Power Quality Investigation of a Grid-Connected Single-Phase Bidirectional AC/DC for Electric Vehicle Applications

Abstract

The number of electric vehicles (EVs) is growing rapidly in almost all countries, and as a result, the power consumption to charge EVs is also sharply increasing. The characteristics of EV charging are extremely variable, which creates negative impacts, including overloading, stability problems, and power quality problems for other users connected to the same distribution network. Therefore, it is important to ensure power quality and grid stability, which can only be obtained through a better understanding of grid behaviors. Recently, power quality studies have redirected their attention to a particular frequency range that was previously overlooked-the supra-harmonic range of 2 kHz to 150 kHz. Unlike the easily identifiable harmonic components of the 50 Hz to 60 Hz mains fundamental, this range comprises a mix of intentional emissions, switching non-linearities, byproducts, and different resonances. Therefore, this paper presents a model study of a grid-connected single-phase bidirectional AC/DC converter for EV applications to investigate power quality issues from 2 kHz to 150 kHz. For the investigation, the converter was modeled in the MATLAB/Simulink environment, which was then used to evaluate conducted emissions caused by the high switching frequency. The operating conditions of 4.4 kW and 18 kHz switching frequency were simulated, and noise-separated signals into differential and common modes were measured. The frequency domain results demonstrate that higher frequency emissions penetrate noise due to the high switching frequency in bidirectional converters.