Optimal Performance Design Guideline of Hybrid Reference Frame Based Dual-Loop Control Strategy for Stand-Alone Single-Phase Inverters

The dual-loop control strategy in a hybrid reference frame (HRF) for single-phase voltage-source inverters in islanded operation mode is studied, which applies a capacitor voltage shaping loop in the synchronous reference frame (SRF) and a capacitor current shaping loop in the stationary reference frame (HRF-based <inline-formula> <tex-math notation="LaTeX">$v+ i_{c}$</tex-math></inline-formula> control strategy). This strategy is able to achieve the purpose of active damping, fast dynamic response, and zero reference tracking error. However, due to the inherent characteristics of SRF-based voltage loop and the digital control delay, the performance of the system is degraded and the control parameter design of the HRF-based <inline-formula><tex-math notation="LaTeX">$v+ i_{c}$</tex-math> </inline-formula> control strategy shows great difficulties. To overcome these shortcomings, in this paper, a systematic parameter design guideline for the HRF-based <inline-formula><tex-math notation="LaTeX">$v+ i_{c}$ </tex-math></inline-formula> control strategy is proposed to ensure the system stability and optimize the performance of the system under control delay condition. The mathematic model of the HRF-based <inline-formula> <tex-math notation="LaTeX">$v+ i_{c}$</tex-math></inline-formula> control strategy is established with the consideration of control delay in this paper. Based on this model, a satisfactory region of the system stability indexes can be obtained by stability specifications of the system, and the optimal control parameters can be calculated according to the stability indexes selected from the satisfactory region. By using this method, the system stability and robustness can be guaranteed. Finally, the experimental results are presented to validate the effectiveness of the presented optimal control parameter design methodologies.