Switching Losses Research Articles

Practical Dead-Time Control Methodology of a Three-Phase Dual Active Bridge Converter for a DC Grid System

An effective dead-time control strategy for the three-phase dual active bridge (3P-DAB) converter of a distribution system is studied to reduce the switching losses of power switches and improve the under-light-load power conversion efficiency. Because of the advantages of a dual-active bridge converter, such as an inherent zero-voltage switching (ZVS) capability without any additional resonant tank and a seamless bi-directional power transition, this is an attractive topology for bi-directional application. The 3P-DAB converter is apt for high-power applications such as aircraft due to an interleaved structure, which can reduce conduction losses. However, the design of the dead time depends on engineering experience and empirical methods. In order to overcome the conventional practicality of the dead-time design method, the effective control of dead time is proposed based on the theoretical analysis. In this paper, the overall explanation of the 3P-DAB converter is shown with operation principles. In addition, the dead-time effect of the 3P-DAB converter is examined and the practical variable dead-time control strategy is studied. Finally, experimental results validate the proposed variable dead-time control strategy using a 25 kW prototype 3P-DAB converter.

A Novel Integrated Electronic Lighting Driver Circuit for Supplying an LED Projection Lamp with High Power Factor and Soft Switching Characteristics

The traditional light source of projection lamps adopts a halogen lamp, which has the advantages of high brightness, but its luminous efficiency is not good and consumes energy. A light-emitting diode (LED) has the characteristics of high luminous efficiency and energy savings and can be used as a new light source for projection lamps. The conventional two-stage electronic lighting driver circuit for supplying an LED projection lamp is composed of an AC-DC converter with power factor correction (PFC) as the first stage and a DC-DC converter for providing rated lamp voltage and current as the second stage. The conventional LED projection lamp driver circuit has more circuit components, a higher cost and limited efficiency. Therefore, this paper proposes a novel electronic lighting driver circuit for supplying an LED projection lamp with PFC function, which integrates a modified stacked dual boost converter and a half-bridge LLC resonant converter into a single-stage power-conversion circuit. The inductor inside the modified stacked boost converter is designed to operate at discontinuous conduction mode (DCM) for the driver circuit achieving PFC. Wide bandgap semiconductor devices silicon carbide (SiC)-based Schottky diodes are utilized to reduce power diode losses, and soft switching is implemented in the proposed LED projector lamp driver circuit to reduce the switching losses of the power switches and thus improve circuit efficiency. This paper has completed a single-stage prototype driver circuit for an LED projection lamp with PFC function, and the prototype circuit has a high power factor (PF > 0.98), low input current total-harmonic-distortion (THD < 6%) and high efficiency (>89%) in the case of an AC input power supply with an RMS value of 110 volts, and both power switches have the characteristics of soft switching.

PV based OFF grid charging station for E-vehicles using PWM and phase shift controlled interleaved three port converter

In recent years, Electric Vehicles are becoming more popular. The pollution level in the atmosphere can be effectively minimized by using Electric vehicles for large-scale transportation. A battery station is required for continuous operation; however, the Photovoltaic-based OFF grid charging station can only operate during the day. Therefore, the three-port converters have started to arise from a number of current EV charging station developments. In this study, a unique PWM and Phase Shift Controller are proposed to reduce switching losses and to improve reliability. In addition, for Maximum PowerPoint Tracking, a Fuzzy is added to the PV system. Furthermore, an appropriate interleaved boost converter topology is used to create the various charging voltages required for EV and battery stations. The proposed topology is simulated, and the hardware prototype has been created and tested. The result shows that the proposed topology has a better efficiency than the traditional converters.Article Highlights.A dual composite charging station for electric vehicle charging in environment friendly manner.Optimization of power electronics required in Electric Vehicle charging stations.Maximum utilization of battery for cyclic charging from charger and discharging through Electric Vehicles.

A selection principle of submodule switching state vectors for switching frequency reduction in voltage self‐balancing half‐bridge modular multilevel converters

AbstractThe problem of submodule switching frequency reduction in half‐bridge modular multilevel converters (HB‐MMCs) with capacitor voltage self‐balancing control is considered and explored in this paper. A selection principle of submodule switching state vectors is proposed based on the voltage self‐balancing switching state matrix, aiming to lower submodule switching frequency and device losses. The relationship between system stability and submodule switching signals is revealed according to the capacitor voltage self‐balancing characteristics, and the full‐rank constraints on the voltage self‐balancing switching state matrix are proposed. Considering the tradeoff between switching loss and capacitor voltage fluctuation, the evaluation indexes of voltage self‐balancing control effect are determined. The selection principle of submodule switching state vectors and the optimized construction method of switching state matrix are presented. Voltage self‐balancing HB‐MMC models are built in MATLAB/Simulink, and it is verified that the submodule switching state vector selection principle proposed in this study can effectively reduce switching frequency while meeting the evaluation requirements of practical engineering projects, so as to achieve the balance between switching loss and steady‐state capacitor voltage fluctuation.

Loss distribution analysis and accurate calculation method for bulk-power MMC

Accurate evaluation of power losses in a modular multilevel converter (MMC) is very important for circuit component selection, cooling system design, and reliability analysis of power transmission systems. However, the existing converter valve loss calculation methods using the nearest level modulation (NLM) method and the traditional sorting-based capacitor voltage balancing strategy are inaccurate since the submodule (SM) switching logics in the MMC arms are uncertain. To solve this problem, the switching principle of the SMs in the sorting-based voltage balancing strategy is analyzed. An accurate MMC power loss calculation method based on the analysis of loss distribution of various SM topologies, including half-bridge submodule (HBSM), full-bridge submodule (FBSM) and clamp double submodule (CDSM), is proposed in this paper. The method can accurately calculate the losses caused by the extra switching actions during the capacitor voltage balancing process, thus greatly increasing the calculation accuracy of switching losses compared with existing methods. Simulation results based on a practical ± 350 kV/1000 MW MMC-HVDC system with variety of MMC topologies with different voltage balancing strategies demonstrate the effectiveness of the proposed method.

Comparison and analysis of gate dielectrics for SiC MOSFET

SiC MOSFET has been widely used for its characteristics of lower on-off resistance, less switching loss, higher working frequency, and high-temperature resistance. With the scale down of Moore's Law, better gate dielectrics should be selected to improve the breakdown voltage and reduce the gate-drain current to ensure a good working mode of MOSFETs. The traditional gate dielectric is SiO2 but their dielectric constant is low and the interface characteristics at the junction of SiO2 and SiC are poor so various emerging materials have been created to replace the traditional SiO2. Emerging gate dielectrics such as high-k gate dielectrics are receiving a lot of attention today, they can increase breakdown voltage and decrease gate-drain current while maintaining oxide thickness. Among many emerging gate dielectrics, Al2O3, HfO2, and HfSiON have been noticed due to their good characteristics and a lot of research on them. This paper will focus on the analysis of the characteristics of these three materials and their applications in MOSFET. Finally, after a detailed analysis of the three materials, they three materials are compared to understand their differences.

A wind speed forecasting method based on EMD-MGM with switching QR loss function and novel subsequence superposition

The ultra-short-term forecasting of wind speed is of great significance to the stable power supply of the power system. Current wind speed forecasting methods aim to improve forecasting precision while disregarding model training speed and model deployment complexity. This research proposes a lightweight hybrid model named SLF-EMD-MGM-NS for wind speed forecasting. EMD-MGM is designed as the network’s fundamental structure for reducing the hybrid model’s training time and ensuring the hybrid model has high forecasting precision. The study presents the switching loss function (SLF) mechanism. When the quantile is 0.5, an MSE-based loss function is employed for training all subsequences. When the quantile is 0.5 and 0.95, first use the wind speed fluctuation threshold to select primary subsequence, and then use the Log-Cosh-based loss function for training primary subsequences. The SLF mechanism can increase point prediction precision and interval prediction boundary stability. Moreover, a novel subsequence superposition (NS) mechanism is proposed for getting high confidence level and narrow-width interval prediction results. The NS mechanism superimposes the interval prediction results of the fluctuation subsequence with the point prediction results of the model to generate the final interval prediction results. According to the experimental results, the SLF-EMD-MGM-NS model has a high confidence level, acceptable prediction results, a narrow-width interval prediction result, and a significantly shorter training time than the other hybrid models.

A single-phase full-bridge soft-switching inverter circuit with an auxiliary resonant circuit

A new topological structure is proposed in this article for the traditional single-phase full-bridge inverter circuit by adding an auxiliary synchronizing resonant circuit. Without extra switching transistors, the complexity of the control circuit is simplified while enabling zero voltage switching (ZVS) functionality. The significance of this proposed topology is that the switching transistors of all bridge arms are sharing one common synchronizing unit which is constructed with an absorbing inductor and capacitor. In this way, the added-on components can be substantially reduced for the main switching transistor circuit. By utilizing a big-volume capacitor as the constant voltage source, the sourceless energy feedback unit can minimize the switching losses. In the meantime, the proportional-resonant feedback circuit can modify the sinusoidal pulse width modulation (SPWM) duty ratio to stabilize the output current. In the PSIM power electronic simulation software environment, the operation of the soft-switching inverter circuit is analyzed to demonstrate our proposed topology can reduce the on-off switching losses as expected for the switching transistors of the soft-switching inverter circuit.

Improved the two DC capacitors’ voltage balancing of three-level NPC inverters applied in electric vehicles

Excessive unbalance of the DC capacitor voltages of the inverter can cause overvoltages on power components and capacitors, causing unintended low-order harmonics on the load side such as second harmonics, 3rd, 4th, 5th, ..., causing direct harm to the motor load, reducing the controllability of the reverse voltage and filter compensating current for the active filter circuit, affect to the performance of electric vehicles (EVs). Therefore, maintaining the DC capacitors' voltage balance will control the multi-level inverter's input quality and ensure the output quality in terms of Total Harmonic Distortion (THD). The paper proposes a method to control the two DC capacitors’ voltage balance of the 3-level inverter, using the principle of offset function separation. The analysis results suggest that the NPC three-level modulation technique should be implemented to satisfactorily achieve the neutral line current (iNP). Compared with recent international publications, the proposed new algorithm can save and reduce switching loss; the transient dynamic response can be adjusted easily. Maintaining the capacitor voltage balance allows the design with the smallest capacity to reduce voltage stress on components. The proposed results are partially verified through simulation and experiment.

Capacitor for the voltage-surge suppression in a SiC-MOSFET half-bridge inverter

This paper explores some efforts to suppress the voltage surge appearing during the operation of a SiC-MOSFET-based half-bridge circuit in an inverter topology. The study is important to carry out, as the voltage surge problem does not come up when a Si-IGBT is used as the switching component in the half-bridge; however, some applications demand certain properties like what is found in a SiC MOSFET. Compared to Si-IGBT with rise-time/fall-time larger than 100 ns in general, the use of SiC MOSFET is preferable due to its much shorter switching time, less than 50 ns, which brings about a much lower switching loss and lower operating temperature. However, the choice of the usual electrolytic capacitor in the dc-link would produce an undesired voltage surge during the half-bridge operation. The origin of the surge is sometimes assigned to the inductance parasitic effect of the SiC-MOSFET high frequency. This research proves the benefit of a film capacitor to suppress the surge due to its lower equivalent series resistance (ESR) than that of the electrolytic capacitor. The results contribute to the consideration to take during the circuit realization in various applications, as there are not many papers yet found discussing the use of film capacitor in the dc-link of a SiC-MOSFET half-bridge inverter. This study also reveals the importance of the film capacitor placement during the design stage of SiC-MOSFET applications; moreover, motor controllers being equipped with an inverter such as described in this study have not been found yet in the market. The efforts investigated in this work would help to control the undesirable voltage spikes that frequently occur when applying a SiC-MOSFET to a half-bridge inverter design

Numerical analysis of an ultralow switching loss IGBT with super junction and blocking junction

In order to reduce the switching loss (ESW) and enhance the breakdown voltage (BV), in this paper, an insulated gate bipolar transistor with an internal blocking junction and super junction (SJBJ-IGBT) is proposed and investigated. By inserting P-pillar and N-pillar on both sides of the drift region, a drift area with auxiliary depletion function can be formed. The junction of the primary blocking layer (JPB) is located internally in the device’s drift region. The JPB is reverse biased and withstand the main E-field during device turn-off. Meanwhile, the JPB is surrounded by P-pillar and N-pillar, reducing the E-field(E-field) peak value of device, and making E-field distribution more uniform. Furthermore, during device turn-on, the reduction of the effective area of drift region makes it easier for the JPB side of the P-drift region to accumulate excess holes. So that the SJBJ-IGBT is easier to turn-on. The snapback phenomenon of SJBJ-IGBT is eliminated. Simulation results demonstrate that, under the same forward conduction voltage (VON) condition, the proposed device exhibits a significantly lower turn-on energy loss (EON) compared to the traditional super junction(SJ-IGBT), and is 44.5% lower than that of IPBJ-IGBT, while their turn-off energy losses (EOFF) are almost equivalent.Besides, the optimized E-field distribution in the SJBJ-IGBT shows 13.2% improvement of BV. Researching results can provide important reference for reducing the ESW of IGBT.

Investigation on the carrier-storage super-junction IGBT: Characteristics, mechanism, and advantages

Operation mechanisms of the N-type Carrier-storage (N-CS) layer and Super-junction (SJ) pillar in Carrier-storage Super-junction Insulated Gate Bipolar Transistor (CS-SJBT) are clearly investigated in paper. It is pointed out that, under the effect of N-CS layer, Von of CS-SJBT is no more constrained by pillar doping as in CP-SJBTs, and the Von−Eoff contradiction along with pillar doping concentration in CP-SJBTs also no more exist in CS-SJBTs. Structural evolutions from CS-NDBT to CS-SJBT shows that, current conduction ability of SJ pillar and N-drift in CS-IGBTs are equivalent, and the role of SJ pillar locates in substantially reduced switching loss due to the two-dimensional electric field morphology in SJ pillar, which are supported by experimental contrasts. After these investigations, the conventional advantage of SJ in reducing on-state loss as in unipolar SJ-MOSFETs is diverted/extended to switching loss reduction ability in bipolar CS-SJBTs.

Zero Voltage Switching Modified Boost Converter

Changing the position of the capacitor from the output to the position between the positive output and input connectors, leads to an interesting modification of the traditional Boost converter. The inrush current, when the converter is applied to a stable voltage source e.g. batteries in cars or a battery-buffered DC micro-grid, is suppressed, and the voltage stress across the capacitor is reduced. To reduce the switching losses and to reduce the disturbances caused by fast voltage rise- and fall-times, a zero voltage switching (ZVS) concept is applied and explained step by step and some interesting aspects of the converter are shown. All explanations are supported by calculations and simulations done with LTSpice.

Bidirectional Six-Pack SiC Boost-Buck Converter Using Droop Control in DC Nano-Grid.

This paper proposes a bidirectional boost-buck converter employing a six-pack SiC intelligent power module using droop control in DC nano-grids. The topology is constructed as a cascaded structure of an interleaved boost converter and buck converter. A six-pack SiC intelligent power module (IPM), which is suitable for the proposed cascaded structure, is adopted for high efficiency and compactness. A hybrid control scheme, in which holding a particular switch always results in a turn-off or turn-on state according to the boost mode and the buck mode, is employed to reduce the switching losses. By applying the hybrid control scheme, the number of switching operations of the switches can be minimized. Since switchover of the current controller is not required, smooth transition is enabled not only from the buck mode to the boost mode but also vice versa. As a parallel control, a secondary control is employed with DC droop control, which has a trade-off relationship between voltage sag and current sharing. It is possible to enhance the accuracy of current sharing while effectively regulating the DC link voltage without voltage sag. This is verified experimentally using two modules as laboratory prototypes, of which the power rating is 20 kW each.

Enhanced marine predators algorithm optimized support vector machine for IGBT switching power loss estimation

As the use of renewable energy generation continues to grow, improving power conversion efficiency has become an urgent task. This study aims to propose a high-precision power module loss estimation method, with a focus on predicting the switching losses of insulated gate bipolar transistor (IGBT) modules, which is crucial for the reliability assessment of IGBT modules. The main objective of this study is to establish a high-precision predictive model for IGBT module switching losses to enhance the reliability and efficiency of these devices. Firstly, a dynamic characteristic test platform was established to acquire relevant data for in-depth analysis of IGBT behavior. Secondly, given the excellent performance of support vector machine (SVM) in handling both strong and small-sized datasets, SVM was chosen as the foundational model for high-precision switching loss estimation. Subsequently, an enhanced marine predatory algorithm (EMPA), known for its superior convergence precision and speed, was introduced to optimize the random parameters of SVM. Finally, a method based on the optimized EMPA-SVM was constructed for predicting IGBT switching power losses. The proposed approach was validated using dynamic characteristic test data. And it indicated that the predictive model achieved the value of R 2 exceeding 99.8% for switching losses. Additionally, the mean absolute error and root mean square error metrics of EMPA-SVM model outperformed other models. Therefore, the research results unambiguously demonstrate the significant benefits of accurately predicting IGBT switching losses in enhancing device performance.

Super-twisting sliding mode control for neutral point voltage of three-phase four-wire inverter based on SiC/Si hybrid switch

The three-phase four-wire voltage source inverter (3P4W VSI) is widely used in applications like uninterrupted power supply (UPS) and bidirectional onboard charger. The increasing power density demand requires higher switching frequency and lower switching loss. To fulfill the conflicting objectives, two-fold methodology is proposed in this paper: 1) SiC/Si hybrid switches (HyS) together with recently reported gate trigger are reported for the first time in the 3P4W VSI; 2) the natural point voltage is controlled to track a sinusoidal voltage with the frequency equal to 3 times of fundamental frequency in order to achieve higher DC-bus voltage utilization rate, and further reduce the switching loss. The traditional PI controller is very hard to achieve desired performance due to both the nonlinearity and the variant reference of the natural point voltage control system. Thereby, the super-twisting sliding mode control (ST-SMC) is proposed in this paper to achieve desired tracking performance and fast dynamic response. The effectiveness and superiority of the system are verified by both simulation and experiment comparison with the existing methods using a 5 kW prototype.

Novel Control Approach for Resonant Class-DE Inverters Applied in Wireless Power Transfer Systems

Regulating the load voltage is of major importance for ensuring high transmission efficiency in wireless power transfer (WPT) systems. In this context, this work presents a novel control strategy applied in the dc-ac converter used in the primary side of a WPT system. The performance of a class-DE resonant inverter is investigated considering that such topology presents inherent soft-switching characteristics, thus implying reduced switching losses. The controller relies on an autoregressive with exogenous output (ARX) model based on an adaptive linear neuron (ADALINE) network, which allows for determining the turn-on time of the active switches accurately while providing the system with the ability to adapt to distinct alignment conditions. The performance of the proposed controller is compared with that of a linear controller, which does not prove to be an effective solution if misalignment occurs.

Low working loss Si/4H–SiC heterojunction MOSFET with analysis of the gate-controlled tunneling effect

A silicon (Si)/silicon carbide (4H–SiC) heterojunction double-trench metal-oxide-semiconductor field effect transistor (MOSFET) (HDT-MOS) with the gate-controlled tunneling effect is proposed for the first time based on simulations. In this structure, the channel regions are made of Si to take advantage of its high channel mobility and carrier density. The voltage-withstanding region is made of 4H–SiC so that HDT-MOS has a high breakdown voltage (BV) similar to pure 4H–SiC double-trench MOSFETs (DT-MOSs). The gate-controlled tunneling effect indicates that the gate voltage (VG) has a remarkable influence on the tunneling current of the heterojunction. The accumulation layer formed with positive VG can reduce the width of the Si/SiC heterointerface barrier, similar to the heavily doped region in an Ohmic contact. This narrower barrier is easier for electrons to tunnel through, resulting in a lower heterointerface resistance. Thus, with similar BV (approximately 1770 ​V), the specific on-state resistance (RON-SP) of HDT-MOS is reduced by 0.77 ​mΩ‧cm2 compared with that of DT-MOS. The gate-to-drain charge (QGD) and switching loss of HDT-MOS are 52.14 ​% and 22.59 ​% lower than those of DT-MOS, respectively, due to the lower gate platform voltage (VGP) and the corresponding smaller variation (ΔVGP). The figure of merit (QGD ​× ​RON-SP) of HDT-MOS decreases by 61.25 ​%. Moreover, the heterointerface charges can reduce RON-SP of HDT-MOS due to trap-assisted tunneling while the heterointerface traps show the opposite effect. Therefore, the HDT-MOS structure can significantly reduce the working loss of SiC MOSFET, leading to a lower temperature rise when the devices are applied in the system.

Predictive Torque Control of the Vehicle’s Permanent-Magnet Synchronous-Motor Model Based on Multi-Objective Sorting

The permanent-magnet synchronous motor (PMSM), with the advantages of low energy consumption and stable operation, is considered a green power source to replace gasoline engines. Motor control is the core problem of the electric-drive system, so it is important to study the high-performance motor control algorithm. The traditional PMSM control strategy has problems such as torque pulsation, large overshoot, and parameters which are not easy to adjust. This work proposes a new model-predictive torque control (MPTC) based on multi-objective ranking for these issues. The Romberg observer was utilized to accurately estimate motor flux and torque across a wide range of speeds and ensure optimal performance of the MPTC. The optional voltage vectors were classified using graph theory. The model’s cost function was optimized and the control delay caused by hardware processing was compensated by a modified Euler method. A multi-objective ranking method was used to avoid the offline selection of MPTC weight coefficients. Additionally, one ranking method was used to reduce the complexity of the algorithm for multiple objectives. Based on the simulation results, the newly proposed MPTC method, when compared with traditional approaches, reduced the total harmonic distortion from 2.78% to 2.26%. Torque ripple decreased by approximately 58.4%, and the switching frequency was reduced by 3.05%, lowering the inverter’s switching losses. Therefore, the newly proposed MPTC had faster torque response, reduced computation time, and less torque pulsation, which further improved the dynamic performance of the permanent-magnet synchronous motor.

A high-efficiency primary-side regulation control strategy for half-bridge LLC resonant converter with wide input voltage range

The requirement of the half-bridge LLC resonant converter with a wide input voltage range is becoming higher in photovoltaic applications because of its simple structure and low switching loss. Conventional frequency modulation (FM) requires a wide switching frequency range and a high-quality factor circuit design, leading to reduced efficiency and large component volumes at light loads. To solve the problems, a high-efficiency control strategy using adaptive pulse-width and frequency modulation (APWFM) is proposed. APWFM adjusts the gain by changing the switching frequency and duty cycle simultaneously. When the output power is below the reference value, the switching frequency decreases linearly as the output power decreases, and the duty cycle is simultaneously modulated to achieve constant output voltage, so the switching frequency variation range is smaller than FM. This results in improved light or medium load efficiency in a limited frequency range while keeping a small volume of magnetic components. Also, the proposed control strategy is realized with primary-side regulation (PSR) to eliminate the optocoupler and simplify the control circuit. Experimental results demonstrate a significant improvement in efficiency at medium and light loads compared to FM, and the average efficiency is improved by 5% based on low cost and simple operation.