Due to the increase of demand in electric energy, the necessity of applying more attention to its quality is necessary. A variety of loads such as rectifier devices, power supplies and speed adjust drives such these loads cause high harmonic in drawn power. In order to investigate the performance, it is required to model 3-phase system with variable loads. In this paper, a conventional proportional plus integral (PI) controller has been used to control this system. To validate the mathematical model for a wide range of loads, two loads are considered with 3-phase AC source in the process of assessment. The first load is considered an unbalanced load. Each phase has a different independent type of load. The second load is a nonlinear load (rectifier load). 3-phase active power filters (APFs) are used to improve the power factor, which reduces the consumed apparently power; consequently, the overall performance will improve. A practical approach for implementing an APF has been presented in this work is a Voltage-source inverter-based shunt active power filter. This approach continuously requires one variable, which is the phase angle between the voltage and current to improve the performance of the system.