Virtual Damping Control Design of Three-Phase Grid-Tied PV Inverters for Passivity Enhancement
Zhiqing Yang, Chirag Shah, Tianxiao Chen, Jakob Teichrib, Rik W. De Doncker, IEEE Transactions on Power Electronics, 03 November 2020, doi: 10.1109/TPEL.2020.3035417
This paper investigates passivity properties influenced by different control loops and operating points in the dq frame, which facilitates the stability assessment in the frequency domain. Based on this, a virtual damping control method is proposed to improve the stability by enhancing the system passivity. By implementing a damping transfer function in the d and q axis individually, non-passive regions can be accordingly reduced over a specific frequency range. Asymmetrical designs can be considered in the d and q axis according to corresponding passivity properties, which is impossible to be realized through symmetric physical filter components. The design procedure is elaborated based on a 2 MW inverter system, which is based on a combined graphical and analytical approach. Verifications are conducted based on a 1 kW prototype including both simulations and experimental results. The method applies to all types of grid-tied inverters with multiple control loops.