POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 17 | NUMBER: 2 | 2019 | JUNE Diagnosis Method for GTO Open Switch Fault Applied to Reconfigurable Three-Level 48-Pulse STATCOM Omar Fethi BENAOUDA 1,2 , Azzedine BENBIABDELLAH 2 , Bilal Djamal Eddine CHERIF 2 1 Research Center in Industrial Technologies CRTI, P.O.Box 64, Cheraga 16014, Algiers, Algeria 2 Diagnostic Group, LDEE laboratory, Electrical Engineering Faculty, University of Sciences and Technology of Oran MB, BP 1505 El-Mnaouer, Oran 31000, Algeria o.benaouda@crti.dz, Benaouda.omar@gmail.com, bendiazz@yahoo.fr, cherif.doc84@gmail.com DOI: 10.15598/aeee.v17i2.3192 Abstract. In the recent years, several research works are focusing on the use of STATCOM in electrical net- works because it is used to regulate the voltage, to im- prove the dynamic stability of the power system be- sides allowing better management of the power flow. All these positive tasks have guaranteed an important position of STATCOM within a family of Flexible Al- ternating Current Transmission System (FACTS). In this paper study, the control and operation of a three levels 48-pulse GTO based STATCOM is implemented with series connected transformers. The system may, unfortunately, be prone to GTO switch faults and there- fore may affect reactive power transiting. In this pa- per, a new diagnostic approach is proposed based on the Single-Sided Amplitude Spectrum (SSAS) method of the three-leg converter currents for detection and lo- calization of open-circuit faults. The integration of the STATCOM reconfigurable fault tolerant to the system is also considered to ensure service continuity. Sev- eral results are presented and discussed in this paper to illustrate the performance of the STATCOM fault- tolerant diagnostic. Keywords Detection, diagnosis, FACTS, GTO, open switch fault, reconfiguration, SSAS, STAT- COM. 1. Introduction The systems of Flexible Alternating Current Transmis- sion (FACTS) have become available worldwide due to the growing demand for energy; these systems gener- ally use power electronics. There are two main trends in the future outlook on the concept of the development of electrical networks; either to improve the quality of the electrical networks or to strengthen these networks [1]; the latter is not an economical solution, the solu- tion is therefore in improving the networks. The use of Flexible AC Transmission Systems (FACTS) has sig- nificantly contributed to enhancing both the voltage control and the network stability and hence allowing better management of the power flow [2]. The basic principle of the STATic COMpensator (STATCOM) is in its ability to generate and absorb reactive power between the AC system and the STATCOM [3] and [4]. This is possible thanks to the topology structure of the power electronics converter which often depends on the high-power compensators due to its operating efficiency [5], [6], [7], [8] and [9]. The three-level power converter is the most popular multi-level topology used in the various industrial applications [10]; these con- verters are particularly used in the FACTS systems which contain GTO thyristor switches since they en- able high power management capability. The use of a large number of the structural semiconductor switches is in fact very important in increasing the converter capability according to the required power levels, but is unfortunately reflected negatively by the increase in the converter structure complexity on the one hand and in increasing the possibility of the exposure to faults in the converter on the other hand [11]. In electrical systems that include power converters, several faults may appear in the converter, on its switch control [12] or in the physical semiconductor compo- nent itself [13]. Many research concerns are about the behaviour study of the converter; especially after the occurrence of a fault in the semiconductor components or a driver fault [14] and [15]. In the STATCOM sys- c  2019 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 114