Robust Circuit Parameters Design for the CLLC-Type DC Transformer in the Hybrid AC–DC Microgrid

Huang, Jingjing; Shuai, Zhikang; Zhang, Xinan; Yang, Shunfeng; Koh, Leong Hai; Xiao, Jianfang; Tong, Xiangqian

doi:10.1109/tie.2018.2835373

Cited by 113 publications

(34 citation statements)

References 30 publications

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“…It can be observed that, the values of inductances and capacitances are changing in practice. This is consistent with the definition in [24]. It is known that more than one resonant frequency f r are available for the GCLLC-DCT, and the changing inductances and capacitances make f r vary online.…”

Section: B) Pt Problem Induced By Parameter Variations In Practicesupporting

confidence: 87%

“…However, the DCSR controlled GCLLC-DCT challenges the resonant parameters design regarding the PT and VCG. Therefore, a robust parameter design approach is presented in [24] to guide the design of the symmetric CLLC-DCT. This approach can guarantee the desired VCG in the full power range to against the parameter variations.…”

Section: Lm1 Lm2mentioning

confidence: 99%

“…This approach can guarantee the desired VCG in the full power range to against the parameter variations. However, when it is applied in the GCLLC-DCT, the PT ability should be further improved to deal with the following problems: · There may exist more than one resonant frequency f r for the GCLLC-DCT, which is not discussed in depth [24]. Besides, the value of f r derived in [23] and [24] is also not accurate enough for the GCLLC-DCT due to the magnetizing inductance is ignored in the symmetric CLLC-DCT.…”

Section: Lm1 Lm2mentioning

confidence: 99%

“…Therefore, how to determine the optimum f r from its available values should be further theoretically analyzed. · It is known that the switching frequency f s is generally selected as f s =f r for the DCT to cooperate with BIC to ensure the PT ability [8], [24]. However, the f s is constant in the DCSR controlled DCT, while the f r varies in practice.…”

Section: Lm1 Lm2mentioning

confidence: 99%

“…An example GCLLC-DCT in [24] is given in Table I to estimate the problems induced by the parameter variations. Fig.…”

Section: B) Pt Problem Induced By Parameter Variations In Practicementioning

confidence: 99%

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Three-Step Switching Frequency Selection Criteria for the Generalized CLLC-Type DC Transformer in Hybrid AC–DC Microgrid

Huang

Zhang

2020

IEEE Trans. Ind. Electron.

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For hybrid AC/DC microgrids, the widely applied high frequency DC transformer (DCT) is usually scheduled to operate at resonant frequency with 50% duty-cycle based semi-regulated control (DCSR) to ensure the power transmission (PT), improve its power-density and simplify the system-level control. However, for a real DCT, it may exist more than one resonant frequency that exhibit totally different features, which may seriously degrade the PT ability if the inappropriate switching frequency is selected. Meanwhile, the actual values of the DCT inductances and capacitances are also changing with the power, temperature, etc., which may lead to the practical resonant frequency's variation. Thus, how to select the suitable switching frequency to guarantee the PT ability against the parameter variation becomes a challenge. In this paper, three-step switching frequency selection criteria (SFSC) are proposed. A generalized CLLC-type DCT (GCLLC-DCT) model is extracted to make the proposed approach available for the LLC-, CLL-, symmetric CLLC-and asymmetric CLLC-type topologies. For convenience, the definition of the active power transmission ratio (APTR) is introduced to help evaluate the PT ability. First, the number, value and impact variables of the resonant frequency are derived and analyzed in Step I as the preliminary. Afterwards, the optimum resonant frequency is confirmed for the GCLLC-DCT as the criterion based on the APTR in Step II. At last, the criterion in Step III is given to finally determine the switching frequency against the parameter variations. The proposed SFSC method is also validated by the experiments. IndexTerms-CLLC, DC transformer, power transmission (PT), resonant frequency, switching frequency.

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Section: B) Pt Problem Induced By Parameter Variations In Practicesupporting

confidence: 87%

Section: Lm1 Lm2mentioning

confidence: 99%

Section: Lm1 Lm2mentioning

confidence: 99%

Section: Lm1 Lm2mentioning

confidence: 99%

“…An example GCLLC-DCT in [24] is given in Table I to estimate the problems induced by the parameter variations. Fig.…”

Section: B) Pt Problem Induced By Parameter Variations In Practicementioning

confidence: 99%

See 3 more Smart Citations

Three-Step Switching Frequency Selection Criteria for the Generalized CLLC-Type DC Transformer in Hybrid AC–DC Microgrid

Huang

Zhang

2020

IEEE Trans. Ind. Electron.

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Robust and low‐cost design of LLC‐type DC transformer in hybrid AC / DC nano‐grids to improve energy conversion ability

Sun

Tong

Huang

et al. 2021

Int Trans Electr Energ Syst

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In the hybrid AC/DC nano‐grid, the LLC‐type DC transformer (DCT) is widely utilized in the DC and AC bus connection system (BCS) with high frequency to improve the system power density. However, it always employs the simple open‐loop scheme for not increasing the control complexity of the nano‐grid system, which creates a big challenge on the inherent features of the DCT circuit for the energy efficiency and conversion ability. Therefore, a robust and low‐cost design approach of the LLC‐type DCT is put forward in this paper based on the specific requirements of hybrid AC/DC nano‐grid. First of all, the design challenges of the LLC‐type DCT are discussed by analyzing the functions of BCS in nano‐grid application. Then, the detailed parameter design approach is presented step‐by‐step to meet the energy efficiency and conversion requirements in the full power range. Finally, a 6 kW nano‐grid prototype is established to verify the effectiveness of the proposed design method. The results show that the designed DCT can enjoy good energy efficiency and conversion ability with simple control and hence accommodate the high‐frequency nano‐grid application.

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On‐board charger applications: A new hybrid control strategy for bidirectional CLLC resonant converter

Shi,

Tang,

Davari

2024

Circuit Theory & Apps

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This paper proposes a new hybrid control strategy to solve the problem of bidirectional wide voltage range regulation in CLLC converters. On the (LLC) side (G2V direction), the SSSA control method is employed for voltage boost, combined with bus voltage and burst control to achieve wide voltage regulation. On the (C) side (V2G direction), the SSSA and full/half‐bridge mode switching control are used to achieve V2G direction wide voltage regulation. This hybrid control strategy also enables high conversion efficiency in both directions without the need for additional components to reduce the converter power density. This is particularly suitable for OBC applications with strict requirements for converter volume and weight. A detailed analysis with mathematical derivation, hybrid control strategy, and converter operation principles is introduced in this paper. The following subchapters supplement the converter voltage gain, soft switching implementation conditions, and design considerations. Finally, the feasibility of the proposed control strategy was verified through an experimental prototype with an input voltage ranging from 340 to 430 V to an output voltage ranging from 225 to 450 V and bidirectional rated power of 6.6/3.3 kW. This prototype achieved a maximum conversion efficiency of 97.7% in the G2V direction and 97.1% in the V2G direction.

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Robust Circuit Parameters Design for the CLLC-Type DC Transformer in the Hybrid AC–DC Microgrid

Cited by 113 publications

References 30 publications

Three-Step Switching Frequency Selection Criteria for the Generalized CLLC-Type DC Transformer in Hybrid AC–DC Microgrid

Three-Step Switching Frequency Selection Criteria for the Generalized CLLC-Type DC Transformer in Hybrid AC–DC Microgrid

Robust and low‐cost design of LLC‐type DC transformer in hybrid AC / DC nano‐grids to improve energy conversion ability

On‐board charger applications: A new hybrid control strategy for bidirectional CLLC resonant converter

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