The proposed model of an electric vehicle charging station is suitable for the fast DC charging of multiple electric vehicles. The station consists of a single grid-connected inverter with a DC bus where the electric vehicles are connected. The control of the individual electric vehicle charging processes is decentralized, while a separate central control deals with the power transfer from the AC grid to the DC bus. The electric power exchange does not rely on communication links between the station and vehicles, and a smooth transition to vehicle-to-grid mode is also possible. Design guidelines and modeling are explained in an educational way to support implementation in Matlab/Simulink. Simulations are performed in Matlab/Simulink to illustrate the behavior of the station. The results show the feasibility of the model proposed and the capability of the control system for fast DC charging and also vehicle-to-grid.

Modeling of an electric vehicle charging station for fast DC charging

In order to further cut down the cost of filter for grid-connected pulsewidth modulation (PWM) converter under the more and more stringent grid code, a new kind of high-order filter, named LCL - LC filter, is presented in this paper. The resonant frequency characteristics of the filter are analyzed, and a parameter design method on the base of the characteristics is also proposed in the paper. The proposed parameter design method can easily make full use of the existing research results about the traditional LCL filter parameter design. And then a parameter robustness analysis method based on four-dimensional graphics is proposed to analyze parameter robustness of the presented filter. Compared with the traditional one, the proposed analysis method can analyze the filter performance under variations of several parameters at a time without any iteration. The comparative analysis and discussion considering the LCL filter, the trap filter, and the LCL - LC filter, are presented and verified through the experiments on a 5 kW grid-connected converter prototype. Experiment results demonstrate the accuracy of theoretical analysis and prove that the presented filter has a better performance than two others.

An LCL - LC Filter for Grid-Connected Converter: Topology, Parameter, and Analysis

This paper presents a design methodology for a high power density converter, which emphasizes weight minimization The design methodology considers various inverter topologies and semiconductor devices with application of cold plate cooling and LCL filter Design for a high-power inverter is evaluated with demonstration of a 50 kVA 2-level 3-phase SiC inverter operating at 60 kHz switching frequency The prototype achieves high gravimetric power density of 649 kW/kg

Design and Demonstration of High Power Density Inverter for Aircraft Applications

This paper proposes a variable DC-link reference voltage algorithm for wide range of maximum power point tracking (MPPT) for two-string photovoltaic (PV) systems. A multi-string system, which is a kind of PV system, is widely used due to its many merits (such as the ability to use low rating devices, high MPPT efficiency, and so forth). PV systems can choose their input voltages on the basis of their PV cell connection structure. The PV cell connection structure can be restricted because the input voltage and current affect the PV system design. This reduces the MPPT range under some weather conditions. In the restricted PV connection structure, this algorithm enlarges the MPPT range and minimizes the increment of the total harmonic distortion (THD) by selecting the appropriate DC-link voltage reference which is changed by comparing the sorted input voltage. To verify the proposed algorithm, simulation and experiments are conducted to show the results of the performance for the proposed algorithm.

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Variable DC-Link Voltage Algorithm with a Wide Range of Maximum Power Point Tracking for a Two-String PV System

In order to reduce cost, size, weight, and volume of on board chargers in electric vehicles, it has been proposed to pursue integration for the dual usage of converters for both charging and propulsion. The solution here goes further in that it also supports the control of slow single-phase and fast three-phase charging through one and the same power electronic converter. A unified control methodology for the on-board chargers in electric vehicles is proposed. The control is distinguished in that it can perform four-quadrant operation while connected in single-phase or three-phase mode. The operation and network synchronization are automatically adjusted based on given terminal voltage and current measurements without the need for supplementary status signals. An analysis illustrates how the various measurements are processed for obtaining single- and three-phase flexibility while retaining compatibility with well-established methods of converter current mode control. The proposed control is validated via detailed simulation and demonstrated in a smart grid laboratory. The hardware implementation in the laboratory substantiates the claims of flexible single- and three-phase control.

A Unified Single- and Three-Phase Control for Grid Connected Electric Vehicles

This paper deals with a design method of LCL filter for grid-connected three-phase PWM voltage source inverters (VSI). By analyzing the total harmonic distortion of the current (THD i ) in the inverter-side inductor and the ripple attenuation factor of the current (RAF) injected to the grid through the LCL network, the parameter of LCL can be clearly designed. The described LCL filter design method is verified by showing a good agreement between the target current THD and the actual one through simulation and experiment.

Em-Cheol Nho

Papers

LCL-filter design for grid-connected PCS using total harmonic distortion and ripple attenuation factor