Performance of reduced switch topology based harmonic current compensator

Diode and thyristor based solid state converters are preferred because of their high reliability in applications for bulk power conversion. These converters generally use Power diodes or SCR (silicon controlled rectifiers) which has non-linear characteristics. Due to this reason such converters generate highly non-sinusoidal currents at the power supply utility. As a result of distorted currents the voltage waveforms at the point of common coupling (PCC) at which other consumers are connected are also exposed to distorted supply. This paper proposes a harmonic compensator using lesser number of power devices controlled by simple and effective current controlled PWM. The reference currents are generated offline based on a particular load current and is used to generate the PWM waveforms to drive the switches intended to reduce the Total Harmonic Distortion (THD) of the input current in the three-phase ac supply system. The performance of the reduced switch harmonic compensator shows significant improvement in the nature of input currents. The power structure of the compensator is a three-limb voltage source converter consisting of four IGBTs, two per leg and the third leg comprising of two split capacitors forming the dc bus and its mid-point acting as the pole point for third wire connection of three-phase.