A SIMPLE SMOOTH TRANSITION TECHNIQUE FOR THE NON-INVERTING BUCK-BOOST CONVERTER

Abstract

The non-inverting buck-boost converter has attracted significant attention in the photovoltaic (PV) module integrated application, as it offers high efficiency while maintaining a low cost and a simple topology. When this converter is employed, special care must be taken at the transition between buck and boost operating modes, as a dead-zone in the voltage transfer function can cause abrupt perturbations in the controlled voltage, decreasing the regulation quality and ultimately lowering the power conversion efficiency. In this project a new deadzone compensation technique is proposed with the scope of smoothing the transition between operating modes, eliminating the voltage ripple and improving the regulation performance, while maintaining high efficiency. The converter under analysis is studied together with its gate driving circuit, which is based on a bootstrap capacitor power supply for the high-side switches. The proposed dead-zone compensation technique is deduced using the principle of maintaining the ideal voltage gain function across the converter operating range. The technique is analyzed, implemented and tested on a purposely built PV module integrated non-inverting buck-boost converter. The experiments reveal a sensible improvement of the voltage regulation during mode transition, confirming the effectiveness of the proposed technique and its fitness for the PV application.

Existing System

In the existing system power optimizers are connected to each PV module and with their output connected in series.

Proposed System

In this project a novel smooth transition technique is presented for the non-inverting buck-boost converter, adopted in the PV application. A specific case of a non-inverting buckboost converter whose switching legs are driven by gate drivers requiring a bootstrap power supply is studied. An overlap of buck and boost operating mode is proposed to resolve the mode transition issue. The principle of the proposed technique is new, and is derived from the idea of maintaining the ideality of the gain function across the dead-zone range, in this way minimizing the input voltage ripple at mode transition. The converter voltage gain function is analysed in the ideal case where buck and boost duty ratios have no limitations. Following, the relation for the converter voltage gain without and with the presence of the dead-zone are deduced. The compensation technique to smooth the transition between buck and boost operating mode is presented, the experimental validation of the compensation technique is carried out.

Architecture

Non-inverting buck-boost, with synchronous rectifier switches, power and control stage.