Description:[001] The present invention pertains to the realm of power electronics, presenting a revolutionary approach harnessing Gallium Nitride (GaN) semiconductor technology within the framework of a Dual Active Bridge (DAB) configuration seamlessly integrated with an LCL resonant circuit. Furthermore, the envisaged converter architecture exhibits versatility across a broad spectrum of power applications, spanning from medium to high power thresholds.
BACKGROUND OF THE INVENTION
[002] The rapid evolution of modern energy applications, encompassing photovoltaic (PV) systems, fuel cells (FC), and wind energy farms, underscores the burgeoning need for innovative power generation solutions. Notably, PV sources, characterized by their low DC voltage, present challenges in direct microgrid utilization, often requiring series connection of photovoltaic modules to attain higher voltages. The Smart Green Power Converter (SGPC) has emerged as a promising modular solution, facilitating intelligent power flow control between solar panels, battery storage, and the utility grid at the residential level.
[003] In this context, efficient DC-DC converters play a pivotal role in transforming low voltages to higher levels for optimal utilization of renewable energy sources. As industrial demands intensify, advanced converters are sought to minimize switching losses and ensure efficient energy conversion across diverse modern energy systems and storage integrations. Consequently, research focus has intensified on DC-DC conversion techniques to enhance power conversion efficiency.
[004] Preliminary investigations into system specifications have highlighted the necessity for the proposed converter to adhere to existing SGPC standards while aiming for heightened efficiency targets. A thorough literature review has underscored the escalating demands within the electric vehicle (EV) charging infrastructure, necessitating higher efficiency and power density.
[005] Conventional two-stage AC-DC power delivery architectures for on-board or off-board battery charging have been extensively explored, emphasizing the transition towards higher power demands for fast charging. This shift necessitates converters capable of accommodating a wide range of battery voltage levels, posing significant challenges in topology selection and modulation. The emergence of wide band gap (WBG) semiconductors, notably Gallium Nitride (GaN) and Silicon Carbide (SiC), has revolutionized power electronics due to their superior switching performance and efficiency compared to conventional silicon-based counterparts.
[006] The Dual Active Bridge (DAB) converter, owing to its galvanic isolation and soft switching advantages, has gained prominence in isolated bidirectional DC-DC converters. However, challenges persist in achieving efficient operation across wide gain ranges. Various strategies, including phase shift control and resonant converters, have been explored to address these challenges. Immittance resonant converters offer constant input voltage-to-output current gain, presenting promising prospects for efficient battery charging across varying modes of operation. Integration of emerging GaN High Electron Mobility Transistor (HEMT) devices further enhances converter performance, leveraging their superior static and dynamic characteristics.
[007] In light of the foregoing, the present invention aims to introduce a Gallium Nitride (GaN)-based Dual Active Bridge (DAB) LCL resonant converter tailored to meet the exigencies of modern power applications. By integrating GaN semiconductor technology within the DAB topology, the proposed converter endeavors to deliver enhanced efficiency, power density, and versatility across a wide spectrum of power levels. Through comprehensive theoretical analysis and empirical validation, this innovation seeks to address the pressing need for efficient energy conversion in contemporary power electronics systems.
SUMMARY OF THE PRESENT INVENTION
[008] The invention disclosed in this application pertains to a Gallium Nitride (GaN)-based Dual Active Bridge (DAB) LCL Resonant Converter designed for a wide range of power applications. In light of the rapid advancements in modern energy applications such as photovoltaic (PV) systems, fuel cells (FC), and wind energy farms, there is a pressing need for efficient power conversion solutions. PV sources, characterized by their low DC voltage, require transformation to higher voltages for optimal utilization in microgrids. The proposed solution, the smart green power converter (SGPC), facilitates this transformation by intelligently interfacing solar panels and battery storage with the utility grid at the residential load level, thereby enhancing the efficiency of renewable energy sources.
[009] To address the challenges posed by diverse modern energy systems and energy storage system integrations, there is a demand for a single converter that embodies features such as low cost, light weight, low voltage switching tension, and high power density. Consequently, there has been a surge in research attention towards DC-DC conversion techniques aimed at achieving better power conversion efficiency. The present invention aims to fulfill these requirements through the development of a GaN-based DAB LCL Resonant Converter, designed to meet system specifications and ensure compatibility with previous versions of SGPC.
[010] The prior arts highlights the increasing demand for higher efficiency and power density in electric vehicle (EV) charging infrastructure, driving the need for wide band gap (WBG) semiconductors like GaN. The advantages of GaN power transistors, including reduced reverse recovery charge and higher switching frequency, make them ideal for achieving bidirectional power flow in converters. The DAB converter, comprising two full bridges connected by a series inductor and a transformer, offers galvanic isolation and soft switching, addressing challenges in isolated bidirectional DC-DC converters.
[011] Furthermore, the invention introduces a novel topology integrating the DAB converter with an LCL-T series parallel resonant converter (SPRC), leveraging the advantages of both topologies for improved efficiency and performance. The proposed converter system, incorporating GaN HEMTs, demonstrates superior static and dynamic performance, contributing to higher efficiency and power density in power converters.
[012] The objectives of the proposed converter system include achieving high efficiency conversion, enhancing power quality, facilitating grid integration of renewable energy, providing flexible operation and control, optimizing resonant network tuning, and ensuring reliability and durability. Potential outcomes encompass increased renewable energy penetration, enhanced grid stability and resilience, reduced environmental impact, technological advancements, cost-effective solutions, and integration with smart grids.
[013] In conclusion, the disclosed GaN-based DAB LCL Resonant Converter presents a promising solution to the challenges in renewable energy integration, offering efficient, reliable, and adaptable power conversion for diverse energy generation scenarios while ensuring compatibility with existing grid infrastructure.
BRIEF DESCRIPTION OF THE DRAWINGS
[014] when considering the following thorough explanation of the present
invention, it will be easier to understand it and other objects than those
mentioned above will become evident. Such description refers to the
illustrations in the annex, wherein:
FIG. 1 illustrates block diagram of LCL-T series parallel resonant converter;
Fig. 2 (a) and 2 (b) illustrates (a) SMART GREEN POWER CONVERTER and (b) LCL-T series parallel resonant converter; and
Fig. 3 Illustrates equivalent circuit Model of LCL-T SPRC, in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[015] The following sections of this article will provide various embodiments of the current invention with references to the accompanying drawings, whereby the reference numbers utilised in the picture correspond to like elements throughout the description. However, this invention is not limited to the embodiment described here and may be embodied in several other ways. Instead, the embodiment is included to ensure that this disclosure is extensive and complete and that individuals of ordinary skill in the art are properly informed of the extent of the invention.
[016] Numerical values and ranges are given for many parts of the implementations discussed in the following thorough discussion. These numbers and ranges are merely to be used as examples and are not meant to restrict the claims' applicability. A variety of materials are also recognised as fitting for certain aspects of the implementations. These materials should only be used as examples and are not meant to restrict the application of the innovation.
[017] Referring to Figs. 1-3, the invention disclosed in this application pertains to a Gallium Nitride (GaN)-based Dual Active Bridge (DAB) LCL Resonant Converter designed for a wide range of power applications. In light of the rapid advancements in modern energy applications such as photovoltaic (PV) systems, fuel cells (FC), and wind energy farms, there is a pressing need for efficient power conversion solutions. PV sources, characterized by their low DC voltage, require transformation to higher voltages for optimal utilization in microgrids. The proposed solution, the smart green power converter (SGPC), facilitates this transformation by intelligently interfacing solar panels and battery storage with the utility grid at the residential load level, thereby enhancing the efficiency of renewable energy sources.
[018] With the rapid advancement of modern energy applications like photovoltaic (PV) systems, fuel cells (FC), and wind energy farms, the demand for efficient power generation has surged. Notably, PV sources exhibit low DC voltage characteristics, rendering them unsuitable for direct microgrid use. Typically, PV modules are serially connected to achieve higher voltages, necessitating numerous components and physical space. One proposed solution is the Smart Green Power Converter (SGPC), a modular intelligent power flow controller facilitating the interface of solar panels and battery storage with the utility grid at the residential load level. Efficient DC-DC converters play a pivotal role in transforming this low voltage to high voltage, enhancing the utilization of renewable energy sources. As a result, DC-DC conversion techniques have garnered significant research attention to achieve better power conversion efficiency.
[019] For compatibility with previous versions of SGPC, the developed converter must adhere to established system specifications, albeit with higher target efficiency. Table I outlines the system specifications, with parameters relevant to the dual active bridge highlighted. Converter design analysis is performed using PLCS software. he objective of this work is to explore the feasibility of a compact, high-efficiency bidirectional DC-DC converter utilizing 650V GaN HEMTs for EV charging applications. The proposed converter integrates a phase shift-controlled bidirectional full-bridge dual active converter with an LCL-T resonant network. Design considerations aim to optimize efficiency, achieving a peak efficiency of 98.3% across a wide input/output voltage range. GaN devices demonstrate superior performance, enhancing power density and overall efficiency.
Table 1: SMART GREEN POWER CONVERTER SYSTEM SPECIFICATIONS

[020] The GaN dual active bridge converter with an LCL-T resonant network aims to address key challenges in renewable energy integration, focusing on high efficiency, power quality improvement, grid integration, flexible operation, and reliability. Potential outcomes include increased renewable energy penetration, enhanced grid stability, reduced environmental impact, technological advancements, cost-effective solutions, and integration with smart grids. Overall, the proposed converter system aims to maximize the benefits of renewable energy while ensuring compatibility with existing grid infrastructure.
METHODOLOGY:
Proposed LCL-T network:
[021] The design and development of various dc–dc resonant converters (RC) have been focused for telecommunication and aerospace applications in the recent past. It has been found that these converters experience high switching loss, reduced reliability, increased electromagnetic interference (EMI) and high acoustic noise at high frequencies. The series and parallel resonant converter (SRC and PRC, respectively) circuits are the basic resonant converter topologies with two reactive elements. The merits of SRC include better load efficiency and inherent dc blocking of the isolation transformer due to the series capacitor in the resonant network.
[022] However, the load regulation is poor and output-voltage regulation at no load is not possible by switching frequency variations. On the other hand, PRC offers no-load regulation but suffers from poor load efficiency and lack of dc blocking for the isolation transformer. It has been suggested to design resonant converter with three reactive components for better regulation. In order to overcome the above limitations, the series parallel resonant converter (SPRC) is found to be reliable due to various inherent advantages. The LCL tank circuit-based dc–dc Resonant Converter has been experimentally demonstrated and reported by many researchers.
[023] It has been found that the LCL tank circuit connected in series-parallel with the load and operated in above resonant frequency improves the load efficiency and independent operation. Borage et al. have developed an LCL-T half bridge resonant converter with clamp diodes. The output current or voltage is sensed for every change in load due to the output voltage or current which increase linearly. The feedback control circuit has not been considered. Later, Borage et al. have demonstrated the LCL-T RC with constant current supply operated at resonant frequency.
[024] It is clear from the output voltage regulation of the converter against load and supply voltage fluctuations have important role in designing high-density power supplies. The LCL-T SPRC is expected to have the speed of response, voltage regulation and better load independent operation. Keeping the above facts in view, the LCL-T SPRC has been modelled and analysed for estimating various responses. The closed loop state space model has been derived and simulated using PLECS software for comparing the performance with the existing converter.
[025] The block diagram of DAB with LCL-T SPRC is shown in Figure 1. The first stage converts the dc voltage to a high frequency ac voltage. The second stage of the converter is to convert the ac power to dc power by suitable high frequency rectifier. Power from the resonant circuit is taken either through a transformer in series with the resonant circuit. In this high frequency feature of the link allows the use of a high frequency transformer to provide voltage transformation and ohmic isolation between the dc source and the load.
[026] In LCL-T SPRC the load voltage can be controlled by varying the switching frequency or by varying the phase difference between the inverters. The phase domain control scheme is suitable for wide variation of load condition because the output voltage is independent of load. The dc current is absent in the primary side of the transformer and there is no possibility of current balancing. Another advantage of this circuit is that the device currents are proportional to load current. This increases the efficiency of the converter at light loads to some extent because the device losses also decrease with the load current. If the load gets short at this condition, very large current would flow through the circuit. This may damage the switching devices.
[027] A schematic diagram of full-bridge LCL-T SPRC is shown in Figure 2(b). The resonant circuit consists of series inductance L1, parallel capacitor C and series inductance L2. The GaN switches GaN1–GaN4 are used to base/gate turn-on and turn-off. The gate pulses for GaN 1 and GaN 2 are in phase but 180? out of phase with the gate pulses for GaN 3 and GaN 4. The positive portion of switch current flows through the GaN. The load is connected across bridge rectifier. The voltage across the point VC, VD is rectified and fed to load. For the analysis it is assumed that the converter operates in the continuous conduction mode and the semiconductors have ideal characteristics.
Gallium Nitride Semiconductor Device:
[028] In addition to topology and modulation technology, emerging power devices such as GaN HEMT offer superior static and dynamic performance that further improve the performance of power converters. GaN device outperforms Si device in terms of small output capacitance, no reverse recovery and low on-state resistance. Applications that benefit from these features include the continuous current mode (CCM) totem pole power factor correction (PFC) rectifier and other CCM applications. Considering large reverse recovery charge (Qrr), it is impractical to adopt the existing Si MOSFET. Meanwhile, the low Qrr, low switching loss GaN HEMT power device enables this topology to achieve high efficiency. GaN device demonstrates its most important salient features in these applications.
Objectives of the Proposed Converter System:
[029] The objective of this work is to investigate the feasibility of a novel compact high efficiency bidirectional DC-DC converter with 650V GaN HEMTs for Electrical Vehicle charging applications. The proposed power stage is a phase shift controlled bidirectional full-bridge Dual active converter along with LCL-T resonant network. 90V to 400V, 1kW bidirectional DC-DC converter based on GaN and Si devices are designed. Efficiency analysis was conducted and serves as the objective function to optimize the efficiency. A peak efficiency of 98.3% in a wide input/output voltage range are achieved. The proposed topology and use of GaN device demonstrate a superior performance in our application. The design method is verified as an effective way to design bidirectional DC-DC converters for such applications.
Preliminary Simulation:
[030] The invention presents a novel isolated bidirectional DC-DC converter topology with GaN HEMTs. The ability of GaN devices to improve efficiency and power density is evaluated in bidirectional power flow and low voltage, high current applications in place of a Si MOSFET. The operation principles of power stage and LCL-T resonant circuit were analyzed in detail. Efficiency analysis and design criteria were discussed. The simulation results verified that the GaN device based bidirectional DC-DC converter is capable of achieving low power loss and high power density for this specified application. Simulation results were presented for a 2kW, 90V-to-380V DC-DC converter switching at 250kHz. A peak efficiency of 98.3% in a wide input/output voltage range are achieved.
[031] In conclusion, the GaN dual active bridge converter with an LCL-T resonant network aims to address key challenges in renewable energy integration by providing efficient, reliable, and adaptable power conversion solutions. The outcomes are geared towards maximizing the benefits of renewable energy while ensuring compatibility with the existing grid infrastructure.

, Claims:1. A Gallium Nitride (GaN)-based Dual Active Bridge (DAB) LCL Resonant Converter for wide-ranging power applications, comprising:
a) two full bridges connected by a series inductor and a transformer;
b) a resonant circuit incorporating series inductance L1, parallel capacitor C, and series inductance L2;
c) GaN switches GaN1 to GaN4 for base/gate turn-on and turn-off;
d) a bridge rectifier connected across the load;
e) a control scheme enabling phase domain control for wide variation of load condition;
f) operation in the continuous conduction mode with ideal semiconductor characteristics; and
g) a peak efficiency of 98.3% achieved across a wide input/output voltage range.
2. The converter of claim 1, wherein the resonant circuit operates at an above resonant frequency to improve load efficiency and independent operation.
3. The converter as claimed in claim 1, wherein the control scheme facilitates voltage regulation and better load independent operation.
4. The converter as claimed in claim 1, wherein GaN switches GaN1 and GaN2 have gate pulses in phase but 180° out of phase with gate pulses for GaN switches GaN3 and GaN4.
5. The converter as claimed in claim 1, wherein the load voltage is controlled by varying the switching frequency or by varying the phase difference between the inverters.
6. The converter as claimed in claim 1, wherein the device currents are proportional to load current, thereby increasing efficiency at light loads.
7. The converter as claimed in claim 1, wherein the resonant circuit allows the use of a high-frequency transformer for voltage transformation and ohmic isolation between the DC source and the load.
8. The converter as claimed in claim 1, wherein the GaN switches exhibit small output capacitance, no reverse recovery, and low on-state resistance, enhancing efficiency and performance.
9. The converter as claimed in claim 1, wherein the peak efficiency of 98.3% is achieved through optimization of the design parameters and semiconductor characteristics.
10. The converter as claimed in claim 1, wherein simulation results demonstrate low power loss and high power density for the specified application, confirming the effectiveness of GaN devices in bidirectional DC-DC conversion.