Variable topology boost-buck converter for maximizing power output from unbalanced electrical generators

Several new distributed generation sources are being proposed today that feature variable frequency multiple unbalanced output voltages. Maximum power transfer in such systems can be challenging and reduces system efficiency by 15–30%. Discontinuous input currents are common in power converters operating from such unbalanced voltages and as a consequence the rms value of the input currents becomes large, thereby limiting the amount of power that can be drawn without tripping the input protection devices. This paper proposes a variable topology Boost-Buck converter for improving power output from unbalanced voltage sources. A single-switch Boost converter is used to improve power output only when the converter input current is discontinuous, and a separate Buck converter with completely decoupled control provides voltage regulation at the same time. The proposed scheme has been compared to passive power maximization schemes using series capacitors at the input to the power converter and also with other combined single-switch Buck-Boost topologies such as the Cuk converter, and is found to offer superior performance with the lowest complexity.