Proposed System Based on a Three-Level Boost Converter to Mitigate Voltage Imbalance in Photovoltaic Power Generation Systems

Voltage imbalance poses a challenge to photovoltaic systems. A modular structure based on a three-level boost converter is proposed to address this problem. The three-level boost converter offers advantages, such as a low current ripple and voltage stress, over a classic boost converter. These advantages offset the use of additional elements in the proposed converter circuit. Two capacitors are used to enable the innovative connection between multiple sources and the three-level boost converter. The second capacitor of the first module is shared with the first capacitor of the second module. This structure is used in conjunction with a controller to balance the voltages in the system. The operating modes of the two-module system in a nominal case are introduced. The controller is based on an indirect sliding model, wherein the input current of each energy source and the output voltage balance are considered. The performance of the current and voltage controllers are studied in two scenarios. The first case involves increasing the reference current and the presence of four sliding surfaces related to the current control and voltage balance, whereas the second case involves the presence and absence of two sliding surfaces related to the voltage balance. The dynamic response of this controller is also compared with the Proportional Integral(PI) controller. Large-signal modeling of the two-module system and the accuracy of this model in two cases of radiation change and panel temperature change is investigated. The robustness of the system is investigated using this large-signal model in two cases that involve changing the inductors and capacitors of the system. A topology consisting of two conventional boost converters is chosen to compare energy stored and efficiency with the proposed topology. The capacitance of the system is calculatedfor two topologies. The energy stored in the two systems is compared. The two-module system is simulated using Simulink MATLAB software. The simulation and experimental results validate the proposed system.