Wide Input Voltage Variation Research Articles

Highly-Efficient and Cost-Effective Ripple-Free Resonant NPC DC–DC Converter

This article presents highly-efficient and inexpensive ripple-free resonant neutral-point-clamped (NPC) dc/dc converter that does not use extra inductors. By using the push-pull transformer itself, with the primary-side switching modulation fixed at 0.5, the proposed converter accomplishes theoretically zero input-current ripple. Because of the resonant NPC cell, the circuit does not experience instantaneous reactive current flow regardless of wide input voltage variation. The resonant NPC structure much reduces the voltage stress at the turn-off instant; this aspect enables use of inexpensive low-voltage-rated active power components. Therefore, the proposed converter is inexpensive, highly efficient, and has high power density. A 1-kW experimental prototype was implemented and it was tested to validate the superior properties of the proposed converter.

New PWM Strategy to Enable Dual-Mode Operation Capability in Common-Grounded Transformerless Inverters

A novel pulsewidth modulation (PWM) technique has been presented in this article, which enables the converter to operate in the conventional (boost) mode as well as in the buck mode (proposed). The proposed buck PWM method significantly reduces the current stresses of the components compared to the boost mode. Using this combined modulation technique, a dual-mode operation of such a class of inverters is demonstrated to accommodate a wide input voltage variation while maintaining the regulation of the output ac voltage. The proposed modulation technique is simple to implement and has been implemented in some of the conventional Type-I and Type-II inverters to demonstrate a very wide input voltage range (200–400 V dc), while keeping a fixed output voltage of 110 V ac rms. The theoretical analysis, key operating circuit, and waveforms are presented along with the thermal profile of various switches. Experimental results show that Type-I and Type-II inverters rated at 500 VA have around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$95.5~\pm ~1$ </tex-math></inline-formula> % efficiency for a wide load range with a peak efficiency of 97.3% in buck * invert mode for Type-I and 95.5% for Type-II inverters.

A non-isolated MIC for PV application with wide input voltage range

ABSTRACT Photovoltaic (PV) systems are widely recognised as one of the most essential renewable energy sources for meeting future energy demands. The use of various multi-input DC–DC converters (MICs) to interface PV systems for output voltage regulation has been reported in the literature. PVs have inherent limitations, such as being extremely sensitive to changes in atmospheric conditions and human design/installation errors. Therefore, output voltage regulation suffers because of wide input voltage variations which have been ignored. In this regard, a novel MIC topology is proposed in this paper and it can operate under wide input voltage variation in buck, boost, and buck-boost modes of operation to achieve desired output voltage. The proposed topology is capable to integrate multiple energy sources and it offers an individual or simultaneous operation of the connected energy sources. Further, it also has additional features including high voltage gain, modularity, and control flexibility. The steady-state and thermal analysis have been presented, as well as a comparison with the state-of-the-art literature to prove the suitability of the proposed topology for PV application. The proposed MIC topology has been validated experimentally with wide input voltage variation.

Enhanced Performance of On-board EV Battery Charger with Universal Power Supply

This paper is intended to provide enhanced features of onboard EV battery chargers in terms of improved power quality feature, reduced voltage stress, reduced filter size, high efficiency and fast dynamic response for universal input voltage range (85–265 V). The proposed configuration comprises of three-level quadratic converter suitable to provide high voltage gain. The detailed operation, analysis and control scheme of the proposed converter rated for 3.2 kW, 400 V are studied under simulation and hardware in a loop environment. The on-board charger performances are assessed by charging a 40 Ah lithium ion EV battery under different charging modes. The state of charge of battery decides converter operating mode i.e. constant current and constant voltage mode to charge the battery. Enhancement in the onboard charger is observed in both operating modes tested for wide variation in supply voltages. The results reveal that the operation of converter depicts unity power factor operation, improvement in supply current harmonics and controlling output voltage/current. Under both operating modes, the proposed charger draws sinusoidal supply current from ac mains and its THD is reduced to specified limit prescribed by IEC-61000-3-2. Furthermore, the charger performance is also investigated for EV battery charging operation at wide input voltage variations and found satisfactory.

Optimal Control of Semi-Dual Active Bridge DC/DC Converter With Wide Voltage Gain in a Fast-Charging Station With Battery Energy Storage

Ultrawide voltage regulation is required in dc/dc converters interfacing battery energy storage systems (BESSs) and electric vehicle (EV) batteries in dc fast-charging stations with energy storage. Attaining high efficiency of this converter can be challenging due to the wide variation of input and output voltage yet is important due to the high power transfer. This article proposes a novel control strategy for the semi-dual active bridge (DAB) converter to achieve wide voltage gain while increasing the efficiency at operational points with high input voltage and low output voltage, which is a commonly occurring scenario when the BESS is fully charged, and the EV battery is at low charge. Furthermore, this article also provides an algorithm to determine the required phase shift in real time for any operating point, eliminating the need to devise the control trajectory offline. A 550-V, 10-kW experimental prototype is built and tested to validate the proposed control strategy. With a 25-A constant charging current, the prototype shows that the proposed control strategy can improve efficiency by up to 3.5% compared to the well-known dual phase shift control at operating points with high input voltage (450–550 V) and low output voltage (150–275 V), with a peak efficiency of 97.6%.

Three Winding Coupled Inductor-Based Dual Active Bridge DC-DC Converter With Full Load Range ZVS Under Wide Voltage Range

In this article, a three winding coupled inductor-based dual active bridge (TWCI DAB) dc-dc converter is proposed. Similar to the current-fed DAB converter, the proposed TWCI DAB has small input current ripple and wide input voltage range. In addition, the zero-voltage switching (ZVS) of all switches in the full load range under wide input voltage variation can be realized. With the magnetic integration structure, the size of the total magnetics can be reduced, and the efficiency is also increased compared with the discrete magnetic case. To better analyze the working principle of the three winding coupled inductor, a general analysis method based on magnetic reluctance model is first introduced to obtain the expressions of high frequency current. Furthermore, ZVS analysis and inductor design to obtain low inductor root mean square (rms) current and full load range ZVS based on the ZVS conditions, maximum power transfer and rms current are presented. Finally, the validity of the proposed topology and design are verified by experimental results from a 1-kW laboratory prototype.

A Family of Interleaved High Step-Up DC–DC Converters by Integrating a Voltage Multiplier and an Active Clamp Circuits

A family of interleaved current-fed high step-up dc–dc converters are introduced and analyzed here by combining a voltage multiplier and an active clamp circuit for high-voltage high-power applications. Low input currents and output voltages ripples values and high voltage-gains characteristics of these converters make them suitable for lots of dc–dc applications. All power devices operate entirely under soft switching conditions, even when wide load and input voltage variations are applied. Thus, they can be designed at high-switching frequencies to reduce passive components sizes to achieve high-power density, one of the main targets of the power electronics researches. Also, their input and output ports common ground simplifies the gate-drives and control circuits. To verify the given analyses and simulations, a 120–320 V to 1 kV, 50–1300 W three-stage two-leg prototype converter has been implemented at 100 kHz. Based on the experimental results, maximum efficiency of 96.5% is achieved.

A High Step-Up Interleaved Current-Fed Resonant Converter for High-Voltage Applications

A current-fed LLC resonant converter is proposed for high-voltage and high-power applications. Here, a two-phase interleaved structure is used in the input stage under the continuous conduction mode (CCM) to effectively reduce the input current and output voltage ripple values and the input filter and the output capacitors volumes. Due to the expandable structure and high voltage gain, the proposed configuration is suitable for high voltage applications since low voltage stresses are applied across its components. In fact, voltage stresses across the power semiconductors, i.e., MOSFETs and output diodes, along with the output capacitors, are almost one-third of the output voltage in the implemented three-stage configuration of the proposed converter. Here, the switching frequency is chosen close to, but less than, the converter series resonant frequency to reduce its different components’ current stresses and perform soft-switching operation for all power devices under wide input voltage and output power variations. Therefore, conduction and switching losses, and EMI noises are effectively reduced. Consequently, efficiency is improved and high-frequency operation is possible, which reduces the volume of passive components to achieve high-power density. The given topology is thoroughly analyzed mathematically. Also, a 1 kW prototype converter has been implemented to validate the given simulations and analyses. Here, wide input voltage (100 V-200 V) and output power (100 W-1000 W) variations are applied, and an asymmetric pulse width modulation (APWM) technique is used at 143 kHz switching frequency to regulate the output voltage at 1 kV. The obtained maximum efficiency value is 95.3%.

A Dual-Transformer Based Hybrid Semi-Dual Active Bridge Converter for Wide Voltage Range Applications Utilizing Simple Segmented Control

A high switching frequency isolated voltage-fed dual-transformer-based hybrid semidual active bridge converter is introduced in this article for unidirectional power flow and wide voltage range applications. The converter embraces the full-bridge and half-bridge properties under varying operating conditions to improve efficiency. Five appropriate working patterns are elaborated, including ideal output power derivation, current stress analysis, working voltage matching, output power distribution, and soft switching features. Afterward, a simple segmented control strategy is adopted in accordance with the analysis results. The zero voltage switching of all switches is achieved by introducing the magnetic current and suitable drive logic. Compared with the existing works, the proposed converter has outstanding merits in terms of reduced conduction loss, switching loss, and peak current of ac inductor, resulting in high conversion efficiency. Hence, the converter is more suitable for cases with wide and frequent input voltage variations. Eventually, the effectiveness of the converter and the control strategy is verified by a 1.0-kW prototype.

A Novel AC/DC Converter Based on Stacked Boost Circuit and Dual-Mode LLC Circuit

In this article, an ac/dc converter based on the stacked boost circuit and dual-mode LLC circuit is proposed. In the power factor correction (PFC) part, two boost circuits are stacked to halve the input voltage and the inductor can be shared. The stacked boost circuit can achieve PFC and soft-switching characteristics with open-loop control with the complementary driving signal. In the dc/dc part, a dual-mode LLC circuit is adopted based on two stacked half-bridge structure. The proposed ac/dc converter can be utilized in wide input voltage variation conditions. A prototype is proposed in the laboratory and the experimental results verify the feasibility of the proposed converter.

An Active-Clamp Forward Inverter Featuring Soft Switching and Electrical Isolation

Traditional photovoltaic (PV) grid-connection inverters with sinusoidal pulse-width modulation (SPWM) control suffer the problem of buck-typed conversion. Additional line-frequency transformers or boost converters are required to step-up output voltage, leading to low system efficiency and high circuit complexity. Therefore, many flyback inverters with electrical isolation have been proposed by adopting a flyback converter to generate a rectified sine wave, and then connecting with a bridge unfolder to control polarity. However, all energy of a flyback inverter must be temporarily stored in the magnetizing inductor of transformer so that the efficiency and the out power are limited. This paper presents a high-efficiency active-clamp forward inverter with the features of zero-voltage switching (ZVS) and electrical isolation. The proposed inverter circuit is formed by adopting a forward converter to generate a rectified sine wave, and combining with the active-clamp circuit to reset the residual magnetic flux of the transformer. Due to the boost capability of the transformer, this inverter is suitable for the PV grid-connection power systems with wide input-voltage variation. The operation principles at steady-state are analyzed, and the mathematical equations for circuit design are conducted. Finally, a laboratory prototype is built as an illustration example according to proper analysis and design. Based on the experimental results, the feasibility and satisfactory performance of the proposed inverter circuit are verified.

Extension of Zero Voltage Switching Capability for CLLC Resonant Converter

TheCLLC resonant converter has been widely used to obtaina high power conversion efficiency with sinusoidal current waveforms and a soft switching capability. However, it has a limited voltage gain range according to the input voltage variation. The current-fed structure canbe one solution to extend the voltage gain range for the wide input voltage variation, butit has a limited zero voltage switching (ZVS) range. In this paper, the current-fed CLLC resonant converter with additional inductance is proposed to extend the ZVS range. The operational principle is analyzed to design the additional inductance for obtaining the extended ZVS range. The design methodology of the additional inductance is proposed to maximize the ZVS capability for the entire load range. The performance of the proposed method is verified with a 20 W prototype converter.

A 10 kW ZVS Integrated Boost Dual Three-Phase Bridge DC–DC Resonant Converter for a Linear Generator-Based Wave-Energy System: Design and Simulation

The design and performance analysis of a 10 kW three-phase DC–DC LCL-type resonant converter having a built-in boost function were carried out. This high-power converter is proposed for its application in grid-interfacing a linear generator (LG)-based wave-energy system. Fixed-frequency control is used, and the converter was designed to operate with a lagging power factor. It is shown that all switches turn on with zero-voltage switching (ZVS) for wide input voltage and load variations. This results in reduced switching losses and stresses, which is very important in large-power applications. The performance of the converter was studied through PSIM simulation software. Theoretical and simulation results are presented for comparison. Power-loss break-down analysis of the designed converter was carried out and the summary of results is presented.

Disturbance Rejection Control Method of Double-Switch Buck-Boost Converter Using Combined Control Strategy

Since it has strong ability to realize a conversion to adapt to a wide variation of input voltage, the double-switch buck-boost (DSBB) converter is usually employed as a front-end converter in two-stage power converter systems, where conversion efficiency is always highly valued. Because there is only one switch in the Pulse Width Modulation (PWM) state in the buck or boost work mode, the combined control scheme was investigated for its advantages in inductor average current and conversion efficiency. However, in this method, the operation mode should be determined by additional logic according to the change of input voltage. Moreover, different control systems should be designed for different operation modes to guarantee dynamic control performance and smooth transition between different work modes. To address these issues, the linear active disturbance rejection control (LADRC) method is introduced to develop an inner current control loop in this paper. In this method, the model deviations in different work modes are considered as a generalized disturbance, and a unified current control plant can be derived for current controller design. Furthermore, the duty cycle limitations in practice are considered, an additional mode for transitional operation is produced, and the corresponding control scheme is also developed. Simulation and experimental test results are provided to validate the correctness and effectiveness of the proposed control scheme.

Analysis and Control of Input-Parallel Output-Series Based Combined DC/DC Converter With Modified Connection in Output Filter Circuit

Input-parallel output-series (IPOS)-based combined converter is usually used in the situation with low input voltage and high output voltage to satisfy the requirements in switch voltage stress reduction and power expansion. In such a system, the voltage balance of filter capacitor in the output side or current sharing in the input side usually used to guarantee the control performance of the conversion system. In this paper, a phase-shifted full bridge (PSFB)-based IPOS converter with modified connection of output filter circuit used for the wide variation of input voltage is proposed, which is beneficial to reduce ripple current of filter inductor significantly. A control scheme using the same phase shifting for the two different modules of this IPOS converter is detailedly investigated with both steady state and small signal model-based analysis, it manifests that special voltage balance and current sharing control scheme are not necessary for IPOS system under the common phase shifting control method. And the small signal transfer functions of this topology used for dual loop control system design are also developed. The simulation and experiment results are presented to validate the analysis and control scheme.

Design and Analysis of Triplen Controlled Resonant Converter for Renewable Sources to Interface DC Micro Grid

This paper presents a triplen controller for a dc–dc resonant converter, which provides excellent load voltage regulation with respect to wide variations in input voltage from renewable sources in a dc micro grid. The control provides enhanced converter efficiency and soft switching of all the switches from rated load to very light load. In the proposed control, duty cycle modulation, switching frequency modulation, and phase shift modulation between active bridges are simultaneously varied in order to maintain constant dc voltage. The two control variables viz., switching frequency and duty ratio are simultaneously adjusted keeping phase shift fixed, in order to regulate voltage with respect to load variations and increase in the input voltage. Whereas, the third control variable, i.e., phase shift regulates output voltage when input from renewable sources is reduced, by keeping frequency and duty ratio fixed. The three control variables provide the greater degree of freedom. The experimental and simulation results of the programmable triplen control are presented for a resonant converter operating from the rated load of 3 kW to 5% of rated load 0.15 kW. The proposed control also tested for the input voltage range of 180–260 V (i.e., 220 V, ± 18% tolerance) in order to validate the functionality of the proposed control.

Step-Down Impedance Control Network Resonant DC–DC Converter Utilizing an Enhanced Phase-Shift Control for Wide-Input-Range Operation

This paper introduces an isolated step-down impedance control network (ICN) resonant dc–dc converter that utilizes enhanced inverter and rectifier phase-shifts to achieve both soft switching and output voltage regulation. Compared to previously presented ICN converters, which utilize burst-mode control to achieve output voltage regulation, this ICN converter with the proposed enhanced phase-shift control has dramatically reduced output capacitance requirement. The avoidance of burst-mode control also simplifies the design of the converter's input electromagnetic interference filter, reduces switch stresses due to overshoots during repeated startup transitions, and improves converter efficiency by eliminating startup and shutdown losses as well as by reducing conduction losses when backing off in power. A closed-loop control architecture for the ICN converter operated under enhanced phase-shift control is also proposed, wherein state-feedback control is incorporated to guarantee stability and achieve good dynamic performance across wide variations in input voltage and output power. A prototype 1-MHz, 120-W step-down ICN converter designed for an input voltage range of 18–75 V, an output voltage of 12 V, and a 10:1 output power range is built and tested with both burst-mode control and the proposed enhanced phase-shift control. When operated with enhanced phase-shift control, the prototype ICN converter achieves a peak efficiency of 95.7% and maintains full-power efficiency above 91.7% across its 4:1 input voltage range. Compared to when operated under burst-mode control, the ICN converter with enhanced phase-shift control reduces converter losses by up to 30% and reduces the output capacitance requirement by two orders of magnitude. The prototype ICN converter is also operated under closed-loop control using a digitally implemented controller based on the proposed architecture, and is shown to successfully regulate its output voltage in the face of input voltage and load variations.

Voltage‐mode robust controller design for DC–DC boost converter at the presence of wide load and input voltage variations based on finite‐state‐machine model

In this study, first, a new definition is proposed for the state of the boost converter. In this approach, the state is defined based on the relative value of two successive samples of the output voltage with respect to the reference voltage. Then a finite-state-machine (FSM) model, which takes into account the possible variations of the input voltage and load resistance, is proposed. This model is discrete-time and represents the evolution of states implicitly based on the events like load and input voltage variation. One advantage of this model is that it is valid both in continuous conduction mode and discontinuous conduction mode. At the next step, a voltage-mode controller, which can regulate the output voltage at the presence of load and input voltage variations, is proposed. Stability of the resulting closed-loop system is studied using the FSM model and the discrete-time Lyapunov method. Simulations and experimental results are presented.

A Fixed-Frequency ZVS Integrated Boost Dual Three-Phase Bridge DC–DC LCL-Type Series Resonant Converter

A new fixed-frequency controlled three-phase dc–dc LCL-type series resonant converter with integrated boost function is proposed for medium to large power applications with wide input voltage variation that is typical of alternate energy sources. The converter includes a dual three-phase LCL-type resonant bridge inverter modules connected in parallel, thus significantly reducing the component stresses when subjected to medium to large power applications. The fixed-frequency control of the output power is achieved by phase shifting the gating signals of one module with respect to the other, while the rectified voltage at the secondary windings of a three-phase high-frequency transformer connected between the two modules is added to the input voltage to boost the supply voltage to the modules. The zero-voltage-switching of all the switches is accomplished by designing the converter to operate in the lagging PF mode for wide variations in the input voltage and the load. Detailed modeling of the three-phase boost section is done and the steady-state analysis of the proposed converter for three-phase LCL-type dc–dc converter modules using complex ac circuit analysis method is presented. For illustration purpose, a dc–dc converter of 600 W is designed, and its performance is verified using PSIM simulations. An experimental model of the converter is built in the laboratory to verify its performance for wide variations in input voltage and load changes.

Implementation of an Active-Clamped Current-Fed Push–Pull Converter Employing Parallel-Inductor to Extend ZVS Range for Fuel Cell Application

This paper proposes a wide-range zero-voltage-switching (ZVS) active-clamped current-fed push–pull converter for fuel cell application. The presented converter achieves ZVS for all of the primary switches and ZCS for secondary diodes from rated load to 10% full load over the wide input voltage variation, improving the overall efficiency. The ZVS of switches is realized by the energy stored in the transformer leakage inductance aided by the secondary parallel inductor. An additional active clamping circuit suppresses the voltage spike as well as assists in realizing ZVS of switches. Low-voltage-rated switches with low on-state resistance can be used. Moreover, the voltage-doubler rectifier is adopted to release the reverse-recovery problem of rectifier diodes and reduce turns ratio of the high-frequency transformer. Detailed steady-state operation, analysis, design, control, comparative study, and experimental results are discussed in depth in this paper. Finally, a 200-W prototype has been built in the laboratory to verify the effectiveness of the proposed converter.