Partial Power Processing Based Charging Unit for Electric Vehicle Extreme Fast Charging Stations

Abstract

This paper presents an analysis and design of a charging unit inside an electric vehicle extreme fast charging station. Due to the benefits that partial power processing achieves in terms of size reduction and efficiency improvement, it is decided to implement a partial power converter architecture. This type of architectures reduce the power to process by the converter but, they require an isolated topology. Therefore, a dual active bridge is selected for the study. Then, design wise, four different turns ratio values are selected and their performance results are compared in terms of processed power by the converter, semiconductors stress factor and energy loss. Finally, it is concluded that the turns ratio value is a key factor that must be correctly selected for optimizing the concerned comparison parameters.

State-of-the-Art Grid Stability Improvement Techniques for Electric Vehicle Fast-Charging Stations for Future Outlooks

“…This technique is implemented in the rectification stage for voltage gain improvement and high efficiency [45], as shown in Figure 8a. The instantaneous power and voltage components are matched for a stable DC-link voltage and to synchronize grid current and voltage for the same phase and frequency alignment at the PCC [46]. Grid current (iabc) is deployed for current control implementation in the rotating direct-quadrature (dq) reference frame [46].…”

“…The instantaneous power and voltage components are matched for a stable DC-link voltage and to synchronize grid current and voltage for the same phase and frequency alignment at the PCC [46]. Grid current (iabc) is deployed for current control implementation in the rotating direct-quadrature (dq) reference frame [46]. The DC-to-DC converter control is implemented using an isolated or non-isolated converter in this strategy, where the phase shift between the voltages, duty ratio (D) of the voltages, and the frequency of operation can be controlled using either a PI or DB controller for transient DC current reduction, as shown in Figure 8b [47].…”

“…The inner-loop current's reference value (In) is generated by the first PI controller and is compared with the reference current (I*) in the inner-loop control, and this is fed to the second PI controller to generate the switching pulse to stabilize the DC output voltage [36]. The technique only processes a fraction of the total power requirement percentage of the EV load [45][46][47].…”

“…The inner-loop current's reference value (In) is generated by the first PI controller and is compared with the reference current (I*) in the innerloop control, and this is fed to the second PI controller to generate the switching pulse to stabilize the DC output voltage [36]. The technique only processes a fraction of the total power requirement percentage of the EV load [45][46][47]. The implementation of partial power control using the PI controller in [36] and the DB controller in [23] for isolated converters showed a high surge current, which caused a slow response and poor efficiency in terms of reactive power control issues and complex control architecture.…”

“…Therefore, the PPC strategy may not be suitable when there is a significant step-up or step-down between the source voltage and the FCS [23]. In addition, the application of isolated converters for the PPC approach is constrained by reactive power control issues [46]. On the other hand, in the non-isolated PPC structure, the converter power injected fundamentally decreased as the voltage gain approached unitary, due to the absence of the isolation barrier, as discussed in [108].…”