Additional Conduction Loss Research Articles

A VSC-Based Isolated Matrix-Type AC/DC Converter Without Bidirectional Power Switches

In this paper, a three-phase voltage-source converter (VSC) based isolated matrix-type AC/DC converter is proposed for wind energy conversion system (WECS). The line-frequency transformer (LFT) is replaced by the high-frequency transformer (HFT), and there is no need for the intermediate electrolytic capacitors used in conventional two-stage power conversion system. Moreover, the bidirectional switches used for conventional matrix converter (MC) are eliminated in the proposed topology. Consequently, the complicated four-step commutation scheme is avoided and the additional conduction loss caused by serial connection of power switches can be eliminated. The proposed isolated matrix-type AC/DC can be regarded as the dual VSC circuit, where two VSCs alternately work during each switching cycle. Hence, the voltage vectors based space vector modulation (SVM) can be employed and the control schemes for non-isolated VSCs can be used for the proposed converter. For safe operation, the commutation strategy is proposed for the leakage-inductor current of HFT. Both simulations and experiments are conducted to verify the performance of the proposed converter.

Drain-Source Voltage-Controllable Three-Switch Active-Clamp Forward Converter for Wide Input/Output Voltage Applications.

Active-clamp forward converters are applied to various medium-capacity power systems because they have a relatively simple structure and are capable of zero-voltage switching. In particular, there is the advantage that a stable output voltage can be obtained by controlling the duty ratio of the power semiconductor switch even in applications with wide input and output voltage ranges. However, the voltage stress on the power semiconductor switches due to the application of active clamp is higher than the input voltage, especially as the duty ratio increases. A three-switch active-clamp forward converter is proposed, which can overcome such shortcomings and can reduce the voltage stress of the power semiconductor switches, but it causes an increase in the DC bias of the magnetizing current and the additional conduction and switching losses. Therefore, in this paper, a voltage-stress-controllable three-switch active-clamp forward converter that can utilize both advantages of the conventional active-clamp forward converter and three-switch active clamp forward converter is proposed and verified through a prototype for 800 W battery charger.

Wide Input Voltage Range Operation of the Series Resonant DC-DC Converter with Bridgeless Boost Rectifier

The series resonant DC-DC converter (SRC) can regulate the input voltage in a wide range at a fixed switching frequency. In this work, the bridgeless rectifier, which is utilized intensively in the applications of the power factor correction, has been integrated into the SRC as a voltage step-up cell at the output-side of the SRC. It is shown that the conventional overlapping pulse-width modulation (PWM) of the two metal oxide semiconductor field-effect transistors MOSFETs in this rectification cell limits the input voltage regulation range of the converter due to excessive power losses in abnormal operating conditions. The abnormal operating conditions occur when the instantaneous voltage across the resonant capacitor is larger than the secondary voltage of the isolation transformer. This happens at high values of the DC voltage gain, i.e., low input voltages and high currents, which causes the resonant current to flow in the reverse direction in the same half-cycle through a parasitic path formed by overlapping PWM of the rectifier MOSFETs. The abnormal operation results in additional conduction loss in the converter as the MOSFETs of the bridgeless boost rectifier turn on at high current at the beginning of each half of the switching period. Accordingly, the overall efficiency of the converter significantly deteriorates. This paper proposes the hybrid PWM aiming to improve the efficiency of the SRC with a bridgeless boost rectifier in a wide input voltage regulation range. The converter swaps between the overlapping and the proposed short-pulse PWM schemes to drive the MOSFETs in the bridgeless boost rectifier. The transition between the two PWM schemes is defined according to the boundary condition that relies upon the operating point of the converter power and the input voltage. The proposed hybrid PWM scheme is analyzed and compared to the overlapping PWM at different levels of the input voltage and the load power. A 300 W prototype was studied in the laboratory to show the feasibility of the proposed hybrid PWM scheme with the closed-loop control system to switch between the two PWM schemes.

Adaptive Hysteresis Current Based ZVS Modulation and Voltage Gain Compensation for High-Frequency Three-Phase Converters

This article proposed a systematic approach for the control of three-phase bidirectional zero-voltage switching (ZVS) converters. Combining the adaptive hysteresis-band current control and turn- on delay modifications, ZVS conditions are realized in full line-cycle in all loading conditions like active power, reactive power, light load, and heavy load. The soft-switching resonant period is carefully analyzed, and the current band is designed accordingly, which minimized the additional conduction loss. Meanwhile, a zero-sequence voltage injection control is included in the approach, which compensates the voltage gain by 15% and narrows down the switching frequency variation range. The hardware design approach is also provided including the LCL filter design and a low-cost high-bandwidth high-accuracy current sensor design. A highly integrated 5-kW silicon carbide implemented three-phase ZVS converter prototype with printed circuit board integrated inductors and customized current sensors is designed. All the control is implemented in a single microcontroller unit, which achieves a high electromagnetic compatibility. The designed prototype achieves a total power density of 5.5 kW/L and a peak efficiency of 98.5%. All the analysis and the proposed control approach are experimentally verified on the designed prototype.

An Interleaved Totem-Pole Bridgeless Boost PFC Converter with Soft-Switching Capability Adopting Phase-Shifting Control

This paper proposes an interleaved totem-pole bridgeless boost power factor correction (PFC) converter with soft-switching capability. In the proposed converter, an inductor is added compared with the conventional interleaved totem-pole bridgeless boost PFC converter. The added inductor is located between two PFC converter units, and by utilizing the energy of the added inductor, all switches can achieve the zero voltage switching (ZVS). In addition, by applying the phase-shifting control between two PFC converter units, the proposed converter can control the magnitude of the current flowing on the added inductor as an optimal value. Therefore, the proposed converter can achieve the ZVS operation, while minimizing the additional conduction loss and core loss of the added inductor. As a result, the proposed converter can achieve the high efficiency. The feasibility of the proposed converter is confirmed with 180–264 Vrms input and 1.6 kW (400 V/4 A) output prototype.

Modular multilevel converter based on arm transfer to clear dc fault

Modular multilevel converter (MMC) has great prospects in voltage source converter-based high-voltage direct current (HVDC) transmission. Although the typical half-bridge MMC can bring huge economic benefits, it is unable to clear dc fault. An MMC based on arm transfer (AT-MMC) and corresponding timing control are presented to effectively solve this drawback. Compared with the half-bridge MMC, the AT-MMC adds the arm-transferring branch to the each phase unit of the converter and adds the current-breaking branch and the energy-absorbing branch to the dc line. Through these branches cooperating with each other, the fault current is cleared. Referring to the half-bridge MMC with the same voltage grade, the AT-MMC has a good economy and its additional device cost is low and additional conduction loss is very small. A model of 51-level MMC–HVDC system is built in RT-LAB OP5600 to verify the effectiveness of the proposed solution.

A Power Quality Improved EV Charger With Bridgeless Cuk Converter

An improved bridgeless (BL) Cuk converter-based electric vehicle (EV) battery charger with high power factor and increased efficiency is designed and developed in this paper. It provides low cost and high-power-density-based charging solution for the EV. This charger incorporates less number of devices operating over one switching cycle, which reduces the additional conduction loss incurred by a diode bridge rectifier of the conventional charger. Hence, it improves the charger's efficiency. The added advantage of the proposed topology is that the unwanted capacitive coupling loop is removed, as well as the unwanted conduction through the body diode of the inactive switch in the previously developed BL Cuk converter is avoided. This significantly improves the charger's efficiency. For the constant current and constant voltage charging, the commands are synchronized by a flyback converter. The proposed charger draws a sinusoidal current from ac mains and the total harmonic distortion in the supply current is reduced to the limits specified by the IEC 61000-3-2 guidelines. The improved efficiency and power quality indices of the proposed charger are investigated to demonstrate its satisfactory charging operation at all operating conditions.

Conduction Loss Analysis According to Variation of Resonant Parameters in a Zero-Current Switching Boost Converter

In this paper, conduction loss analysis of a zero-current switching (ZCS) boost converter with variations of the resonant parameters in the auxiliary circuit is performed. Generally, the auxiliary circuit for soft switching of the main device generates additional losses. An improperly designed auxiliary circuit part cannot improve the efficiency of the overall system and, even make it worse. For this reason, an auxiliary resonant circuit should be designed based on the selected parameters through accurate and detailed analysis. First, a design procedure considering practical aspects to implement ZCS is proposed in this paper. Equations associated with additional conduction losses caused by resonant parameters are proposed through a mathematical analysis. The conduction losses at various design values of the resonance parameters are calculated and compared through the proposed equations. To verify the proposed analysis, the experimental results about additional conduction loss analysis with the variations in the resonant parameters of the auxiliary circuit for soft switching implementation are provided.

Design and simulation of bi-directional DC-DC converter with dual switch forward snubber

A novel isolated bi-directional buck-boost converter is presented for energy storage application. Isolated boost bi-directional DC-DC converters are required to meet the wide voltage variation demand. The conventional isolated boost converters have some auxiliary circuits to provide an auxiliary path for mismatch current between source inductance and leakage inductance of the transformer. The dual switch forward snubber circuit is adopted as auxiliary circuits along with dual active bridge (DAB) converter in the proposed converter. The proposed converter has distinct advantages like zero voltage switching starting (ZVS), no voltage stress on main switches, no additional conduction losses and improved efficiency as compared to RCD snubber-based converter system. The wide voltage variation in output side for 45V to 320V bi-directional DC-DC converter has been simulated with PSIM. The charging mode and discharging mode with energy storing mode has been explained in detail. The simulation results show the effective performance of proposed converter system. The loss comparison has been shown between RCD snubberbased converter and dual switch forward snubber which proves that dual switch forward snubber has high efficiency compared to RCD snubber circuit.

Design and simulation of bi-directional DC-DC converter with dual switch forward snubber

A novel isolated bi-directional buck-boost converter is presented for energy storage application. Isolated boost bi-directional DC-DC converters are required to meet the wide voltage variation demand. The conventional isolated boost converters have some auxiliary circuits to provide an auxiliary path for mismatch current between source inductance and leakage inductance of the transformer. The dual switch forward snubber circuit is adopted as auxiliary circuits along with dual active bridge (DAB) converter in the proposed converter. The proposed converter has distinct advantages like zero voltage switching starting (ZVS), no voltage stress on main switches, no additional conduction losses and improved efficiency as compared to RCD snubber-based converter system. The wide voltage variation in output side for 45V to 320V bi-directional DC-DC converter has been simulated with PSIM. The charging mode and discharging mode with energy storing mode has been explained in detail. The simulation results show the effective performance of proposed converter system. The loss comparison has been shown between RCD snubberbased converter and dual switch forward snubber which proves that dual switch forward snubber has high efficiency compared to RCD snubber circuit.

A Modular Multilevel Converter Integrated With DC Circuit Breaker

The direct-current (dc) fault-clearance capability of the modular multilevel converter (MMC) is a key issue for overhead line applications of voltage source converter-based high-voltage dc (VSC-HVDC) transmission systems. An MMC integrated with a dc circuit breaker (IDCB-MMC) is proposed to provide a cost-effective DC fault clearance and isolation solution. A mechanical switch (MS) and a load commutation switch are connected in series as the main branch of the dc circuit breaker. DC fault currents can be forced to transfer to converter- and line-side energy absorbing branches when submodule bypass protection and dc circuit breaker interrupting operations are coordinated. Therefore, the bulky and costly solid-state branch that uses numerous semiconductor devices and surge arresters can be eliminated. The dc fault clearance and isolation capability of the IDCB-MMC were verified through the simulation results for one pole of a 1000 MW/±320 kV VSC-HVDC system. Compared with an MMC that uses half-bridge SMs, the IDCB-MMC only requires few additional capacitors and switching devices and a simple MS, thereby resulting in several advantages, such as low cost, footprint requirements, and additional conduction losses.

A Bridgeless Dual Boost Rectifier With Soft-Switching Capability and Minimized Additional Conduction Loss

A bridgeless dual boost rectifier is proposed to achieve a soft switching for power factor correction circuit. Based on the conventional bridgeless dual boost rectifier, an auxiliary circuit is employed in the proposed converter to perform zero-voltage switching of the main switches and zero-current switching of the auxiliary switches. As a result, switching losses can be significantly reduced. In addition, the design guideline for the optimized turn-on time of the auxiliary switches is presented to minimize the additional conduction loss in the auxiliary circuit. The validity of the proposed converter is confirmed by the experimental results of a prototype converter with 100–240 $V_{{\text{AC}}}$ universal-line input and 800-W (400 V/2 A) output.

A unified model of density limit in fusion plasmas

In this work we identify by analytical and numerical means the conditions for the existence of a magnetic and thermal equilibrium of a cylindrical plasma, in the presence of Ohmic and/or additional power sources, heat conduction and radiation losses by light impurities. The boundary defining the solutions’ space having realistic temperature profile with small edge value takes mathematically the form of a density limit (DL). Compared to previous similar analyses the present work benefits from dealing with a more accurate set of equations. This refinement is elementary, but decisive, since it discloses a tenuous dependence of the DL on the thermal transport for configurations with an applied electric field. Thanks to this property, the DL scaling law is recovered almost identical for two largely different devices such as the ohmic tokamak and the reversed field pinch. In particular, they have in common a Greenwald scaling, linearly depending on the plasma current, quantitatively consistent with experimental results. In the tokamak case the DL dependence on any additional heating approximately follows a 0.5 power law, which is compatible with L-mode experiments. For a purely externally heated configuration, taken as a cylindrical approximation of the stellarator, the DL dependence on transport is found stronger. By adopting suitable transport models, DL takes on a Sudo-like form, in fair agreement with LHD experiments. Overall, the model provides a good zeroth-order quantitative description of the DL, applicable to widely different configurations.

An Interleaved Half-Bridge Three-Port Converter With Enhanced Power Transfer Capability Using Three-Leg Rectifier for Renewable Energy Applications

In this paper, an interleaved half-bridge (IHB) three-port converter (TPC) is proposed for a renewable power system. The IHB-TPC is used to interface three power ports: 1) one source port; 2) one battery port; and 3) one isolated load port. The proposed IHB-TPC is derived by integrating two half-bridge TPC modules. A parallel configuration is adopted for the primary side of the two half-bridge modules, while a parallel–series configuration is adopted for the secondary side of the two modules. The power can be transferred from the source and the battery to the load within the whole switching cycle with the proposed IHB-TPC. It means there are no additional conduction losses caused by the circulating current or the free-wheeling operation stage. Hence, the voltage gain can be extended, and the output filter can be reduced. Zero-voltage switching is realized for all the four main switches to reduce the switching losses. Two of the three ports can be tightly regulated by adopting pulsewidth modulation plus phase-shift control, while the third port is left unregulated to maintain power balance for the system. The operation principles and the performances of the proposed converter are analyzed in detail. The experimental results are given to verify the feasibility and the effectiveness of the proposed converter.

Analysis, design and performance of a zero‐current‐switching pulse‐width‐modulation interleaved boost dc/dc converter

A novel interleaved boost dc/dc converter with zero-current-switching pulse-width-modulation (ZCS-PWM) characteristic using a simple ZCS-PWM auxiliary circuit is presented in this paper. The proposed converter combines the conventional PWM technique and ZCS technique to promote the circuit performance. The proposed converter uses dual boost converters which are operated at interleaved mode to increase the output power level. Thus, the proposed converter does not only decreases the current stress on main circuit devices but reduces the input ripple current and output capacitor size. Because the proposed converter establishes a common ZCS-PWM auxiliary circuit on used dual boost converters, it can greatly reduce the size and cost. And, it can provide the ZCS characteristic on main switches and auxiliary switches with a wide range of load to improve the problem of switching losses and EMI. Thus, its topology is simple and compact. Besides operating at constant frequency and reducing commutation losses, the proposed converter has no additional current stress and conduction loss in the main switch compared with the conventional interleaved boost dc/dc converter. The principle of operation, theoretical analysis and experimental results of the proposed boost converter, rated 1 kW and operating at 40 kHz, are provided in this paper to verify the performance of this new family of converters.

Integrated Inverter/Converter Circuit and Control Technique of Motor Drives With Dual-Mode Control for EV/HEV Applications

A new integrated circuit for motor drives with dual-mode control for EV/HEV applications is proposed. The proposed integrated circuit allows the permanent magnet synchronous motor to operate in motor mode or acts as boost inductors of the boost converter, and thereby boosting the output torque coupled to the same transmission system or dc-link voltage of the inverter connected to the output of the integrated circuit. In motor mode, the proposed integrated circuit acts as an inverter and it becomes a boost-type boost converter, while using the motor windings as the boost inductors to boost the converter output voltage. Moreover, a new control technique for the proposed integrated circuit under boost converter mode is proposed to increase the efficiency. The proposed control technique is to use interleaved control to significantly reduce the current ripple and thereby reducing the losses and thermal stress under heavy-load condition. In contrast, single-phase control is used for not invoking additional switching and conduction losses under light-load condition. Experimental results derived from digital-controlled 3-kW inverter/converter using digital signal processing show the voltage boost ratio can go up to 600 W to 3 kW. And the efficiency is 93.83% under full-load condition while keeping the motor temperature at the atmosphere level. These results fully confirm the claimed merits for the proposed integrated circuit.

Family of ZC-ZVS converters with wide voltage range for renewable energy systems

This paper presents a new family of soft switched pulse-width modulated (PWM) quadratic converters which are suitable for systems with a wide fluctuating DC input voltage range, e.g. photovoltaic (PV) and fuel cells systems. In the proposed scheme, an auxiliary circuit is added to the conventional quadratic converters and used to achieve soft-switching for both the active and passive switches while not incurring any additional losses due to the unique location of the snubber capacitor and inductor in the auxiliary circuit. The active switches in the new converters are turned-on with zero-current and zero-voltage switching (ZC-ZVS) and turned-off with zero-voltage switching (ZVS). The diodes commutate softly and the reverse-recovery problems are greatly alleviated. Besides operating at a constant frequency and with reduced commutation losses, the proposed converters are subjected to minimum voltage and current stresses and have output characteristics similar to their hard-switching PWM quadratic converters counterparts. As a result, there are no additional conduction losses in the semiconductor devices. A quadratic boost converter adopting this technique is presented as an example. The principle of operation, theoretical analysis, design equations, simulation and experimental results of the new ZC-ZVS quadratic boost converter are provided to verify the performance of this new family of converters.

Resonant Energy-Recovery Circuit With Asymmetric Voltage Excitation and No Circulating Current for Plasma Display Panel

A sustain driver with a resonant energy recovery circuit is proposed based on asymmetric voltage excitation for a complete resonant commutation of panel capacitor in plasma display panels (PDPs). The developed driver configures the sustain circuit and the resonant circuit in such a way that the resonant network is energized by higher voltage level and lower level than half sustain voltage in charging and discharging the panel capacitor, respectively. This proposed operation can guarantee perfect commutation of the panel capacitor voltage, zero-voltage switching of the sustain switches, and reduced electromagnetic interference due to no surge current. Furthermore, the developed sustain circuit is designed to eliminate the conduction losses and the current stresses on the circuit and the switching devices caused by the reverse recovery operation of the diodes. The energy trapped in the resonant inductors due to the inevitable diode reverse-recovery phenomena, which generates additional conduction losses and thermal problem with circulating currents, is recovered in the proposed circuit.

Simplified loss analysis and comparison of full-bridge, full-range-ZVS DC-DC converters

The loss of zero-voltage-switching (ZVS) of active switches has been a serious limitation of full-bridge (FBZVS) converters. Many techniques have been proposed in the past to extend the range of ZVS operation over the wider and also the full range of operation. However, in these techniques ZVS is achieved at the expense of additional conduction loss in active switches and losses in the auxiliary components. In this paper, the analysis for the additional losses in various full-range FBZVS DC-DC converters and their comparative evaluation is reported. Closed form expressions are derived for average value of device currents and losses. The loss curves for various topologies are plotted and compared. The analytical results are found to be consistent with the experimental efficiency tests performed on 500 W, 100 kHz prototype. It is concluded that a recently proposed new topology has the least penalty of additional losses.

Full ZVS-Range Transient Current Buildup Half-Bridge Converter With Different ZVS Operations to Load Variation

A full zero voltage switching (ZVS) range transient current buildup half-bridge converter is proposed. The proposed converter controls the secondary synchronous switches to build up the current for the ZVS operation. In addition, the blocking capacitor in the secondary side of the transformer is used to make the different current buildups and different ZVS operations with the load variation. Furthermore, it eliminates the DC offset of the magnetizing current. Therefore, the considerably effective ZVS characteristics can be ensured in the full-load ranges without any additional conduction losses.