Manufacturers and users of uninterruptible power supply have long noticed the cooperation between generator set and UPS, especially the adverse impact of current harmonic generated by rectifier on power supply system, such as voltage regulator of generator set and synchronous circuit of ups. Therefore, UPS system engineers designed the input filter and applied it to UPS, and successfully controlled the current harmonic in the application of ups. These filters play a key role in the compatibility between ups and generator set.

事實上所有的輸入濾波器都使用電容器和電感來吸收UPS輸入端 具破壞性的電流諧波。輸入濾波器的設(shè)計考慮了UPS電路固有的和在滿載情況下的 大可能的全部諧波畸變的百分比。大多數(shù)濾波器的另一個益處是提高帶載UPS的輸入功率因數(shù)。然而輸入濾波器的應(yīng)用帶來的另一個后果是使UPS整體效率降低。絕大多數(shù)濾波器消耗1%左右的UPS功率。輸入濾波器的設(shè)計一直在有利和不利因素之間尋求平衡。

In fact, all input filters use capacitors and inductors to absorb destructive current harmonics at the input of ups. The design of the input filter takes into account the percentage of all possible harmonic distortion inherent in the ups circuit and under full load. Another benefit of most filters is to improve the input power factor of on-board ups. However, another consequence of the application of input filter is to reduce the overall efficiency of ups. Most filters consume about 1% of UPS power. The design of input filter always seeks a balance between favorable and unfavorable factors.

為了盡可能提高UPS系統(tǒng)的效率，近期UPS工程師在輸入濾波器的功耗方面做了改進。濾波器效率的提高，從很大程度上取決于將IGBT(絕緣門級晶體管)技術(shù)應(yīng)用到UPS設(shè)計中。IGBT逆變器的高效率導致了對UPS的重新設(shè)計。輸入濾波器可以吸收某些電流諧波，同時吸收很小一部分有功功率?？傊瑸V波器中感性因素對容性因素的比率降低了，UPS的體積變小了，效率提高了。然而新問題是UPS與發(fā)電機的兼容性又出現(xiàn)了，替代了老問題。

In order to improve the efficiency of UPS system as much as possible, UPS engineers have recently made improvements in the power consumption of input filter. The improvement of filter efficiency largely depends on the application of IGBT (insulated gate transistor) technology to UPS design. The high efficiency of IGBT inverter leads to the redesign of ups. The input filter can absorb some current harmonics and a small part of active power at the same time. In short, the ratio of inductive factor to capacitive factor in the filter is reduced, the volume of UPS is reduced and the efficiency is improved. However, the new problem is that the compatibility between ups and generator appears again, replacing the old problem.

功率因數(shù)的問題

Power factor problem

通常，人們把注意力放在UPS電源滿載或接近滿載情況下的工作狀態(tài)。絕大多數(shù)工程師都能表述滿載情況下的UPS工作特性，特別是輸入濾波器的特性，然而很少有人對濾波器在空載或接近空載時的狀況感興趣。畢竟UPS及其電氣系統(tǒng)在輕載狀態(tài)下的電流諧波影響很小。然而，UPS空載時的工作參數(shù)，特別是輸入功率因數(shù)對于UPS與發(fā)電機的兼容性相當重要。

Usually, people pay attention to the working state of UPS under full load or near full load. Most engineers can describe the working characteristics of UPS under full load, especially the characteristics of input filter. However, few people are interested in the condition of filter under no-load or near no-load. After all, ups and its electrical system have little influence on current harmonics under light load. However, the working parameters of UPS under no-load, especially the input power factor, are very important for the compatibility between ups and generator.

新設(shè)計的輸入濾波器，在減少電流諧波及提高滿載情況下的功率因數(shù)方面有了較好的效果。但是在空載或很小負載情況下卻衍生出一個電容性超前的極低的功率因數(shù)，特別是那些為了滿足5% 大電流失真度的濾波器。一般情況下，當負載低于25%時大多數(shù)UPS系統(tǒng)的輸入濾波器會導致明顯的功率因數(shù)降低。盡管如此，輸入功率因數(shù)卻很少會低于30%，有些新的系統(tǒng)甚至已達到空載功率因數(shù)低于2%，接近于理想的容性負載。

The newly designed input filter has a good effect in reducing current harmonics and improving power factor under full load. However, in the case of no-load or very small load, a very low power factor with leading capacitance is derived, especially those filters that meet 5% high current distortion. In general, when the load is less than 25%, the input filter of most UPS systems will lead to significant power factor reduction. Nevertheless, the input power factor is rarely lower than 30%, and some new systems have even reached no-load power factor lower than 2%, which is close to the ideal capacitive load.

這種情況不影響UPS電源輸出和關(guān)鍵負載，市電變壓器和輸配電系統(tǒng)也不受影響。

This situation will not affect the output of UPS power supply and key loads, and the municipal power transformer and transmission and distribution system will not be affected.

但發(fā)電機就不同了，發(fā)電機工程師知道：發(fā)電機帶大容性負載時工作會不正常，當接入較低功率因數(shù)負載，典型的低于15%～20%容性時，由于系統(tǒng)失調(diào)，可能導致發(fā)電機停機。在市電停電后出現(xiàn)這種停機?應(yīng)急發(fā)電機系統(tǒng)帶動UPS系統(tǒng)負載將造成災難性事故。

However, the generator is different. The generator engineer knows that the generator will not work normally when it is loaded with large capacitive load. When it is connected to a load with low power factor, typically lower than 15% ~ 20%, the generator may be shut down due to system imbalance. Such shutdown after mains power failure? The load of UPS system driven by emergency generator system will cause catastrophic accident.

由于下述兩種原因停機給關(guān)鍵負載帶來危險： ，發(fā)電機需要人工重啟，并且必須在UPS電池放電結(jié)束前;第二，在停機前發(fā)電機可能引起系統(tǒng)的”過壓”，它可能損壞電話設(shè)備、火警系統(tǒng)、監(jiān)控網(wǎng)絡(luò)甚至UPS模塊。更糟糕的是，在事故發(fā)生后，很難區(qū)分責任，找出問題所在并予以糾正。UPS廠商說UPS系統(tǒng)測試完好，并指出其它地方相同的設(shè)備沒有發(fā)生類似問題。發(fā)電機廠商說是負載的問題，無法調(diào)整發(fā)電機來解決問題。同時，用戶工程師則說明他的規(guī)格要求，希望兩個廠商相互兼容。要了解為何會發(fā)生事故及如何避免(或如何在關(guān)鍵應(yīng)用中找出解決方案)，需要了解發(fā)電機與負載的工作關(guān)系。

Shutdown brings danger to key loads due to the following two reasons: the generator needs to be restarted manually and must be restarted before the discharge of UPS battery; Second, before shutdown, the generator may cause "overvoltage" of the system, which may damage telephone equipment, fire alarm system, monitoring network and even UPS module. Worse, after the accident, it is difficult to distinguish responsibilities, find out the problem and correct it. The ups manufacturer said that the UPS system was tested in good condition and pointed out that there were no similar problems with the same equipment in other places. The generator manufacturer said it was a load problem and it was impossible to adjust the generator to solve the problem. At the same time, the user engineer explained his specification requirements and hoped that the two manufacturers would be compatible with each other. To understand why accidents occur and how to avoid them (or how to find solutions in key applications), we first need to understand the working relationship between generator and load.

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