Sensorless Predictive Current Control of Multiphase Buck Converter for MPPT Application

Abstract

The commercial MPPT solar charge controllers are mostly single phase buck converters which take the power from solar panels and charge the battery bank connected at the output as well as provide power to the DC loads. As the current rating of these converters increases, the size of the magnetics element also increases which increase the overall cost and weight of the converter. In order to make the converters small in size and weight yet deliver high output current, a multiphase buck converter is envisioned to be used in MPPT solar charge controller applications. Multiphase buck converters have several advantages over single phase versions, such as small inductor size, small output current ripple and improved efficiency. This works describes the development of a sensorless current control strategy for a multiphase buck converter. The sensorless current control eliminates the need for costly current sensors. The current of each phase of multiphase buck converter is estimated and the estimated value is used to control the current of the converter. The current estimation and current control algorithms are based on predictive current control theory. The model of the power stage of the converter is used to derive the current estimation and current control xiv equations. Furthermore, the current estimation and control equations are derived for single phase buck versions and then seamlessly expanded to the four phase versions. It is shown that this is indeed possible and simulation results are presented to corroborate the theoretical working. The equations are derived in discreet domain and are tailored for implementation on a digital controller such as STM32G474 device. The proposed current sensorless approach is implemented and simulated in MATLAB/SIMULINK environment. The results obtained affirm the usefulness of current sensorless approach. A hardware prototype setup is attempted for the implementation of the proposed sensorless current control of the multiphase buck converter. The development of this hardware prototype as well as the issues encountered are also discussed.