INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH C. Koseoglu et al., Vol.10, No.1, March, 2020 A Hybrid Overload Current Limiting and Short Circuit Protection Scheme for Voltage Mode Inverters Cem Koseoglu*, Necmi Altin **, Fevzi Zengin*, Hasan Kelebek*, and Ibrahim Sefa** * Inform Elektronik Sanayi ve Ticaret A.S., 34785, Istanbul, Turkey ** Electrical Electronics Engineering Department, Faculty of Technology, Gazi University, 06500, Ankara, Turkey (cem.koseoglu@inform.com.tr, naltin@gazi.edu.tr, fevzi.zengin@inform.com.tr, hasan.kelebek@inform.com.tr, isefa@gazi.edu.tr) ‡ Cem Koseoglu, 34785, İstanbul, Turkey, Tel: +90 (262) 751 16 00 /8311, cem.koseoglu@inform.com.tr Received: 30.11.2019 Accepted:21.01.2020 Abstract- In this study, a current limiting technique which combines an analog comparator circuit and a digital current limiting algorithm is proposed for voltage mode – controlled inverters. Thus, providing smooth output voltage waveform feature of digital current limiting technique and very fast response feature of the analog technique are combined. A three-phase 10kVA voltage mode – controlled inverter has been used to test the performance of the proposed method. Besides, the digital and the analog current limiting techniques have been tested separately to highlight and compare the performance of the proposed hybrid method. It is seen from experimental tests that the proposed technique provides fast response and a successful current limiting performance at short circuit and overcurrent conditions. In addition, the proposed method improves the reliability and fault tolerance capability of the inverter significantly. Moreover, the proposed current limiting algorithm adds fault clearing capability function to the inverter. Keywords Overcurrent protection; overload; short circuit protection; current limiter; fault-tolerant inverter; voltage source inverter (VSI). Nomenclature VSI Voltage Source Inverter Inverter Output Reference Voltage UPS Uninterruptible Power Supply Digital Current Limiter Input Signal Measured DC Bus Voltage Digital Current Limiter Output Signal Measured Inverter Output Voltage Positive Alternance Analog Current Limit Peak Value Measured Inverter Output Current Negative Alternance Analog Current Limit Peak Value Digital Current Limiter Parameter Analog Current Limiter Measured Current Digital Current Limit Value 1. Introduction The voltage source inverters (VSIs) which are employing several semiconductor power switches, such as IGBTs and MOSFETs are commonly used in industrial applications including the Uninterruptible Power Supplies (UPSs), Distributed Generation (DG) systems, and motor drives [2 – 8]. Among the other causes, power switch faults are the major reason of power circuitry damages. It is reported that about 38% of the faults in a power circuitry of the VSI is due to failures of switching devices [2]. Therefore, designing a proper protection and fault detection system for these inverter circuits is very important requirement to obtain a high-reliability inverter especially for high power systems [2].