Comparison of different control methods used in multi-frequency grid-forming converters

Abstract This article investigates and compares various control methods for a three-phase multi-frequency grid-forming converter tasked with producing a multi-frequency voltage profile comprising 50 Hz positive sequence and 150 Hz zero sequence signals. Different control strategies including proportional-integral (PI), proportional-resonant (PR), repetitive (RC) and state-feedback (SF) controllers are investigated to assess their efficacy in generating and regulating the desired multi-frequency voltage output. This study suggests that the PR-based control system exhibits notable potential due to its inherent frequency filtering capabilities and simplicity of the tuning and implementation, making it well-suited for multi-frequency applications. This approach effectively amplifies desired frequencies while suppressing others, showcasing superior multi-frequency performance compared to other mentioned methods. This ability of the PR controllers aligns well with the specific demands of the multi-frequency application. This contention is validated by simulating the multi-frequency grid-forming converter using the four mentioned control methods. Therefore, this paper provides crucial insights into control strategies for multi-frequency grid-forming converters, emphasizing the importance of control method selection based on application needs and performance metrics. Ultimately, these findings contribute significantly to advancing the development and refinement of multi-frequency grid-forming converters for microgrid and islanded mode scenarios.