Among the various supply voltage abnormalities, unbalance and distortion are some of the major threats to the dc bus capacitor of adjustable speed drives. The effect of supply voltage unbalance on the dc bus capacitor changes in the presence of supply voltage harmonics. Further, the value of grid impedance and the load on the drive influences the response of these supply voltage abnormalities on the dc bus capacitor. This article analyzes the impact of unbalance, distortion, and simultaneous presence of unbalance and distortion in the supply voltage, on the dc bus capacitor, along with the effect of grid impedance and the load on the drive. As a result of the analysis, the article proposes the derating of load required to keep the capacitor current within the safe value irrespective of the level of abnormalities and grid impedance. The effects are analyzed by simulations and validated by the hardware test setup.

中文翻译：

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电源电压不平衡和谐波对调速驱动器直流母线电解电容器的影响

在各种电源电压异常中，不平衡和失真是对可调速驱动器直流总线电容器的一些主要威胁。在电源电压谐波存在的情况下，电源电压不平衡对直流母线电容器的影响会发生变化。此外，电网阻抗值和驱动器上的负载会影响这些电源电压异常对直流总线电容器的响应。本文分析了电源电压中不平衡、失真以及同时存在的不平衡和失真对直流总线电容器的影响，以及电网阻抗和负载对驱动器的影响。作为分析的结果，文章建议降低负载以将电容器电流保持在安全值内，而不管异常水平和电网阻抗如何。