The virtual infinite capacitor-based active submodule for MMC

Lin, Jun

doi:10.1109/icsee.2016.7806038

Cited by 9 publications

(8 citation statements)

References 19 publications

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“…ΔI zhu is defined as the difference between I zhu and I x. I zhu can be obtained by (12). By substituting ΔI zhu for I zhu in the terms containing I zhu in (17), h can be obtained as…”

Section: Methods 2 For Reducing the Extra Loss Based On Real-time Calcmentioning

confidence: 99%

“…On the basis of (10), (12), (15) and (16), when i z_ac is injected, u c_p_ac , the ac component of the SM capacitor voltage of the upper arm can be obtained as…”

Section: Design Of the Sm Capacitance Valuementioning

confidence: 99%

“…On the basis of (11), (12) and 17, the second-harmonic frequency component is zero and the third-order frequency component is very small in (17). To simplify the expression of ΔU max , the amplitude is considered, and the phase is not considered for the third-order frequency component.…”

Section: Design Of the Sm Capacitance Valuementioning

confidence: 99%

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Adaptive loss and capacitance‐reduction control strategy based on second‐harmonic circulating current injection for MMC

Jiang

Xiao

Wang

2019

IET Power Electronics

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The submodule (SM) capacitance value of a modular multilevel converter (MMC) is so large that the reliability and cost of the MMC are affected. By existing methods of second-harmonic circulating current injection with a closed-loop control strategy, the SM capacitance value can be greatly reduced. However, the design of the SM capacitance value is not given, and extra loss is brought in. This study gives the design of the SM capacitance value when the second-harmonic circulating current is injected with a closed-loop control strategy. Then, an adaptive control method based on SM capacitor voltage fluctuation feedback is proposed to reduce the extra loss caused by the second-harmonic circulating current injection. In addition, for the case without SM capacitor voltage sensors, a method based on real-time calculation of the injected second-harmonic circulating current is proposed to reduce the extra loss without SM capacitor voltage sensors. Finally, the accuracy of the design and the validity of the proposed methods are verified by simulation and experimental results.

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“…ΔI zhu is defined as the difference between I zhu and I x. I zhu can be obtained by (12). By substituting ΔI zhu for I zhu in the terms containing I zhu in (17), h can be obtained as…”

Section: Methods 2 For Reducing the Extra Loss Based On Real-time Calcmentioning

confidence: 99%

“…On the basis of (10), (12), (15) and (16), when i z_ac is injected, u c_p_ac , the ac component of the SM capacitor voltage of the upper arm can be obtained as…”

Section: Design Of the Sm Capacitance Valuementioning

confidence: 99%

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Adaptive loss and capacitance‐reduction control strategy based on second‐harmonic circulating current injection for MMC

Jiang

Xiao

Wang

2019

IET Power Electronics

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“…In this range, the gate control signals q andq are controlled in such a way as to transfer the excess charge that would create voltage ripples in V to the capacitor C s and thus constrain the voltage V to a small neighbourhood of V re f . This VIC configuration was found to be quite effective in suppressing unpredictable voltage fluctuations, through both simulations [17,18] and experiments [15,19]. When we compute the output impedance of a VIC (as is done, for instance, in [15]), we find that it is high for frequencies near zero (as it should), it has a region where it is very low (as desired), but it grows for higher frequencies.…”

Section: Introductionmentioning

confidence: 99%

The Parallel Virtual Infinite Capacitor Applied to DC-Link Voltage Filtering for Wind Turbines

2018

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Abstract:We propose the parallel virtual infinite capacitor (PVIC) concept, which refers to two virtual infinite capacitors (VIC) connected to the same DC link and sharing one capacitor, one tuned to low frequencies (LF) and one tuned to high frequencies (HF). A PVIC can suppress voltage variations (ripple) in a wider frequency range than a usual VIC. The LF-VIC is controlled by a sliding mode controller to regulate the low-frequency component of the voltage to its reference value, and by a proportional-integral (PI) controller to maintain its state of charge within the desired operating range and achieve the 'plug-and-play' pattern of PVIC. The HF-VIC is controlled by another sliding mode controller to limit the high-frequency ripples and also to keep its state of charge within a reasonable operating interval. As our main application, we use the PVIC to replace a DC-link capacitor for voltage filtering on the DC link of a doubly fed induction generator (DFIG), which is driven by a WindPact (WP) 1.5-MW wind turbine under different grid conditions with turbulent wind input. The simulation study indicates that the PVIC provides much better voltage stabilisation than a DC-link capacitor with the same capacitance, especially in the low frequency range.

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“…We modified VIC in both control algorithm and circuit design in [3], and achieved better filtering performance, lower switching frequency, and lower power loss, which laid the foundation for the hardware implementations of VIC. This modified VIC has been tested by simulations in the applications of PFC [3] and MMC [13]. The modified circuit is shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Experimental ripple suppression performance of a virtual infinite capacitor

Lin

Pan

Lin

et al. 2017

2017 International Conference on Applied Electronics (AE)

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We experimentally show the performance of a Virtual Infinite Capacitor (VIC) in suppressing the voltage ripple. VIC mainly uses a bi-directional DC-DC converter with only two small capacitors inside to mimic the filtering process of a large capacitor by applying suitable control algorithms. It was firstly proposed in [1], [2] and then improved in [3] in both control algorithms and circuit designs. Based on VIC's control algorithm in [3], we injected the DC voltage together with a 50Hz, 85V (peak-to-peak) sinusoidal ripple to the VIC, and we achieved outstanding filtering performance in both the simulation and experiment. The 85V voltage ripple is eliminated and the DC voltage is extracted with no visible 50Hz ripples.

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The virtual infinite capacitor-based active submodule for MMC

Cited by 9 publications

References 19 publications

Adaptive loss and capacitance‐reduction control strategy based on second‐harmonic circulating current injection for MMC

Adaptive loss and capacitance‐reduction control strategy based on second‐harmonic circulating current injection for MMC

The Parallel Virtual Infinite Capacitor Applied to DC-Link Voltage Filtering for Wind Turbines

Experimental ripple suppression performance of a virtual infinite capacitor

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