High gain dc-dc converters are used in several applications which include solar photovoltaic system, switch-mode power supplies and fuel cells. In this paper, an ultra-high gain dc-dc boost converter is proposed and analyzed in detail. The converter has a gain of six times as compared with the boost converter. The high gain is achieved by utilizing switched inductors and switched capacitors. A modified voltage multiplier cell (VMC) with switched inductors is proposed. The converter has a single switch which makes its operation easy. Moreover, the voltage across the switch, diodes and capacitors are less than the output voltage which increases the overall efficiency of the converter. The converter performance in steady-state is analyzed in detail and it is compared with other latest high gain converters. The working of the converter in non-ideal conditions is also discussed in detail. The loss analysis is done using PLECS software by incorporating the real models of switches and diodes from the datasheet. To confirm and validate the working of the proposed converter a hardware prototype of 200 W is developed in the laboratory. The converter achieves high gain at low duty ratios and its performance is found to be good in open and closed loop conditions.

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A New Transformerless Ultra High Gain DC–DC Converter for DC Microgrid Application

In this article, three switched-capacitor-based Z-source equivalent dc–dc boost converter (SCZEBC) topologies are proposed. The basis for these topological evolutions is the shifted L-C-D cell of the fourth-order boost converter on the front-end side, whereas a charge-pump cell on the upstream side. This hybrid combination results in quasi-Z-source equivalent dc–dc boost conversion along with enhanced voltage boosting capability. The operating duty ratio of the proposed topologies is less than 0.5 like in the conventional Z-source dc–dc converter (ZSC) topologies. In comparison to the existing Z-source topologies, remarkable features of the proposed SCZEBC topologies are: low source current ripple, common ground, and low voltage stress on capacitors and active devices. A detailed steady-state analysis is presented to identify the salient features of the proposed topologies and is thereafter compared with the existing ZSCs. Small-signal analysis is established and a voltage-mode controller is designed. In the controller design stage, a modulus margin 0.5–0.75 is adopted to ensure tradeoff between robustness and performance of the proposed converter topologies. A 48 to 220 V, 100-W prototype is built to demonstrate the effectiveness of the SCZEBC. The steady-state and closed-loop response measurements validate the theoretical studies.

Analysis and Design of Quasi-Z-Source Equivalent DC–DC Boost Converters

This article proposes three high step-up Z-source (ZS)-based dc–dc converters by integrating the conventional ZS network with switched-capacitor (SC) cells. The proposed converters offer a simple structure with a smooth input current, a high-voltage gain, and low voltage stress on the semiconductor devices. In addition, the proposed converters, unlike some existing ZS-based topologies in the literature, do not impose any limitation on the duty cycle of the power switch. These characteristics make the proposed converters excellent candidates to interface a low-voltage solar photovoltaic (PV) panel with a high-voltage dc bus in PV applications. Among the proposed three converters, the operating principles and steady-state analysis of the one with more components are presented in detail. However, the steady-state voltage and current relationships are also tabulated for two other proposed converters. In addition, design considerations are presented. The performance of the proposed converters is compared against similar existing high step-up dc–dc converters with regards to the component count, normalized voltage stress on the power switch and diodes, and voltage gain. Finally, the theoretical analyses and calculations are validated through experimental results using a 400-W/400-V laboratory prototype.

Z-Source-Based High Step-Up DC–DC Converters for Photovoltaic Applications

In this paper, a Z-network plus switched-capacitor based DC-DC boost converter (ZSCBC) is proposed. The integration of the Z-network with a switched capacitor is responsible for yielding a high-voltage gain and that too at lower duty ratios compared to the conventional quasi-Z-source dc–dc converter (QZSC). Since the proposed converter contains Z or impedance network, the operating duty ratio is less than 0.5, such as in QZSC, and retains its advantages, such as common ground and low-voltage stress on Z-network capacitors. Unlike QZSC, the switch and all the diode voltage stresses in the proposed converter are low even at high-voltage gains. A detailed steady-state analysis is presented to identify the salient features of the proposed Z-network-based boost converter and thereafter compared with other Z-source-based configurations. The small-signal analysis is established, and a single-loop voltage-mode controller is designed. A 48–250-V, 130-W prototype is built to demonstrate the effectiveness of the ZSCBC. The steady-state and closed-loop response measurements validate the theoretical studies.

Z-Network Plus Switched-Capacitor Boost DC–DC Converter

A high gain noninverting DC–DC converter with low voltage stress for industrial applications

This paper presents modeling and control of a standalone photovoltaic (PV) system in which a battery is used as a backup source for power management between the source and the load. Lead-acid battery is commonly used in high power PV applications due to its low cost and availability in large size. The modeling of PV system and lead-acid battery by using the corresponding equivalent circuits are discussed here. Three independent control loops are proposed to control the standalone PV system; MPPT control loop for extracting maximum power from PV module under different solar irradiation, battery control loop for bidirectional power flow between battery and dc-link through buck-boost converter to keep the input dc voltage constant, and inverter control loop for maintaining good voltage regulation and achieving fast dynamic response under sudden load fluctuations. The stability of the above control loops are verified by using Bode diagram. Finally the proposed method is applied to 2 kW, 110 V, 50 Hz, two-stage single-phase standalone PV system. The simulation and the experimental results are presented to validate the theoretical analysis, effectiveness and feasibility of the proposed control strategy.

Modeling and control of a battery connected standalone photovoltaic system

A high voltage gain sixth order quasi-Z-source dc-dc boost converter (SOQZSC) is proposed in this paper. It provides higher voltage gain at low duty ratio, reduced voltage stress across all the components in comparison with traditional impedance source based dc-dc converters. The operation principle along with steady-state and small-signal analysis of SOQZSC is presented. The design guidelines are formulated for inductors and capacitors of the proposed converter. The comparison of SOQZSC with other existing converters is also presented. A voltage-mode controller is designed to regulate load voltage against source and load disturbances. A 42 V to 120 V, 100 W laboratory prototype verifies the mathematical analysis of proposed SOQZSC.

Analysis and Design of Sixth Order Quasi-Z-Source DC-DC Boost Converter

A fourth-order quasi-Z-source equivalent DC-DC boost converter (FOEBC) exhibiting the voltage gain conversion ratio identical to Z-source dc-dc boost converter (ZSC) is proposed in this paper. It provides voltage gain identical to ZSC but with smooth source current waveform and thus leads to reduced EMI. On the basis of steady-state analysis, the principle of operation, exchange of energy among various inductive and capacitive elements is explained. Subsequently, design guidelines for inductors and capacitors is established. To highlight the controller design issues, small-signal analysis of the proposed converter is presented. A voltage-mode controller is designed to demonstrate its feasibility both in simulation and experiments. A 42 V to 100 V, 50 W laboratory prototype verifies the converter regulation capability against source and load disturbances. The comparison of proposed converters with other conventional power converters is also described.

Punit Kumar

Papers

Analysis and Design of Quasi-Z-Source Equivalent DC–DC Boost Converters

Z-Network Plus Switched-Capacitor Boost DC–DC Converter

Modeling and control of a battery connected standalone photovoltaic system

Analysis and Design of Sixth Order Quasi-Z-Source DC-DC Boost Converter

Analysis and Design of Fourth-order Quasi-Z-Source Equivalent DC-DC Boost Converter