Source-Side Series-Virtual-Impedance Control to Improve the Cascaded System Stability and the Dynamic Performance of Its Source Converter

Zhang, Xin; Zhong, Qing-Chang; Kadirkamanathan, Visakan; He, Jinsong; Huang, Jingjing

doi:10.1109/tpel.2018.2867272

Cited by 112 publications

(38 citation statements)

References 23 publications

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“…where Δβ is the parameter variation of β. Taking C2M0080120D as an example, in (2) - (6), [36], parasitics L g = 9.2 nH, L s = 7.5 nH [37]. According to (4) and 5, the numerical results of Δi d caused by ΔV th and influenced by v gs is illustrated in Fig.…”

Section: A Impact Of Dispersing Device Parametersmentioning

confidence: 99%

“…IGH-frequency and high-capacity power converters are increasingly demanded for transportation electrification and smart grid applications to reduce cost, improve power-density, and save manpower [1]- [3]. Thanks to the high switching speed and low switching loss, SiC MOSFET device becomes more and more popular for high-frequency power converters [4]- [6]. However, due to the low yield rate in the wafer and high thermal-mechanical stress in the device, the active area of SiC chip is limited, and the current rating of commercial SiC chip is within 100A [4], generally.…”

Section: Introductionmentioning

confidence: 99%

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Imbalance Current Analysis and Its Suppression Methodology for Parallel SiC MOSFETs with Aid of a Differential Mode Choke

Zeng

Zhang

2020

IEEE Trans. Ind. Electron.

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Parallel connection of SiC MOSFETs is a cost-effective solution for high-capacity power converters. However, transient imbalance current, during turn-on and-off processes, challenges the safety and stability of parallel SiC MOSFETs. In this paper, considering the impact factors of device parameters, circuit parasitics, and junction temperatures, in-depth mathematical models are created to reveal the electro-thermal mechanisms of the imbalance current. Moreover, with the incorporation of a differential mode choke (DMC), an effective approach is proposed to suppress the imbalance current among parallel SiC MOSFETs. Physic concepts, operation principles, and design guidelines of the DMC suppression method are fully presented. Besides, to reduce the equivalent leakage inductance and equivalent parallel capacitance of the DMC, winding patterns of the DMC are comparatively studied and optimized to suppress turn-off over-voltage and switching ringing. Concerning the influence of winding patterns, load currents, gate resistances, and junction temperatures, experimental results are comprehensively demonstrated to confirm the validity of theoretical models and the function of the proposed DMC suppression method. It is turned out the low-cost DMC is easy to design and utilize without complex feedback circuits or control schemes, which is a cost-effective component to guarantee consistent and synchronous on-off trajectories of parallel SiC MOSFETs. Index Terms-Parallel SiC MOSFETs, mechanism of imbalance current, consistency and synchronization of on-off trajectories, differential mode choke.

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Section: A Impact Of Dispersing Device Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Imbalance Current Analysis and Its Suppression Methodology for Parallel SiC MOSFETs with Aid of a Differential Mode Choke

Zeng

Zhang

2020

IEEE Trans. Ind. Electron.

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“…The VI is added to the existing control block diagram to perform the same behavior as the dotted line circuit. By adding a VI, the output impedance is reshaped at frequencies where impedance overlap occurs due to insufficient damping in the source converter [32], [33]. Thus, it can meet Middlebrook's stability criterion and stabilize the system.…”

Section: Stability Enhancement Control Schemementioning

confidence: 99%

Impedance-Based Modeling and Common Bus Stability Enhancement Control Algorithm in DC Microgrid

Lee

Park

et al. 2020

IEEE Access

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In this paper, impedance modeling of a DC microgrid system consisting of a source and load converter, including an input filter, is performed. Impedance-based modeling has been used to derive mathematical models of the output impedance of the source converter and the input impedance of the load converter. The correlation between the converter interaction and system stability is analyzed based on the mathematical model. An impedance-based stability analysis is used to determine the system stability by analyzing the interactions among the converters in the DC microgrid system. Middlebrook's stability criterion, which uses the impedance transfer function, is applied to determine system stability. Moreover, in this paper, a stability enhancement control algorithm is proposed to resolve the system instabilities resulting from interaction among the converters and the distortion caused by the harmonics emanating from the AC input. The proposed stability enhancement control algorithm consists of a feed-forward type virtual impedance (VI) and a proportional-resonant (PR) controller. The validity of the proposed method is demonstrated by the results of the response characteristics in the frequency domain, and the effectiveness of the proposed control algorithm is verified via simulations and prototype experimental models.

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“…The line frequency AC transformer (ACT) is deployed in [3] to realize the galvanic isolation and to match the voltage-grade. However, the bulky ACT hinders the efficiency and powerdensity of the hybrid AC/DC microgrid [5], [6]. Therefore, the high frequency DC transformer (DCT) has been proposed to replace the bulky ACT in the microgrid application to reduce weight and space occupation [7], [8].…”

Section: Introductionmentioning

confidence: 99%

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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Source-Side Series-Virtual-Impedance Control to Improve the Cascaded System Stability and the Dynamic Performance of Its Source Converter

Cited by 112 publications

References 23 publications

Imbalance Current Analysis and Its Suppression Methodology for Parallel SiC MOSFETs with Aid of a Differential Mode Choke

Imbalance Current Analysis and Its Suppression Methodology for Parallel SiC MOSFETs with Aid of a Differential Mode Choke

Impedance-Based Modeling and Common Bus Stability Enhancement Control Algorithm in DC Microgrid

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

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