Design of AC-DC control power supply with wide input voltage variation

This paper presents the design of ac-dc Control Power Supply (CPS), which feeds power to sub-systems of High Power Converters (HPC) such as gate drive card, annunciation card, protection and dead time generation card, sensor cards etc., even under abnormal grid input voltage conditions. The CPS presented here, maintains the dc supply voltage to the control circuitry of a HPC constant (V_out=24V), over a wide range of ac input voltage variation, from 90V_rms to 270V_rms. The CPS not only maintains the power factor close to unity but also maintains a low total harmonic distortion in the input ac current. This paper presents the choice of the circuit topology and the design of various components of the CPS. This paper also discusses the various closed loop strategies incorporated and their design for the CPS. The CPS was tested for wide input voltage range (v_in) and the performance validate the design. In a micro-grid, the CPS might be exposed to transients such as large voltage sags. The CPS has been tested in such a situation and its performance allows the HPC to meet the low voltage ride-through requirements.