Modeling and Control Parameters Design for Grid-Connected Inverter System Considering the Effect of PLL and Grid Impedance

Zhiwei Xie,An Luo,Haining Wang,Yandong Chen,Wenhua Wu,Yuancan Xu,Jian Guo

doi:10.1109/access.2019.2950933

Zhiwei Xie, An Luo + Show 5 more

Open Access

https://doi.org/10.1109/access.2019.2950933

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Abstract

Small-signal stability problems often occur when the inverter for renewable energy generation is connected to weak grid. A small-signal transfer function integrated model reflecting the interaction of grid impedance, phase locked-loop (PLL), and current control loop is established in this paper. Based on the established model, the oscillation mechanism of the grid-connected inverter system is revealed: the inductance current flowing through the grid impedance can produce a voltage disturbance, which will eventually affect the inductance current through PLL and current control loop. Therefore, the loop composed of the grid impedance and PLL can easily lead to the oscillation of the grid-connected inverter system under weak grid condition. To suppress the oscillation, a control parameters design method of the grid-connected inverter is proposed. Without changing the control method, the proposed control parameters design method can ensure the stable operation of the grid-connected inverter system under the very weak grid condition when the short-circuit ratio (SCR) is 2. Finally, the experimental results verify the correctness of the stability analysis and the effectiveness of the control parameters design method proposed in this paper.

Highlights

Renewable energy generation has been developed rapidly in response to the crisis of energy shortage and increased environmental pollution [1]
The voltage disturbance affects the output of the current control loop through phase locked-loop (PLL), and acts on the inductance current
Considering the influence of grid impedance and PLL, a small-signal transfer function integrated model is established in this paper; the mechanism of the influence of grid impedance, PLL, and current control loop on the stability of grid-connected inverter system is analyzed; and the control parameters design method of the grid-connected inverter considering interaction between PLL and current control loop under weak grid condition is proposed

Summary

INTRODUCTION

Renewable energy generation has been developed rapidly in response to the crisis of energy shortage and increased environmental pollution [1]. To address the above issues, a control parameters design method of the grid-connected inverter considering the interaction between PLL and current loop under weak grid condition is proposed in this paper. In order to explore the interaction mechanism between grid impedance, PLL, and current control loop, a small-signal transfer function integrated model of current control loop considering the effect of grid impedance and PLL is established.

INTERACTION BETWEEN PLL AND CURRENT CONTROL LOOP UNDER WEAK GRID CONDITION

EXPERIMENTS

CONCLUSION