Control Techniques and Power Factor Correction Methods: A Review

The ratio of real power flowing into the load to the apparent power in a circuit is referred to as the power factor (PF). It has no unit as its values lie between 0 and 1. Power factor correction (PFC) leads to a reduction in apparent power drawn from the ac source which in turn saves energy and minimizes the transmission losses. This paper reviews various methods used for PFC as well as the various control measures for power factor. The correction methods include distributed PFC, group PFC, centralized PFC and combined PFC. Distributed PFC is applicable to large electrical equipment with constant load and power with long connection times. Combined PFC is the hybrid between a distributed and a centralized correction method. Peak current control technique makes use of constant switching frequency even though, the presence of sub-harmonic oscillations at a duty cycle greater than 50% is a disadvantage. The presence of constant switching frequency and better input current waveforms are some of the applications of average current control. In the discontinuous current pulse width modulation (PWM) control, the internal current loop is completely eliminated so that the switch is at a constant frequency. In nonlinear carrier controllers, the duty ratio is determined by comparing a signal derived from the main switch current with a periodic nonlinear carrier waveform. Therefore, combined PFC and nonlinear carrier controllers are more accurate PFC methods for the power plant because they employ a high power factor boost converter with low total harmonic distortion for installations of large equipment with a constant load. This research paper forms a basis for power system planning as it assists in recommending the appropriate and adequate technique(s) for correcting and controlling the pf of the factory.