Low Voltage Ride-Through Capability Enhancement of Grid-Connected Photovoltaic Systems- A Hybrid Control Approach

Abstract

Under the demands of contemporary grid code (GC), the solar PV system should stay attached to the grid for a certain time period depend on the voltage sag level under the fault condition. The voltage of the point of common coupling (PCC) is very low when the fault appears on the grid side, resulting in a very high DC connection voltage for the power balance. This high voltage of the intermediate circuit can damage the drive. Moreover, the deflection of the voltage will cause the PV plant to be disconnected from the network based on the modern GCs. This study proposes a hybrid control approach for the two-stage grid-integrated solar PV system to enhance low voltage ride through (LVRT). The hybrid control approach proposed consists of a braking chopper and a neutral connected braking resistor (NCBR).The braking chopper resistance absorbs the excess energy in DC link capacitor during the fault, which will regulate the DC-link overvoltage. The NCBR is stabilized the impact of grid faults and therefore the voltage sag is improve in the grid side, which is boost the PV system's LVRT capability. For this work, the algorithm of synchronization evolved to trigger both controls simultaneously under the fault. Simulations are carried out using the MATLAB/Simulink software under all types of fault and results indicate that the proposed hybrid control scheme can enhance the LVRT capability of the system.