Dynamic Short-Circuit Current Characterization for Bipolar Photovoltaic Units Under Fault Ride-Through Conditions

The calculation of short-circuit current during the entire fault ride-through process of photovoltaic (PV) power generation units is a crucial prerequisite for equipment selection and protection strategy design after their large-scale integration into the system. Currently, research on the short-circuit current of PV power generation units primarily focus on the transient process calculation at the initial stage of a short-circuit, while analytical calculation of the short-circuit current during the entire fault ride-through process is rarely addressed. Moreover, most studies do not consider the actual operating conditions of the units, neglecting the impact of fault ride-through strategies, and the short-circuit current calculation methods are only applicable to specific single-fault scenarios. This study, based on a detailed electromagnetic transient model of a bipolar PV power generation unit, analyzes the characteristics of short-circuit current during the entire fault ride-through process. Combined with the fault ride-through control strategy, the analytical expression of short-circuit current during the fault transient period is derived, and an analytical calculation method suitable for the entire fault ride-through process is proposed. Finally, the effectiveness of the analytical method for short-circuit current during the low-voltage ride-through process of bipolar PV power generation units is verified by comparing it with the manufacturer's encapsulated model.