Hybrid Voltage-Current Control of Grid-Forming and Grid-Following Inverters

TL;DR

This paper introduces a hybrid voltage-current control method for grid inverters that combines GFL and GFM characteristics, ensuring stability across various grid conditions.

Contribution

A novel hybrid control strategy that integrates voltage and current controls to enhance inverter stability under diverse grid scenarios.

Findings

Maintains stable operation under different grid conditions.

Effectively combines GFL and GFM control features.

Validated through simulations and experiments.

Abstract

Grid-connected inverters are required to operate stably under a wide range of grid conditions. However, conventional grid-following (GFL) control may suffer from instability under weak-grid conditions, while grid-forming (GFM) control may exhibit unstable oscillations under strong-grid conditions. To address these issues, a hybrid voltage-current control method is proposed in this article. A voltage control is introduced on the d-axis, while a current control is adopted on the q-axis, enabling the inverter to exhibit voltage-source characteristics on the d-axis and current-source characteristics on the q-axis. In this way, the proposed control integrates the characteristics of both conventional GFL and GFM control. A full-order model is established to analyze the port characteristics and small-signal stability of the systems. Finally, the effectiveness of the proposed control strategy is validated through simulations and experiments on a 1.5 kW inverter experimental platform. The results show that the proposed control maintains stable operation under different grid conditions with varying short-circuit ratios (SCRs).