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A load sharing control based on the frequency and voltage droop concept for parallel operation of two three-phase uninterruptible power supply (UPS) systems with no control interconnection lines is presented in this paper. First of all, due to the use of active power and reactive power as control variables, the characteristics of output powers according to amplitude and phase differences between output voltages of two UPS systems are analyzed. Secondly, simulation results with different line impedance are demonstrated the feasibility of the wireless load sharing control. Finally, experiments are presented to verify the theoretical discussion with two three-phase 20 kVA UPS systems employed TMS320C32, a kind of real time digital signal processor (DSP).