FPGA based novel voltage balancing technique for series input boost pre-regulator

Diode bridge rectifier is one of the simplest and most adopted technologies for ac-dc rectification. However, it injects a lot of harmonics into the source apart from lacking the control over output. Keeping adherence to the power quality standards, a pre-regulator stage is augmented with diode bridge for achieving better power factor and output voltage control. Multiple units of such power-factor corrected rectifiers are connected in series at the input in high voltage, high power implementations. At the output, dc voltages of each unit are regulated to equal value. However, maintaining the output voltage balance between different units is a challenge if the units are non-identical or subjected to unequal loading. This paper proposes a novel control technique to address this issue. Closed loop control of the series connected diode bridge rectifier with boost pre-regulator has been implemented in FPGA using the proposed strategy. Configuration of FPGA as digital controller facilitates high frequency switching, which in effect reduces the size of magnetic components. The proposed control scheme has been verified in laboratory using a scaled down prototype of two series connected stages of diode bridge rectifier with boost pre-regulator which shows good regulation under unequal loading and dynamic load variation.