Modeling and dynamic performance of a line-commutated photovoltaic inverter system

A three-phase line-commutated utility-interactive photovoltaic (PV) inverter system is described. A simplified computer model of this system is established and presented in block-diagram form. This model is suitable for use in transient stability programs. The accuracy of the simplified model is verified by comparing the response calculated therefrom with that of a highly detailed photovoltaic system model in which the inverter is represented in valve-by-valve detail. The computer studies indicate that the simplified model is reasonably accurate when used to predict the PV system response following, for example, step changes in the inverter delay angle, rapid increases or decreases in solar insolation, and step changes in AC voltage magnitude or phase. In each case, the PV system response predicted using the simplified model closely follows the average response of the detailed model exclusive of the harmonics, which are neglected in the simplified model