Electric Vehicle DC Research Articles

Supercharged Solutions

How to design safe, efficient and reliable solutions for the next generation of electric vehicle DC charging stations

Configuring products using NSGA-II: warranty profits, performance–price, and environmental emissions from the contractor perspective

In the context of mass customization business activities, product configuration (PC) can assist companies in quickly occupying the market and improving their competitive advantage. In this paper, contractors are defined as outsourcing companies for producers and manufacturers that do not possess self-developed product module technology and who are more knowledgeable and discerning consumer representatives. This study focused on a PC approach that includes optional, redundant, and common modules. In this approach, three objective functions were considered and solved using NSGA-II: warranty profit, performance-price, and environmental emissions. Warranty profit is calculated by forcing the product failure probability to satisfy a power-law distribution and the user selection behavior to satisfy a multinomial logit (MNL) model. Kano’s model-based user satisfaction and the relative importance of the product module instance are used to calculate performance-price. The environmental emissions were determined from both production and assembly emissions of the module instance. Additionally, a chromosome encoding method and a chromosome crossover operation were designed for the PC problem. Finally, the feasibility and effectiveness of the proposed method were verified by taking an electric vehicle DC charging pile configuration project as an example, and discussing and explaining the practical significance of each parameter in the example.

Thermal Characterization Approach for In Situ Estimation of Thermophysical Properties of Magnetic Components of Electric Vehicle Fast Chargers

This article presents a cost-effective thermal characterization approach that relies on temperature measurements and numerical simulations to solve an inverse heat transfer (IHT) problem for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> estimation of thermophysical properties of high-frequency magnetic components. This approach is applied to the magnetic components of a commercial electric vehicle dc fast charger, specifically, to an air-cooled inductor-transformer assembly. Numerical simulations solve a conjugate conduction–convection IHT problem based on surface temperature measurements collected during realistic operating conditions of the charger. These simulations enable rapid <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> estimation of the specific heat capacities, thermal conductivities, volumetric heat generation rates, and convective heat transfer coefficients of the cores and windings of these magnetic components. These estimated properties are then used as inputs in a direct heat transfer (DHT) simulation for the thermal analysis of these components under different cooling conditions, namely natural and forced convection. The thermal analysis of the inductor-transformer assembly shows that active air cooling with forced convection allows sustaining the measured charging power (28.8 kW) up to 6630 s when the surface temperatures of the cores reach the 100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C threshold. This charging time is 61.7% longer than that allowed by the passive air cooling at the same charging power.

Review of Solid-State Transformer Applications on Electric Vehicle DC Ultra-Fast Charging Station

The emergence of DC fast chargers for electric vehicle batteries (EVBs) has prompted the design of ad-hoc microgrids (MGs), in which the use of a solid-state transformer (SST) instead of a low-frequency service transformer can increase the efficiency and reduce the volume and weight of the MG electrical architecture. Mimicking a conventional gasoline station in terms of service duration and service simultaneity to several customers has led to the notion of ultra-fast chargers, in which the charging time is less than 10 min and the MG power is higher than 350 kW. This survey reviews the state-of-the-art of DC ultra-fast charging stations, SST transformers, and DC ultra-fast charging stations based on SST. Ultra-fast charging definition and its requirements are analyzed, and SST characteristics and applications together with the configuration of power electronic converters in SST-based ultra-fast charging stations are described. A new classification of topologies for DC SST-based ultra-fast charging stations is proposed considering input power, delta/wye connections, number of output ports, and power electronic converters. More than 250 published papers from the recent literature have been reviewed to identify the common understandings, practical implementation challenges, and research opportunities in the application of DC ultra-fast charging in EVs. In particular, the works published over the last three years about SST-based DC ultra-fast charging have been reviewed.

PV/Battery Grid Integration Using a Modular Multilevel Isolated SEPIC-Based Converter

Photovoltaic (PV) plants can be built rapidly when compared with other conventional electrical plants; hence, they are a competent candidate for supplying the electricity grid. The output power of the PV modules can be used in plug-in electric vehicles (PEVs) DC charging stations to reduce the burden on the electricity grid, particularly during peak load hours. To integrate PV modules and electric vehicles (EVs) with the electricity grid, the modular multilevel converters (MMCs) topologies producing staircase voltage waveforms are preferred as they are able to deliver less total harmonic distortion (THD) and higher efficiency in addition to lower voltage stress on semiconductor switches. In conventional centralized MMC topologies, a direct connection to a high-DC-link input voltage is required which is not appropriate for PV plants. A new MMC topology for PV/EV/grid integration is proposed in this paper, where the individual PV arrays are directly connected to each phase of the AC grid to harvest the maximum available power point. A current-source converter (CSC) based on a single-stage isolated SEPIC converter is adopted as the submodule (SM) for the proposed MMC topology given its outstanding features, such as low input ripple current, high efficiency, high power factor, and flexible output voltage higher or lower than the input voltage. The single-stage SMs can operate in both DC/DC and DC/AC operating modes. Proper controllers for each mode of operation are designed and applied to supply constant current from either the PV modules or the battery cells by eliminating the second-order harmonic component. The performance of the proposed converter is verified by simulations and a downscaled prototype controlled by TMSF28335 DSP.

A Stand Alone Building Integrated PV Tied Bidirectional Capability Direct DC Electric Vehicle Charging System Through Z-Source Inverter Impedance Network Capacitors

Due to the rise of gasoline prices and depletion of fossil fuels, electric vehicles have gained a popularity. EVs can be charged at homes using the utility grid, but using a PV integrated system reduces the demand on grid and also contributes to the environmental sustainability. For the past few years there is a lot of interests shown in the building-integrated PV systems. They are designed and implemented to meet required building load demand. As the number of EV users increase in the commercial complexes, there is a need to provide adequate power requirement for EV fast charging. The power demand increases particularly in the daytime due to rush hour charging, so similar to rooftop solar energy system, building-integrated PV is a system which can provide power for EV charging. According to our proposed topology if PV system is offline, grid can act as a backup source. The Z-source inverter able to boost, buck ,and invert has got a lot of attention in PV grid applications. In this paper, a modified Z-source inverter-based charging system is proposed, and a step-up converter is used in the charging side of the system. This PV-Grid connected with MZSI topology. This topology demonstrates the bidirectional flow of power.

Large-Signal Stability Analysis and Design of Finite-Time Controller for the Electric Vehicle DC Power System

In the electric vehicle dc power system (EVDCPS), a motor or converter can be regarded as a constant power load (CPL) when tightly controlled. Different from the resistive load, CPL may make the EVDCPS unstable. Thus, in addition to less overshoot and shorter setting time, the controller of the converter applied in EVDCPS should maintain the system stable. In this article, the finite-time controller (FTC) is proposed based on exact feedback linearization (EFL) to stabilize the EVDCPS feeding CPL. First, to handle the nonlinearity caused by the CPL, the affine nonlinear model of EVDCPS is transformed into the Brunovsky canonical form by using EFL. Then, the finite-time control is adopted and a PI compensator is designed to eliminate the steady-state error. Under the proposed control algorithm, rigorous proofs indicate that not only the closed system can be large-signal stable, but also the EVDCPS bus voltage can converge the reference in finite time. Furthermore, to reduce the design difficulty of FTC, the backstepping method is adopted to design a backstepping finite-time controller(BFTC). Finally, simulations and experiments of FTC and BFTC are carried out. Results indicate that both FTC and BFTC have large-signal stability, and although the robustness of BFTC is inferior to FTC, the setting time and overshoot are greatly improved compared with the traditional linear feedback controller.

Modeling for Electric Vehicle Dc Fast Charging Station

Modeling for Electric Vehicle Dc Fast Charging Station

Modeling for Electric Vehicle DC Fast Charging Station for Future Siting and Sizing

Modeling for Electric Vehicle DC Fast Charging Station for Future Siting and Sizing

Python supervised co-simulation for a day-long harmonic evaluation of EV charging

To accurately simulate electric vehicle DC fast chargers' (DCFCs') harmonic emission, a small time step, i.e., typically smaller than 10 &#x03BC;s, is required owing to switching dynamics. However, in practice, harmonics should be continuously assessed with a long duration, e.g., a day. A trade-off between accuracy and time efficiency thus exists. To address this issue, a multi-time scale modeling framework of fast-charging stations (FCSs) is proposed. In the presented framework, the DCFCs' input impedance and harmonic current emission in the ideal grid condition, that is, zero grid impedance and no background harmonic voltage, are obtained based on a converter switching model with a small timescale simulation. Since a DCFC's input impedance and harmonic current source are functions of the DCFC's load, the input impedance and harmonic emission at different loads are obtained. Thereafter, they are used in the fast-charging charging station modeling, where the DCFCs are simplified as Norton equivalent circuits. In the station level simulation, a large time step, i.e., one minute, is used because the DCFCs' operating power can be assumed as a constant over a minute. With this co-simulation, the FCSs' long-term power quality performance can be assessed time-efficiently, without losing much accuracy.

Research on control strategy of VIENNA rectifier based on electric vehicle DC charging module

Because the VIENNA rectifier has fewer switching devices, a high power factor and no need to set dead zone time, the front rectifier of the DC charging module of ev mostly uses VIENNA circuit. However, the DC charging module has higher requirements on the dynamic response capability and stability of the VIENNA rectifier system. The traditional PI double closed loop control strategy has poor dynamic response capability. For this reason, a hybrid control strategy of PI control for current loop and sliding mode control for voltage loop is used to control the VIENNA rectifier to improve the dynamic response and stability of the system. Finally, through the simulation of the rectifier circuit, and the comparison of the simulation results, it can be proved that the dynamic response ability and stability of the hybrid control strategy is relatively good. Finally, a simulation model of VIENNA rectifier is built, and the hybrid control strategy is proved to have good dynamic performance and stability by comparison.

Control of power converter used for electric vehicle DC charging station with the capability of balancing distribution currents and reactive power compensation

The global interest in electric cars aims to achieve sustainability in the transportation sector and reduce dependence on conventional cars that mainly depend on fossil fuels, the main source of emissions polluting the environment. However, the electric cars required electric fast chargers to charge the batteries with high currents in order to make the electric cars competitive with conventional cars that required a short time for filling fuel. Single-phase electric chargers make the distribution feeders with unbalanced currents as the single-phase loads and single-phase PV inverters. In the case of the unbalanced operation, one of the three phases may reach its maximum limit before other phases which leads to disconnect the transformer and thereby inefficient and unreliable system operation. This paper presents a control scheme for a three-phase, four-leg power converter that can be used as a fast charger for electric cars. Moreover, it can be used for balancing grid currents and for reactive power compensation. This will avoid frequent interruptions of distribution transformers due to unbalanced operation and reactive power loads. The distribution feeder considered to evaluate the control scheme consists of single-phase loads and inverters in addition to the proposed converter. The converter controls the charging power effectively and balancing the feeder currents. Moreover, during off charging time which is a possible manner for the charging station when the EV battery is fully charged the converter is effectively used for unbalanced mitigation and reactive power compensation. The simulated results show the effectiveness of the proposed control scheme.

High Penetration of Electric Vehicles Could Change The Residential Power System: Public dc Fast Chargers Will Not Be Enough

In the near future, the massive production and deployment of electric vehicles (EVs) will need to be matched by the availability of an equivalently large number of dc fast-charging capabilities. This article explores the possibilities that public dc fast-charging systems will not be enough to satisfy the demand for a convenient network of EV-charging stations, creating the need for a residential dc fast charger that has the potential to become the enabling block for dc residential systems. DC residential systems also present a natural solution for the integration of solar panels and battery storage. DC fast chargers can efficiently and easily integrate solar energy produced and currently stored on the ac power grid, forming the backbone for a dc residential grid. Furthermore, the infrastructure needed for EV dc fast chargers can easily accept a future migration of other natural dc systems, such as modern air conditioning (A/C), heat pumps, refrigeration, lighting, and, ultimately, the other remaining appliances.

Adaptive identification methods of nonlinear random electrical signal

The nonlinearity of the electric vehicle DC charging equipment and the complexity of the charging environment lead to the complex and changeable DC charging signal of the electric vehicle. It is urgent to study the distortion signal recognition method suitable for the electric vehicle DC charging. Focusing on the characteristics of fundamental and ripple in DC charging signal, the Kalman filter algorithm is used to establish the matrix model, and the state variable method is introduced into the filter algorithm to track the parameter state, and the amplitude and phase of the fundamental waves and each secondary ripple are identified; In view of the time-varying characteristics of the unsteady and abrupt signal in the DC charging signal, the stratification and threshold parameters of the wavelet transform are corrected, and a multi-resolution method is established to identify and separate the unsteady and abrupt signals. Identification method of DC charging distortion signal of electric vehicle based on Kalman/modified wavelet transform is used to decompose and identify the signal characteristics of the whole charging process. Experiment results demonstrate that the algorithm can accurately identify ripple, sudden change and unsteady wave during charging. It has higher signal to noise ratio and lower mean root mean square error.

Erratum to “Reconfigurable Hybrid Energy Storage System for an Electric Vehicle DC–AC Inverter” [Dec 20 12846-12860

Presents corrections to the above named paper.

Thermal analysis of electric vehicle DC charging pile power module based on two-dimensional ordered porous structure radiator

In order to improve the heat dissipation performance and study the factors affecting the heat dissipation effect of a two-dimensional ordered porous structure, a thermal analysis of the radiator in the power module of a DC charging pile was carried out. Based on the thermal analysis of the grid-type radiator, the square-hole radiator is subjected to a thermal analysis, the heat dissipation performance of the two radiators is compared, and the factors affecting the heat dissipation effect of the square-hole radiator are explored. Research shows that the heat dissipation effect of the square-hole radiator, which represents a twodimensional ordered porous structure, is better than that of the grid-type radiator. The factors affecting the heat dissipation effect of the square-hole radiator are mainly related to the height of the radiator and are positively related to the heat dissipation effect of the radiator.

Design of Program Control Interface of DC Charging Pile Verification Device

Design and manufacture a multi-function verification device for electric vehicle DC charging pile. This device is suitable for all levels of measurement department, charging pile Use Company and DC charger manufacturer. The accuracy of the DC charging pile verification device is 0.05, which is used for full-function verification before charging pile installation. It is mainly composed of high-precision standard electric energy meter, high-power program-controlled DC electronic load, main control unit and various functional modules. The DC charging pile verification device adopts the latest design technology and has stable and reliable performance.

Technology solutions to mitigate electricity cost for electric vehicle DC fast charging

Widespread adoption of alternative fuel vehicles is being hindered by high vehicle costs and refueling or range limitations. For plug-in electric vehicles, direct-current fast charging (DCFC) is proposed as a solution to support long-distance travel and relieve range anxiety. However, DCFC has also been shown to be potentially more expensive compared to residential or workplace charging. In particular, electricity demand charges can significantly impact electricity cost for fast charging applications. Here we explore technological solutions that can help reduce the electricity cost for electric vehicle fast charging. In particular, we consider thousands of electricity rates available in the United States and real-world vehicle charging load scenarios to assess opportunities to reduce the cost of DCFC by deploying solar photovoltaics (PV) panels and energy storage (battery), and implementing a co-location configuration where a DCFC station is connected to an existing meter within a commercial building. Results show that while the median electricity cost across more than 7000 commercial retail rates remains less than $0.20/kWh for all charging load scenarios considered, cost varies greatly, and some locations do experience significantly higher electricity cost. Co-location is almost always economically viable to mitigate fixed cost and demand charges, but the relative benefit of co-locating diminishes as station size and utilization increase. Energy storage alone can help mitigate demand charges and is more effective at reducing costs for “peaky” or low-utilization loads. On the other hand, PV systems primarily help mitigate energy charges, and are more effective for loads that are more correlated with solar production, even in areas with lower solar resource. PV and energy storage can deploy synergistically to provide cost reductions for DCFC, leveraging their ability to mitigate demand and energy charges.

Review of power electronics in vehicle-to-grid systems

Abstract Vehicle-to-Grid (V2G) is a promising technology that allows the batteries of idle or parked electric vehicles (EVs) to operate as distributed resources, which can store or release energy at appropriate times, resulting in a bidirectional exchange of power between the ac grid and the dc EV batteries. This bidirectional exchange of power is realized using bidirectional power electronic converters that connect the grid with the EV battery. Most research on bidirectional converters for V2G applications focuses on using two dedicated power conversion stages – a bidirectional ac-dc conversion stage that helps in power factor correction, followed by a bidirectional dc-dc conversion stage that provides voltage matching. However, a single bidirectional ac-dc conversion stage can also facilitate V2G and grid-to vehicle (G2V) active power transfers. This paper reviews and compares the various bidirectional ac-dc and dc-dc converter topologies that facilitate V2G and G2V active power flows. Moreover, the paper discusses the various classes of charger/discharger systems reported for V2G applications, like on-board/off-board, integrated/non-integrated and conductive/inductive, and a comparative statement is made based on certain proposed criteria. Further, the current trends in the application of wide band-gap devices in high power-dense V2G capable converters and integration of renewable energy sources into EV charging/discharging infrastructures have also been discussed.

PID Control for Electric Vehicles Subject to Control and Speed Signal Constraints

A PID control for electric vehicles subject to input armature voltage and angular velocity signal constraints is proposed. A PID controller for a vehicle DC motor with a separately excited field winding considering the field current constant was tuned using controlled invariant set and multiparametric programming concepts to consider the physical motor constraints as angular velocity and input armature voltage. Additionally, the integral of the error, derivative of the error constraints, and λ were considered in the proposed algorithm as tuning parameters to analyze the DC motor dynamic behaviors. The results showed that the proposed algorithm can be used to generate control actions taking into account the armature voltage and angular velocity limits. Also, results demonstrate that a controller subject to constraints can improve the electric vehicle DC motor dynamic; and at the same time it protects the motor from overvoltage.