Frequency-dependent Feedforward Compensation for Reshaping the Output Impedance of Grid-connected Converter

doi:10.11985/2021.04.017

Abstract

Abstract:

Grid-connected converter is acting as the critical AC/DC interface in distributed power generation system. Aiming at solving the harmonic resonance over the wide-frequency band and the system instability problem caused by interactions between the grid impedance and the grid-connected converter, the influence of the traditional unit grid voltage feedforward (GVF) compensation on the magnitude-phase characteristic through the cascaded impedance model is revealed. The frequency-dependent feedforward compensation strategy based on the digital filter is further proposed, which includes the reduction of the gain and the delay of the low-frequency component of the grid voltage, and the increase of the delay of the high-frequency component of the grid voltage. The design guideline of the feedforward parameters is further elaborated, which reshapes the inverter output impedance to be passive. The adaptability to the variation of the grid impedance is enhanced, and the wide-frequency band harmonics under the weak grid are also suppressed. Simulation and experimental results finally verify the correctness of the theoretical analysis and the effectiveness of the proposed frequency-dependent GVF compensation strategy.

Key words: Grid-connected converter, harmonic resonance, weak grid, grid voltage feedforward

CLC Number:

TM46

CAO Jianwei, ZHANG Lei, QIAN Qiang, ZHANG Li, DING Yong. Frequency-dependent Feedforward Compensation for Reshaping the Output Impedance of Grid-connected Converter[J]. Journal of Electrical Engineering, 2021, 16(4): 135-142.

Figures/Tables 14

References 23

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参数	数值	参数	数值
逆变器侧电感L_i1/mH	0.8	控制频率f_s/kHz	15
滤波电容C_f/μF	7	开关频率f_s/kHz	15
网侧电感L_i2/mH	0.5	LCL谐振频率f_r/kHz	3.43
比例增益k_p	9.75	积分因子k_i	16 250