This article presents a dual-side capacitor tuning and cooperative control strategy for wireless electric vehicle (EV) charging. To improve the efficiency of wireless EV charging across broad output voltages and wide-range load variations, this article introduces a reconfigurable WPT system by incorporating two switch-controlled-capacitors (SCCs) into the double-sided LCC (DLCC) compensation network. Based on the analytical model of the system, optimal capacitor tuning factors are derived to reduce the rms values of the inductor currents and to minimize the turn-off currents across the semiconductors. Furthermore, a dual-side cooperative control strategy is proposed. Through the collaborative control of the inverter, rectifier, and SCCs, the proposed method achieves dual-side optimal zero-voltage-switching (ZVS), wide power regulation, and maximum efficiency tracking simultaneously. Compared with the existing triple-phase-shift (TPS) method, the proposed approach improves the system efficiency across a wide range of dc output voltages and power levels. Experimental results demonstrate that the proposed method achieves a maximum efficiency improvement of up to 1.8% in the boost mode and 1.9% in the buck mode.

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In this chapter, various electric vehicle (EV) charging technologies are reviewed, including onboard charging, offboard charging, and contactless charging. The focus is on charging power control as well as its converter topology. Because EV charging significantly influences the grid, the power quality of EV charging is thoroughly reviewed in terms of modeling, analysis, and mitigation measures. EV charging, especially overnight, gives a lot of flexibility to instant charging power, which can be used to improve the load flow in the electric grid. Smart charging describes those approaches, which are also reviewed.

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To test high-voltage (HV) equipment with increasingly complex transients obtained from various power system studies, this article demonstrates a hardware implementation of a medium-voltage (MV) submodule (SM) to be used in a modular multilevel converter (MMC)-based HV arbitrary wave shape generator (AWG). The MV SM is scalable with its own onboard auxiliary power supply (APS), and it is constructed by connecting three full-bridge SMs in series from the commercially available component. The designed MV SM can be operated for a wide voltage range of 0.8-2.7 kV to incorporate different test objects ranging from HV insulation material to MV equipment and generate a wide output range of 0.12-1.2 kV. Considering the hardware nonidealities in the APS, gate driver, and switches, the series operation of three SMs is ensured using an arm energy controller. Based on the current-based model of APS, SM capacitance design criteria are updated for variable-frequency output waveform, and the minimum dc-link voltage is calculated for the proper start-up of this scalable MMC module. Apart from the variable voltage per SM, the HV AWG application poses different conditions, such as a low value of SM capacitance value and the HV dc sources with a current rating of a few tens of milliamperes. Hence, this article proposes exclusive design guidelines for the proper start-up, steady-state, and shutdown operation of the MMC-based AWG. In addition, this article dives deeper analytically into the soft start-up algorithm to understand its working principle and to design the average charging current within the limit for any number of SMs of the arm. In the end, their performance is showcased with a single MV SM per arm, operating at a different voltage (0.8-2.7 kV) and frequency levels (1-600 Hz) and generating different wave shapes, such as triangular, sinusoidal with different harmonics, and pulse waveforms. In addition, the fault ride-through capability is verified for the MMC-based HV AWG.

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With the great emphasis from the international standard-setting community on the so-called supra-harmonics emissions (2-150 kHz), there are increasing research efforts in this noise level identification, measurement, standard setting and mitigation. The periodic variable switching frequency PWM method, which is known as VSFPWM, can reshape the generated output harmonics spectrum of the grid-connected PWM converter, leading to a significantly lower harmonics peaks, thus keeping the harmonics emission strictly below the harmonics emission standards e.g., IEEE519 & IEC-61000 series. This work conducted an insightful analysis on the harmonics spectra generated by the periodic VSFPWM based on newly derived analytical models. Besides, the sinusoidal VSFPWM which is often used in AC/DC PWM converter, is taken as an example of periodic VSFPWM profile to achieve the minimum efforts of AC filtering. Finally, experimental tests are conducted to verify the analysis and the design guideline provided in this paper.@en

This paper proposes two modulation schemes for Dual Active Bridge (DAB) converters, with the aim of maximizing Zero Voltage Switching (ZVS) operation over a wide operational range. The first is a ZVS-optimized constant frequency modulation scheme, constructed based on the boundary conditions of ZVS operation. This scheme maximizes the number of ZVS events across a broad operational range and is easy to implement. Additionally, a variable frequency modulation scheme is proposed, enabling continuous full ZVS operation for the DAB converter at full power and eliminating the loss of ZVS due to transitioning between modulation regions. This functionality extends the full ZVS range, yielding improved Electromagnetic Interference (EMI) performance and overall power efficiency. The synergy of the proposed modulation schemes is particularly well-suited for applications like off-board Electric Vehicle (EV) charging. Experimental validation, conducted on an 11-kW DAB converter prototype with an output voltage range of 250V to 950V, demonstrates the efficacy of the proposed schemes in achieving ZVS and boosting converter efficiency.

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Light-duty electric vehicles (EVs) typically have a rated voltage of either 400 or 800 V. Especially when considering public parking infrastructures or owners with multiple EVs, e.g., car rental companies, EV wireless chargers must efficiently deliver electric power to both battery options. For this purpose, this article proposes an advanced and compact version of the previously defined voltage/current doubler (V/I-D) converter, here comprising two coupled series-compensated bipolar pads (BPPs). The presented system can efficiently charge EVs with both battery voltage classes at the same power level without affecting the current rating of the converter's circuit components. The control scheme is implemented at the power source side in terms of switching frequency and input voltage, and only passive semiconductor devices are employed on board the EV. The equivalent circuit is analyzed, focusing on the BPPs' undesired cross-coupling and its effect on the power transfer. Methods to compensate for the cross-coupling are proposed regarding the BPP design and operating strategy. At 7.2 kW and aligned BPPs, the dc-to-dc efficiency of 96.34% and 96.53% have been measured at 400 and 800 V, respectively. The proposed method has been experimentally validated at different misalignment profiles while considering battery voltages 300-400 V and 600-800 V, which proves that the V/I -D converter is a universal charging solution for EV batteries.

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A Modular Multilevel Converter (MMC)-based Arbitrary Wave shape Generator (AWG) for High Voltage (HV) testing faces challenges in the control hardware to generate kHz-range high-frequency waveforms. Real Time Simulators (RTS) provide a simple way to implement the control of the MMC-based AWG in the FPGA. One of the commercially available RTS named Typhoon HIL is found to satisfy the small simulation step requirement such as minimum of 200 ns for generating kHz-range high-frequency waveforms. The performance of Typhoon HIL device is demonstrated with a scaled-down prototype of MMC-based AWG where sinusoidal and other arbitrary waveforms are generated up to 5kHz with a THD less than 5 %.@en

Compact and efficient power converter solutions are seen to be the backbone of future transportation systems in order to cope with the ongoing transition toward greener systems. Such systems usually comprise a main load section, in which one or more propulsion or traction motors are connected, in addition to an auxiliary load, which might comprise the hotels and air conditioning for example. This auxiliary load can be as low as 5-10% of the main load power. Therefore, it can be challenging to drive this power from a typical high-power system that employs a medium-voltage (MV) dc (MVDC) grid, which is typical in high-power systems. In such MVDC-integrated systems, neutral-point-clamped and active neutral-point-clamped (ANPC) converters are commonly used, where the auxiliary load converter is overrated in this case, resulting in a bulky and inefficient power system. Thus, in order to enable a lighter and efficient transportation power system, a multiport hybrid converter (MHC) is presented in this article. This converter can feed the main MV motor, in addition to two auxiliary low-voltage loads. Compared with the state-of-the-art ANPC converter, the proposed MHC utilizes only two extra switches per phase leg in order to achieve this multiport operation along with increasing the voltage rating of another two switches. The proposed MHC is analyzed in this article, where its operation, modulation, and mathematical derivation are presented. These analyses are supported by simulation and experimental results utilizing a reduced-scale 5-kW system.

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The sinusoidal Triangular-Current-Mode (S-TCM) method has been proposed in the AC/DC power-factor-correction (PFC) converter to achieve the zero-voltage-switching (ZVS) which can lead to both, high efficiency operation and a high power density design. Nevertheless, the necessary wide range variation of the sinusoidal switching frequency profile imposed by the S-TCM results in a larger generated voltage harmonic peak due to the overlapping between different order carrier-frequency harmonics. In this work, the S-TCM is used in the interleaved 2-level converter to minimize the undesirable effects of such overlapped voltage harmonics while maintaining ZVS via S-TCM. Meanwhile, the necessity of coupled inductors (CIs) in the interleaved topology is avoided by implementing the S-TCM. Both simulation and experimental tests conducted in a 3.3 kW interleaved 2-level converter system are used to verify the study.

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In order to damp the resonance in the MMC-based Arbitrary Wave shape Generator (AWG) used for high voltage testing, an active damping control methodology is proposed in this paper instead of the passive damping with an arm resistor. It is vital to ensure the system’s stability when such an active damping closed loop control is implemented. Consequently, optimal parameters of a PI controller are designed by analyzing the stability margins of the involved transfer function using Bode-Plots. The performance of the designed active damping control methodology and the PI controller have been demonstrated with a 50 Hz sinusoidal waveform and arbitrary waveforms such as triangular, trapezoidal, and complex waveforms in MATLAB-Simulink. These results proves that the output voltage can track the reference without any reasonable error and does not contain any resonant frequency. Additionally, the Total Harmonic Distortion (THD) of the sinusoidal waveform and other arbitrary waveforms is less than 1% with the Phase Shift Carrier (PSC) modulation technique.@en

This work proposes a hybrid space vector modulation (HSVM) scheme for multiport hybrid converters (MHCs). Moreover, the impact of shifting the auxiliary currents from the main ones is proposed and investigated in order to enhance the converter efficiency. The proposed operational schemes have been implemented in a three-phase 5 kW MHC prototype. It is shown that the proposed HSVM scheme can improve the MHC efficiency by 0.3% at full load with respect to space vector modulation. At partial loads, the improvement is even more significant, reaching +0.7% at 30% of the rated power. A further 0.15% increase in efficiency at full power can be achieved by a 180$^{\circ }$ phase shifting of the auxiliary currents with respect to the main terminal currents, reaching a peak efficiency of 98.5%.

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The lithium-ion battery of an electric vehicle (EV) is typically rated at either 400 or 800 V. When considering public parking infrastructures, EV wireless chargers must efficiently deliver electric power to both battery options. This can be normally achieved by regulating the output voltage through a dc-dc converter at the cost of higher onboard circuit complexity and lower overall efficiency. This article proposes a wireless charging system that maintains a high power transfer efficiency when charging EVs with either 400- or 800-V nominal battery voltage at the same power level. The control scheme is implemented at the power source side, and only passive semiconductor devices are employed on board the EV. The presented system, called voltage/current doubler (V/I-D), comprises two sets of series-compensated coupled coils, each of them connected to a dedicated H-bridge converter. The equivalent circuit has been analyzed while explaining the parameters' selection. The analytical power transfer efficiency has been compared to the one resulting from the conventional one-to-one coil system at 7.2 kW. For the same power level, the dc-to-dc efficiency of 97.11% and 97.52% have been measured at 400-V and 800-V voltage output, respectively. Finally, the functionality of the V/I-D converter has been proved at both the even and uneven misalignments of the two sets of coupled coils.

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This article gives an overview of challenges in primary distribution, protections, and power scalability for shipboard dc systems. Given that dc technology is in development, several aspects of shipboard systems have not yet been sufficiently devised to ensure the protection and efficiency demanded. Several issues in dc systems arise from the lack of complete relevant standardization from different regulation bodies. Unipolar and bipolar bus architectures have application-specific advantages that are discussed and compared. The placement of power electronics in dc systems creates opportunities for switchboard design, and this article compares the centralized and distributed approaches. Likewise, protection architectures for shipboard dc systems have challenges. Breaker-based protection utilizes slow fuses, mechanical circuit breakers, and solid-state circuit breakers. In addition, power-electronics-based protection embeds the protective circuit in the power converters, but its development lags. This article compares the state-of-the-art technologies, reviewing their main features. Finally, the power requirement of various applications and the low production rate of vessels force the designers to utilize commercial off-the-shelf converters to scale up power. The misuse of such converters, the modular topologies, and power electronics building blocks are exposed highlighting challenges and opportunities toward the mass adoption of dc systems onboard maritime vessels.

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In this article, a reconfigurable two-stage dc/dc resonant topology with a wide output voltage range of 150-1000 V is proposed for electric vehicle (EV) charging with high efficiency over the entire load range. The proposed topology consists of an LLC resonant converter with dual secondary sides; two interleaved triangular current mode (TCM) buck converters, and three additional auxiliary switches for reconfiguration. Two possible arrangements of the proposed topology are considered and compared. The analytical model of the topology is developed, which is used for the efficiency estimation of different configurations and the design of the prototype converter. An 11 kW hardware demonstrator is built and tested. The maximum measured efficiency of the converter is 97.66%, with a >95% efficiency over the complete 150-1000 V range at full power. The proposed two-stage converter achieves the widest output voltage range reported in literature for resonant power converters (RPCs), thereby capable of charging existing and future EVs very efficiently over any charging cycle.

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This paper introduces variable-frequency zero voltage switching (ZVS) modulation strategy for the four-switch buck+boost converter with one operating pattern for the inductor current, i.e., three-segment inductor current modulation control. The proposed modulation scheme guarantees a smooth transition from step-up to step-down or from step-down to step-up operating modes without abrupt duty cycle or switching frequency change. Triangular current mode (TCM) ZVS control could be derived from this three-segment inductor current modulation strategy. Moreover, the controller design can be simplified compared with other multi-mode control methods. Experimental results were given to validate the modulation control strategy based on a 300−600 V input, 400 V output, 3.3 kW prototype.@en

A variable switching frequency modulation for the Dual Active Bridge (DAB) converter is proposed in this paper. With this variable switching frequency modulation, the DAB converter can be operated in the ZVS-beneficial operational modes without the necessity to transition to others, thus a larger ZVS range for the DAB converter can be achieved. This modulation has potential of providing higher power efficiency and better EMI performance for the DAB converter in wide voltage range applications such as Electric Vehicle (EV) charging. A DAB converter with the variable frequency modulation method is simulated, and its effectiveness on the ZVS performance is demonstrated.

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This paper investigates the interoperability of the proposed voltage/current doubler (V/I-D) converter used for wireless charging of electric vehicles (EVs), which achieves high efficiency when charging both 400V and 800V batteries at the same power. Nominally, the V/I-D converter employs bipolar pads (BPP) at both the primary and the secondary circuits. In this study, the functionality of the converter is assessed when the primary BPP is coupled with a standard secondary coil, here being the VA test station WPT2/Z2 from SAE J2954. First, the intended operation of the V/I- D converter is explained. After that, the equivalent circuit of the BPP primary coupled with the standardized secondary coil is modeled analytically. The operation based on the misalignment is discussed. Then, the interoperability is verified through experimental results for the entire constant current charging mode for a rated output power of 7.2kW. Even though the functionality of the V/I-D converter is not optimal during the interoperability, the measured DC-to-DC power transfer efficiency in the considered operating range reaches the maximum at 95.22%, while the minimum is 92.86%.@en

Variable switching frequency PWM (VSFPWM) modulation can be advantageously implemented in industrial applications, such as renewable energy, motor drives, and uninterrupted power supply (UPS) systems, to reduce the injected current harmonic amplitudes, to suppress audible noise, and to improve semiconductor power efficiency. In this article, the usage of periodic VSFPWM methods in a voltage source converter (VSC) is proposed, analyzed, and benchmarked in terms of harmonic spectrum spreading, following the IEEE-519 current harmonic standard for the connection to the distribution grid. Particular attention is paid to the influence of VSFPWM on the ac filter design. First, the analytical model of the voltage harmonic spectrum generated by a three-phase three-wire two-level VSC implementing several periodic VSFPWM methods is derived. Subsequently, a design guideline for the commonly used LCL filter in the grid-tied VSC application is proposed, which minimizes the size requirement of the necessary components. The voltage spectrum models of the proposed VSFPWM method and the optimal switching profiles are verified by MATLAB/Simulink simulations and a 5-kW three-phase two-level VSC hardware demonstrator. The study shows that the ac filter power density for the studied VSFPWM methods can be greatly increased when compared with the conventional and widely employed constant switching frequency continuous PWM strategies.

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This article compares the pulse current capability of various Semiconductor (SM) device technologies for Modular Multilevel Converter (MMC)-based High Voltage (HV) Arbitrary Waveform Generator (AWG) for dielectric testing of grid assets to find the most suitable SM device technology which can perform well in generating lightning impulse that demands a high peak current for a relatively short time. For the typical HV loads of the AWG, Lightning Impulse (LI) test may require a pulse current to rise to 1.7 kA in 0.2 µs. It is essential to highlight that most other dielectric tests performed with an HV AWG demand a relatively low current such as less than 10 A. Therefore, TO-packaged semiconductors would be well-suited for a large number of tests other than short impulses. To optimize the size and cost of the HV AWG, this paper evaluates the pulse current capabilities of TO-packaged semiconductors for the above-mentioned current requirement to generate LI waveform. The first comparison is made among Non-Punch Through (NPT) Si IGBT, Field Stop (FS) Si IGBT, Si MOSFET, and SiC MOSFETs with roughly the same current rating of 40 A. It is found that the Si MOSFET gives the fastest rise time of 0.42 µs and the NPT IGBT gives the highest current amplification factor of almost 12 times greater than its own rated current. However, 3rd Generation SiC MOSFET combines Si MOSFET and NPT IGBT capabilities to generate a fast rise time and high peak pulse current. Additionally, the FS IGBT is compared with the SiC MOSFET. The SiC MOSFET performs better in peak current capability and the obtained rise time. All in all, the research results and the stringent HV AWG requirements for LI show that the application requires a relatively complex switch implementation with far superior current capability than in normal operation. Therefore, a parallel connection of several TO-packaged devices is necessary to generate LI from MMC-based HV AWG.@en

Battery Energy Storage Systems typically procure their primary revenues from regulated energy and ancillary services markets; nonetheless, they have great potential in supporting distribution network operators and their users. This paper evaluates the potential business case of battery storage systems integrating market application and services to a photovoltaic assisted electric vehicle fast-charging station. A mathematical deterministic optimization problem is formulated using mixed-integer linear programming to combine battery storage system operation in the day-ahead and frequency regulation market and the remunerated services offered to the charging station. The technical and economic feasibility of the solution and the applicability of the proposed framework is verified through a case study reflecting an existing photovoltaic assisted charging station in the Netherlands and considering the Dutch energy market framework and prices. The study shows that such battery storage system implementation is economically and technically advantageous for the players involved. The battery storage system can stack additional revenues on top of the market revenues. The charging station benefits from a reduced peak power and a 30% tariff reduction, and the system operator would indirectly benefit from the shaved charging station profile. Furthermore, the analysis shows that providing services to the charging station from the battery storage system does not significantly impact its market-related revenues.@en