGBT inverters led to a module-wide redesi

6、gn in search for higher efficiencies overall. It was found that input filters can be tuned to certain current harmonics and draw very little real power. Generally, the ratio of inductive elements to capacitive elements in filters went down, module footprint became smaller and efficiency went up. Thi

7、ngs seemed to bode well in the UPS industry until an old problem resurfaced with a new twist ?generator compatibility. 为了尽可能提高UPS系统的效率，UPS工程师近期在输入滤波器的功耗方面做了改进。滤波器效率的提高，从很大程度上讲是将IGBT技术应用到UPS设计中的结果。为了寻求系统全面的高效率，IGBT逆变器的高效率导致了对UPS的重新设计。输入滤波器可以吸收某些电流谐波，同时吸收很小一部分有功功率。总之，滤波器中感性因素对容性因素的比率降低了，UPS的体积变小了，效率提高

8、了。在UPS领域的事情好象得以解决了，而老问题却又被新问题-与发电机的兼容性所替代。A Matter of Power FactorMuch attention has been placed on the operation of UPS systems at or near full load. Most engineers specify the operating characteristics of a module at full load, especially input filter characteristics; few are interested in filter

9、performance at or near no load. After all, current harmonics have negligible impact when the UPS and upstream electrical system are working lightly loaded. However, the no-load operating parameters of a UPS system, specifically the input power factor, have become critical to UPS/E-G compatibility. 功

10、率因数的问题通常人们大多把注意力放在UPS满载或接近满载情况下的工作状态。绝大多数工程师都表述了满载情况下的UPS工作特性，特别是输入滤波器的特性，很少有人对滤波器在空载或接近空载时的状况感兴趣。毕竟UPS及其电气系统在轻载状态下电流谐波影响很小。然而，UPS空载时的工作参数，特别是输入功率因数，对于UPS与发电机的兼容性是相当重要的。The newer input filter designs, while doing a good job reducing current harmonics and improving full-load power factor, were seen t

11、o exhibit an extremely low capacitive leading power factor at no-load and very small loads. This was especially true of filters built to the commonly specified 5% maximum current THD requirement. Historically, most UPS system input filters see a pronounced decrease in power factor when loads dip bel

12、ow 25%. Rarely, though, did input power factors fall below 30%. However, some new systems now show no-load power factors less than 2% ?nearly perfect capacitive loads. 最新设计的输入滤波器，在减少电流谐波及提高满载情况下的功率因数方面有了较好的效果。但是空载或很小负载情况下却衍生出一个电容性超前的极低的功率因数。特别是那些为了满足5%最大电流失真度的滤波器。一般情况下，当负载低于25%时大多数UPS系统的输入滤波器会导致明显的功

13、率因数的降低，尽管如此，输入功率因数很少会低于30%。然而，有些新的系统已达到空载功率因数小于2%。接近于理想的容性负载。This condition has no effect on the UPS system output and critical loads. Utility transformers and electrical distribution systems also seem to be unaffected. That is not the case with engine-generators. As any experienced engine-generator

14、 technician knows, E-Gs do not work well with highly capacitive loads. When feeding very low power factor loads, typically below 15 or 20% capacitive, generators may experience shutdown due to overvoltage or loss of excitation. Such a shutdown coming just after a utility outage （when the emergency g

15、enerator system is attempting to pickup the UPS system load） will produce a catastrophic event. The shutdown puts the critical load in jeopardy for two reasons. First, a manual restart of the E-Gs is required, and it must be performed before battery run time is expired. Second, a system-wide overvol

16、tage caused by the E-Gs may occur just before shutdown, and it can damage telephone equipment, fire alarm systems, monitoring networks and even UPS modules. 这种情况不影响UPS输出和关键负载，市电变压器和输配电系统也不受影响。但发电机就不同了，有经验的发电机工程师知道：发电机带大容性负载时工作会不正常。当接入较低功率因数负载，典型的低于15-20%容性，由于后力不能系统失调，导致发电机可能停机。在市电停电后出现这种停机（应急发电机系统带动

17、UPS系统负载）将造成灾难性事故。由于下述两种原因停机给关键负载带来危险：第一，发电机需要手动重起，并且必须在UPS电池放电结束前；第二，在停机前发电机可能引起系统的“过压”，它可能损坏电话设备，火警系统，监控网络，甚至UPS模块。Making matters worse, it is often difficult to assign, after the fact, the responsibility for identifying and correcting this problem. The UPS manufacturer may say the UPS system teste

18、d perfectly, and besides, he can point to several sites where the same equipment causes no such problems. The E-G manufacturer may say that the problem is load-related and that there is nothing that can be done within the E-G equipment to solve the problem. The engineer, meanwhile, may state that hi

19、s specs call for both manufacturers to be compatible with each other. To understand why such an event is possible and how to avoid it （or how to find a solution should it appear at a mission-critical facility）, it is necessary to understand how engine-generators operate in relationship to their load

20、s.更糟糕的是,在事故发生后,很难区分责任,找出问题所在并予以纠正。UPS厂商说UPS系统测试完好，并指出其它地方相同的设备没有发生类似问题。发电机厂商说是负载的问题，无法调整发电机来解决问题。同时，用户工程师则说明他的规格要求，希望两个厂商相互兼容。要了解为何会发生事故及如何避免（或如何在关键应用中找出解决方案），首先需要了解发电机与负载的工作关系。The Leading Question主要问题Generators rely on voltage regulators to control their output terminal voltage. The voltage regulat

21、or senses the output voltage on all phases, averages them and compares the value with the desired voltage level. The regulator then takes power from an auxiliary power source within the E-G, usually a small auxiliary power generator on the same shaft as the main generator, and delivers DC power to t

22、he generator rotor抯 magnetic field exciter windings. The field winding current is raised or lowered, controlling the magnitude of the rotating magnetic field （referred to as the electro-motive force or EMF） in the generator抯 stator windings. The magnetic flux levels in the stator windings determine

23、the generator抯 terminal voltage. 发电机依靠电压调节器控制输出电压。电压调节器检测三相输出电压，以其平均值与要求的电压值相比较。调节器从发电机内部的辅助电源取得能量，通常是与主发电机同轴的小发电机，传送DC电源给发电机转子的磁场激励线圈。线圈电流上升或下降，控制发电机定子线圈的旋转磁场（或称为电动势EMF）的大小。定子线圈的磁通量决定发电机的输出电压。 Figure 1 shows a greatly simplified schematic drawing of a generator connected to a purely inductive load.

24、 The phasor diagram represents the voltages and currents in the schematic as vectors that rotate counterclockwise at 60 cycles per second or 60Hz. 图1所示为发电机带纯感性负载的简化示意图。矢量图表示电压和电流矢量以每秒60周逆时针旋转（60HZ）。Figure 1. Simplified schematic diagram, generator with inductive load. The generator stator winding in

25、ternal impedance, designated Z, consists of inductive and resistive elements. The generator抯 EMF as controlled by the field excitation windings on the rotor is represented by an alternating voltage source, designated E. Since the load in this example is purely inductive, the current, I, in the phaso

26、r vector diagram is lagging the voltage, V, by exactly 90 electrical degrees of rotation. If the load was purely resistive, the two vectors, I and V, would be exactly lined up, or in phase. Most loads are actually somewhere between purely resistive and purely inductive. The voltage drop caused by th

27、e current flow through the stator windings is represented as voltage vector IxZ. This voltage is actually a vector sum of two smaller voltage vectors ?a resistive voltage drop in phase with I and an inductive voltage drop 90 degrees ahead of I. In this example, I happens to be in phase with V. Since

28、 the EMF generated must equal the voltage drops in the internal generator impedance and external load, vector E equals the vector sum of V and IxZ. The voltage V is effectively controlled by varying E using the voltage regulator. 发电机定子线圈的内阻，以Z表示，包括感性和阻性部分。由转子励磁线圈控制的发电机电动势用交流电压源E表示。因为假设负载是纯感性的，在相量图中电

29、流I滞后电压V正好90度电相位角。如果负载是纯阻性的，V和I的矢量将重合，或同相。实际上多数负载介于纯阻性和纯感性之间。电流通过定子线圈引起的电压降用电压矢量IxZ表示。它实际上是两个较小的电压矢量之和，与I同相的电阻压降和超前 90度的电感压降。在本例中，它恰好与V 同相。因为电动势必须等于发电机内阻的电压降和输出电压之和，即矢量E等于V和IxZ的矢量和。电压调节器改变E可以有效地控制电压V。Figure 2. Simplified schematic diagram, generator with capacitive load. Now consider how the internal

30、 conditions in the generator change when a purely capacitive load is substituted for the inductive load in our example. The schematic diagram and phasor diagram for this case are shown in Figure 2. In this case the current has virtually reversed itself from the previous inductive load case. Current, I, is now leading the voltage vect