In the conventional DC-AC inverter consisting of two DC-DC converters with unipolar output capacitors, the output capacitor voltages of the DC-DC converters must be higher than the DC input voltage. To overcome this weakness, this paper proposes a single-phase DC-AC inverter consisting of two embedded Z-source converters with bipolar output capacitors. The proposed inverter is composed of two embedded Z-source converters with a common DC source and output AC load. Though the output capacitor voltages of the converters are relatively low compared to those of a conventional inverter, an equivalent level of AC output voltages can be obtained. Moreover, by controlling the output capacitor voltages asymmetrically, the AC output voltage of the proposed inverter can be higher than the DC input voltage. To verify the validity of the proposed inverter, experiments were performed with a DC source voltage of 38 V. By controlling the output capacitor voltages of the converters symmetrically or asymmetrically, the proposed inverter can produce sinusoidal AC output voltages. The experiments show that efficiencies of up to 95% and 97% can be achieved with the proposed inverter using symmetric and asymmetric control, respectively.

An effective control method, including system-level control and pulsewidth modulation for quasi-Z-source cascade multilevel inverter (qZS-CMI) based grid-tie photovoltaic (PV) power system is proposed. The system-level control achieves the grid-tie current injection, independent maximum power point tracking (MPPT) for separate PV panels, and dc-link voltage balance for all quasi-Z-source H-bridge inverter (qZS-HBI) modules. The complete design process is disclosed. A multilevel space vector modulation (SVM) for the single-phase qZS-CMI is proposed to fulfill the synthetization of the step-like voltage waveforms. Simulation and experiment based on a seven-level prototype are carried out to validate the proposed methods.

The quasi-Z-source cascaded multilevel inverter (qZS-CMI) presented many advantages over conventional CMI when applied in photovoltaic (PV) power systems. For example, qZS-CMI provides the balanced dc-link voltage and voltage boost ability, saves one-third modules, etc. However, current research studies only disclosed control of single-phase qZS-CMI-based PV power systems, and there was no literature related to control of three-phase qZS-CMI-based PV power systems. In this paper, for the first time, three-phase qZS-CMI's control is proposed and demonstrated for application to PV power systems. The models of PV-panel-fed qZS H-bridge module and qZS-CMI-based PV power system are built to accurately design control algorithms for each module and the whole system. The proposed control method includes the distributed maximum power point tracking for each module, dc-link peak voltage balance control for all modules, and grid-tie control for the whole system; moreover, a new multilevel space vector modulation method is proposed for the three-phase qZS-CMI. Simulation and experimental results on a test bench with a three-phase seven-level qZS-CMI-based PV power system verify the proposed control and modulation methods.

分析了双向功率流阻抗源逆变器系统工作原理、脉冲调制方式。采用开关信号流图方法建立了统一的控制系统模型，从稳态直流模型推导出系统额定工作点，从动态小信号模型推导出系统传递函数。阻抗源逆变器控制系统是含有二维参数的非线性系统，对相互关联的2个控制变量(直通占空比D和调制系数M)进行动态解耦，对解耦系统设计了电压电流双环控制器以提高系统的动态性能和稳定程度，基于伯德图分析了控制系统的稳定性和动态特性。研制了一台55 kVA双向功率流阻抗源逆变器，实验结果表明，系统具有优良性能，可以有效应用于电动汽车和可再生能源发电系统等领域。

分析了双向功率流阻抗源逆变器系统工作原理、脉冲调制方式。采用开关信号流图方法建立了统一的控制系统模型，从稳态直流模型推导出系统额定工作点，从动态小信号模型推导出系统传递函数。阻抗源逆变器控制系统是含有二维参数的非线性系统，对相互关联的2个控制变量(直通占空比D和调制系数M)进行动态解耦，对解耦系统设计了电压电流双环控制器以提高系统的动态性能和稳定程度，基于伯德图分析了控制系统的稳定性和动态特性。研制了一台55 kVA双向功率流阻抗源逆变器，实验结果表明，系统具有优良性能，可以有效应用于电动汽车和可再生能源发电系统等领域。

Z-源逆变器由于采用独特的X型Z-源网络，可以利用逆变器桥臂直通状态实现升压功能，从而使单级Z-源逆变器具有与两级并网系统相类似的性能。该文论述基于Z-源逆变器的光伏并网系统在变换效率、可靠性以及成本方面的优势，提出了一种新的单级Z-源逆变器并网系统两级控制策略, 该控制策略实现了MPPT控制和逆变器并网控制，使Z-源光伏并网系统能够动态跟踪光伏电池最大功率点电压，输出电流与电网电压同相位，从而达到较高的功率因数。软件仿真和实验分析证明了该控制方法具有优良的动、静态特性，适合各种变化的天气情况。

Z-源逆变器由于采用独特的X型Z-源网络，可以利用逆变器桥臂直通状态实现升压功能，从而使单级Z-源逆变器具有与两级并网系统相类似的性能。该文论述基于Z-源逆变器的光伏并网系统在变换效率、可靠性以及成本方面的优势，提出了一种新的单级Z-源逆变器并网系统两级控制策略, 该控制策略实现了MPPT控制和逆变器并网控制，使Z-源光伏并网系统能够动态跟踪光伏电池最大功率点电压，输出电流与电网电压同相位，从而达到较高的功率因数。软件仿真和实验分析证明了该控制方法具有优良的动、静态特性，适合各种变化的天气情况。

This paper presents a detailed operation analysis, controller design, and realization of a high-power, bidirectional quasi-Z-source inverter (BQ-ZSI) for electric vehicle applications. The circuit analysis shows that with a bidirectional switch in the quasi-Z-source network, the performance of the inverter under small inductance and low power factor can be improved. Based on the circuit analysis, a small signal model of the BQ-ZSI is derived, which indicates that the circuit is prone to oscillate when there is disturbance on the dc input voltage. Therefore, a dedicated voltage controller with feed-forward compensation is designed to reject the disturbance and stabilize the dc-link voltage during a non-shoot-through state. An 85-kW prototype has been built. Both simulation and experimental results are presented to prove the functionality of the circuit and the effectiveness of the proposed control strategy.

Voltage-type Gamma-Z-source inverters are proposed in this letter. They use a unique G-shaped impedance network for boosting their output voltage in addition to their usual voltage-buck behavior. Comparing them with other topologies, the proposed inverters use lesser components and a coupled transformer for producing the high-gain and modulation ratio simultaneously. The obtained gain can be tuned by varying the turns ratio gamma(Gamma Z) of the transformer within the narrow range of 1 < gamma(Gamma Z) <= 2. This leads to lesser winding turns at high gain, as compared to other related topologies. Experimental testing has already proven the validity of the proposed inverters.

研究将无电解电容的单级升压逆变技术应用于变频调速系统。采用的抽头电感单级升压逆变器(tapped- inductor single-stage boost inverter,TISSBI)包含由1个抽头电感和2个二极管构成的无源网络,通过调节直通占空比和电感抽头的位置,能够实现单级升降压功能。将无电解电容的TISSBI应用于单相输入的变频调速系统,实现抗电网电压跌落、母线脉动抑制和提高输入功率因数的功能。用实验验证了理论分析方法的可行性。

研究将无电解电容的单级升压逆变技术应用于变频调速系统。采用的抽头电感单级升压逆变器(tapped- inductor single-stage boost inverter,TISSBI)包含由1个抽头电感和2个二极管构成的无源网络,通过调节直通占空比和电感抽头的位置,能够实现单级升降压功能。将无电解电容的TISSBI应用于单相输入的变频调速系统,实现抗电网电压跌落、母线脉动抑制和提高输入功率因数的功能。用实验验证了理论分析方法的可行性。

分析提出的抽头电感单级升压逆变器所有可能的运行状态，揭示在一个直通周期内，除了期望的3种运行状态外，还存在4种对能量传递过程不起作用，甚至给电路运行造成一定危害的运行状态。这4种运行状态可通过合理设计电感和电容值加以避免。从稳态分析中得到描述电路运行的状态方程组，展示能准确设计无源网络的方法，使其运行于期望的直通和非直通状态。提供的方法还可预测估计电感和电容的极限值，避免电路出现不正常的运行状态。仿真和实验验证了该设计方法的有效性和精确性，同时展示了当电感和电容低于极限值时出现的不正常运行状态。

分析提出的抽头电感单级升压逆变器所有可能的运行状态，揭示在一个直通周期内，除了期望的3种运行状态外，还存在4种对能量传递过程不起作用，甚至给电路运行造成一定危害的运行状态。这4种运行状态可通过合理设计电感和电容值加以避免。从稳态分析中得到描述电路运行的状态方程组，展示能准确设计无源网络的方法，使其运行于期望的直通和非直通状态。提供的方法还可预测估计电感和电容的极限值，避免电路出现不正常的运行状态。仿真和实验验证了该设计方法的有效性和精确性，同时展示了当电感和电容低于极限值时出现的不正常运行状态。

提出一种高升压比的单级升压逆变器，它在传统准Z源逆变器拓扑中引入抽头电感无源网络，因此称为&#x00093;抽头电感准Z源逆变器&#x00094;(tapped inductor quasi-Z-source inverter，TL-qZSI)。该抽头电感无源网络包括一个抽头电感和两个二极管，替代了原准Z源逆变器中的一个电感。类似于抽头电感Z源逆变器(tapped inductor Z-source inverter，TL-ZSI)，所提出的逆变器也能提供高升压能力，但比TL-ZSI略低些。分析电路的工作机理、升压能力和控制策略，讨论设计上的考虑。最后通过基于简单升压控制方法的实验结果验证该拓扑的实际性能。

提出一种高升压比的单级升压逆变器，它在传统准Z源逆变器拓扑中引入抽头电感无源网络，因此称为&#x00093;抽头电感准Z源逆变器&#x00094;(tapped inductor quasi-Z-source inverter，TL-qZSI)。该抽头电感无源网络包括一个抽头电感和两个二极管，替代了原准Z源逆变器中的一个电感。类似于抽头电感Z源逆变器(tapped inductor Z-source inverter，TL-ZSI)，所提出的逆变器也能提供高升压能力，但比TL-ZSI略低些。分析电路的工作机理、升压能力和控制策略，讨论设计上的考虑。最后通过基于简单升压控制方法的实验结果验证该拓扑的实际性能。

传统的两级式升压变换器通常由Boost变换器作为前级，以提升输入电压至合适的母线电压，防止输入电压较低时无法输出所需的交流电压。当升压比要求很高时，Boost变换器的占空比就会接近极限，过大的占空比会恶化Boost变换器的二极管反向恢复问题，增加开关管的开关损耗，降低效率。提出一种新型单级升压逆变器，在典型三相桥前加入包括耦合电感在内的无源网络，通过对耦合电感的设计和逆变桥直通时间的控制，可以使逆变器在直流输入电压较低时仍实现中间母线电压幅值的较大提升，输出稳定的交流电压。理论分析和实验结果表明该单级升压逆变器具有良好的性能。

传统的两级式升压变换器通常由Boost变换器作为前级，以提升输入电压至合适的母线电压，防止输入电压较低时无法输出所需的交流电压。当升压比要求很高时，Boost变换器的占空比就会接近极限，过大的占空比会恶化Boost变换器的二极管反向恢复问题，增加开关管的开关损耗，降低效率。提出一种新型单级升压逆变器，在典型三相桥前加入包括耦合电感在内的无源网络，通过对耦合电感的设计和逆变桥直通时间的控制，可以使逆变器在直流输入电压较低时仍实现中间母线电压幅值的较大提升，输出稳定的交流电压。理论分析和实验结果表明该单级升压逆变器具有良好的性能。

On the basis of the classical Z-source inverter (ZSI), this paper presents a novel ZSI which only contains inductors and diodes in Z-source network. The inverter uses a unique inductor and diode network for boosting its output voltage, provides a common ground for the dc source and inverter, and avoids the disadvantage causing by capacitor in the classical ZSI and SL-ZSI, especially in prohibiting the inrush current at startup and the resonance of Z-source capacitors and inductors. The inverter can increase the boost factor through adjusting shoot-through duty ratio and increasing the number of inductor. The working principle of the proposed ZSI and comparison with the classical ZSI and SL-ZSI are analyzed in detail. Simulation and experimental results are given to demonstrate the operation features of the inverter.

This paper deals with a new family of high boost voltage inverters called switched-inductor quasi-Z-source inverters (SL-qZSIs). The proposed SL-qZSI is based on the well-known qZSI topology and adds only one inductor and three diodes. In comparison to the SL-ZSI, for the same input and output voltages, the proposed SL-qZSI provides continuous input current, a common ground with the dc source, reduced the passive component count, reduced voltage stress on capacitors, lower shoot-through current, and lower current stress on inductors and diodes. In addition, the proposed SL-qZSI can suppress inrush current at startup, which might destroy the devices. This paper presents the operating principles, analysis, and simulation results, and compares them with those of the SL-ZSI. To verify the performance of the proposed converter, a laboratory prototype was constructed with 48V(dc) input and an ac output line-to-line voltage of 120 V(rms). The simulation and experimental results verified that the converter has high step-up inversion ability.

Ultra-wide bandgap (UWBG) β-Ga₂O₃ is a promising material for next-generation power electronic devices. An enhancement-mode (E-mode) device is essential for designing power conversion systems with simplified circuitry and minimal loss. The integration of an E-mode FET with a depletion-mode (D-mode) FET can build a high-performance logic circuit. In this study, we first demonstrated the realization of an E-mode quasi-two-dimensional (quasi-2D) β-Ga₂O₃ FET with a novel graphene gate architecture via a van der Waals heterojunction. Then we monolithically integrated it with a D-mode quasi-2D β-Ga₂O₃FET, achieving an area-efficient logic circuit. The threshold voltage of the n-channel UWBG β-Ga₂O₃ material was controlled by forming a novel architecture of double-gate graphene/β-Ga₂O₃ heterojunction, where both graphene and β-Ga₂O₃ were obtained by a mechanical exfoliation method. The fabricated double graphene-gate β-Ga₂O₃ MESFET was operated in E-mode with a positive threshold voltage of +0.25 V, which is approximately 1.2 V higher than that of a single-gate D-mode β-Ga₂O₃ MESFET. Both E-/D-modes β-Ga₂O₃ MESFETs showed excellent electrical characteristics with a subthreshold swing of 68.9 and 84.6 mV/dec, respectively, and a high on/off current ratio of approximately 10⁷. A β-Ga₂O₃ logic inverter composed of E-/D-mode β-Ga₂O₃ devices exhibited desired inversion characteristics. The monolithic integration of a E-/D-mode quasi-2D FET with an UWBG channel layer can pave the way for various applications in smart and robust power (nano)electronics.

The quasi-Z-source inverter (qZSI) with battery operation can balance the stochastic fluctuations of photovoltaic (PV) power injected to the grid/load, but its existing topology has a power limitation due to the wide range of discontinuous conduction mode during battery discharge. This paper proposes a new topology of the energy-stored qZSI to overcome this disadvantage. The operating characteristic of the proposed solution is analyzed in detail and compared to that of the existing topology. Two strategies are proposed with the related design principles to control the new energy-stored qZSI when applied to the PV power system. They can control the inverter output power, track the PV panel's maximum power point, and manage the battery power, simultaneously. The voltage boost and inversion, and energy storage are integrated in a single-stage inverter. An experimental prototype is built to test the proposed circuit and the two discussed control methods. The obtained results verify the theoretical analysis and prove the effectiveness of the proposed control of the inverter's input and output powers and battery power regardless of the charging or discharging situation. A real PV panel is used in the grid-tie test of the proposed energy-stored qZSI, which demonstrates three operational modes suitable for application in the PV power system.

Recurrent episodes of ventricular tachycardia in patients with structural heart disease are associated with increased mortality and morbidity, despite the life-saving benefits of implantable cardiac defibrillators. Reducing implantable cardiac defibrillator therapies is important, as recurrent shocks can cause increased myocardial damage and stunning, despite the conversion of ventricular tachycardia/ventricular fibrillation. Catheter ablation has emerged as a potential therapeutic option either for primary or secondary prevention of these arrhythmias, particularly in post-myocardial infarction cases where the substrate is well defined. However, the outcomes of catheter ablation of ventricular tachycardia in structural heart disease remain unsatisfactory in comparison with other electrophysiological procedures. The disappointing efficacy of ventricular tachycardia ablation in structural heart disease is multifactorial. In this review, we discuss the issues surrounding this and examine the limitations of current mapping approaches, as well as newer technologies that might help address them.

This paper proposes the pulsewidth modulation (PWM) strategy of Z-source inverters (ZSIs) with minimum inductor current ripple. In existing PWM strategy with single-phase shoot-through, the shoot-through time interval is divided into six equal parts, therefore the three phase legs bear the equal shoot-through time interval. In this manner, the allotment and arrangement of the shoot-through state is easy to realize, but the inductor current ripple is not optimized. This causes to use relatively large inductors. In the proposed PWM strategy, the shoot-through time intervals of three phase legs are calculated and rearranged according to the active state and zero state time intervals to achieve the minimum current ripple across the Z-source inductor, while maintaining the same total shoot-through time interval. The principle of the proposed PWM strategy is analyzed in detail, and the comparison of current ripple under the traditional and proposed PWM strategy is given. Simulation and experimental results on the series ZSI are shown to verify the analysis.

Vascular devices generating high shear stress can cause type 2A acquired von Willebrand disease, which is characterized by low von Willebrand factor activity accompanied by hemorrhagic complications. The braided mesh structure of flow-diverting stents with a relatively small strut size can create abnormally high shear stress while arterial blood flows through the stent struts into the aneurysm, and flow-diverting stent may be associated with reduced von Willebrand factor activity.

Fault detection (FD) in power electronic converters is necessary in embedded and safety critical applications to prevent further damage. Fast FD is a mandatory step in order to make a suitable response to a fault in one of the semiconductor devices. The aim of this study is to present a fast yet robust method for fault diagnosis in nonisolated dc-dc converters. FD is based on time and current criteria which observe the slope of the inductor current over the time. It is realized by using a hybrid structure via coordinated operation of two FD subsystems that work in parallel. No additional sensors, which increase system cost and reduce reliability, are required for this detection method. For validation, computer simulations are first carried out. The proposed detection scheme is validated on a boost converter. Effects of input disturbances and the closed-loop control are also considered. In the experimental setup, a field programmable gate array digital target is used for the implementation of the proposed method, to perform a very fast switch FD. Results show that, with the presented method, FD is robust and can be done in a few microseconds.

Switch fault diagnosis is an important design aspect for pulse width modulation (PWM) dc-dc power converters. It can prevent power converters from further damage, and also make preparations for remedial actions. In this paper, a fast switch fault diagnostic method is proposed for PWM dc-dc converters operating in continuous conduction mode. The proposed method utilizes the magnetic component (inductor or transformer) voltage for fault diagnosis. Based on the real-time voltage measurement and switch gate-driver signals, characteristics of switch open-circuit faults and short-circuit faults are rapidly extracted, and thus, switch faults can be quickly detected. The magnetic component voltage can be measured by an auxiliary winding in the magnetic core, and gate-driver signals can be easily got from the control circuit. Moreover, the fault detection can be implemented by a low-cost logical hardware circuit, and this circuit can be integrated into the control circuit. The fault diagnosis principle, design considerations, and implementation are discussed in this paper. Experiments are conducted to verify the theoretical analysis.