Admittance modeling of voltage and current controlled inverter for harmonic instability studies

This paper proposes an impedance/admittance-based model for voltage and current controlled inverters with passive elements suitable for harmonic instability study of grid connected inverters in frequency domain. This linearized model of inverters, significantly simplifies investigation of resonance instability and control loop interaction of wind turbines with each other and/or with the grid, while they are installed in wind farms. The derived impedance ratio at point of common connection demonstrates how the inverters participate in harmonic stability of the grid.