input voltage sharing (IVS) is necessary for the stable operation of an input-series-output-parallel (ISOP) dual-active-bridge (DAB) converter. However, the nonidentical high-frequency link (HFL) inductor is unavoidab...
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input voltage sharing (IVS) is necessary for the stable operation of an input-series-output-parallel (ISOP) dual-active-bridge (DAB) converter. However, the nonidentical high-frequency link (HFL) inductor is unavoidable, causing mutual interferences among submodules, and deteriorating the decoupling and voltage balance performances of conventional IVS strategies. Thus, a general decoupling IVS control strategy is proposed for ISOP DAB converter with nonidentical HFL inductors. First, an improved small-signal state-space model of ISOP DAB converter with a full-rank matrix is proposed to present the coupled performance of the ISOP DAB converter with nonidentical HFL inductors. Based on the improved model, a general decoupling method is proposed by invertible and gain-regulated matrices to achieve a diagonal matrix with uniform diagonal elements in the small-signal model, revealing and solving the sneak coupled performances among control loops. Next, a decoupling IVS control strategy is proposed by shaping full-order input impedance to solve the issues and coupled effects of multiple modes in the operation submodules. Then, the IVS controller is designed and detailed in the frequency and time domains, achieving input voltage balance and avoiding oscillation among submodules with better dynamics and more stable responsiveness. Moreover, the better characteristics of input impedance, output impedance, and input voltages in the proposed decoupling IVS control strategy are discussed and compared with traditional strategies. Finally, experiments are set up to verify the proposed general decoupling IVS control strategy for ISOP DAB converter with nonidentical HFL inductors.
input-series-output-parallel (ISOP) LLC converters have the capability to leverage lower voltage semiconductor devices, thereby enabling applications with higher voltage requirements. The primary advantages lie in enh...
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input-series-output-parallel (ISOP) LLC converters have the capability to leverage lower voltage semiconductor devices, thereby enabling applications with higher voltage requirements. The primary advantages lie in enhanced efficiency and power density attributed to improved device performance. Given the utilization of multiple modular LLC converters, the potential impact of component parameter mismatch becomes a significant concern. Specifically, issues related to input voltage sharing (IVS) and device zero voltage switching (ZVS) are critical considerations. This paper develops a precise mathematical model during deadtime to determine ZVS boundaries, taking into account parameter mismatches. Within the developed boundaries, all LLC sub-modules are assured of ZVS operation. To assess IVS performance, a mathematical model is formulated using the first harmonic approximation (FHA) equivalent circuit. To validate the proposed modeling and analysis, a 3 kW 1 MHz GaN-based ISOP LLC is constructed, comprising four modular 750W-LLC units. Experimental results showcase successful ZVS operations and natural voltage balancing of the ISOP LLC converter across a broad range of parameter mismatches.
Modular input-series-output-parallel (ISOP) converters are very suitable for high-voltage and high-power applications. In order to ensure the normal operation of ISOP converters, it is necessary to realize the input-v...
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Modular input-series-output-parallel (ISOP) converters are very suitable for high-voltage and high-power applications. In order to ensure the normal operation of ISOP converters, it is necessary to realize the input-voltage and output-current equalization of each submodule. However, there are few studies on the input-voltage and output-current equalization performance of the ISOP system. In this paper, the input-voltage and output-current equalization characteristics of a Boost + LLC modular ISOP converter are studied based on the small-signal model. In this paper, the small-signal model of an ISOP system is first established, and then the input-voltage and output-current equalization performance of the ISOP system under the condition of inconsistent submodule parameters are analyzed. Finally, simulations and experiments are reported to verify the results. The experimental results show that the ISOP system composed of a Boost + LLC cascaded module has excellent voltage and current self-equalization performance.
input-series-output-parallel (ISOP) converters enable the use of low voltage devices in high voltage applications. Additional benefits include modularity and increased efficiency due to improved device figure-of-merit...
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ISBN:
(纸本)9781728151359
input-series-output-parallel (ISOP) converters enable the use of low voltage devices in high voltage applications. Additional benefits include modularity and increased efficiency due to improved device figure-of-merit (FOM) for low voltage devices. A ISOP system typically consists of many converter modules. In order to ensure proper system operation, voltage and current among each module should be equal. However, parameter mismatch is inevitable between converter modules, causing input voltage and current unbalanced. In this paper, performance of an ISOP LLC converter with resonant tank parameter mismatch is analyzed. Impedance model analysis of system input voltage sharing (IVS) is established and conducted under first harmonic approximation (FHA) assumption. Analysis shows that the ratio of resonant inductor Lr and magnetizing inductor Lm has a major impact on input voltage sharing, while voltage sharing is not affected significantly by L-m value. To achieve an ISOP LLC with good input voltage sharing, small L-r/L-m ratio is expected. A 3kW, 400V to 48V four-module ISOP LLC is developed to verify the conclusion and good input voltage sharing property is demonstrated by simulations and experiments.
As an eventual replacement of the century-old line frequency transformer (LFT), the Solid-State Transformer (SST) has been investigated intensively in the past decade due to its ability to offer many smart functionali...
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ISBN:
(纸本)9781728103952
As an eventual replacement of the century-old line frequency transformer (LFT), the Solid-State Transformer (SST) has been investigated intensively in the past decade due to its ability to offer many smart functionalities such as voltage regulation and power flow control in the distribution power grid. For the medium voltage and high voltage SSTs, the availability and cost of high voltage power devices are the major limitations. One possible solution is to use modular SST architecture in an input-series-output-parallel (ISOP) configuration to reach high input voltage and high-power capacity. However, modular SST introduces additional challenges in control due to the need for many voltage and current sensors, multiple control loops to achieve cell to cell level voltage and power balancing. To address these problems, this paper introduces a novel modular SST solution utilizing single stage AC-AC resonant converter as the modular cell with distributed open loop control. The proposed modular SST is therefore capable of reaching medium and high voltages easily with simple and robust control. The proposed architecture eliminates the DC-DC stage hence the associated bulky DC link capacitors. Higher power density can therefore be achieved. 10 kW modular LLC converter prototype is developed based on 1.2kV SiC MOSFETs. Peak AC-AC efficiency up to 97.3% is achieved and demonstrated. Voltage and power balancing among modular cells are analyzed against cell to cell variations, including resonant frequency, switching frequency and losses. Simulation results show that the proposed modular SST has no performance degradation even considering those variations in a practical system. An ISOP architecture using two LLC converters is also demonstrated with preliminary experimental results, showing that with LLC converters working close to resonant frequency, the input voltage balancing can be achieved.
input-series-output-parallel (ISOP) inverter system is very suitable for high input voltage and large output current power conversion applications. One of many merits of this assembly system lies in that its character...
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input-series-output-parallel (ISOP) inverter system is very suitable for high input voltage and large output current power conversion applications. One of many merits of this assembly system lies in that its characteristic of multimodule series-parallel combination can significantly improve the reliability of the operation. To address this point, redundancy should be realized for the whole system. However, the existing methods for the ISOP inverter system all belong to centralized control, which restricts the modularity of the system. From the above perspective, this paper proposes a new scheme to achieve both power balance and distributed configuration according to the conception of compound control. Also, the relationship of control loops is analyzed and the design procedure of them is given. Based on the fully modular system actualized by the distributed control, the hot-swap technique is then raised to get a redundant system with superior reliability. Here, the way of bypassing other than cutting off is adopted to fulfill withdrawal of the faulty module from the system due to series connection at the input terminal. In addition, the detailed timing sequence of system operation is provided to ensure the smooth transition during the hot-plugging transient. Finally, a three-module prototype is built and the experimental results validate the effectiveness of the presented strategy.
Aiming at the problem that silicon-controlled rectifiers (SCR) and pulse width modulation (PWM) rectifiers cannot balance high power levels, high hydrogen production efficiency, and high grid connected quality in the ...
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Aiming at the problem that silicon-controlled rectifiers (SCR) and pulse width modulation (PWM) rectifiers cannot balance high power levels, high hydrogen production efficiency, and high grid connected quality in the current research on rectifier power supplies for electrolytic hydrogen production, a new hybrid rectifier topology based on a modular multilevel converter (MMC) is proposed. The hybrid topology integrates a silicon-controlled rectifier (SCR) with an auxiliary power converter, wherein the SCR is designated as the primary power source for electrolytic hydrogen production. The auxiliary converter employs a cascaded modular multilevel converter (MMC) and an input-series-output-parallel (ISOP) phase-shifted full-bridge (PSFB) arrangement. This configuration allows the auxiliary converter to effectively mitigate AC-side harmonics and minimize DC-side ripple, concurrently transmitting a small amount of power. The effectiveness of the hybrid rectifier in achieving low ripple and harmonic distortion outputs was substantiated through hardware-in-the-loop experiments. Notably, the hybrid topology is characterized by its enhanced electric-to-hydrogen conversion efficiency, elevated power density, cost efficiency, and improved grid compatibility.
The input-series-output-parallel (ISOP) inverter system, which consists of standard DC/AC modules connected in series at the input side and in parallel at the output side, is very suitable for high input voltage as we...
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The DC transformers (DCTs) constructed by input-series-output-parallel (ISOP) structure with dual active bridge (DAB) submodules (SMs) would face the risk of instability due to the equivalent inductance of input power...
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input-series-output-parallel (ISOP) modular converters consisting of multiple modular DC/DC converters can enable low voltage rating switches for use in high voltage input applications. In this paper, an input voltage...
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input-series-output-parallel (ISOP) modular converters consisting of multiple modular DC/DC converters can enable low voltage rating switches for use in high voltage input applications. In this paper, an input voltage sharing control strategy for input-series-output-parallel (ISOP) full-bridge (FB) DC/DC converters is proposed. By sensing the difference in the input current of two modules, the system can achieve input voltage sharing for DC-DC modules. The effectiveness of the proposed control strategy is verified by simulation and experimental results obtained with a 200w-50kHz prototype.
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