Analysis and Control of Grid-Tied Quad-PV LLC Converter with MPPT

This paper proposes a multi input DC-DC converter that integrates four photovoltaics (PV) panels that is typically followed by a second stage of grid-tied inverter. This topology uses single LLC resonant tank to supply the output using four half-bridge converters. Maximum power point tracking (MPPT) algorithm for all four PV module is designed using four degrees of freedom. The switching frequency and three phase shifts ensures the accurate pulse width modulation (PWM) for all switches while achieving zero-voltage switching (ZVS) across all the switches for a wide input range and load variations. The dc link voltage is maintained at 300V by using outer voltage loop of the inverter controller. To reduce the harmonic distortion in injected current, a phase locked loop (PLL) with proportional resonant (PR) based controller is developed to regulate the power with single phase grid. Finally, a 1.2kW quad-PV model has been simulated and the gain equation is derived for the proposed model. The simulation results ensure that the proposed converter with closed loop control successfully agree with the derived mathematical model.