Hulong Zeng

Wireless power transfer via harmonic current for electric vehicles application

A method that only using harmonic current to transfer wireless power for electric vehicles (EV) is proposed in this paper. The frequency limit of most high voltage high current IGBT is around 20 kHz which also limits the system frequency of the transformer. Due to the gain characteristic of the resonant tank is actually a band-pass filter, using one specific harmonic current to transfer power becomes available. By doing so, the system frequency can be raised up several times while the switching frequency remain the same. Higher system frequency leads to a more compact system. A 1 kW prototype with 20 cm air gap using 3rd harmonic power is built to verify the method.

Z-Source Resonant Converter With Power Factor Correction for Wireless Power Transfer Applications

In this paper the Z-source converter is introduced to power factor correction (PFC) applications. The concept is demonstrated through a wireless power transfer (WPT) system for electric vehicle battery charging, namely Z-source resonant converter (ZSRC). Due to the Z-source network (ZSN), the ZSRC inherently performs PFC and regulate the system output voltage simultaneously, without adding extra semiconductor devices and control circuitry to the conventional WPT system such as conventional PFC converters do. In other words, the ZSN can be categorized as a family of the single stage PFC converters. In addition, the ZSN is suitable for high power applications since it is immune to shoot-through states, which increases reliability and adds a boost feature to the system. The ZSRC-based WPT system operating principle is described and analyzed in this paper. Simulations, and experimental results based on a 1-kW prototype with 20-cm air gap between the system primary and secondary side are presented to validate the analysis, and demonstrate the effectiveness of the ZSN in the PFC of the WPT system.

SiC-Based Z-Source Resonant Converter With Constant Frequency and Load Regulation for EV Wireless Charger

Traditional load regulation methods for a resonant converter mainly rely on frequency modulation. It is always a tradeoff between the design of the resonant network and the range of load. Especially for wireless power transfer (WPT) systems, the resonant network usually has a high quality factor. Small variation on frequency leads to huge drop in gain and efficiency. Due to this problem, many WPT systems are unregulated and they need one or two more front-end stages to regulate the dc bus voltage and perform power factor correction (PFC). In order to lower the cost and complexity of two- or three-stages structure, a single-stage solution with a silicon carbide (SiC) based Z-source resonant converter (ZSRC) was recently proposed. The Z-source network provides high reliability as being immune to shoot-through problems. Additionally, a ZSRC can boost the dc bus voltage while the traditional voltage-source inverter can only produce a lower voltage. However, the load regulation of this new topology has not been addressed. Two effective load regulation methods with constant frequency are presented for this SiC-based ZSRC specifically. Operation principle of the two load regulation methods are described in this paper. Experimental results based on a 200-W scale-down prototype with a full-bridge series resonant dc–dc converter are presented to illustrate the mechanism of these two methods.

Development of 2-kW interleaved DC-capacitor-less single-phase inverter system

This paper presents the development and experimental performance of a 2-kW interleaved DC-capacitorless single-phase inverter. By utilizing an AC capacitor to absorb the ripple power pulsating at twice the line frequency, the proposed interleaved DC-capacitor-less single-phase inverter significantly reduced the total capacitor size. The adoption of SiC MOSFET with 216-kHz switching frequency and the interleaved structure further reduce the filtering components size. A comparison of existing topologies for inverter application and the design considerations of interleaved PWM scheme and integrated coupled inductors are described in details. Experimental results are provided to verify the performance and feasibility of the proposed inverter system.

High power factor Z-source resonant wireless charger

Wireless charger for Electric Vehicles (EVs) is an off-line application and it needs power factor correction (PFC) function, which usually consists of a front-end boost PFC and a cascaded DC/DC converter. Recently, Z-source resonant converter (ZSRC), a single-stage solution with low cost and high efficiency, was proposed for EV wireless charger. Combining with the Z-source network, the control scheme is more challenged and sophisticated. Traditional phase-shift control can generate arbitrary combination of shoot-through state and active state over one fundamental cycle. However, ZSRC enters discontinuous mode at light loads, and huge current distortion and voltage stress are observed with phase-shift control. This paper presents a PFC control method specific for ZSRC in discontinuous mode. It can pass IEC61000-3-2 Class A criterion with all the double line frequency power absorbed in the Z-source network. Experimental results based on a 1-kW prototype with 20-cm air gap between the primary and secondary side are presented to illustrate the proposed control scheme.

Harmonic Burst Control Strategy for Full-Bridge Series Resonant Converter-Based EV Charging

An effective output voltage regulation method using harmonic burst control is presented. This method can greatly improve operating performance of the full-bridge series-resonant dc–dc converter (SRC) applied to electric vehicle (EV) battery charging. The proposed harmonic burst control not only provides load regulation, but it also achieves soft switching at both turn-ons and turn-offs under all load conditions. As a result, it improves the system efficiency over 10% for light-load conditions without any extra hardware, compared to that of the traditional frequency modulation method. Moreover, it has much smaller pulsed power over a wide range load compared to the traditional bang-bang burst control. Theoretical analysis of the series-resonant circuit and power loss analysis are discussed in detail in this paper. Experimental results based on a 1-kW prototype with 20-cm air gap between the primary and secondary sides of the series-resonant converter are presented to demonstrate the effectiveness of the proposed control strategy.

Multi-objective design and optimization of inductors: A generalized software-driven approach

This paper presents a generalized method which can facilitate the design and optimization of an inductor regardless of its application scenarios (DC inductors or AC inductors). It is a software-driven approach and also applicable to both entry level and experienced designer. User inputs just require the voltage/current waveform data across the inductor, desired inductance, and the design optimum goal along with the constraints. A user-friendly front panel (graphical user interface) is designed to reduce the difficulty of inductor design. The software analyzes inductor using magnetic equivalent circuit and explores the pareto-optimal designs by means of multi-objective evolutionary algorithm such as NSGA-II. Buck converter filter inductor is designed to illustrate the software workflow.

Z-source resonant converter with power factor correction for wireless power transfer applications

In this paper, the Z-source converter is introduced to power factor correction (PFC) applications. The concept is demonstrated through a wireless power transfer (WPT) system for electric vehicle battery charging, namely Z-source resonant converter (ZSRC). Due to the Z-source network (ZSN), the ZSRC inherently performs PFC and regulate the system output voltage simultaneously, without adding extra semiconductor devices and control circuitry to the conventional WPT system such as conventional PFC converters do. In other words, the ZSN can be categorized as a family of the single-stage PFC converters. In addition, the ZSN is suitable for high-power applications since it is immune to shoot-through states, which increases reliability and adds a boost feature to the system. The ZSRC-based WPT system operating principle is described and analyzed in this paper. Simulations and experimental results based on a 1-kW prototype with 20-cm air gap between the system primary and secondary sides are presented to validate the analysis and demonstrate the effectiveness of the ZSN in the PFC of the WPT system.

Harmonic burst mode control strategy for full-bridge series resonant convertersfor electric vehicles application

An effective output voltage regulation method using harmonic burst mode control strategy is presented. By using this strategy, the operating performance of the full-bridge series resonant dc-dc converter (SRC) applied to electric vehicle (EV) battery charging is improved. The proposed control strategy not only performs load regulation, but it also achieves soft switch both at turn-on and turn-off under any load condition. It also improves the system efficiency over 10% for light load conditions compared to the traditional frequency modulation control method, without adding extra hardware. Theoretical, compensation and loss analysis are discussed in details along this paper. Experimental results based on a 1-kW prototype with 20 cm air gap between the primary and secondary side of the SRC converter are presented to demonstrate the effectiveness of the proposed control strategy.

High power density Z-source resonant wireless charger with line frequency sinusoidal charging

Wireless charger for electric vehicles (EVs) is an offline application and it needs power factor correction (PFC) function, which usually consists of a front-end boost PFC and a cascaded dc–dc converter. Z-source resonant converter (ZSRC), a single-stage solution with low cost and high efficiency, was proposed for EV wireless charger lately. The Z-source capacitors in the ZSRC are designed to absorb the double-line frequency ripple in this single-phase application. Sinusoidal charging, which allows the double-line frequency ripple propagate to the output, is another solution aiming at reducing the bulky capacitors. Recently, a comparison of low-frequency (120 Hz) sinusoidal charging and dc charging shows a negligible impact on Li-ion batteries’ performance. Therefore, the ZSRCs capacitor, the biggest component, can be reduced dramatically from millifarad to several microfarads with a sinusoidal charging technique, which features the ZSRC high power density. Also, it keeps the Z-sources benefit of boost ability and being immune to shoot-through problems. In this paper, the sinusoidal charging behavior for the ZSRC is modeled, and a control scheme that has both PFC function and load regulation for sinusoidal charging is proposed. This control scheme can pass IEC61000-3-2 Class A criterion. Experimental results based on a 1-kW prototype with 20 cm air gap between the primary and secondary side are presented to illustrate the proposed control scheme.