Zero-current Switching Operation Research Articles

A Modified SVM Method for Three-Phase Quasi-Z-Source Rectifier With Fully Soft Switching Operation and Low Conduction Losses

The conventional ZSVM3 (quasi-Z-source space vector modulation) has been used for quasi-Z-source rectifier because it achieves zero voltage switching(ZVS) and zero current switching(ZCS) operation with wide range of output power and without any auxiliary circuits. However, this method can not realize ZVS or ZCS at fully switching period, especially at the sector boundary, leading to low efficiency. To address this problem, in this paper, a modified modulation based on ZSVM3 is proposed. The sequence of active vectors and zero vectors has been modified. Therefore, the ZVS and ZCS operation occurs at any time in one switching cycle, and the conduction losses decrease. Besides, the distribution of Mode 3 duration time is optimized, which increases the range of soft switching conditions. The operating principle of the proposed modified SVM is explained in detail. Then the parameters design is developed. An experimental prototype is constructed to verify the effectiveness of the proposed modulation. Experimental results show that the grid-side THD and conduction losses reduce, all switches and free-wheeling diodes realize ZVS and ZCS operation at full range without any auxiliary circuit, and the highest efficiency is up to 96.87%.

Fully Soft-Switched DC Solid-State Circuit Breakers

This letter presents a new fully soft-switched dc solid-state circuit breaker (SSCB). During dc current interruption, both main and auxiliary switches turn off under zero current switching (ZCS). A novel inductor-capacitor-capacitor (LCC)-based active injection circuit (AIC) is proposed. It eliminates transient power on switches with a fast operation, which enhances reliability. Experiments of a 350 V/90 A prototype validate ZCS operation for both switches. The response speed reaches 4 μs, and the maximum voltage on switches is 759V, which is within a safe range. This letter is accompanied by slides as multimedia material demonstrating major innovations and contributions.

A Constant-Frequency High-Voltage Gain Resonant Converter Module With Semiactive Phase-Shifted Voltage Multiplier for MVdc Distribution

A constant-frequency step-up LLC resonant converter module that employs a new phase-shifted semiactive voltage multiplier technique is proposed in this article for a medium-voltage dc distribution grid. In the proposed converter, a wide voltage gain for different loading conditions can be realized by adaptively controlling the phase shift of the auxiliary switch in a voltage quadrupler-based semiactive voltage multiplier. Zero-voltage switching turn-on is always achieved for all the primary side switches with a constant-frequency operation. In the proposed semiactive voltage multiplier, zero-current switching (ZCS) turn-on is achieved for the auxiliary switch with ZCS operations provided for all the output diodes over a wide range of voltage gain and loading conditions. The operating principles of the proposed circuit are discussed in this article. Simulation results on a 120-kW, 10-kV output and experimental results on a modular laboratory-scale silicon carbide (SiC)-based 5-kW (per-module), 240–440-V/5-kV prototype are provided to demonstrate the performance of the proposed converter.

Hybrid Control Strategy for an Integrated DAB–LLC–DCX DC–DC Converter to Achieve Full-Power-Range Zero-Voltage Switching

In this article, a dual active bridge (DAB)-LLC-DCX dc-dc converter with integrated magnetics and shared rectifier is proposed for point of load applications, which is able to achieve tight voltage regulation, zero-voltage switching (ZVS) operation for all switches and zero-current switching operation for rectifier. The challenge of the proposed converter is the realization of ZVS operation for all the switches within full power range to achieve high efficiency and high reliability, which is beneficial for light load efficiency improvement of microprocessors. Therefore, with different input voltage range, a hybrid control strategy is proposed to realize ZVS operation for all switches of the proposed converter within full power range in this article. When at high input voltage, extended phase shift control is applied to extend the ZVS range. When at low input voltage, variable gain LLC converter is designed to regulate the voltage distribution among DAB converter and LLC converter for the ZVS operation of DAB converter. Besides, the charging/discharging of junction capacitors are added into consideration of ZVS analysis. The operating principle, design considerations, and control schemes are presented. Finally, the experimental results of an 80-W prototype verified the theoretical analysis.

Full Soft-Switching Ultra-High Gain DC/DC Converter Using Three-Winding Coupled-Inductor with Modular Scalability for Renewable Energy Applications

This paper proposes a new non-isolated single-switch DC/DC converter with an ultra-high voltage gain, low input current ripple, low voltage stress, soft-switching operation, and modular scalability for renewable sources applications. Here, with the help of a Three-Winding Coupled-Inductor (TWCI) and Voltage Multipliers circuits, ultra-high voltage gains can be achieved without needing a large duty cycle. A regenerative clamp capacitor recycles the energy stored in the leakage inductor; thus, the maximum voltage across the single power switch is restricted. Moreover, at the turn-on instant of the power switch, a Zero Current Switching (ZCS) condition is achieved. By designing a resonant tank, the switched current value of the main switch at the turn-off instant is reduced significantly. Also, the leakage inductor of the TWCI helps all converter diodes to operate under the ZCS condition. Due to full soft-switching performance, the introduced topology can provide a wide output voltage range under a high conversion efficiency. The steady-state analysis and comprehensive comparisons are provided in this paper. A 160 W prototype with 24 V input and 250 V output voltage is developed to validate the theoretical analysis. Due to ZCS operation and low voltage stress (VDS ≈ 40 V), the power loss portion of the MOSFET is low. Moreover, the maximum voltage stresses of the diodes are measured 40 V, 60 V, 90 V, and 110 V that are well below the output voltage. Furthermore, at the full-load condition, the input current ripple is about 20 % and the measured efficiency is about 96.3%.

Continuous Control Set Model Predictive Control for an Indirect Matrix Converter

A continuous control set model predictive power control strategy for an indirect matrix converter is proposed in this paper. The load reactive power, the load active power, and the input reactive power are controlled simultaneously. This control strategy can obtain output waveforms with fixed switching frequency. Additionally, an optimal switching sequence is proposed to simplify the commutations of the indirect matrix converter. To suppress the input filter resonance, an active damping method is proposed. Experimental results prove that the proposed method features controllable input reactive power, controllable load active and reactive power, fixed switching frequency output waveforms, zero-current switching operations, and effectively suppresses input filter resonance.

Vector Modulation-Based Model Predictive Current Control with Filter Resonance Suppression and Zero-Current Switching Sequence for Two-Stage Matrix Converter

This paper proposes a novel model predictive current control scheme for two-stage matrix converter. The switching frequency is kept constant by fixing the switching instant. The control strategy achieves to control source reactive power in the input side and output currents in the output side. In addition, the advantage of the proposed strategy compared with conventional model predictive control is firstly proved using the principle of vector synthesis and the law of sines in the vector distribution area. Moreover, a zero-current switching sequence is proposed and implemented to insure zero-current switching operations and reduce the switching losses. Furthermore, in order to suppress the input filter resonance, which is easier to be inspired by the model predictive control, compared with traditional control strategies, an innovative active damping technique is proposed and implemented. Finally, both simulation and experiment are implemented to verify the performance of the proposed strategy. The results demonstrate that the control system features both good steady and transient performance.

A Novel Predictive Control Method with Optimal Switching Sequence and Filter Resonance Suppression for Two-Stage Matrix Converter

This paper proposes a vector modulation-based model predictive current control strategy for a two-stage matrix converter. The switching frequency is kept constant by fixing the switching instantly. The control scheme controls the source reactive power on the input side and output currents on the output side. Besides, the advantage of the proposed strategy compared with conventional model predictive control is firstly proved using the principle of vector synthesis and the law of sines in the vector distribution area. Moreover, to ensure zero-current switching operations and reduce the switching losses, an optimal switching sequence is proposed and implemented. Furthermore, considering that the input filter resonance is easier to be inspired by the model predictive control, compared with conventional linear control strategies, an innovative active damping technique is proposed to suppress the input filter resonance. To assess the performance of the proposed method, simulation and experimental results are demonstrated, showing that the control system features both good steady-state and transient performance.

16.8 nW Ultra-Low-Power Energy Harvester IC for Tiny Ingestible Sensors Sustained by Bio-Galvanic Energy Source.

Herein, we present a 16.8 nW ultra-low-power (ULP) energy harvester integrated circuit (IC) for ingestible biomedical sensors. The energy harvester can be powered from the electro-galvanic operation inside a human body, which provides a sustainable and long-term energy source. The challenge of dealing with relatively high input impedance (∼kΩ) of the bio-galvanic energy source is addressed by introducing two design techniques. The first technique is an adaptive VMPP-controlled algorithm (AVCA) for a maximum power point tracking (MPPT) controller, and the second technique is a ULP delay-line-based zero current switching (ZCS) controller. Different from the conventional fractional open-circuit voltage (FOCV) method for MPPT, the proposed AVCA allows continuous source tracking without detachment of the harvester from the source. The ZCS operation is achieved using a delay-line controller without using either a comparator or an opamp. The proposed AVCA is realized using a 12.1 nW MPPT controller. Successful ZCS operation is achieved using a 2.1 nW delay controller. Overall power consumption of the IC is 16.8 nW. The converter has been fabricated in a 0.18μm CMOS process with 2μm thick top-metal option. The measured result shows that the converter achieves a peak efficiency of 72.1% to generate 507 nW output power. The ULP operation allows a significant reduction in electrode size down to the submillimeter scale (∼0.4mm2), demonstrating the good potential of the proposed energy harvester IC.

DC-DC High Voltage Gain Switched Capacitor Converter With Multilevel Output Voltage and Zero-Voltage Switching

This paper presents the concept and results of a novel resonant DC-DC converter which achieves high voltage gain at a low number of utilized switches, low voltage stress on transistors, ZVS and ZCS operation, high efficiency and variable voltage gain. The converter uses resonant switched-capacitors (SC) circuits with five switches which allows it to reach a six-fold voltage gain. By the application of adequate switching patterns, seven levels of voltage adjustment can be achieved. The basic operation mode of the converter is at zero current switching (ZCS) but a part of the existing transitions can be switched-on at a zero drain-source voltage. Zero voltage switching (ZVS) allows for a reduction of $C_{\mathrm {oss}}$ losses and a decrease in disturbances of voltages and currents. In the proposed converter, voltage stress on switches are noticeably lower than the output voltage which is beneficial from viewpoint the cost reduction and switching quality improvement. The converter output stage consists of two series connected capacitors which allows for a supply of 3-level NPC inverters. Resonant inductors, used in the proposed topology, store very low amount of energy and their volume is significantly lower than in case of chokes typically used in switch-mode converters. Qualities of the converter such as low switch count, efficiency, ZCS and ZVS operation as well as voltage gain variation are demonstrated in this paper. Furthermore, an impact of MOSFET transistors type on the efficiency of the converter is investigated. The design based on low $C_{\mathrm {oss}}$ superjunction (SJ) MOSFETs is compared with the implementation where $R_{\mathrm {ds(on)}}$ of switches is minimized. Due to low voltage stress, application of Schottky rectifiers is also demonstrated in the converter. The concept of the topology and switching patterns is verified by the results of analysis, simulations and experiments.

Analysis and Design of Series LC Resonance-Pulse Based Zero-Current-Switching Current-Fed Half-Bridge DC–DC Converter

This article investigates upon partial resonance in current-fed converter using series LC resonant circuit to attain zero-current-switching (ZCS) of the semiconductor devices. A resonance pulse appears during overlap conduction time of the semiconductor devices causing natural current reduction in an outgoing device to zero before the gating signal is forced-off achieving ZCS commutation of the devices. Soft device turn-off eliminates the turn-off switching losses and more importantly, avoids the traditional requirement of additional snubber to clamp the voltage across the semiconductor devices in current-fed converters. Partial resonance reduces the circulating current and so rms current through the devices limiting the conduction losses. The proposed idea is analyzed and implemented on current-fed half-bridge isolated voltage doubler topology. It has been experimentally demonstrated to achieve wide range ZCS operation along with high efficiency.

Extended ZCS Region of AAC-HVDC Systems Through On-Load Tap Changer Coordination

Arm inductances and the operation of two arms of a phase leg in an alternate arm converter (AAC) can lead to hard-switching of the director switches (DSs) during steady-state operation, increasing voltage stresses across the DSs. The DS voltage stress also depends on the magnitude of the interrupted arm current, which, in turn, depends on the output active/reactive power. Hard-switching of the DSs limits the operating region of the AAC. This article characterizes the zero-current switching (ZCS) capability of the AAC and proposes extended ZCS operation in steady state for HVDC applications. This is achieved by coordinating the AAC operating point and the transformer on-load tap changer (OLTC). The coordinated operation utilizes the tap positions of the HVDC transformer effectively to extend the ZCS operating region with no added effort on circulating current control. Results based on an AAC-HVDC transmission system demonstrate the effective coordination of the transformer OLTC and the converter operating point to achieve extended ZCS performance.

Implementation of a Parallel-Series Resonant Converter with Wide Input Voltage Range

A new resonant converter is presented to have the advantages of soft switching operation on power devices, without reverse recovery current loss on power diodes and wide input voltage range operation. Resonant converter with frequency modulation is adopted in the proposed circuit to accomplish the low switching loss on power switches and possible zero current switching operation on fast recovery diodes. To improve the problem of limit voltage range operation in the conventional resonant converter, a new parallel-series structure resonant converter is studied to achieve wide input voltage operation capability, such as from Vin,min to 4Vin,min. A 1.8 kW laboratory circuit is implemented, and the measured results are provided to confirm the theoretical analysis and circuit performance.

Multi-Resonance-Core-Based Dickson Resonant Switched-Capacitor Converters With Wide Regulation

The Cuk dual resonance core (DRC) realizes overlapped dual resonance to regulate its output voltage. However, the DRC configuration was only applied to the Fibonacci switched-capacitor converter (SCC), series–parallel SCC, and voltage doubler. In this paper, the Cuk DRC is modified and then is extended to the Dickson SCC to form a multi-resonance-core-based (MRC) Dickson resonant switched-capacitor converter. All charging and discharging loops achieve soft charging, and so the inherent capacitor charge sharing loss and the high current transient spikes are eliminated. The modular configuration makes the MRC Dickson easy to be extended to a higher voltage level. The on -time fixed frequency modulation is adopted, all transistors being turned on with zero-current-switching (ZCS) operation and all diodes being turned off with ZCS operation. Most importantly, the conversion ratio of the MRC Dickson can be regulated continuously, widely, and efficiently even at light load condition, which is a huge advantage over the traditional Dickson SCC with limited control headroom. A comprehensive analysis of the operation principle, voltage-gain curve, component stress analysis, and output characteristic is provided. The converter operation principle and regulation capability were verified by both simulation and experiment.

Soft-Switching High Step-Up/Down Bidirectional DC–DC Converter

A nonisolated bidirectional dc-dc converter with high voltage gain, low voltage stress, low component count, and soft-switching features is presented in this paper. In this topology, coupled inductors and voltage multiplier cells are merged to achieve high step-up/down voltage gain. Also, due to using active clamp circuits, the voltage stress of power switches is relatively low. Thus, the low voltage switches with low on-resistance can be employed to reduce the conduction losses. Furthermore, zero-voltage switching is accomplished in both high step-up and high step-down modes for all power switches, and due to zero-current switching operation of all antiparallel diodes, the reverse recovery losses are reduced. In order to verify the theoretical analysis and the converter performance, a 200 W prototype circuit of the proposed converter is implemented in the laboratory.

Development and Evaluation of an Isolated Resonant Converter for Auxiliary Power Supply in DC Traction

This paper presents the implementation and evaluation of an isolated resonant converter and also compares the efficiencies of hard and soft switching isolated converter topologies using high-frequency transformer for auxiliary power supplies in DC traction. The half-bridge DC-DC converter with resonant network has been tested under zero voltage switching (ZVS), zero current switching (ZCS) operations, and also dead time variation of the power switches improving the overall system efficiency. This paper provides guidelines for a cost effective DC-DC converter design based on discrete 1200V/40A IGBTs driven with high switching frequency. That would allow optimization of passive elements by reducing their mass making the converter suitable for traction application. Simulations and test results of an experimental setup with output power up to 3kW are presented. The overall system efficiency of the ZVS and ZCS operations of half-bridge LLC DC-DC converter were compared with a classic hard switching topology.

Capacitive Coupling Wireless Power Transfer Circuit with a Compensated L for High Voltage Gain and Soft Switching

A Capacitive coupling wireless power transfer (WPT) circuit with a compensated L is proposed. Two pairs of small area metal electrodes are used to produce two coupling capacitors and a resonant inductor is employed for the capacitive coupling wireless power transfer. By adding one parallel inductor to the series resonant circuit, an output voltage gain greater than 1 can be achieved. In addition, zero voltage switching (ZVS), zero current switching (ZCS), and higher output voltage can be obtained using the compensated inductor even at high frequency operation. A 6.3W Capacitive coupling WPT system is implemented with an approximately 700pF coupling capacitance by two 108cm2 copper plates and 6.78MHz operation for charging a small power electric device. The experimental results confirm the ZVS and ZCS operation, higher efficiency, and larger output voltage.

Generalized Step-Down Switched-Capacitor Converter Under ZCS for Photovoltaic Applications

Resonant switched-capacitor converters (SCCs) are being increasingly used in energy conversion systems due to their low cost, low weight, and high efficiency. The zero-current switching (ZCS) feature of an SCC, which can be achieved at a switching frequency below the resonant frequency, not only results in soft switching and, hence, low switching losses, but also reduces the electromagnetic interference caused by the converter. This paper proposes a cascaded step-down SCC (CSD-SCC) with an arbitrary number of converter stages and an exponential output-to-input voltage ratio. This SCC reduces the number of required converter stages for a low voltage conversion ratio and has a low ripple in the output voltage. A mathematical study is proposed to analyze the operating modes of this generalized CSD-SCC under ZCS operation. This study also enables the calculation of the output voltage, the output voltage ripple, and the efficiency for different switching frequencies and loads. The proposed analysis is validated via several simulation and experimental case studies, including a photovoltaic energy conversion system. The experimental CSD-SCC has two converter stages with an efficiency higher than $\text{95}\%$ .

Double‐boost switched‐resonator converter

A new high-efficiency resonant boost converter is presented. The topology is a hybrid circuit between switched-resonator and switched-capacitor converters. The proposed converter can efficiently provide voltage conversion ratio between 1 and 2. The voltage gain is adjustable, and full-range zero-current switching operation is provided for switches independent from operating voltages and load power. The structure is formed by an inverter arm without employing any additional switch in the circuit. Passive elements are all high-frequency resonant type and then small size realisation is possible. The converter stability is guaranteed. Complete theoretical analysis along with simulation and practical results are presented. Finally, the converter is compared with its most recent counterparts.

Modulation Method of a Full-Bridge Three-Level LLC Resonant Converter for Battery Charger of Electrical Vehicles

This paper proposes a modulation method for a full-bridge three-level LLC resonant converter. The target converter is known to enable fixed frequency operation, small resonant inductance ratio, and zero-current switching operation of rectifier diodes under wide output-voltage variation. Therefore, it is suitable for an application such as in battery chargers. A new parameter named “master duty,” which determines each voltage-level duty, is introduced to this modulation method. It simplifies the modulation method; therefore, a modification of the modulation is easy. It also makes possible seamless handling of two-level, three-level, and mixed modes. The modulation method is represented by the relationship between the master duty and each gate-pulse edge position. This representation can clearly depict a complex modulation such as a combination of pulse-width and phase-shift modulations. The voltage gain of the converter is analyzed using the first-harmonic approximation technique. The result of the analysis is verified by the circuit simulation. The voltage gain is also analyzed using lossy components, which is verified by the experimental result. A 385-V input 225- to 378-V/6.6-kW output prototype converter is fabricated for this verification. It shows 98.14% peak efficiency, and its power density is 1036 W/L.