The performance of three-phase active power filters under nonideal voltage scenarios is investigated in this paper. It begins with the analysis of an instantaneous reactive power algorithm applied for the three-phase active power filter design, which was found to present poor performance under nonideal test scenarios. This motivates our proposed design of a new active power filter for solving such problems. In the proposed scheme, the circuit not only shows its effectiveness in the tests, but also implements with a simpler control circuit when compared with the other algorithm. The method has been implemented as a prototype and tested through various simulation cases, including ideal mains voltage, unbalanced three-phase mains voltage, and distorted mains voltage. Test results have demonstrated the feasibility and practicality of the proposed method approach for the applications.