Detailed Estimation of Grid-Side Current and Its Oscillations Caused by Adjustable Speed Drive Systems

The current oscillations (ringings) associated with the voltage notches at the Point of Common Coupling (PCC), caused by the function of Diode Rectifiers (DRs) in Adjustable Speed Drives (ASDs), can impair the power quality and make Electro-magnetic Interference (EMI) issues. Considering these transients, this paper proposes an analytical approach to estimate the time-domain behavior of ASD systems with the focus on the operation of their DR. With the aim of simplifying the derivation of equations that govern the time-domain response of the ASD system, a new set of approximations are introduced. These approximations are carried out to find the contributing factors (parameters) in the formation of the undesirable Current Ringings (CRs) occurring in the grid-side of the ASD system. As power converters with a similar topology are used for different applications, such as in renewable energies, these new approximations and the derived equations can be applied in other fields (and other similar systems). The investigations suggest more design limitations for the passive components of the ASD system, such as the EMI filters. To prove the validity of the proposed approach, the obtained numerical results are verified by the simulation and experimental results.