Low Switching Losses Research Articles

Hybrid DC-DC Converter with Low Switching Loss, Low Primary Current and Wide Voltage Operation

A full-bridge converter with an additional resonant circuit and variable secondary turns is presented and achieved to have soft-switching operation on active devices, wide voltage input operation and low freewheeling current loss. The resonant tank is linked to the lagging-leg of the full bridge pulse-width modulation converter to realize zero-voltage switching (ZVS) characteristic on the power switches. Therefore, the wide ZVS operation can be accomplished in the presented circuit over the whole input voltage range and output load. To overcome the wide voltage variation on renewable energy applications such as DC wind power and solar power conversion, two winding sets are used on the output-side of the proposed converter to obtain the different voltage gains. Therefore, the wide voltage input from 90 to 450 V (Vin,max = 5Vin,min) is implemented in the presented circuit. To further improve the freewheeling current loss issue in the conventional phase-shift pulse-width modulation converter, an auxiliary DC voltage generated from the resonant circuit is adopted to reduce this freewheeling current loss. Compared to the multi-stage DC converters with wide input voltage range operation, the proposed circuit has a low freewheeling current loss, low switching loss and a simple control algorithm. The studied circuit is tested and the experimental results are demonstrated to testify the performance of the resented circuit.

The design of an efficient class E-LCCL capacitive power transfer system through frequency tuning method

In this work, the optimum zero voltage switching (ZVS) of Class E-LCCL capacitive power transfer (CPT) was determined via frequency tuning method. Through this an efficient system can be guanranteed although there is a change in the capacitive plates distance. This study used a Class-E LCCL inverter, as it can operate at a high alternate current frequency, besides producing low switching losses and minimal power losses. Specifically, this study conducted simulations and experiments to analyse the performance of an LCCL CPT System at 1 MHz operating frequency and 24 V DC supply voltage. Using an air gap distance of 0.1 cm, the designed CPT system prototype successfully achieved an output power of 10W and an efficiency of 95.45%. This study also found that by tuning the resonant frequency of the Class E-LCCL system, the optimum ZVS can be obtained although capacitive plate distance was varied from 1-3 cm via experimental. The results of this study could benefit medical implant and portable device development, consumer electronics, and environments that involve electrical hazards.

A hybrid two‐stage modular DC–DC converter with zero‐voltage switching

AbstractConventional modular multilevel converters (MMCs) are widely used in high power applications due to their various astonishing advantages; however, they fail to achieve balanced capacitor voltage in DC operation. In this paper, a hybrid two‐stage modular DC–DC converter is proposed to solve the issue of unbalanced capacitor voltages. The proposed converter consists of a single‐phase half‐bridge MMC with half‐bridge submodules followed by a medium voltage valves‐based H‐bridge rectifier. The proposed converter is used in medium‐voltage applications such as feeding a DC‐load or interconnection between two DC grids of different voltage levels. The proposed configuration achieves successful DC–DC conversion with a low number of switches, a high conversion ratio with bidirectional power flow, low current stresses, soft switching across the second stage, and low switching losses. The operational concept and the control algorithm have been illustrated in detail. Finally, the effectiveness of the proposed DC–DC converter is evaluated based on simulation studies of MATLAB SIMULINK and a scaled‐down laboratory experimental test rig.

Low Switching Loss and EMI Noise IGBT With Self-Adaptive Hole-Extracting Path

A superjunction insulated gate bipolar transistor (SJ-IGBT) featuring a self-adaptive hole-extracting (SAHE) path is proposed and investigated by simulation. The SAHE path is formed by a narrow p-type mesa between the two trench gates. In the ON-state, the p-type mesa is depleted by the trench gates and the hole path is pinched off so as to maintain high injection efficiency, and thus a low ON-state voltage ( V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> ) is achieved. During the turn-off period, the p-type mesa recovers into neutral region adaptively and then the hole-extracting path is opened, which helps decrease the turn-off loss ( E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</sub> ) and suppress the dynamic avalanche. Moreover, at the initial turn-on stage with the SAHE path opening, the P-pillar in the proposed device is shorted to the emitter electrode rather than floating, which suppresses the negative capacitance effect. Therefore, compared with the SJ-IGBT with floating P-pillar, the SAHE SJ-IGBT not only achieves better V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> ON</sub> -E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> OFF</sub> tradeoff but also reduces the surge current by 23% at the turn-on stage and obtains better controllability on the turn-on dV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CE</sub> / dt and dI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> /dt characteristics, greatly decreasing the electromagnetic interference (EMI).

New Sub-Module with Reverse Blocking IGBT for DC Fault Ride-Through in MMC-HVDC System

When integrating multi-grid renewable energy systems, modular multi-level converters (MMCs) are promising for high-voltage DC (HVDC) transmission. Because of the characteristics of the system, however, it is more difficult to prevent a fault at the DC terminal than at the AC terminal of the MMC. Accordingly, a fault ride-through (FRT) strategy for the operation of the MMC in the DC terminal is required for stable system operation. In this paper, a solution for closed-circuit overcurrent caused by a permanent line-to-line DC fault is proposed. This method is able to reduce the fault current through the adjustment of the slope of the total voltage in the system by operating a sub-module having lower switching losses and fewer passive devices compared with existing topologies. Additionally, through the equivalent circuit of the proposed scheme in a sub-module in case of a fault, the FRT mechanism for the fault current is explained. The feasibility of this proposed technique was verified through time-domain simulations implemented by Powersim, Inc.

Performance Evaluation of Seven Level Reduced Switch ANPC Inverter in Shunt Active Power Filter With RBFNN-Based Harmonic Current Generation

One of the serious issues that a Power System faces is the Power Quality (PQ) disturbance which occur mainly because of the non-linear loads. Among these PQ disturbances, harmonics play a vital role which should to be mitigated along with reactive power compensation. In this paper, a modified seven-level boost Active-Neutral-Point-Clamped (7LB-ANPC) inverter is utilized as a Shunt Active Power Filter (SAPF). Another vital aspect of this work is to retain the link voltage across the capacitor, which is accomplished through a PI controller tuned with an Adaptive Neuro-Fuzzy Inference System (ANFIS). An adaptive instantaneous p-q theory is instigated in the direction of extracting reference current and the harmonic extraction is carried out by using Radial Basis Function Neural Network (RBFNN). Gating sequence of inverter is generated for the outputs, which are attained from ANFIS and RBFNN and thus the opposite harmonics are injected to the Point of Common Coupling (PCC) by which current harmonics are eliminated with reactive power compensation. The 7Lb-ANPC inverter has a minimized number of switching devices with low switching losses and high boosting ability. By RBFNN based reference current generation, the source current THD of 0.89% is achieved. The proposed methodology is simulated through MATLAB and in hardware by utilizing FPGA Spartan 6E.

Application of SHEPWM in Helicopter Transient Electromagnetic Based on the Subsection Control Approach

Guaranteeing the quality of the transmitting current under low switching frequency conditions is the crucial point in the helicopter transient electromagnetic (HTEM) system which affects the efficiency and exploration accuracy. HTEM requires high efficiency and low switching loss of the inverter power supply due to the facts that HTEM uses air-launched and air-received measurement methods, and the power storage capacity of the airborne transmitting system is limited. Paradoxically, low switching frequency directly affects the transmitting waveform quality and thereby affects the detection accuracy. In this study, we present a semiperiodic mirror symmetry selective harmonic elimination pulse width modulation (SHEPWM) based on the subsection control approach to balance transmitting current quality and switching loss. In the SHEPWM method, the semiperiodic mirror symmetry SHEPWM nonlinear equations are established by the time frequency domain information of the inverter output voltage and resolved by the artificial neural network (ANN) algorithm to attain switching time sequence of desired transmitting current. The simulation and experimental results verify the effectiveness of the SHEPWM subsection control strategy, which can reduce the switching loss while ensuring the current waveform quality and detection accuracy.

Thermal Performances and Annual Damages Comparison of MMC Using Reverse Conducting IGBT and Conventional IGBT Module

Insulated gate bipolar transistor (IGBT) modules in modular multilevel converters (MMCs) have inherent unbalanced power loss distribution and temperature swing. Some chips may become the hotspots and have much larger temperature swing than others, which seriously compromises the lifetime of the IGBT modules. Therefore, effective improvement measures that are low cost become crucial for the IGBT modules in MMC. Reverse conducting IGBT (RC-IGBT) constructs the IGBT and freewheel diode in a single chip, which has the advantages of lower thermal resistance, lower switching loss, and larger heat capacity. In this article, a new generation of RC-IGBT module and conventional IGBT (Con-IGBT) module from Fuji Electric with the same packaging are both used in the MMC. A newly defined current density for RC-IGBT and Con-IGBT module is proposed. The thermal performances and annual damages of the two modules under different power factors are comprehensively compared at the same module current density. The results show that when the power factor is greater than 0.4, using RC-IGBT can significantly improve the thermal performance of MMC submodules (SMs) and extend their lifetime. In addition, the reasons for the comparison results are also discussed in this article. Finally, the advantages of RC-IGBT in terms of thermal performances are verified by experiment. This article also provides a guideline for the design of MMC SMs.

Evaluation of silicon MOSFETs and GaN HEMTs in soft‐switched and hard‐switched DC‐DC boost converters for domestic PV applications

Hard‐switched high‐gain DC‐DC converters such as the boost converter play an important role in renewable energy systems. Research to increase their efficiency is important and can be achieved using soft‐switching techniques; however, that approach requires an auxiliary circuit. The auxiliary circuit decreases power density and reliability while increasing the cost. Moreover, soft‐switching topologies usually cannot improve the efficiency for all power and voltage ranges. Wide bandgap (WBG) devices, such as gallium nitride (GaN), result in lower switching losses than silicon (Si), can be used while retaining the simple structure of a hard‐switched topology. However, the high cost of these devices is problematic for their frequently cost‐sensitive applications. To quantify the cost and efficiency, this study compares soft‐switching techniques and WBG‐based switches in DC‐DC boost converters for a photovoltaic (PV) energy application. The performance of four prototypes including the soft‐switched and hard‐switched DC‐DC converters with both state‐of‐the‐art Si and GaN switches are evaluated in terms of cost, power density, efficiency, and reliability using theoretical analysis, simulation and experimental results. It is shown that the GaN‐based hard‐switched converter provides higher efficiency and power density; it is more expensive than its Si‐based counterpart, yet is cheaper than soft‐switched converters.

A Universal Modular Hybrid LDO With Fast Load Transient Response and Programmable PSRR in 14-nm CMOS Featuring Dynamic Clamp Strength Tuning

This article presents a universal modular hybrid low-dropout regulator (MHLDO) to provide any desired combination of the power supply rejection ratio (PSRR) and power conversion efficiency (PCE) with in-compliance output ripple, load transient response, and operating range while minimizing losses and decoupling capacitor. The hybrid architecture eliminates the need for the fine quantization of the digital LDO power gates and prevents any associated limit cycle oscillation while keeping the overheads low. It is configurable at design-time and robustly self-adjusts across different operating points via a scalable architecture. The modular topology overcomes significant challenges of developing a large variety of analog and digital LDOs in order to meet the varying PSRR and power budget requirements for systems on a chip (SoCs) in scaled CMOS. A nonlinear control (NLC) feature provides an energy-efficient way to respond to fast load transients, while the dynamic clamp strength tuning (DCST) technique prevents unnecessary oscillations stemming from the input parasitic inductances and improves stability while lowering switching losses. The designed MHLDO provides a programmable PSRR capability of up to -42 dB with a quiescent current of less than 27.3 μA as ALDO and a 133-mV worst droop against a >1-A/ns fast di/dt load change as DLDO. A new figure of merit (FoM) with improved accuracy demonstrates performance of 83 fs.

Design and Development of Modular Dual-Input DC–DC Step-Up Converter for Telecom Power Supply

A modified modular dual-input dc-dc step-up converter along with a battery charging/discharging bidirectional converter that is suitable for telecom load applications is proposed in this article. The proposed converter has two individual input modules with the three-leg semiactive rectifier connected in parallel at secondary side for achieving constant voltage across the load with reduced circulating power. This results in an advantage of having compact structure with reduced number of components. The proposed converter works under a zero-voltage switching condition, it has favorable advantage such as low switching losses and high efficiency of the system. The complete design and steady-state analysis of the proposed converter utilizing field programmable gate array (FPGA)-based digital control strategy have been investigated in this article. A scaled down laboratory prototype of 1 kW has been developed and the robustness of the proposed converter is validated by extensive test results under variable input voltage and load conditions.

Dual-Inverter PWM Scheme for DC-Biased Vernier Reluctance Machines With Reduced Switching Frequency Capable of Zero-Sequence Current Regulation

This article proposes a dual-inverter pulsewidth modulation (PWM) scheme for dc-biased vernier reluctance machines (dc-biased-VRMs) with reduced switching frequency capable of zero-sequence current regulation. The dc-biased-VRM utilizes the additional dc bias current in armature winding to construct the rotor flux. To regulate the dc bias current, two sets of three-phase inverters with common dc bus are used to provide dc current flow path. In each switching cycle, the number of switching actions is doubled compared with the conventional three-phase inverter. There is still a certain optimization space for adjusting the dc bias current and reducing the switching loss. The proposed scheme reconfigures the zero voltage vector based on the discontinuous PWM (DPWM) scheme, it effectively reduces the switching actions, thus reducing the switching frequency and ensuring the low switching loss of the inverter. In addition, an inserted zero voltage vector regulation method is associated with the proposed DPWM scheme, and it assures the zero-sequence current regulation ability. Besides, by adopting complementary zero voltage vector distribution in odd and even sectors, the balanced voltage stress of upper and lower switching devices in each bridge arm is realized. The proposed dual-inverter PWM scheme does not require any additional devices, and it provides an effective solution to improve the efficiency of the dc-biased-VRM drive system. Finally, the effectiveness of the proposed scheme is verified experimentally.

Research on Control Strategy of Three-Phase Inverter Based on Fractional Calculus

Three-level inverters has widely used in Medium pressure due to its advantages of low total harmonics, low voltage resistance of power switch tubes and low switching losses. In order to further improve the output voltage waveform quality and optimal control effect of the Three-level inverter, this paper introduces fractional calculus in the control method of the three-level inverter circuit. First, designed a control strategy for the fractional voltage outer loop. Secondly, the use of vector representation simplifies the parameter tuning of fractional-order controller, the optimization process of the parameters of the fractional order PIλ and integer-order PI is completed by utilizing the ITAE rules. At the same time, the Oustaloup approximation method realizes the fractional integral operator in the controller, thereby achieving the purpose of improving the output voltage of the system. For three-level inverter circuit model, comparative analysis of the control effects of the fractional-order PIλ and integer-order PI. Finally, simulation results show that fractional-order PIλ controllers have excellent flexibility, robustness.

Mitigation and analysis of sub synchronous resonance for DFIG based wind farm using STATCOM controller

Large-scale integration in transmission networks has led to several challenges; one of which is the need for increased transmission capacity to transport a bulk amount of power without affecting the voltage. In case of transmitting power to large distances series compensation is used along with Doubly-Fed Induction Generator (DFIG) wind turbine and it is simulated using MATLAB Simulink and the results obtained are validated. DFIG wind turbine is operated at normal operating state. Due to series compensation Sub Synchronous Resonance (SSR) occurs which is quite harmful to the wind generator because of the frequency variation, the gear mechanics of the generator gets damaged. When a larger disturbance occurred in any part of the study system at any bus bar, the effect of SSR would be more harmful. The effect of SSR depends on the compensation percentage we used for series compensation. SSR can be mitigated by using Flexible AC transmission System (FACTS) devices such as STATCOM, SVC, and SSSC. We use STATCOM because of its high stability margin, low switching loss and variable voltage rating. Whenever disturbance occurs in the transmission line then STATCOM comes into action by supplying reactive power and absorbing real power thus maintaining the system stability. The STATCOM controller gives pulse to the STATCOM for respective action such as real power absorption or reactive power injection. Thus the Wind turbine is protected and system stability is maintained.

Novel Level Shifted PWM Technique for Unequal and Equal Power Sharing in Quasi Z-Source Cascaded Multilevel Inverter for PV Systems

Conventional phase-shifted pulsewidth modulation (PS-PWM) is a usual switching technique for Z-source/quasi-Z-Source (qZS)-based cascaded multilevel inverters (CMIs) (qZS-CMIs). The PS-PWM scheme causes higher switching losses and creates an electromagnetic interference (EMI) problem for higher number of cascaded modules. To address these issues, a novel, modified level-shifted PWM (LS-PWM) technique is proposed with the aim of obtaining equal power from cascaded modules under abnormal conditions. The direct use of the alternate phase-opposed disposed PWM (APOD-PWM) results in unequal power sharing between the qZSI modules, under all operating conditions. An effective carrier rotation is incorporated in the conventional APOD-PWM to make equal power sharing between the qZSI modules. The proposed scheme is an excellent solution for photovoltaic (PV) systems to address the problem of partial or complete shading, temperature variation, PV module failure, and dust accumulation on the PV panels. Furthermore, the relationship between PS-PWM and APOD-PWM is geometrically obtained, which indicates that the proposed modulation scheme gives higher voltage gain over LS-PWM and PS-PWM techniques. In addition, detailed switching loss analysis for the proposed PWM methods is added to validate low-switching losses, and thus high efficiency. The MATLAB Simulink simulations are presented to verify the proposed modulation. An experimental prototype is developed, and the experimental outcomes validate the improved performance of the multilevel qZSI with proposed modulation.

Elimination of Abnormal Output Voltage in a Hybrid Active NPC Inverter

This article proposes a method to eliminate abnormal output voltages generated in three-level hybrid active neutral-point clamped (ANPC) inverters. The hybrid ANPC inverter is a topology in which silicon (Si) devices are replaced with silicon-carbide (SiC) devices in part from the conventional ANPC topology. The hybrid ANPC inverters have the advantages of high switching frequency and low power switching loss due to the SiC devices. In this hybrid ANPC inverter, abnormal output voltages occur when the polarity of the output pole voltage is changed from positive to negative. The cause of the abnormal voltages is the switching time difference between the Si and SiC devices, and it is various from a few nanoseconds to a few microseconds. These abnormal output voltages need to be eliminated as it leads to degraded output power quality in the hybrid ANPC inverters. The proposed switching method effectively eliminates the abnormal output voltages and reduces output current distortion. The performance of the proposed method is verified using a prototype of the new three-level hybrid ANPC inverter type through both simulations and experiments.

99% Efficient 2.5-kW Four-Level Flying Capacitor Multilevel GaN Totem-Pole PFC

In this article, a high-efficiency and high-density 2.5 kW four-level flying capacitor multilevel (FCML) totem-pole bridgeless power-factor-correction (PFC) rectifier with 200 V GaN devices is analyzed, designed, and tested. This 2.5 kW four-level continuous conduction mode (CCM) GaN totem pole PFC operates with 360 kHz current ripple frequency which significantly reduces the inductor size while keeping a very low switching loss. This article compares the device loss of the four-level and two-level CCM GaN totem-pole PFC with the same ripple frequency (360 kHz) and shows that the four-level CCM GaN PFC has much less device loss. In addition, this article introduces the detailed design of a compact and low-profile matrix inductor based on the commercial composite inductors. This article also introduces the design of a high-density and low-loss flying capacitor. A 2.5 kW four-level FCML GaN totem-pole PFC prototype with 120 kHz switching frequency (360 kHz current ripple frequency) is developed and tested in this article. The tested peak efficiency is 99.25%. The PFC system power density is 104 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , without a heatsink and with forced air cooling.

A Hybrid Control Method for Neutral-Point Voltage Balancing in Three-Level Inverters

Neutral-point (NP) voltage fluctuation is an inherent problem in three-level inverters. Without any control measures, the NP voltage will deviate, and the dc bias and ac oscillation can be observed, which may lead to the failure of power devices and capacitors, so as to damage the system security. In this letter, a hybrid control method is proposed, which it combines zero-sequence voltage regulation with the decomposition of modulation waveform organically. This carrier-based method is simple with lower switching loss due to the unchanged switching events per switching cycle. Experiments are carried out in a 10-kVA three-level platform, which demonstrate the validity of proposed method.

A Modular Multilevel Converter with an Advanced PWM Control Technique for Grid-Tied Photovoltaic System

Due to global warming and shortage of fossil fuels, the grid-connected solar photovoltaic (PV) system has gained significant popularity all over the world. The modular multilevel cascaded (MMC) inverter is the natural choice for step-up transformer and line filter less direct medium voltage grid integration of solar PV systems. However, power quality and loss are the important issues while connecting the PV system to the medium voltage grid through MMC inverter. Modulation technique is the key to maintain output power quality, e.g., total harmonic distortion (THD) and to ensure low switching and conduction losses. In this paper, an advanced modulation technique named “triangle saturated common mode pulse width modulation (TSCMPWM)” control is proposed for a 3-phase 5-level MMC inverter-based grid-tied PV system. Compared to traditional modulation techniques, the proposed TSCMPWM control offers the lowest voltage THD as well as lower inverter power losses. Performance of the proposed modulation technique is evaluated in MATLAB/Simulink environment and tested with a reduced scale prototype test platform. Both simulation and experimental results show the effectiveness of the proposed modulation technique.

Recent Achievements in Model Predictive Control Techniques for Industrial Motor: A Comprehensive State-of-the-Art

Model predictive control (MPC), manly based on a direct use of an explicit and identifiable model, has been widely used in controller design in different applications both by academia and industry. The reason for such popularity is due to its strong ability for providing high performance electric drive systems, as highly recognized as the most reliable control approach compared with field-oriented control (FOC) and direct torque control (DTC). In general, the MPC has numerous features and advantages, such as direct switching states to the converter without any modulation, online optimization with multivariable control, low current total harmonic distortion, low switching loss, etc . The aim of this paper is to provide a comprehensive review for major development and achievements of the recent progress on the MPC for electrical machines and drives. This review begins with the innovative topologies and operating principles of fundamental MPC, and ends to summary on different advanced MPC algorithms. Typical MPC techniques have been fully adopted to enhance the drive performance of the electrical drives, mainly including finite-set model predictive control (FS-MPC) based on tuning weighting factors, without weighting factors, maximum torque per ampere, low number of switching vectors, and multi voltage vectors in one sample period. Finally, great attention has been paid to the discussion of the new trends and future research topics.