Comparative evaluation of a Triangular Current Mode (TCM) and Clamp-Switch TCM DC-DC boost converter

A design methodology is presented for a full-bridge Power Factor Corrector (PFC) converter with two control schemes: the well-known Continuous Current Mode (C.C.M) and Triangular Current Mode (T.C.M). The second one is an extension of the Discontinuous Current Mode (D.C.M). The converter is composed of one high frequency leg and one leg switching at the grid frequency and includes the EMC (common and differential mode) filter. This work highlights the impact of the modulation scheme on the design of passive components and on the overall losses. A pareto front in the efficiency (η) vs power density (ρ) domain is derived for both modulation schemes and for natural convection cooling. We show that, when EMC issues are considered, the T.C.M poses more constraints for partial load operation, superseding the full-load design. Finally, it is shown that for non-interleaved converters C.C.M modulation is better than T.C.M modulation, resulting in higher density converters.

This article presents a soft-switched buck converter employing autonomous gate drivers (AGDs) for high-performance power electronic systems. Operating at a 400~V dc-link, representative of electric vehicle (EV) and industrial applications, the converter achieves zero-voltage switching (ZVS) during both turn<sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-on</small> and turn<sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-off</small> through fully analog AGD circuitry and optimized snubber capacitance. The converter operates in triangular current mode (TCM), leveraging the inherent inductor current ripple to enable ZVS without digital control. Experimental results demonstrate reliable soft switching, reduced switching losses, and effective suppression of voltage overshoot under realistic operating conditions. Although validated using a buck converter, the proposed AGD concept is directly applicable to more complex topologies, including three-phase inverters with sinusoidal reference currents, relevant to EV traction drives, renewable energy systems, and industrial converters. This work highlights a scalable, hardware-efficient approach for improving efficiency and performance in next-generation high-voltage power converters.

This paper proposes a hybrid current mode between Triangular current mode (TCM) and Discontinuous current mode (DCM) in order to achieve Zero-voltage switching (ZVS) for a bidirectional buck/boost DC-DC converter. In the proposed Hybrid Discontinuous Current Mode entitled HDCM, the TCM operation is applied during the zero-current interval of DCM. Therefore, both ZVS and the variable current ripple, which result in the high efficiency at wide load range, are achieved. The achievement of ZVS with HDCM is confirmed by a 600-W prototype. Compared to TCM, the Root-Mean-Square current is reduced by 47.2% at most with HDCM, which further contributes to the loss reduction. Moreover, under the condition of the same boost inductor, the efficiency of HDCM at load of 0.2 p.u. is improved by 1.5% compared to TCM.

A significant influence of parasitics is perceived in high voltage low power flyback converters. The sinusoidal resonance between the magnetising inductance and the parasitic capacitance results in apparent deviations in voltage gain unlike the conventional flyback converter. This effect is predominant in case of very lightly loaded converter where the major portion of the input energy is consumed in charging the parasitic capacitances. The paper presents an analytical expression for steady state voltage gain of flyback converter in high voltage low power applications. Insight on sinusoidal resonance between the magnetising inductance and the parasitic capacitances is outlined and the effects of converter operating with fixed frequency is addressed. Profile of converter voltage gain and switch stress with variation in switching frequency is examined from which a range of frequency which offers optimal gain along with zero voltage stress during turn on is observed. A control scheme which deploys variable switching frequency thereby facilitating Zero Voltage Switching is investigated. Analysis of converter employing zero voltage switching scheme is carried out and the analytical equations governing the operation are derived. Simulation model and hardware prototype is built to validate the analytical results.

The use of advanced modulation and control schemes for power converters, such as a Feedback Quantizer and Predictive Control, is widely studied in the literature. This work focuses on improving the closed-loop modulation scheme called Feedback Quantizer, which is applied to a three-phase voltage source inverter. This scheme has the natural behavior of mitigating harmonics at low frequencies, which are detrimental to electrical equipment such as transformers. This modulation scheme also provides good tracking for the voltage reference at the fundamental frequency. On the other hand, the disadvantage of this scheme is that it has a variable switching frequency, creating a harmonic spectrum in frequency dispersion, and it also needs a small sampling time to obtain good results. The proposed scheme to improve the modulation scheme is based on a Discrete Space Vector with virtual vectors to obtain a better approximation of the optimal vectors for use in the algorithm. The proposal improves the conventional scheme at a high sampling time (200 μs), obtaining a THD less than 2% in the load current, decreases the noise created by the conventional scheme, and provides a fixed switching frequency. Experimental tests demonstrate the correct operation of the proposed scheme.

The demand for highly efficient and dynamic electric vehicles (EVs) has increased dramatically. The traction inverter, a pivotal component in an EV powertrain, plays a crucial role. This study is dedicated to designing a traction inverter with focus on achieving high efficiency and elevated power density and mitigating electromagnetic interference (EMI) issues. To realize these objectives, autonomous gate drivers (AGDs) are proposed and designed using LTspice simulation software. The aim is to achieve zero voltage switching (ZVS) at both turn-on and turn-off through the utilization of triangular current mode (TCM) control on the gate driver. The AGDs implement a current modulation scheme by sensing the current and voltage and generating gate-source voltage signals with minimal delays. The implemented current modulation scheme by the AGDs results in an efficiency exceeding 99% for a 10 kW power rating. The sinusoidal output waveforms not only contribute to extending the motor lifespan by mitigating sharp-edge voltages but also bring advantages such as reduced switch stress, decreased EMI, and simplified thermal management.

THIS dissertation addresses the technical challenges associated with the operation and control of high-power modular multilevel converters. To improve the performance of modular multilevel converter (MMC), a generalized three-phase mathematical model with common-mode voltage (CMV) is proposed. By using the proposed mathematical model, the magnitude of circulating currents, capacitors voltage ripple, and the ripple in DC-link current during balanced and unbalanced operating conditions can be minimized. The modulation scheme and switching frequency are directly affected the output power quality and the performance of the converter and control method. In this dissertation, a novel sampled average and space vector modulation scheme is proposed. These modulation schemes are suitable to control the MMC with any number of submodules (without modifications), operates at low switching frequency, minimizes the ripple in output current and voltage harmonic distortion, and reduces the output filter size. For reliable operation of MMC, the voltage balancing among submodules is mandatory. This dissertation proposes a generalized single-stage balancing approach with reduced current sensors to control the MMC. The proposed balancing approach is suitable to implement with both phase-shifted and level-shifted pulse width modulation schemes. With the proposed approach, it is also possible to control the MMC with half-bridge and three level flying capacitor submodules. Also, an improved balancing approach often referred as the dual-stage balancing approach is proposed to minimize the voltage harmonic distortion and device power losses. This dissertation also proposes a direct model predictive control (D-MPC) approach to minimize the ripple in submodule capacitors voltage. To implement D-MPC approach, a discrete-time model of MMC with CMV is proposed. With the use of proposed model, the D-MPC approach does not require a cost function to minimize the circulating currents. The computational complexity is one of the major issues in the implementation of D-MPC approach for MMC. In this dissertation, a novel reduced computational MPC approaches named as dual-stage D-MPC and indirect model predictive control (I-MPC) approach are proposed. These approaches significantly minimize the computational complexity and, improve the voltage and current waveform quality while operating at the low switching frequency. Finally, the simulation and experimental studies are presented to validate the dynamic and steady-state performance of proposed methodologies. Index Terms • Modular Multilevel Converters. • Capacitors Voltage Balancing. • Pulse Width Modulation Schemes. • Circulating Currents. • Capacitors Voltage Ripple • Direct Model Predictive Control. • Dual-Stage Direct Model Predictive Control. • Indirect Model Predictive Control. • Total Harmonic Distortion.

Front end PFC (power factor correction) boost ac-dc converter is an intrinsic part of applications like telecom servers, electric vehicle (EV) charging, and microgrids. In this paper a bridgeless PFC boost rectifier with two dc/dc boost circuits topology is employed to convert universal ac input to a fixed and regulated output dc voltage. High efficiency and power density are key figure-of-merits of boost PFC ac-dc converters. In this converter the conduction losses are reduced owing to the bridgeless topology and the boost diode reverse recovery is eliminated using MOSFETs for synchronous rectification. The converter operates in continuous conduction mode (CCM), at a switching frequency of 500 kHz. At high switching frequency and at CCM, soft-switching is necessary, therefore a passive auxiliary circuit is used to achieve zero voltage switching (ZVS). In order to increase the power density, the boost and the auxiliary inductors are magnetically coupled with a very low coupling coefficient. This coupling reduces the volume of the magnetics, although there is some loss due to the additional circulating current resulting from the coupling, however this loss is not that significant. Although passive auxiliary circuit adds more components, however at 500 kHz switching frequency these passive components do not occupy significant space. The soft-switching improves the efficiency and reduces EMI noise and cooling requirements. The detailed analysis, design and simulation results using PSIM are provided to validate the theoretical claims.

Finite control set model predictive control (FCS‐MPC) has been widely used in the control of grid‐connected converters with the advantages of fast dynamics, multi‐objective control, and easy implement. However, the conventional FCS‐MPC bears with variable switching frequency, high current ripple and computational burden. An improved current model predictive with the cost function‐based modulation scheme (CFM‐MPC) is proposed for a three‐phase three‐level VIENNA rectifier to improve the power quality. First, the mathematical model and voltage vector are given according to the principle of deadbeat control. Then, the voltage vector of different voltage vectors are selected according to the location of the voltage vector reference, and the switching action time of the selected are directly calculated by the inversely proportional with cost function value of the selected vectors. It remains the merits of both the conventional MPC and space vector pulse width modulation schemes to track the optimum voltage vector without increasing the computational burden. Finally, a comparative study with the proposed CFM‐MPC and conventional FCS‐MPC has been conducted to verify the superiority of the proposed scheme. The results show the proposed CFM‐MPC has the advantages of lower power ripple, fixed switching frequency, lower total harmonic distortion and neutral point potential balance.

The hysteresis current controllers (HCC) for grid-connected inverter (GCI) system is a well-known controller for its robustness, fast reference tracking, better dynamics, and easier implementation compared to other controllers. This article proposes a modified double-band HCC (MDBHCC) for single-phase GCI system with LCL -filter. The proposed algorithm implements an unipolar symmetrical pulse width modulation (PWM) strategy for reducing inverter switching losses through a sequential logic, with an adaptive clock. It improves the variation in switching frequency and limits the maximum switching frequency of HCC while enhancing the total harmonic distortion (THD) of the injected current into the grid. In order to alleviate power quality problems, two such MDBHCC schemes, i.e., MDBHCC1 and MDBHCC2, are implemented. Where MDBHCC2 operates at the higher switching frequency with lesser % THD and MDBHCC1 operates at lower switching frequency. Simulation and experimental results are presented with a significant decrease in switching frequency and an improvement in grid current harmonics at both steady-state and dynamic conditions.

This paper proposes a predictive zero-voltage-switching (ZVS) control with improved ZVS time margin and limited variable switching frequency range for a 99% efficient megahertz (MHz) GaN totem-pole power-factor-correction (PFC) rectifier. The conventional ZVS control methods for totem-pole PFC may lead to zero ZVS time margin and ultra-wide switching frequency range. This paper proposes that the synchronous rectifier (SR) turn- off current is a new degree of freedom for the ZVS control. Thus, the proposed cycle-by-cycle predictive ZVS control method controls the SR turn- off currents to extend the ZVS time margin and to reduce the maximum switching frequency. With the proposed ZVS control, the minimum ZVS time margin and a limited maximum switching frequency can be realized in a MHz GaN-based totem-pole PFC. With the improved ZVS time margin, the reliability for realizing ZVS is significantly improved. With the limited maximum frequency and the limited frequency range, the difficulty in high-speed current sensing and digital control is reduced, and the frequency-related loss is also reduced, which is important for improving the light-load efficiency. To accurately extract the current and timing parameters for the proposed ZVS control, an analytical model for the ZVS totem-pole PFC is proposed. The proposed ZVS control and analytical model are applicable over the full input and output voltage range, and over the full load range. In addition, a hybrid current control is proposed and implemented based on the proposed ZVS control. Finally, a 3.2-kW MHz GaN totem-pole PFC prototype is developed and tested with full-range ZVS, minimum ZVS time margin, limited switching frequency range, 99% peak efficiency, and 130-W/in3 power density based on the proposed ZVS control and system control strategy. The realized efficiency, power level, and power density are among the best ever reported for the GaN-based totem-pole PFC.

In single-phase ac/dc applications where reliability and/or power-density are critical, active power decoupling (APD) circuits can be employed to reduce the required capacitance on the dc-link. Various APD circuits have been proposed so far, all with their advantages and disadvantages. However, many confusions still exist in the literature on this topic which is mainly attributed to a lack of unified and comprehensive assessment criteria. In this paper, first the decisive criteria for a modern APD circuit are established, and the buck APD is identified as the current state-of-the-art, based on them. Then the buck-plus-unfolder topology with triangular current mode (TCM) modulation is proposed as an improvement, and a simple, yet solid foundation is introduced to choose the superior decoupling solution at different specifications. The operation equations for the APD with TCM modulation are derived next, and the operation of the proposed solution is demonstrated using a hardware prototype.

Apart from variable switching frequency, a major issue in direct torque controlled (DTC) induction motor drives is the high torque ripple, which can be minimized by incorporating suitable pulsewidth modulation schemes such as space vector pulsewidth modulation (DTC-SVPWM) and duty ratio control DTC. However, the simplicity and robustness of the DTC scheme are compromised due to the high computational complexity and requirement of a number of motor parameters for the control. In this article, a simple and elegant control algorithm for the realisation of the DTC-SVPWM that is less dependent on motor parameters is proposed. The stator flux-linkage space vector angle needed to generate the reference torque for the DTC operation is computed based on the basic torque equation and the reference stator phase voltage needed for the SVPWM is determined in turn in every sampling period. For the modulation, a carrier-based space vector pulsewidth modulation (CSVPWM) scheme is adopted to get low torque ripple at constant switching frequency. The proposed speed control scheme avoids the use of rotor parameters and rotating reference frame transformations. It requires no sector identification and only one PI controller is needed for the speed control. Though the scheme has comparable torque ripple as that of the conventional DTC-SVPWM scheme, it significantly reduces the computational burden. Hardware results on a three-phase, 2 HP, 415 V induction motor are presented to validate the performance of the proposed control scheme.

This article introduces a three-mode variable-frequency zero-voltage switching (ZVS) modulation method for the four-switch buck+boost converter. This method makes this circuit concept well suited for applications, such as wireless power charging of electric vehicles, where this circuit operates as a power buffer between the resonant converter and the battery with the function to implement the required charging profile. Herein, the buck+boost converter operation is subdivided into three operating regions according to the converter static voltage gain, i.e., buck-, buck-boost- and boost-type modes. A ZVS turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> triangular current mode (TCM) control is adopted for buck-type and boost-type modes. In the buck-boost-type mode when the input-to-output voltage gain is close to unit, all the possible modulation cases are studied thoroughly based on the phase shift of the two half bridges in a full switching period. The selection of the most suitable modulation scheme is performed to minimize the rms value of the inductor current while taking into account the simplification of the practical implementation. Closed-form equations are derived, which makes it easy to implement in practice. The proposed strategy is described, analyzed, and finally verified through a 3 kW surface mounted device (SMD) silicon carbide (SiC) <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> -based laboratory prototype with designed input voltage of 300–600 V and the typical output voltage of 400 V class battery. The efficiency from the measured results is remarkably high, i.e., between 99.2% and 99.6% in a power range from 1 to 3 kW. Finally, tests for the operating mode transitions demonstrated the feasibility of the proposed modulation method. The power density of this converter is 4.86 kW/L.

This paper proposes and develops a hybrid QCM/CCM soft-switching scheme for a single-phase PV inverter with two or multiple SiC MOSFETs in parallel. When implemented in a DC-AC converter, conventional soft-switching modulation like critical conduction mode (CRM) suffers from increased condition loss at high load conditions and variable switching frequency. In the proposed modulation technique, a phase-shift modulation scheme is applied to inductor-decoupled parallel half-bridge legs, generating a controllable circulating current flowing through these commutation inductors. Thus, the current of each half-bridge leg is reshaped as quadrilaterals, which enables all the parallel MOSFETs to achieve zero-voltage switching (ZVS). The proposed switched QCM/CCM soft-switching scheme is featured by partial soft-switching, constant switching frequency, seamless and load-dependent mode transition, and high full-power-range efficiency. A 4.4 kW single-phase PV inverter is developed and tested to verify the advantages of the hybrid QCM/CCM operation in power loss reduction and efficiency improvement.