Five-Level Reduced-Switch-Count Boost PFC Rectifier with Multicarrier PWM


A multilevel boost PFC (Power Factor Correction) rectifier is presented in this paper controlled by cascaded controller and multicarrier pulse width modulation technique. The presented topology has less active semiconductor switches compared to similar ones reducing the number of required gate drives that would shrink the manufactured box significantly. A simple controller has been implemented on the studied converter to generate a constant voltage at the output while generating a five-level voltage waveform at the input without connecting the load to the neutral point of the DC bus capacitors. Multicarrier PWM technique has been used to produce switching pulses from control signal at a fixed switching frequency. Multi-level voltage waveform harmonics has been analyzed comprehensively which affects the harmonic contents of input current and the size of required filters directly. Full experimental results confirm the good dynamic performance of the proposed five-level PFC boost rectifier in delivering power from AC grid to the DC loads while correcting the power factor at the AC side as well as reducing the current harmonics remarkably.


  1. Multilevel Converter
  2. Active Rectifier
  3. Multicarrier PWM
  4. Cascaded Control
  5. Power Quality



Fig. 1. Proposed five-level boost PFC rectifier with reduced number of switches


Fig. 2. Experimental results from steady-state operation of the rectifier

Fig. 3. Experimental results during 50% increase in the load

Fig. 4. Experimental results during AC source voltage variation

Fig. 5. Experimental results during 25% raise in the DC voltage reference


In this paper a reduced switch count 5-level boost PFC rectifier has been presented. A cascaded PI controller has been designed to regulate the output DC voltage and to ensure the unity power factor mode of the input AC voltage and current. Moreover, low harmonic AC current waveform has been achieved by the implemented controller and employing a small inductive filter at the input line. One of the main issues of switching rectifiers is the high switching frequency that has been reduced in this work using PWM technique through adopting multicarrier modulation scheme. Moreover, DC capacitors middle point has not been connected to the load that had required splitting the load to provide a neutral point. Using a single load with no neutral point makes this topology practical in real applications. Comprehensive experimental tests including change in the load, AC voltage fluctuation and generating different DC voltage values have been performed to ensure the good dynamic performance of the rectifier, adopted controller and switching technique. Moreover, the low THD of the input current has been measured to validate the advantage of multilevel waveforms in reducing harmonic contents and consequently diminishing the size of required filters at the input of the converters.


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