A finite state machine model to represent inverters in photovoltaic system simulations

The simulation of photovoltaic (PV) power systems relies on appropriate models of the PV array, power conversion electronics, operating conditions and sometimes, energy storage and loads. This paper presents a model of intermediate complexity for grid-tie inverters that can capture many differences between specific products, yet remains generic enough to be used without expert knowledge of their internal circuits. The core of this model is a finite state machine (FSM) that defines the typical operating modes, or states, of grid-tie inverters and the conditions that lead to transitions from one state to another. Each state also defines parameters related to the transfer of electrical power, such as operating limits, conversion losses and maximum power point tracking efficiency. The increase in inverter temperature resulting from electrical losses is also modeled.