Interface problems related to adapting available 3-phase inverter designs between a photovoltaic array and an AC motor generator without a battery, have been partly solved. However, instability and nonminimal phase responses have been observed on the experimental array. So, the contributing research that will be described in the paper is (i) modelling the photovoltaic system by means of state representation, (ii) studying stability and nonminimal phase responses with the control functions and (iii) describing a method to compute optimal control functions. If the control function is the amplitude stator frequency, the system may be unstable. Replacing the stator frequency control function by a rotor frequency allows the system to remain stable. The phase of the transient response of the speed state variable always is non-minimal when the voltage cell is lower than the optimal voltage cell.