A NON-ISOLATED HIGH VOLTAGE GAIN DC-DC CONVERTER WITH REDUCED SWITCH VOLTAGE STRESS

Abstract

The present invention is related to a non-isolated high voltage gain DC-DC converter with reduced switch voltage stress. this DC-DC converter is specifically designed for renewable energy applications such as photovoltaic systems and fuel cells. the converter efficiently connects low-voltage sources to DC microgrids, providing significant voltage gain while minimizing voltage stress on semiconductor components. key components include switches (Q1, Q2), diodes (D1-D5), inductors (L1, L2), and capacitors (C1-C5). a modified switched inductor network eliminates intermediate diodes and incorporates boost capacitors (C1, C2) to enhance energy storage and efficiency. the voltage multiplier network, cascaded with a modified switched-inductor cell, lowers the voltage stress on semiconductor devices while boosting the output voltage gain. Both switches operate with the same duty ratio, simplifying control and improving component utilization. the combination of the switched inductor and voltage multiplier techniques results in a high-efficiency converter, achieving 95% efficiency in a 200W.

Specification

Description:TECHNICAL FIELD OF INVENTION

The present invention is related to the field of electrical engineering. More specifically, it relates to a non-isolated DC-DC converter configured to reduced switch voltage stress, high voltage gain, and high component utilization ratio for solar photovoltaic (PV) applications

BACKGROUND OF THE INVENTION

The background information herein below relates to the present disclosure but is not necessarily prior art.

Various technologies and solutions are available to address common challenges. These encompass conventional boost converters, voltage multipliers, cascaded converters, and isolated DC-DC converters. While conventional boost converters cannot attain significant voltage gain as their performance is constrained at high duty ratios, leading to issues with conduction losses and diode reverse recovery. Voltage multipliers and cascaded converters respond to the demand for high voltage gain by introducing extra components, resulting in heightened losses and increased costs. Isolated converters deal with the same challenge by augmenting the turns ratio, potentially exacerbating electromagnetic interference (EMI) and electromagnetic compatibility (EMC) effects. Achieving substantial gain often necessitates a sizable high-frequency transformer, thereby amplifying costs and enlarging the physical footprint of the converter.

US20110103118A1 related to a non-isolated DC-DC converter assembly includes a boost converter and a Cuk converter connected together in a specific way. The non-isolated DC-DC converter assembly allows for grounding of a source and load at the same time, and provides a complete adjustability of the output voltage of the non- isolated DC-DC converter. Further, the DC-DC converter assembly of the disclosure has a current source input characteristic, whereby the current absorbed from the power supply is continuous

CN104218801A this invention presents a non-isolated high-gain DC/DC converter that achieves efficient voltage conversion without the use of transformers or coupling inductors. The converter comprises two inductors, two power switches, four diodes, and four capacitors. The design features a straightforward circuit topology where the inductors are connected in series with the power switches and the diodes are arranged to facilitate optimal current flow. The power switches are controlled by respective controllers, allowing precise regulation of the conversion process. This innovative converter offers several advantages over traditional boost converters, including improved electromagnetic interference (EMI) characteristics, reduced circuit complexity, and simplified control system design.

OBJECTIVE OF THE INVENTION

The primary objective of the present invention is to provide a non-isolated DC-DC converter that delivers substantial voltage gain and high efficiency, particularly for renewable energy applications.

Another objective of the invention is to minimize voltage stress on semiconductor components, such as switches and diodes, by incorporating innovative techniques like combination of modified switched inductors and switched capacitors.

Yet Another objective of the invention is to streamline control techniques by utilizing synchronized switching with a single duty ratio.

SUMMARY OF THE INVENTION

Accordingly, the following invention provides a non-isolated high voltage gain DC-DC converter. the present invention provides a novel non-isolated DC-DC converter specifically designed for renewable energy applications, including photovoltaic (PV) systems and fuel cells. This converter features a dual-switch configuration (Q1, Q2) that facilitates the efficient connection of lower voltage sources to DC microgrids. Key components include modified switched inductors (L1, L2), boost capacitors (C1, C2), multiplier cell capacitors (C3, C4, C5). The integration of a modified switched inductor and voltage multiplier cell enhances voltage gain while significantly improving energy transfer efficiency. By replacing an intermediate diode with an additional switch, the design minimizes stress on the active switches to less than 25% of the output voltage, thus enhancing the overall reliability and lifespan of the converter.

Moreover, the innovative incorporation of a boost capacitor further increases voltage gain. Both switches operate with the same duty ratio, simplifying the control mechanism and making the converter more compact and cost-effective. Experimental results from a 380V, 200W prototype demonstrate an impressive efficiency of 95% at full load, confirming the effective utilization of the converter's components. This invention represents a significant advancement in DC-DC converter technology, making it highly suitable for a variety of renewable energy systems.

BRIEF DESCRIPTION OF DRAWING

This invention is described by way of example with reference to the following drawings where,

Figure 1 of sheet 1 illustrated the circuit diagram of the proposed converter.
Where,
Vin denotes an input voltage,
D1, D2, D3, D4, D5 denotes diodes,
C1, C2, C3, C4, C5 denotes capacitors,
L1, L2 denotes inductors,
Q1, Q2 denotes switches,
Vout/V0 denotes an output voltage.
Figure 2 of sheet 2 illustrated the mode 1 operation of the converter. In this mode both the first switch and the second switch are turned on. D1, D2, and D4 diodes are in a forward bias state, while D3 and D5 are in a reverse bias state. Simultaneously, L1, L2, C1, and C2 charge in parallel from the input DC source, and C3 charges from C5 while C4 and C5 discharge in series through the load. Since C1, C2, and SIs are charged in parallel, the voltage across C1, C2, and the SIs remains the same.

Figure 3 of sheet 3 illustrated the mode 2 operation of the converter. In this mode both the first switch and the second switch are turned off. D1, D2, & D4 are in reverse bias, whereas D3 & D5 are in forward bias. Both the SIs and C1, C2, and C3 discharge in series, while C4 and C5 undergo charging.
The output voltage gain of the proposed converter is

Figures 4, 5, and 6 of sheet 4,5 illustrated show the output voltage gain of the converter at α=45, α=50 and α=72 respectively. Here, the duty ratio is denoted as α.

Figure 7 of sheet 5 illustrated the voltage stress on D1, D2, and D3 at an output voltage of 380V.

Figure 8 of sheet 6 illustrated the voltage stress on Q1, Q2, D4, and D5 at an output voltage of 380V.

Figures 9, 10, 11, and 12 of sheet 6,7,8 illustrated the input voltage (Vin), input current (Iin), output voltage (V0), and output current (I0) for power levels of 190W, 200W, 220W, and 230W, respectively, which are used for efficiency calculations.

Figure 13 of sheet 8 illustrated the ideal and actual efficiency of the converter across different output power levels.


DETAILED DESCRIPTION OF THE INVENTION

As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

The present invention is related to a non-isolated high voltage Gain DC-DC converter with reduced switch voltage stress and high component utilization ratio for solar PV applications. non-isolated DC-DC converter that tackles existing challenges in renewable energy systems. By combining modified switched inductor and voltage multiplier techniques, the converter achieves a substantial voltage gain. Notably, the elimination of an intermediate diode in switched inductor cell and the addition of a boost capacitor streamlines the conversion process, improving overall efficiency. Further, the incorporation of a second switch and a voltage multiplier cell reduces voltage stress on components, addressing issues related to reverse recovery. Simultaneous operation of both switches with the same duty ratio simplifies control techniques, enhancing practicality. Overall, our converter offers significant advancements, making it a promising solution for distributed power generation and renewable energy systems.

The non-isolated DC-DC converter features a first switch and a second switch, a modified switched inductor, a voltage multiplier cell, a boost capacitor, an output diode, and a capacitor. The combination of modified switched inductor and voltage multiplier cell are designed to achieve substantial voltage gain. Both the first and second switches operate simultaneously with the same duty ratio, which simplifies control techniques. The design of the converter eliminates the need for an intermediate diode. Additionally in switched inductor cells, incorporating the boost capacitor streamlines the conversion process and improves overall efficiency. Incorporation of the voltage multiplier cell and the second switch help reduce voltage stress on components. The converter also addresses reverse recovery issues by minimizing voltage stress on its components. configured for use in distributed power generation and renewable energy systems, the converter offers significant advancements in voltage gain and efficiency. The combination of the modified switched inductor and voltage multiplier techniques contributes to enhanced performance, making it particularly suitable for renewable energy applications.

Invention aimed at improving the efficiency and performance of power conversion processes in renewable energy systems. This includes applications in photovoltaic (solar) power systems, battery energy storage systems, electric vehicles, distributed power generation, microgrids, and other related fields. The invention addresses key challenges such as achieving high voltage gain, reducing component stress, high component utilization ratio, and simplifying control techniques, thereby enhancing the overall efficiency and reliability of power electronic systems in various industrial and renewable energy applications. Objective is to high voltage gain, high efficiency, less voltage stress on switches, high component utilization, and easy switch control.

Figure 1 shows the non-isolated high voltage gain DC-DC converter with reduced switch voltage stress, comprising an input voltage source (Vin), a first switch (Q1) and a second switch (Q2), a first inductor (L1) and a second inductor (L2) connected to the input voltage source (Vin) and configured to operate in conjunction with the first switch (Q1) and second switch (Q2). The converter further comprises a first capacitor (C1) and a second capacitor (C2), which are coupled to the first inductor (L1) and second inductor (L2) and are configured to charge and discharge based on the switching states of the first and second switches (Q1, Q2). A capacitor (C3) is connected in between modified switched inductor cell and output diode. while an output diode (D5) is connected to the output side of the voltage multiplier cell. Multiplier cell capacitors (C4, C5) store the energy and supply it to the load. Both the first switch (Q1) and the second switch (Q2) operate with the same duty cycle. The combination of the modified switched inductors (L1, L2) and boost capacitors (C1, C2), along with the voltage multiplier cell enhances voltage gain while reducing voltage stress on the switches (Q1, Q2) and diodes (D1, D2, D3, D4, D5).

The voltage stress on the first switch (Q1) and second switch (Q2) is maintained at less than 25% of the output voltage (Vout). The first inductor (L1), second inductor (L2), and boost capacitors (C1, C2) are arranged in parallel during the charging phase when the first switch (Q1) and second switch (Q2) are turned on, and are arranged in series during the discharging phase when the switches are turned off. The converter further comprises a voltage multiplier cell configured with a plurality of diodes (D3, D4, D5) and capacitors (C3, C4, C5) to provide additional voltage gain by multiplying the voltage from the input side. The control mechanism for the first and second switches (Q1, Q2) is synchronized using a single-duty ratio to simplify control, reduce complexity, and improve system reliability. The combination of the modified switched inductors and voltage multiplier cells minimizes reverse recovery issues in the diodes, improving efficiency and reducing losses. Additionally, an output capacitor (C4) and an additional capacitor (C5) discharge in series during specific operating modes to enhance voltage transfer efficiency and output stability. The converter operates with high efficiency at various power levels, with demonstrated efficiency of 95% at a full load of 200W. The duty cycle of the switches (Q1, Q2) is adjusted so that voltage gain varies in accordance with the duty ratio (α), which is optimized for specific output voltage levels.

The inventive step of the novel non-isolated DC-DC converter is characterized by several innovative features and improvements over existing technologies, particularly in the context of renewable energy systems. The invention presents the following inventive steps:

Combination of Modified Switched Inductor and Voltage Multiplier Techniques: The invention combines modified switched inductor and voltage multiplier techniques to achieve a substantial voltage gain. This novel combination optimizes the performance of the converter, providing higher efficiency and voltage levels compared to conventional methods.

Addition of Boost Capacitors: The inclusion of boost capacitors further enhances the voltage gain and efficiency of the converter. This feature allows for better energy storage and release, contributing to the system's overall performance improvement.

Incorporation of a Second Switch and voltage multiplier cell: The invention incorporates a second switch and a voltage multiplier cell to reduce voltage stress on components. This addresses the common problem of reverse recovery, which can lead to inefficiencies and potential damage in conventional converters. By mitigating these issues, the invention increases the reliability and lifespan of the converter.

Simultaneous Operation of Both Switches with the Same Duty Ratio: The innovative control technique, where both switches operate simultaneously with the same duty ratio, simplifies the control strategy. This simplification makes the converter easier to implement and more practical for real-world applications, particularly in distributed power generation and renewable energy systems.

High Component Utilization Ratio: The design of the converter ensures a high component utilization ratio, meaning that the components are used more effectively and efficiently. This leads to better performance and cost-effectiveness, as fewer components are required to achieve the desired voltage gain and efficiency.

Enhanced Practicality and Suitability for Renewable Energy Systems: The overall design and features of the converter make it particularly well-suited for renewable energy applications. Its high efficiency, reduced component stress,
high component utilization ratio, and simplified control make it an ideal solution for distributed power generation systems, addressing the specific challenges of renewable energy integration.

Industrial applications: Solar Power Systems, Battery Energy Storage Systems, Electric Vehicles (EVs), Distributed Power Generation, Microgrids, Telecommunications, Industrial Automation, and Smart Grid Applications.

While various embodiments of the present disclosure have been illustrated and described herein, it will be clear that the disclosure is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the disclosure, as described in the claims.
, Claims:1. A non-isolated high voltage gain DC-DC converter with reduced switch voltage stress, comprising of;

an input voltage source (Vin);

a first switch (Q1) and a second switch (Q2);

a first inductor (L1) and a second inductor (L2) connected to the input voltage source (Vin) and configured to operate in conjunction with the first switch (Q1) and second switch (Q2);

a first capacitor (C1) and a second capacitor (C2) coupled to the first inductor (L1) and second inductor (L2), and configured to charge and discharge based on the switching states of the first and second switches;

a boost capacitor (C3) coupled in parallel to a voltage multiplier cell comprising at least one diode and capacitor arrangement;

an output diode (D5) connected to the output side of the voltage multiplier cell;

an output capacitor (C4) configured to store the output voltage (Vout/V0) and supply it to the load, wherein the first switch (Q1) and the second switch (Q2) operate with the same duty cycle to achieve high voltage gain, and wherein the combination of the modified switched inductors (L1, L2) and switched capacitors (C1, C2) in conjunction with the boost capacitor (C3) enhances the voltage gain while reducing the voltage stress on the switches (Q1, Q2) and diodes (D1, D2, D3, D4, D5).

2. The non-isolated high voltage gain DC-DC converter with reduced switch voltage stress as claimed in claim 1, wherein the voltage stress on the first switch (Q1) and second switch (Q2) is less than 25% of the output voltage (Vout).

3. The non-isolated high voltage gain DC-DC converter with reduced switch voltage stress as claimed in claim 1, wherein the boost capacitor (C3) is configured to reduce the voltage stress on the output diode (D5) to less than 50% of the output voltage (Vout).

4. The non-isolated high voltage gain DC-DC converter with reduced switch voltage stress as claimed in claim 1, wherein the first inductor (L1) and second inductor (L2) are arranged in parallel during the charging phase when the first switch (Q1) and second switch (Q2) are turned on, and arranged in series during the discharging phase when the first switch and second switch are turned off.

5. The non-isolated high voltage gain DC-DC converter with reduced switch voltage stress as claimed in claim 1, further comprising a voltage multiplier cell configured with a plurality of diodes (D3, D4, D5) and capacitors (C3, C4, C5) to provide additional voltage gain by multiplying the voltage from the input side.

6. The non-isolated high voltage gain DC-DC converter with reduced switch voltage stress as claimed in claim 1, wherein the control mechanism for the first switch (Q1) and second switch (Q2) is synchronized using a single duty ratio to simplify the switching control, reducing complexity and improving system reliability.

7. The non-isolated high voltage gain DC-DC converter with reduced switch voltage stress as claimed in claim 1, wherein the combination of the modified switched inductors (L1, L2) and switched capacitors (C1, C2) operates to minimize reverse recovery issues in the diodes, thereby improving efficiency and reducing losses.

8. The non-isolated high voltage gain DC-DC converter with reduced switch voltage stress as claimed in claim 1, further comprising an output capacitor (C4) and additional capacitor (C5) configured to discharge in series during specific operating modes to enhance voltage transfer efficiency and output stability.

9. The non-isolated high voltage gain DC-DC converter with reduced switch voltage stress as claimed in claim 1, wherein the converter is configured to operate with high efficiency at various power levels, as demonstrated by its efficiency of 95% at a full load of 200W.

10. The non-isolated high voltage gain DC-DC converter with reduced switch voltage stress as claimed in claim 1, wherein the duty cycle of the switches (Q1, Q2) is adjusted such that the voltage gain varies in accordance with the duty ratio (α), wherein α is optimized for specific output voltage levels.

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