A Dispatchable Virtual Oscillator Controller in the dq Frame With Enhanced Grid-Forming Power Reference Tracking Capability
Zheran Zeng, Jiayu Fan, Yin Sun, Songda Wang, Dongsheng Yang
Abstract
The classic implementation of dispatchable virtual oscillator control (dVOC) in the stationary <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha \beta$</tex-math></inline-formula> frame results in suboptimal steady-state and dynamic power reference tracking performance in grid-connected converters. This occurs because the control variables are AC components, while the converter phase angle cannot be directly controlled in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha \beta$</tex-math></inline-formula> frame. To enhance power reference tracking capability, a new dVOC controller implemented in the dq frame is proposed by transforming the dynamics of the instantaneous angular frequency and voltage magnitude of the dVOC-controlled voltage vector into the local synchronous rotating frame of the converter. The dq-frame implementation not only eliminates steady-state power tracking errors but also significantly enhances dynamic power reference tracking speed through direct control of the converter phase angle, without compromising the inherent working principle of dVOC. Additionally, for the first time, the proposal of the dq-frame dVOC controller explicitly reveals the intrinsic connection between dVOC and power-synchronization control, two predominant GFM methods, in terms of their control block structures. It also streamlines the small-signal modeling of the dVOC controller. The effectiveness of the new dVOC controller in the dq frame is validated through experimental results.