Low Switching Losses Research Articles

Single-Switch High-Frequency DC–DC Converter Using Parasitic Components

This paper presents a single-switch isolated dc-dc converter suited for a very high-frequency switching operation, especially above 10 MHz. The converter features a small number of passive components, low-switching loss, and low-voltage stress on the switch. In order to achieve low-voltage stress while maintaining zero voltage switching, the voltage waveform across the switch is shaped by designing the resonant network of the converter. The resonant network includes main parasitic components, such as leakage inductances of the transformer and the junction capacitance of the switch. Furthermore, some resonant elements are entirely replaced by these parasitic components under the specific condition. This paper derives the conditions and then minimizes the number of passive components. To validate the design procedure and the performance of the proposed converter, a GaN-based prototype was implemented. It operates at 10 MHz and provides the output power of 10 W from the dc input voltage of 50 V. The output voltage is regulated to 20 V by the ON-OFF control. Experimental results show that the peak voltage on the switch is reduced to 2.2-2.3 times the dc-input voltage and the efficiency of 69% is achieved under the full load.

Comparison of Switching Loss of Single‐Phase Step‐Up/Step‐Down Bidirectional Converter with Voltage‐Fed/Current‐Fed Hybrid‐Type Operation

SUMMARYElectric energy storage systems are very important as one of the solutions to global warming. Step‐up/step‐down characteristics are required for electric energy storage systems. In addition, such systems must have high efficiency, low cost, and small scale. Therefore, the authors proposed a single‐phase step‐up/step‐down bidirectional converter with voltage‐fed and current‐fed hybrid‐type operation. The proposed converter consists of a two‐quadrant dc–dc converter and a single‐phase voltage‐fed converter. The circuit has several advantages such as low switching loss, use of very small capacitance, and so on. In this paper, the authors compare a comparison of the switching losses with a simple analysis.

A 6.7-GHz Active Gate Driver for GaN FETs to Combat Overshoot, Ringing, and EMI

Active gate driving has been demonstrated to beneficially shape switching waveforms in Si- and SiC-based power converters. For faster GaN power devices with sub-10-ns switching transients, however, reported variable gate driving has so far been limited to altering a single drive parameter once per switching event, either during or outside of the transient. This paper demonstrates a gate driver with a timing resolution and range of output resistance levels that surpass those of existing gate drivers or arbitrary waveform generators. It is shown to permit active gate driving with a bandwidth that is high enough to shape a GaN switching during the transient. The programmable gate driver has integrated high-speed memory, control logic, and multiple parallel output stages. During switching transients, the gate driver can activate a near-arbitrary sequence of pull-up or pull-down output resistances between 0.12 and 64 Ω. A hybrid of clocked and asynchronous control logic with 150-ps delay elements achieves an effective resistance update rate of 6.7 GHz during switching events. This active gate driver is evaluated in a 1-MHz bridge-leg converter using EPC2015 GaN FETs. The results show that aggressive manipulation of the gate-drive resistance at sub-nanosecond resolutions can profile gate waveforms of the GaN FET, thereby beneficially shaping the switch-node voltage waveform in the power circuit. Examples of open-loop active gate driving are demonstrated that maintain the low switching loss of constant-strength gate driving, while reducing overshoot, oscillation, and EMI-generating high-frequency spectral content.

The Benefits of SiC <sc>mosfet</sc>s in a T-Type Inverter for Grid-Tie Applications

It is well known that multilevel converters can offer significant benefits in terms of harmonic performance and reduced switching losses compared to their two-level counterparts. However, for lower voltage applications the neutral-point-clamped inverter suffers from relatively large semiconductor conduction losses because the output current always flows through two switching devices. In contrast, the T-type multilevel inverter has less conduction losses because only a single outer loop switching device is required to connect the converter output to the upper and lower dc buses, albeit at the expense of increased switching losses since these outer switches must now block the full dc link voltage. Silicon carbide (SiC) mosfet devices potentially offer substantial advantage in this context with their lower switching losses, but the benefit of replacing all switching devices in a T-type inverter with SiC mosfets is not so clear-cut. This paper now explores this issue by presenting a detailed comparison of the use of Si and SiC devices for a three-level T-type inverter operating in grid-tie applications. The study uses datasheet values, switching loss measurements, and calibrated heat sink thermal measurements to precisely compare semiconductor losses for these two alternatives for a T-type inverter operating at or near unity power factor. The results show that replacing only the dc bus connection switches with SiC devices significantly reduces the semiconductor losses, allowing either the converter power level or the switching frequency to be significantly increased for the same device losses. Hence, the use of SiC mosfets for T-type inverters can be seen to be an attractive and potentially cost-effective alternative, since only two switching devices per phase leg need to be upgraded.

A Highly Efficient and Reliable Inverter Configuration Based Cascaded Multilevel Inverter for PV Systems

This paper presents an improved cascaded multilevel inverter (CMLI) based on a highly efficient and reliable configuration for the minimization of the leakage current. Apart from a reduced switch count, the proposed scheme has additional features of low switching and conduction losses. The proposed topology with the given pulse width modulation (PWM) technique reduces the high-frequency voltage transitions in the terminal and common-mode voltages. Avoiding high-frequency voltage transitions achieves the minimization of the leakage current and reduction in the size of electromagnetic interference filters. Furthermore, the extension of the proposed CMLI along with the PWM technique for 2 m + 1 levels is also presented, where m represents the number of photovoltaic (PV) sources. The proposed PWM technique requires only a single carrier wave for all 2 m + 1 levels of operation. The total harmonic distortion of the grid current for the proposed CMLI meets the requirements of IEEE 1547 standard. A comparison of the proposed CMLI with the existing PV multilevel inverter topologies is also presented in the paper. Complete details of the analysis of PV terminal and common-mode voltages of the proposed CMLI using switching function concept, simulations, and experimental results are presented in the paper.

Power Quality Enhancement in Grid Connected PV Systems using High Step Up DC-DC Converter

Renewable energy sources (RES) are gaining more importance in the present scenario due to the depletion of fossil fuels and increasing power demand. Solar energy is the one of the most promising as it is clean and easily available source. The voltage obtained from the PV system is low. This voltage is increased by high step up dc-dc converter which uses only one switch leads to low switching losses and hence the efficiency of this converter is high. To get the good response this converter is operated in closed loop manner. Integration of PV system with existing grid has so many issues like distorted voltage, current and reactive power control etc. This paper presents a four leg inverter which works on hysteresis current control technique to address the power quality issues like reactive power compensation, balanced load currents and compensation of neutral current. The switching to the inverter is designed in such a way that it supplies the extra current to stabilise the current of the grid that is being supplied to the loads. Finally, the proposed technique is validated by using mat lab/Simulink software and corresponding results are presented in this paper.

A Low-Loss Hybrid Bypass for DC Fault Protection of Modular Multilevel Converters

Without additional circuitry, the half-bridge modular multilevel converter (HB-MMC) is endangered under dc-side faults. Typically, a bypass thyristor is augmented to each HB cell to take up fault current until ac circuit breakers interrupt the dc fault. This paper proposes a dc fault protection concept for HB-MMC stations that requires insignificant extra silicon area relative to the thyristor bypass concept. Herein, bypass thyristors of typical HB cells are rearranged such that an independent modular shadow rectifier bridge (SRB) is formed. A low-loss switch assembly is utilized to immediately isolate the MMC following fault detection and the SRB suppresses the fault current by injecting a reverse dc voltage. Among several advantages, the proposed arrangement incurs insignificant losses in steady state, and in some arrangements the MMC is capable of operating in STATCOM mode briefly after fault inception to support ac grid voltage. The proposed concept may be suitable for clearing temporary faults on overhead HVdc lines. Several structural variations will be viewed and discussed. Applicability for a two-level voltage source converter will be addressed. The concept is validated by detailed numerical simulations of a ±200-kV HB-MMC station under dc fault.

Design of Speed Control System for PMSM Based on Three-Level Structure

三相永磁同步电机在节约电能方面具有非常广阔的前景，它具有结构简单、体积小、效率高、易于散热和维护简单等优点。相比传统的两电平逆变器，三电平逆变器具有很多优点：单管耐压低、开关损耗降低、谐波含量小等，因此将三电平技术应用到永磁同步电机调速系统中，具有重要的理论意义和实用价值。本文主要研究了基于三电平中点箝位型(NPC)逆变器的永磁同步电机(PMSM)调速系统。电机采用转子磁场定向的矢量控制。为了达到控制目的，在三电平逆变器控制系统中引入了零序电压注入法。这种方法很好地控制了中点电压的平衡，以期降低逆变器输出电压谐波含量，改善电机定子电流波形，这将减小电机转矩脉动，改善电机控制性能。本文介绍了永磁同步电机的数学模型和矢量控制方法，阐述了中点箝位型三电平逆变器的拓扑结构和换流模式，分析了中点电位平衡算法和调制策略，最后通过实验验证了系统的可靠性和稳定性。 The three-phase PMSM has a very broad prospect in saving electrical energy. It has the characte-ristics of simple structure, small volume, high efficiency and good heat radiation. Compared with conventional two-level inverters, three-level inverter has a series of advantages such as low vol-tage-proof for single transistor, low switching loss and low harmonic content, etc. Therefore, it is of great theoretical significance and practical value to apply the three-level inverter to the speed regulating system of permanent magnet synchronous motor (PMSM). In this paper, the speed regulating system of permanent magnet synchronous motor on the basis of three level neutral point clamped (NPC) inverter is studied. Rotor flux oriented vector control method is applied on the motor. In order to implement the control process, zero sequence voltage injection method is introduced in the proposed three-level inverter control system. With this method, the balance of the neutral point voltage can be well achieved to reduce the harmonic content of the output voltage of the inverter and improve the stator current waveform, which will further minimize the motor torque ripple, and improve motor control performance. The mathematical model and vector control method of PMSM are introduced in this paper, both the topology and commutation mode of three-level inverter with neutral point clamping mode are described, and the neutral point potential balance algorithm and modulation strategy are also analyzed. Finally, the experiment verified the reliability and stability of the system.

All-SiC 9.5 kW/dm3On-Board Power Electronics for 50 kW/85 kHz Automotive IPT System

Inductive power transfer (IPT) is widely discussed for the automated opportunity charging of plug-in hybrid and electric public transport buses without moving mechanical components and reduced maintenance requirements. In this paper, the design of an on-board active rectifier and dc-dc converter for interfacing the receiver coil of a 50 kW/85 kHz IPT system is designed. Both conversion stages employ 1.2 kV SiC MOSFET devices for their low switching losses. For the dc-dc conversion, a modular, nonisolated buck+boost-type topology with coupled magnetic devices is used for increasing the power density. For the presented hardware prototype, a power density of 9.5 kW/dm 3 (or 156 W/in 3 ) is achieved, while the ac-dc efficiency from the IPT receiver coil to the vehicle battery is 98.6%. Comprehensive experimental results are presented throughout this paper to support the theoretical analysis.

A Single-Stage Grid-Connected High Gain Buck–Boost Inverter With Maximum Power Point Tracking

Converter system that does both dc–dc conversion and dc–ac conversion in a single stage is called a single-stage converter system (SSCS). Compared to a two-stage converter, SSCS is more efficient and compact in size. In this paper, a grid-connected SSCS (GCSS) system for photovoltaic (PV) applications is presented. This GCSS transfers power from PV to grid while tracking maximum power point (MPP) continuously. The proposed system has several desirable features such as low switching loss, high gain, and compact size that makes this GCSS suitable for PV systems, where the PV system output voltage is low and varies with time. Design of the presented GCSS components with necessary equations and derivation of both current control loop and voltage control loop required for operation are given. Proposed GCSS is simulated using MATLAB/SIMULINK. Detailed simulation and experimental results are given to verify the efficacy of the proposed GCSS.

Non-iterative Wide-modulation-index Switching-angle Calculation Techniques for 15-level Binary Cascaded H-bridge Multilevel Inverter

Cascaded H-bridge multilevel inverter (CHBMI) is able to generate a staircase AC output voltage with low switching losses. The switching angles applied to the CHBMI have to be calculated and arranged properly in order to minimize the total harmonic distortion (THD) of the output voltage waveform. In this paper, two non-iterative switching-angle calculation techniques applied for a 15-level binary asymmetric CHBMI are proposed. Both techniques employ a geometric approach to estimate the switching angles, and therefore, the generated equations can be solved directly without iterations, which are usually time-consuming and challenging to be implemented in real-time. Apart from this, both techniques are also able to calculate the switching angles for a wide range of modulation index. The proposed calculation techniques have been validated via MATLAB simulation and experiment.

Design and Implementation of a Modular Multilevel Converter With Hierarchical Redundancy Ability for Electric Ship MVDC System

Modular multilevel converter (MMC) can be considered as a promising candidate for modern electric ship medium-voltage direct current (MVDC) power system due to its high-voltage quality, low switching loss, good expansibility, and good redundancy. As the voltage level in MVDC is much lower than that in high-voltage direct current case, the number of submodules (SMs) of MMC in MVDC system is also much less. Therefore, the SM failure will have more significant effect on the safety operation. Since uninterrupted operation is one of the most important requirements in electric ship application, the special redundancy design for MMC is required. This paper thus proposes an MMC system with hierarchical redundancy ability, aiming to guarantee the ride-through operation under SM failure. The “hot-reserved” and “cold-reserved” SMs are prepared in the MMC by compromising the faulty SM number, voltage and current stress of SMs, SM power loss, and so on, and the hierarchical redundancy strategy is divided into several progressive layers to ride through the SM failure in different cases. The pretreatment units are designed to realize the proposed hierarchical redundant strategy smoothly, and without changing the existent modulation and sort-and-selection strategies designed for normal condition. The proposed design is explained in this paper, and verified by a three-phase MMC simulation and a single-phase MMC prototype.

A 2-kW, 95% Efficiency Inductive Power Transfer System Using Gallium Nitride Gate Injection Transistors

This paper presents an inductive power transfer (IPT) system targeting at electric vehicles (EVs) and hybrid EVs. IPT systems provide significant benefits over the conventional plug-in chargers. However, in order for IPT to be adopted for EV charging, efficiency is a key figure of merit, which needs to be achieved. This paper presents a high-frequency inverter using gallium nitride (GaN) power transistors that have the benefit of low on-resistance and gate charge to reduce the switching and conduction loss. The switching characteristics of the GaN GIT are studied, and the inverter is designed to ensure low switching losses while keeping overshoot and slew rates under control. An efficiency centric mode of operation is proposed to improve the efficiency of the system while ensuring sufficient power transfer. The system efficiency peaks at 95% at 100-kHz operation and 92% at 250-kHz operation for a coil gap of 80 mm at 2-kW output power. At a coil gap of 150 mm, the system obtains above 90% efficiency at 1.3 kW. The IPT system is compared with a similar system using SiC power transistors and outperforms it by 1% at 2 kW.

Next Generation IGBT and Package Technologies for High Voltage Applications

In this paper, we will present an overview of the latest results covering both Insulated Gate Bipolar Transistor (IGBT) and packaging technologies intended for demanding high-power applications. We will present the recently developed press pack module rated at 4500 V and 3000 A utilizing an advanced reverse conducting RC-IGBT for hard switching application, which together with the improved module layout yields the most powerful IGBT-based device up to date. For applications that require isolated modules, we will show our new dual IGBT module rated up to 3.3 kV and 450 A. The module layout was optimized to allow highly scalable converter designs with overall low stray inductances. This opens up new possibilities to further reduce losses due to the fact that the devices can be made thinner than today’s limits for achieving lower switching losses with soft performance. We will show the latest results from the enhanced trench IGBT-cell development and give an outlook for the power levels that can be achieved by combining the new cell with the RC-IGBT concept.

Parallel full-bridge converter with wide ZVS and low freewheeling current

ABSTRACTThe main objective of this paper is to present a direct current to direct current topology with high circuit efficiency. In this studied circuit, two full-bridge circuits and a half-bridge circuit connected in parallel are introduced to achieve the advantages of low switching loss, less primary current, low conduction loss and low filter size compared to the traditional parallel full-bridge converters. The circuit diagram, operation principles, steady-state analysis and experiments are provided to demonstrate the effectiveness of the studied topology. Finally, a 1.44-kW laboratory prototype is constructed to verify the validity of the theoretical analysis. Experimental results show that highest efficiency of 95.3% can be achieved.

Model Predictive-Sliding Mode Control for Three-Phase Grid-Connected Converters

This paper focuses on the implementation of an extended model predictive-sliding mode control (EMP-SMC) for three-phase grid-connected converters (GcCs). The proposed control considers the GcC model in the dq synchronous reference frame to forecast possible future behavior of the grid current. After that, the applied voltage vector is selected so that a predefined cost function is minimized. This function is aimed to reduce the grid current ripples during steady-state operation. Compared to the conventional MPC, the proposed EMP-SMC algorithm uses 19 voltage vectors (7 real voltage vectors and 12 additional virtual voltage vectors) for the prediction process. Accordingly, lower grid current THD and lower switching losses are obtained. However, the increase of voltage vectors number will lead to higher computation time delay that may affect the control performances. To overcome this problem, the proposed control uses a sliding mode-based preselection step that limits the prediction process to only ten voltage vectors at the most and a table-based implementation process that reduces significantly the execution time of the whole control algorithm. Simulation and experimental results are presented in order to show performances and effectiveness of the proposed EMP-SMC algorithm.

High Order Voltage and Current Harmonic Mitigation Using the Modular Multilevel Converter STATCOM

Due to the increase of power electronic-based loads, the maintenance of high power quality poses a challenge in modern power systems. To limit the total harmonic distortion in the line voltage and currents at the point of the common coupling (PCC), active power filters are commonly employed. This paper investigates the use of the multilevel modular converter (MMC) for harmonics mitigation due to its high bandwidth compared with conventional converters. A selective harmonics detection method and a harmonics controller are implemented, while the output current controller of the MMC is tuned to selectively inject the necessary harmonic currents. Unlike previous studies, focus is laid on the experimental verification of the active filtering capability of the MMC. For this reason an MMC-based double-star STATCOM is developed and tested for two representative case studies, i.e., for grid currents and PCC voltage harmonics. The results verify the capability of the MMC to mitigate harmonics up to the thirteenth order, while maintaining a low effective switching frequency and thus, low switching losses.

Fifth- and Seventh-Order Harmonic Elimination With Multilevel Dodecagonal Voltage Space Vector Structure for IM Drive Using a Single DC Source for the Full Speed Range

This paper presents a method for generating a multilevel dodecagonal voltage space vector structure using a single dc source for induction motor drives. Multilevel dodecagonal structure combines the advantages of both multilevel and dodecagonal structures, and hence, generates low d v /d t phase voltage along with the elimination of fifth- and seventh-order harmonics over the entire modulation range. This eliminates low-order harmonic currents and prevents the generation of sixth-order torque ripple in the motor. The topology used requires only one dc source making four-quadrant operation of the drive system simpler compared to previously proposed multilevel topologies generating dodecagonal space vector structures. The topology used consists of a three-level flying capacitor (FC) inverter cascaded with a capacitor fed H-bridge. The FC inverter operates at a lower switching frequency and the low-order harmonics are eliminated by the switching action of the cascaded H-bridge inverter. The capacitors in the cascaded H-bridge modules are maintained at a substantially smaller voltage compared to the dc-link voltage and are inherently balanced during the pulsewidth modulation operation. This results in low switching loss, in the FC inverter as well as in the cascaded H-bridge inverter. Experimental results are included to validate the operation of the topology and modulation scheme presented in this paper.

Analysis and design for interleaved ZCS buck DC-DC converter with low switching losses

Analysis and design for interleaved ZCS buck DC-DC converter with low switching losses

Analysis and design for interleaved ZCS buck DC-DC converter with low switching losses

This paper presents an interleaved buck DC-DC converter using zero current switching (ZCS) resonant with additional inductor and capacitor that mainly used for battery charging applications. The proposed novel converter has advantages of its simplicity, low cost, high efficiency and behaviour of easy control under the (ZCS) condition so that reducing the switching losses. Therefore, the proposed converter offers lower switching losses with a higher power density. The performance of the converter system is improved using coupled inductors. These coupled inductors reduce the magnetic size and also improve the converter's transient performance without increasing the steady-state current ripple. The detailed study of operating principle and design considerations is presented. The effectiveness of the proposed control scheme is demonstrated through PSIM simulations. Calculated efficiency of the converter is ensured about 94%, which is substantially considered to be a satisfactory performance.