Double Boost Power-Decoupling Topology Suitable for Low-Voltage Photovoltaic Residential Applications Using Sliding-Mode Impedance-Shaping Controller

Abstract

This paper proposes a practical sliding-mode controller design for shaping the impedances of cascaded boost-converter powerdecoupling circuits for reducing the second order harmonic ripple in photovoltaic (PV) current. The cascaded double-boostconverter, when used as power decoupling circuit, has some advantages in terms of a high step-up voltage-ratio, a small numberof switches and a better efficiency when compared to conventional topologies. From these features, it can be seen that thistopology is suitable for residential (PV) rooftop systems. However, a robust controller design capable of rejecting double frequencyinverter ripple from passing to the (PV) source is a challenge. The design constraints are related to the principle of the impedanceshapingtechnique to maximize the output impedance of the input-side boost converter, to block the double frequency PV currentripple component, and to prevent it from passing to the source without degrading the system dynamic responses. The design hasa small recovery time in the presence of transients with a low overshoot or undershoot. Moreover, the proposed controllerensures that the ripple component swings freely within a voltage-gap between the (PV) and the DC-link voltages by the smallcapacitance of the auxiliary DC-link for electrolytic-capacitor elimination. The second boost controls the main DC-link voltagetightly within a satisfactory ripple range. The inverter controller performs maximum power point tracking (MPPT) for the inputvoltage source using ripple correlation control (RCC). The robustness of the proposed control was verified by varying systemparameters under different load conditions. Finally, the proposed controller was verified by simulation and experimental results.