Modelling a droop controlled multi PV inverter system to study effects of system parameters on oscillatory modes

This paper presents the small signal model of a multi Photovoltaic (PV) inverter system to study the effect of controller and system parameters on the frequency modes of a microgrid. The paper describes the state space model of a system having two PV inverters connected by a line and working under droop control mode for active power sharing. The PV sources are working under load following mode and P-f, Q-V droops are used for power sharing between the inverters. The complete linear model of the system is developed by linearising the differential equations around an operating point. Eigen value and sensitivity analysis is then done to observe the effect of various controller gains and system parameters on the oscillatory modes. The study concludes that these quantities impacts the damping of few oscillatory modes which even gets unstable for specific values of parameters.