An Asymmetric Short-Circuit Fault Ride-Through Strategy Providing Current Limiting and Continuous Voltage Supply for Three-Phase Three-Wire Stand-Alone Inverters

Abstract

The three-phase three-wire stand-alone inverter is required to have short-circuit fault ridethrough ability to achieve continuity of power supply. Generally the inverter works in current-controlled mode in symmetric short-circuit conditions, but voltage limiting and harmonic distortion will appear under this method when asymmetric short-circuit fault occurs. Several existing methods for asymmetric fault ridethrough can achieve current limiting without voltage limiting, however, none of them can guarantee that the healthy phase voltage keeps constant before and after fault. This article proposes a fault ride-through strategy for asymmetric short-circuit conditions, which not only keeps the healthy phase voltage constant with different loads, but also makes the fault phase current limited and controllable. This goal is achieved by a simple control structure combining α-axis voltage control and β-axis current control at the same time. Furthermore, the voltage and current characteristics of this method under different load conditions have been analyzed, the analysis results indicate that the impact of different loads on fault ride-through performance is almost negligible. The correctness of theoretical analysis and the effectiveness of proposed strategy is verified by experimental results.

Keywords

• Asymmetric short-circuit
• fault ride-through
• current limiting
• three-phase three-wire stand-alone inverter