It is known that simulation of PV systems permits to study their performance helping engineers to design them. This paper deals with the dynamic simulation and modelling of stand-alone PV systems by using state variables and numerical integration methods. Two PV systems have been modelled and simulated: a PV array directly connected to a resistive load and a PV array with batteries also connected to a resistive load. A double exponential model, together with the procedure 1 for temperature and irradiance corrections of the IEC 60891 standard, has been used to model the PV array and considering the general battery model of Coppety with some modifications, the system with batteries was simulated. The obtained results from the simulations and experimental tests have been analysed and have shown that this methodology is a good option to simulate these systems.