Adaptive Control of Photovoltaic Systems Based on Dual Active Bridge Converters

Abstract

Dual active bridge converters (DAB) are used to interconnect photovoltaic (PV) generators with AC and DC buses or isolated loads. However, a controller is needed to provide a stable and efficient operation of the DAB converter when the PV generator must be interconnected with a DC bus, which is particularly important in microinverter applications. Therefore, this paper proposes the design of a cascade controller for a PV system based on a DAB converter. The converter is controlled using a peak current control and an adaptive PI voltage control; thus the methodology to design the cascade controller is developed in two steps; first, the PV system formed by a PV generator, a DAB converter, and an inverter or load is introduced, including the description of the leakage current; as a second step, the model of the PV system to design the cascade controller is presented. Then, a relationship between the phase shift factor and the peak current of the leakage inductor is derived, which is used to design the peak current controller to ensure the DAB converter operation at the most efficient operating condition. On the other hand, an adaptive PI controller for the PV voltage is designed to ensure the reference tracking provided by a maximum power point (MPP) algorithm. The effectiveness of the proposed cascade controller is demonstrated through realistic examples simulated in PSIM. The power and control circuits implemented in PSIM are presented to encourage the use of the proposed solution. The simulation results confirm the correct operation of the control system, which mitigates the oscillatory perturbation produced by an inverter connected to the PV system, and also ensures the maximum power extraction from the PV panel by following the MPP reference.

Keywords

• DC microgrid
• adaptive PI controller
• cascade controller
• DAB converter
• high efficiency
• high voltage conversion ratio