High DC Gain Research Articles

A New High Voltage Gain DC to DC Converter with Low Voltage Stress for Energy Storage System Application

Increasing energy demand globally has led to exploring ways of utilizing renewable resources for sustainable development. More recently, the integration of renewable distributed resources in small- and large-scale grid has been seriously researched. Development in renewable power sources and its integration with the grid require voltage level conversion to match the grid/micro-grid level. The voltage level conversion is brought about by employing Direct Current-Direct Current (DC-DC) converters with boosting features. The paper presents a wide gain range DC-DC boost converter with a low-stress on switching devices. The proposed converter’s voltage gain is high compared with the conventional quadratic boost converter and other recently developed high gain boost converters. The topology has been compared with recently proposed topologies, and comparative analysis based on various performance parameters has shown that the topology is suitable for renewable and sustainable energy storage and grid integration. The power loss analysis has been done by incorporating the switching and conduction losses. A hardware prototype of 150 W has been developed to validate the converter’s performance in steady-state as well as in dynamic conditions.

Non‐isolated DC–DC converter with cubic voltage gain and ripple‐free input current

In this study, a non-isolated high gain DC–DC converter is presented. The proposed converter yields a voltage conversion ratio value which is a cubic function of the voltage gain obtained from a boost converter. The proposed converter is synthesised by judiciously interfacing a two-phase interleaved boost converter with voltage-lift capacitor and a quadratic boost converter. Resultantly, the proposed converter yields a practical voltage gain of 21.11. Further, due to the use of interleaving technique, the input current is completely free from ripples. The proposed concept is validated by conducting experiments on 18/380 V, 160 W prototype converter. The experimental results clearly demonstrate that the proposed converter operates at a full-load efficiency of 95.6%. Further, by practically implementing a simple closed-loop control, the output voltage of the converter is quickly regulated against variations in input voltage and load current so as to provide the desired 380 V across the load terminals.

Adaptive biased current differencing trans-conductance amplifier

A power-efficient, high DC gain adaptive biased Current Differencing Trans-conductance Amplifier (AB-CDTA) is proposed in this paper. The proposed circuit consists of four sub-circuits namely Current Differencing Unit (CDU), Current Replication Unit (CRU), Current Squarer Unit (CSU) and Trans-conductance Amplifier Unit (TAU). The bias current of the TAU varies in a square relation with the input current difference. The proposed structure thus provides tunable gain depending on the input current difference with improved transient characteristics, reduced standby power dissipation and linearity for large range of inputs. Complete mathematical formulation has been presented to establish the characteristics of the proposed AB-CDTA. The proposed structure is validated through SPICE simulations using 180 nm CMOS technology. The proposed structure operates with a stand-by power dissipation of 47.6 µW only. Figure of merit (FoM) is also used to enumerate large signal performances of the proposed AB-CDTA. The proposed structure shows a 45.22 dB enhancement in the DC gain and a 94.29% reduction in the settling time compared to the conventional structure.

SiC‐based high‐gain DC–DC converters with fault ride‐through capability

This study presents active switched passive network-based high-gain DC–DC converters. The active switched network is formulated using two inductors, one capacitor and two diodes. Hence, the network is named as a 2L–C–2D network. Using ten components, an asymmetric high-gain DC-DC converter is proposed. This converter achieves a gain of 29 at an 80% duty ratio. In the asymmetric converter structure by replacing the inductor by another 2L–C–2D network, the symmetric converter structure is proposed using 14 components. This converter structure achieves the gain of 49 at the same 80% duty ratio. Apart from increasing the voltage gain, the 2L–C–2D network helps to reduce the voltage and current stresses of the converter. The utilisation of two semiconductor switches in the proposed converter structures permits a fault ride-through capability even when any one of the switches fails. Operations of the converters in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are discussed, and the boundary condition between CCM and DCM is derived. To limit the effect of parasitic elements on the converter performance, SiC-based semiconductor devices are used in the 500 W hardware prototype. The maximum efficiency of 92.8% is achieved in the case of a symmetric converter.

Experimental validation of solar-panel-tied three-port switched-inductor-based dual-boost DC–DC-converter-fed three-phase micro-inverter

This paper proposes a solar-panel-integrated modified high-gain three-port dual-boost switched-inductor-based DC–DC-converter-operated micro-inverter for grid-connected applications. Solar-panel-integrated grid-connected micro-inverters need a high-gain front-end DC–DC converter to regulate and step up the output voltage of the solar panels. The proposed three-port dual-boost DC–DC converter offers high voltage gain at low duty ratio and efficiently transfers the power produced by the solar panel to the utility grid. The power losses and steady-state analysis of the proposed converter working in continuous conduction mode are examined. Examinations among the conventional boost converter are presented, and it is discovered that the proposed converter has the largest voltage transformation. Finally, the results obtained from simulated and experimental prototype models are presented to confirm the power conversion capability of the proposed converter.

Sliding mode controller-based switched-capacitor-based high DC gain and low voltage stress DC-DC boost converter for photovoltaic applications

High-gain DC-DC power boost converters blocks have been converted to the main transitional topologies for the PV applications to enhance the level of the generated voltages of these panels for grid applications. The single-switched and transformer-less converters due to their higher efficiency, and cheaper and light-weighted features are the first selection for these converters design. This study presents a transformer-less DC-DC power boost converter with a switched-capacitor structure with a sliding mode controller (SMC) to increase the DC voltage gain and decrease the voltage stress on the power switch. This advantage is doing based on the preamplifier block by using an extra inductor at the input side. Also, the switched-capacitor block easily decreases the voltage stresses on the main power switch and other diodes. Presenting high voltages under the small duty cycles is one of the most important features of the proposed converter that allows longer off-time duration for power switch for Continuous Current Mode (CCM) operations. This leads to lower amounts of the dynamic losses for the power switch and higher efficiency. On the other hand, the control process of the proposed converter under the different input voltages and output powers and loads due to using only one power switch is simpler compared with multi-switched topologies. All calculations for obtaining the gain, currents follow through the components, voltage ripples through the capacitors, and efficiency is presented. The hardware prototype with 300 W power is tested and the results confirm the theoretical calculations.

Robust output voltage control of a high gain DC–DC converter under applied load and input voltage uncertainties

In this study, using robust and adaptive approaches, two controllers are designed to compensate for the applied load and input voltage uncertainties of a high voltage gain dc–dc converter. These controllers are designed based on measuring only the output voltage of the converter. The permissible ranges of the uncertainties are calculated using dynamics equations analysis while practical limitations are considered. In the first approach, an input multiplicative uncertainty is considered for the model of the converter by linearisation of non-linear equations as well as using permissible ranges of the uncertainty. Then, a robust H∞ controller is designed. In the second approach, the converter model is considered as a first-order dynamics model with the unknown parameters and an unknown additive term while a direct robust model reference adaptive controller is designed for it. Finally, the non-linear equations of the converter are simulated and the performances of the controllers are compared with each other. The control methods are then implemented on a 200 W prototype of a converter for evaluating the simulations results.

Optimized Active Power Management in Solar PV-Fed Transformerless Grid-Connected System for Rural Electrified Microgrid

Dynamic voltage instability is one of the major issues faced by grid-connected renewable energy systems due to fluctuations in the generation and sudden variation in the loads. The primary objective of this paper is to propose a method for constant power consumption from the grid to maintain a stable DC-link voltage during peak and nonpeak hours. It can be achieved by implementing an optimized active power management (OAPM) scheme between the photovoltaic (PV) and the grid by enabling a battery energy storage system (BESS). The intelligent constant power balance (ICPB) algorithm and detailed control strategies for dual active bridge (DAB) isolated DC–DC converter and grid-connected voltage source inverter (VSI) are discussed in this paper. Moreover, the high-gain step-up DC–DC converter (HSDC) is utilized to perform maximum power point tracking (MPPT) operation and to meet the required DC-link voltage. The accuracy of power transmission of DAB gets improved by imposing a curve-fitting interpolation (CFI) approach, thereby maintaining a constant DC-link voltage. Furthermore, an instantaneous sinusoidal current control (ISCC) scheme assures the feeding of active power with better power quality. The measured results are obtained and verified under different dynamic conditions of load and generation. Based on the validation, we conclude that the proposed OAPM scheme is most suitable for grid-connected renewable energy systems in the rural electrified microgrid.

High-Gain Bidirectional Quadratic DC–DC Converter Based on Coupled Inductor With Current Ripple Reduction Capability

In this article, a high-gain bidirectional quadratic dc-dc converter is proposed. This converter is studied under step-up and step-down modes. In each power flow direction, two switches and two antiparallel diodes of the other switches operate. Therefore, the switching losses depend only on the operation of two switches in each direction. The use of coupled inductor in the proposed converter significantly reduces the input and output current ripples of the step-up and step-down modes, respectively, at all operating points of continuous and discontinuous conduction modes (CCM and DCM). The voltage gain of the proposed converter in the step-up mode is as high as that of the cascaded boost converter, and in the step-down mode, the converter voltage gain is similar to that of the cascaded buck converter. Thus, the high-voltage conversion ratio with an appropriate duty-cycle in both power flow directions can be achieved. The operating principles and steady-state analysis of the proposed converter in CCM, DCM, and the boundary-conditions between these modes are discussed in detail. Finally, a prototype of the converter is implemented in the laboratory and the experimental results are presented to validate the effectiveness of the proposed converter.

Improved Hybrid Switched Inductor/Switched Capacitor DC–DC Converters

High voltage gain dc–dc converters are widely used in various applications like low-voltage sustainable sources. In traditional boost converters, the voltage gain is limited by high voltage stress, high current ripple, and low efficiency due to employing a high duty cycle ratio. In this article, we propose converters that are a combination of four substructures, namely active switched inductor, passive switched inductor, switched capacitor cell, as well as an auxiliary switch with nonisolated configuration. The proposed structures have high voltage gain compared to the conventional either switched inductor-based or switched capacitor-based ones in addition to a low duty cycle ratio. By adding an auxiliary switch, the efficiency is improved, particularly for high voltage gains. The principle of operation and steady-state analysis are discussed in detail. Also, simulation results from PSCAD/EMTDC software are validated by a prototype built for experimental examination. The results demonstrated that the voltage gain and efficiency could be improved by utilizing the auxiliary switch.

A Novel Algorithm for MPPT of an Isolated PV System Using Push Pull Converter with Fuzzy Logic Controller

Photovoltaic (PV) is a highly promising energy source because of its environment friendly property. However, there is an uncertainty present in the modeling of PV modules owing to varying irradiance and temperature. To solve such uncertainty, the fuzzy logic control-based intelligent maximum power point tracking (MPPT) method is observed to be more suitable as compared with conventional algorithms in PV systems. In this paper, an isolated PV system using a push pull converter with the fuzzy logic-based MPPT algorithm is presented. The proposed methodology optimizes the output power of PV modules and achieves isolation with high DC gain. The DC gain is inverted into a single phase AC through a closed loop fuzzy logic inverter with a low pass filter to reduce the total harmonic distortion (THD). Dynamic simulations are developed in Matlab/Simulink by MathWorks under linear loads. The results show that the fuzzy logic algorithms of the proposed system efficiently track the MPPT and present reduced THD.

A High Voltage Gain DC–DC Converter With Common Grounding for Fuel Cell Vehicle

The essential features of a DC–DC converter for fuel cell vehicle are to ensure the higher voltage gain to meet out the higher DC link voltage demand, continuous input current to improve the life span of the fuel cell, presence of common grounding to avoid electromagnetic interference issue and lower voltage stress with reduced components. This paper presents a high voltage gain DC–DC converter by combining the switched capacitor and quasi switched boost network modules. The proposed high voltage gain converter provides the continuous input current, lower voltage stress, utilizes a fewer number of elements and common grounding feature. The operating characteristics, steady-state analysis both in continuous current mode (CCM) and discontinuous current mode (DCM), comparative analysis with contemporary converters are discussed. The theoretical claimed analysis is validated by the simulation and experimental study. The proposed converter is operated for 200 W output power rating and tested for providing the voltage gain in the range of 5–8 times the input voltage gain by varying the input voltage from 25 V–40 V. The efficiency of the proposed converter is also reported for different output power rating which is in the range 91.3%–93.7%.

Design and analysis of robust fuzzy logic maximum power point tracking based isolated photovoltaic energy system

SummaryPhotovoltaic (PV) energy is highly promising because of its renewable, green, and environment‐friendly nature. In this article, the design and analysis of an isolated PV system using a push‐pull converter with a fuzzy logic‐based maximum power point tracking (MPPT) algorithm is presented. Furthermore, DC‐DC converters, along with intelligent controllers fed with MPPT algorithms, are used to ensure the maximum extraction of incident energy. The proposed methodology utilizes fuzzy logic MPPT techniques based on an isolated push‐pull boost converter to optimize the power output of PV modules, as well as to achieve isolation and high DC gain for DC/AC inversion. This work also presents a single‐phase inverter with fuzzy logic close loop control analysis with LCL filter design. A Canadian solar panel of 250 W is assumed in this research work, which has an open circuit voltage 59.9 V, short circuit current 5.49 A at 25°C temperature, and 1000 W/m2 irradiance. The voltages are tracked, through the MPPT algorithm. These voltages represent a boost to 340 V DC through push‐pull boost converter and are inverted up to 220 V AC through fuzzy logic voltage source inverter. In addition, a unipolar switching technique is used to remove the total harmonic distortion under linear load. The proposed methodology is simulated in MATLAB/Simulink. The simulation results verify that the proposed methodology can efficiently track the MPPT. Finally, the hardware prototype of the proposed system has been experimentally validated.

Step-Up Series Resonant DC–DC Converter with Bidirectional-Switch-Based Boost Rectifier for Wide Input Voltage Range Photovoltaic Applications

This paper proposes a high gain DC–DC converter based on the series resonant converter (SRC) for photovoltaic (PV) applications. This study considers low power applications, where the resonant inductance is usually relatively small to reduce the cost of the converter realization, which results in low-quality factor values. On the other hand, these SRCs can be controlled at a fixed switching frequency. The proposed topology utilizes a bidirectional switch (AC switch) to regulate the input voltage in a wide range. This study shows that the existing topology with a bidirectional switch has a limited input voltage regulation range. To avoid this issue, the resonant tank is rearranged in the proposed converter to the resonance capacitor before the bidirectional switch. By this rearrangement, the dependence of the DC voltage gain on the duty cycle is changed, so the proposed converter requires a smaller duty cycle than that of the existing counterpart at the same gain. Theoretical analysis shows that the input voltage regulation range is extended to the region of high DC voltage gain values at the maximum input current. Contrary to the existing counterpart, the proposed converter can be realized with a wide range of the resonant inductance values without compromising the input voltage regulation range. Nevertheless, the proposed converter maintains advantages of the SRC, such as zero voltage switching (ZVS) turn-on of the primary-side semiconductor switches. In addition, the output-side diodes are turned off at zero current. The proposed converter is analyzed and compared with the existing counterpart theoretically and experimentally. A 300 W experimental prototype is used to validate the theoretical analysis of the proposed converter. The peak efficiency of the converter is 96.5%.

A High-Gain Interleaved DC–DC Converter with Passive Clamp Circuit and Low Current Ripple

In this paper, a novel non-isolated interleaved DC/DC boost converter is presented in which coupled inductors and a passive clamp circuit are employed. ZCS turn-on condition for main switches is provided, and the stored energy in leakage inductance is recycled by means of a passive clamp circuit. Therefore, the voltage stress across switches is reduced resulting in circuit efficiency improvement. Due to interleaved structure and cross-coupled inductors, the input current ripple is reduced and the input current is continuous. To achieve ZCS turn-on condition, the intrinsic leakage inductance of the coupled inductors is used which leads to improving the power density and reducing the switching losses. In order to confirm the theoretical analysis, a prototype with 30 V input voltage, 300 V output voltage, and 300 W is implemented and tested.

Active Switched Capacitor Network in High Gain DC DC Converter with PI Controller

In this paper, PI controller in the active switched capacitor network is employed to achieve robust control under disturbance by maintaining sustained output voltage for varying input voltage. Active switched capacitor in the high gain DC–DC circuit efficiently increases voltage gain due to the combination of LC network with minimum duty cycle. The proposed circuit is the modification of typical high gain DC converter and modified network is simple in structure due to reduce in number of switch components and the voltage stress on the capacitor, diodes and across switches are reduced compared to base network. This paper presents the design, operation and analysis of the modified topology and the performance comparison with base converter is presented. Simulation is carried out using MATLAB software for the proposed system with and without PI controller and variation in the output voltage between both the circuits is tabulated and comparative analysis is discussed.

Novel high gain DC–DC converter based on coupled inductor and diode capacitor techniques with leakage inductance effects

In this study, due to the low output voltage that often is presented by renewable energy sources like photovoltaic panels, a single switch high step-up dc–dc converter with high efficiency is proposed. The presented step-up dc–dc converter uses a coupled inductor and diode-capacitor technique to achieve high voltage gain. By changing the turns ratio of the coupled inductor, this novel topology does not need to operate at a high duty cycle conditions to obtain the high voltage gain. Moreover, the leakage inductance energy of the coupled inductor is recovered by using two passive clamp circuits to reduce the stress across the semiconductor devices, which improve efficiency. The operating modes of the proposed converter and the theoretical analysis are considered and finally, a prototype setup has been implemented to accredit the accuracy of the theoretical and simulation analysis.

A Robust Local Positive Feedback Based Performance Enhancement Strategy for Non-Recycling Folded Cascode OTA

In this study, a local positive feedback technique is proposed to enhance the performance of the folded cascode (FC) operational transconductance amplifier (OTA) when working in its saturation region. The enhanced FC-OTA has a higher gain bandwidth (GBW), higher DC gain and higher slew rate (SR) over its conventional counterparts and popular recycling FC-OTAs. The proposed enhanced FC-OTA is implemented by reusing the current generated by the input transistors through the proposed local positive feedback loop to provide additional transconductance and negative resistance. It is then fabricated with SMIC 180nm process. To verify the effectiveness of the proposed FC-OTA performance enhancement strategy, extensive mathematical analysis, small-/large-signal stability analysis, simulation and experimentation are thoroughly investigated in this study. Simulation and experimental results agree well with the theoretical analysis and the expected performances, which corroborates the control design.

Family of modular, extendable and high gain dc–dc converter with switched inductor and switched capacitor cells

This study presents a family of novel high gain non-isolated hybrid dc–dc converter for dc micro grid application. The proposed family of the converter is developed by employing both inductor-capacitor-inductor (LCL) based switched inductor (SI) and switched capacitor (SC) technique to achieve high voltage gain. Appropriate increase in the number of LCL-based SI cells in the power circuits in order to achieve ultra-high voltage gain allows formulating a generalised structure of the circuit. Incorporation of SI & SC techniques and the structure of the circuit with one stage power transfer ensure high voltage gain at low voltage stress across the switches and diodes. The study includes the principle of operation, steady-state analysis and performance analysis in detail for the converters. Experimental results from the developed hardware prototype of 380 V/250 W validate the adopted concept, design and exemplify that the proposed family of converter operates at a full load efficiency of 94%.

Switched-LC Based High Gain Converter With Lower Component Count

A compact high step up dc–dc converter with continuous input current and lower device voltage stress is a prime requirement for renewable application. In this article, a high gain dc–dc converter is proposed, which combines the concept of switched inductor and switched capacitor along with a unique interconnection of input–output. This arrangement reduces capacitor voltage stress. The proposed converter has reduced conduction losses, reduced components count, and low voltage stress across the devices. Besides, the proposed converter has lower inductor current ripple, which is suitable for renewable integration. The operation and steady-state analysis of the converter are done in continuous current mode. For the proposed converter, voltage and current stress and the losses are calculated analytically. A comparative analysis is presented to prove the potential of the proposed converter. The dynamic analysis of the proposed converter is performed to regulate the output voltage. Finally, an experimental set up is designed to test the converter under both distinct power ratings and closed loop.