Investigation of Voltage Sags Effects on ASD and Mitigation using ESRF theory-based DVR

Voltage sag is a frequently occurring power quality disturbance in the industries equipped with adjustable speed drives (ASD). A detailed investigation of voltage sag effects on ASD performance with the novel mathematical analyses to estimate the ASD parameters during different types of voltage sag is discussed in this article. The effects of voltage sags are mitigated using an enhanced synchronous reference frame (ESRF) theory-based dynamic voltage restorer (DVR). 

The working principle of the ESRF theory-based DVR during sag is also described. The investigation of the effects of type A, type B and type F voltage sags on ASD parameters are verified using the simulation and the experimental studies. Further, these effects are mitigated by the ESRF theory-based DVR using the developed simulation and experimental models. 

The ESRF controller of DVR is working effectively during voltage sags by improving its transient response, which tightly regulates the DC link voltage of ASD around its reference value. Also, the steady state response of DVR is enhanced during severe voltage sag, which further validates the ability of the ESRF theory-based DVR. This type of improved performance of ASD during voltage sags cannot be obtained using other existing SRF theories of the DVR.

Index Terms—Adjustable speed drives, DC-link voltage, Symmetrical sag, Unsymmetrical sag, Dynamic voltage restorer.