An Electrolytic capacitor less non-isolated Microinverter with Integrated Battery Storage System for Residential Applications

Conventional hybrid PV-Battery converters encounter several challenges in power management, power density, polluted grid and power conversion efficiency when interfaced with residential electrical system. In response to these challenges this paper proposes an electrolytic capacitor less non-isolated Microinverter with combined battery storage system (ECLNIM-BSS) converter. The power sharing unit is introduced to enable both the PV maximum power point tracking feature and the charging controller for the battery system. A two-stage double DC-DC interleaved modular multilevel converter (IMMC) unit is placed after the power-sharing unit to increase the dc bus voltage to 400VDC. Moreover, voltage ripple is eliminated because of the upper and bottom parts of the DC-DC IMMC units' symmetry and 180-degree phase shift control. An integrated active decoupling (APD) stage in the DC-AC inverter stage cancels the second harmonic ripple in the electrolytic dc link capacitor voltage. This feature, in addition to the DC-DC IMMC stage's 180-degree phase shift control allows to substitute the bulky/faulty electrolytic capacitor with condensed, highly efficient, reliable film capacitor. On-grid and off-grid converter operation is discussed. Nonlinear and linear loads were demonstrated in the analysis. Simulation results are presented to examine the concept.