Power factor improvement using nine switch AC-DC-AC converter

This paper presents an application of nine switch converter (NSC) for power factor improvement of 3-phase supply. Power factor improvement is achieved by controlling DC link capacitor voltage. To control capacitor voltage PID controller is used. Modified pulse width modulation with third harmonic injection technique is incorporated in NSC. An angle delta; between grid voltage and rectifier reference modulation is selected in such a way that bidirectional active power flow is controllable. Variation in amplitude modulation index is made to control reactive power flow. Maintaining delta angle and modulating references, appropriate gate signal is generated so as to make power factor unity as well as leading. The application of NSC for power factor improvement is well suited and verified using MATLAB/Simulink.