An improved BOOST dual-loop control for improving the MPPT efficiency in photovoltaic systems

BOOST circuit is usually used in the front-end of a two-stage transformerless grid-connected photovoltaic inverter. The control performance of the BOOST circuit will significantly affect the MPPT efficiency because its settling time and anti-disturbance performance limit the sampling interval and perturbation amplitude of the MPPT. Aiming to improve the control performance of the BOOST, an optimized dual-loop control is proposed. Firstly, according to the established average BOOST model that considers the nonlinearity of photovoltaic array, the disturbance mechanism of the voltage fluctuation in the inverter dc bus is obtained, with the output change characteristics of the photovoltaic array to the control system discussed in detail. Secondly, compared with the following performance and anti-interference performance of the existing dual-loop control, the improved dual-loop control method with active damping and differential calculation of the capacitor current is presented, which can achieve satisfactory control performance while not introduce the hardware cost. Thirdly, the influence of control delay is considered. And an improved regulator parameter design method is put forward. Finally, simulation and experiments validate the effectiveness of the proposed dual-loop control and regulator design method.