This paper presents the design of a PV interconnection system based three-phase uninterruptible power supply (UPS) systems that are operating under highly nonlinear loads. The classical high-performance sinusoidal pulse width modulation (SPWM) control method is quite effective in controlling the RMS magnitude of the UPS output voltages. However, it is not good enough in compensating the harmonics and the distortion caused specifically by the nonlinear currents drawn by the rectifier loads. This study proposes a new design strategy that overcomes the limitations of the classical RMS control. It adds inner loops to the closed-loop control system. Simulink is used to analyze, develop, and design the controller using the state-space model of the inverter. By the implementation of PV system based inverter we are analyzing the efficiency of proposed model of SPWM. Simulation performance is evaluated for a three-phase 10 kVA transformer isolated UPS under all types of load conditions. In conclusion, the simulation results demonstrate that the controller successfully achieves the steady-state RMS voltage regulation specifications as well as the total harmonic distortion and the dynamic response requirements of major UPS standards.