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

Jian He,Peng Liu,Shanxu Duan,Bangyin Liu

doi:10.1109/access.2020.3038220

Jian He, Peng Liu + Show 2 more

Open Access

https://doi.org/10.1109/access.2020.3038220

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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.

Highlights

With the development of industrial technology, the threephase stand-alone inverter is playing a more and more important role in various applications, such as Uninterruptible Power Supply (UPS), distributed power system, microgrid and so on, which requires high commands on power quantities, power supply continuity and reliability [1]–[5]
Focusing on the fault ride-through issue under asymmetric short-circuit situation, firstly this article makes the goals of fault ride-through process clear, which are: 1) the healthy phase voltage should keep constant before and after fault and under different loads; 2) the fault phase current should be limited and controllable to trigger the action of protection devices like breakers to clear the fault branch
The main idea is to assign different tasks of α-axis and β-axis controller, the β-axis controller worked in current-controlled mode (CCM) to limit current during the fault, while the α-axis controller still worked in voltagecontrolled mode (VCM) to supply the load of healthy phase continuously and steadily

Summary

INTRODUCTION

With the development of industrial technology, the threephase stand-alone inverter is playing a more and more important role in various applications, such as Uninterruptible Power Supply (UPS), distributed power system, microgrid and so on, which requires high commands on power quantities, power supply continuity and reliability [1]–[5]. Focusing on the fault ride-through issue under asymmetric short-circuit situation, firstly this article makes the goals of fault ride-through process clear, which are: 1) the healthy phase voltage should keep constant before and after fault and under different loads; 2) the fault phase current should be limited and controllable to trigger the action of protection devices like breakers to clear the fault branch. These goals are easy to achieve in three-phase four-wire system since the fault phases could work in CCM while the healthy phases continue to work in VCM during the fault [17]–[19]. The β-axis controller works in CCM while the α-axis controller still works in VCM during the fault

CIRCUIT MODEL

PROPOSED CURRENT LIMITING AND FAULT

FAULT CURRENT CHARACTERISTICS UNDER THE PROPOSED METHOD

EXPERIMENTAL RESULTS

CONCLUSION