Stability-Oriented Design for LCL-LC-Trap Filters in Grid-Connected Applications Considering Certain Variation of Grid Impedance

Xu, Jinming; Bian, Shenyiyang; Qian, Qiang; Xie, Shaojun

doi:10.1109/peac.2018.8590452

Cited by 6 publications

(7 citation statements)

References 11 publications

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“…In order to address the first issue, various modified configurations of LCL filters have been presented [4][5][6][7][8][9][10][11][12][13][14][15][16]. These modified filters have additional components such as resonant LC traps connected in series or parallel, which are resonated at the switching frequency and its multiples to bypass or block the selected harmonics by these LC traps.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic integrated LLCL filter with resonant frequency above Nyquist frequency

Al-Barashi

Liu

et al. 2022

IET Power Electronics

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This paper presents a design technique of magnetic integrated LLCL filters for grid-tied inverters. With the proposed design technique, the LLCL filter's resonant frequency can be higher than the Nyquist frequency. Furthermore, the proposed concept was only reported for the LCL filter in the previous research works. In addition, the modulation process will produce dominant switching harmonics for unipolar PWM H-bridge inverters at the double switching frequency. Thus, putting the resonant frequency beyond the Nyquist frequency will increase the stability zone. The proposed design methods maximize the filter inductors' utilization and resist the grid impedance variations under weak grid conditions, depending on the improved stability zone. Comparative simulation and HIL experimental results are presented to confirm the effectiveness of the proposed magnetic integrated LLCL filter design. The HIL experimental results and the simulation results agree well with each other.

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Section: Introductionmentioning

confidence: 99%

“…FIGURE16 Simulation results of the grid-tied inverter with magnetic integrated LLCL filter when the dc load steps up by 10 Ω and L s = 3 mH…”

mentioning

confidence: 99%

Magnetic integrated LLCL filter with resonant frequency above Nyquist frequency

Al-Barashi

Liu

et al. 2022

IET Power Electronics

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“…These resonant peaks are obtained by putting the denominator of GDTLCL(s) in ( 10) equals zero, substituting s with jω. The first resonant frequency of the magnetic integrated DTLCL filter can be approximated as in (13) [42], [43], where ωres1 represents the resonant angular frequency and fres1 represents the resonant frequency.…”

Section: Integrated Dtlcl Filter's Properties and Filtering Effective...mentioning

confidence: 99%

Magnetic Integrated Double-Trap Filter Utilizing the Mutual Inductance for Reducing Current Harmonics in High-Speed Railway Traction Inverters

Al-Barashi,

Wang,

Lan

et al. 2024

Preprint

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Current harmonics are generated at the switching frequency and its multiples when the traction converters are modulated. The multi-trap filters can eliminate the harmonic at these frequencies. Therefore, total inductance and filter size can be reduced. Comparatively to traditional inductor-capacitor-inductor (LCL) filters, more magnetic cores are needed for trap inductors. Furthermore, the traction systems have not been examined in conjunction with multi-trap filters. To reduce the filter size and investigate its application in traction converters, this paper presents an integrated double-trap LCL (DTLCL) filter. A tiny capacitor is connected in parallel with the grid-side inductor to form one LC-trap. In addition, another LC-trap is formed by connecting the equivalent trap inductor, introduced through the magnetic coupling between inverter-side and grid-side inductors, in series with the filter capacitor. The presented filters' features are thoroughly analyzed, and the design method has been developed. Finally, the simulation and hardware-in-the-loop (HIL) experiment results validate the proposed method's viability and efficacy. Compared to the discrete windings, the integrated ones enable a size decrease of 35.4%. Furthermore, the proposed filters can meet IEEE criteria with 0.3% for all the harmonics and total harmonic distortion (THD) of 2.36% of the grid-side current.

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“…However, the LCL filters have severe limitations, including poor switching harmonics absorption, significant passive components, and electrical network resonance [11]. Different LCL-modified filter configurations have been presented in [12][13][14][15][16][17][18][19][20][21][22][23], where most of them are with extra LC traps connected in parallel or series and resonated to the dominant switching frequency. These traps enable bypassing or blocking of particular harmonics.…”

Section: Introductionmentioning

confidence: 99%

High-frequency harmonics suppression in high-speed railway through magnetic integrated LLCL filter

Al-Barashi,

Wang,

Bhutta

2024

PLoS ONE

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The traction converter modulation generates switching-frequencies current harmonics. The trapped filters can eliminate these switching harmonics, reducing total inductance and filter size. Nonetheless, in comparison with the typical inductor-capacitor-inductor (LCL) filter, the trap inductor needs a larger magnetic core. Moreover, the trapped filter has not been analyzed in the traction systems. This paper proposes a magnetic integrated inductor-trap-inductor (LLCL) filter to decrease the filter’s size and investigate its application in traction converters. In fact, the application range of this filter is quite broad, and it can be used in various electrical power systems, including industrial power systems, renewable energy systems, transportation systems, and building power systems. The LC-trap may be formed by connecting the equivalent trap inductor, introduced through the magnetic coupling between inverter-side and grid-side inductors, in series with the filter capacitor. Furthermore, for H-bridge unipolar pulse width modulation (PWM) traction converters, the prominent switching harmonics are concentrated at the double switching frequencies. Therefore, the stability zone is expanded by moving the resonance above the Nyquist frequency. The presented filter’s features and design are thoroughly analyzed. The proposed method is finally validated by the MATLAB/Simulink simulation and hardware-in-the-loop (HIL) experimental results. Compared to the discrete windings, the integrated ones can save two magnetic cores. Furthermore, the proposed filter can meet IEEE criteria with 0.3% for all the harmonics and total harmonic distortion (THD) of 2.15% of the grid‐side current.

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Stability-Oriented Design for LCL-LC-Trap Filters in Grid-Connected Applications Considering Certain Variation of Grid Impedance

Cited by 6 publications

References 11 publications

Magnetic integrated LLCL filter with resonant frequency above Nyquist frequency

Magnetic integrated LLCL filter with resonant frequency above Nyquist frequency

Magnetic Integrated Double-Trap Filter Utilizing the Mutual Inductance for Reducing Current Harmonics in High-Speed Railway Traction Inverters

High-frequency harmonics suppression in high-speed railway through magnetic integrated LLCL filter

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