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      Analysis of Six-Phase Grid Connected Synchronous Generator in Wind Power Generation

       Arif Iqbal1* and Girish Kumar Singh2

       ¹ Department of Electrical Engineering, Rajkiya Engineering College Ambedkar Nagar, Akbarpur, India

       ² Department of Electrical Engineering, Indian Institute of Technology Roorkee, Roorkee, India

       Abstract

Owing to meet the incremental need of energy with exhaustion of fossil fuel in few upcoming years, renewable power generation has emerged as a potential and permanent solution in present scenario. In this regard, research has diverted toward exploration and development of various new techniques of renewable power generation for last few decades, and various systems have been adopted in both isolated and grid connected modes. Among various available options (solar, wind, biomass, tidal, etc.), the wind power generation system has a major market share due to its pollution-free operation together with its economic viability and mature technology. Presently, wind power generation system is increasing exponentially, particularly in on-shore sites of India and European subcontinents. Wind power generation system works on a successful operation and coordination of various parts, where an electric generator is an important component. Hence, the selection of suitable electrical machine (as generator) is of paramount importance for reliable operation of complete wind power generation system. Conventionally, three-phase electrical machine is employed. But, in last two decades, the multiphase (more than three-phase) machine is replacing the conventional one. This is because of various inherent potential advantageous features present in multiphase machines, when compared with its three-phase equivalent. This includes the elimination of lower order space, resulting in lower torque pulsation, enhanced power handling capability in the same frame (approximately 175%), and higher degree of freedom with improved reliability. Hence, multiphase machines have to be explored and investigated in various operational aspects for power generation. In this chapter, a six-phase synchronous machine is selected as a potential option as generator in grid connected mode for wind power generation system. An exhaustive dynamic analysis has been presented during various working conditions. Moreover, generator has been further investigated under steady state with the inclusion of small disturbance (i.e., small signal stability) through linearized model using dq0 approach. Linearized model was used to determine the absolute stability using eigenvalue criteria wherein, the effect of parametric variation is presented, related with both stator and rotor side. It was noted that the stability of generator operation can be enhanced with increased values of stator resistance. On rotor side, with higher value of leakage reactance of field winding circuit and/or by increased resistance of damper winding along q axis.

      Keywords: Wind power generation, six-phase synchronous generator, small-signal stability, dynamic analysis

1.1 Introduction

      The development of human civilization resulted in a tremendous demand of electrical power with a fear of fossil fuel exhaustion within a few years. This has diverted the researcher’s attention to explore and develop the renewable resources for power generation as a potential and permanent solution in present scenario. Motivation toward the development of different types of renewable power generation (like solar, wind, biomass, and tidal) is also due to the presence of various attractive advantages, particularly pollution-free operation, free availability with economic viability, and advanced technology [1, 2]. Among the various developed options, wind power generation has been adopted worldwide and exhibits a major market share in the field of renewable resources. Presently, wind power generation system is increasing exponentially, particularly in on-shore sites of India and European subcontinents. According to report updated on Global Wind Energy Council (GWEC) [3], power extraction is drastically increased by 52 GW and 60 GW by 2017 and 2020, respectively, and expected to reach a total of 840 GW by 2022.

Wind power generation system works on a successful operation and coordination of various parts, where an electric generator is an important component. Hence, the selection of suitable electrical machine (as generator) is of paramount importance for reliable operation of wind power generation system. Conventionally, three-phase electrical machine (mostly synchronous machine) is employed. But, in last two decades, the multiphase (more than three-phase) machine is replacing the conventional one. This is because of the presence of various potential advantages when compared with its three-phase equivalent. This includes the elimination of lower order space harmonics, resulting in lower torque pulsation, higher power handling capability in the same frame (approximately 175%), and higher degree of freedom with improved reliability [4]. This signifies the technical and economic suitability of using multiphase machine when compared with its three-phase equivalent. Hence, an enhanced use of multiphase drives have been reported in different high power applications, not limited to ship propulsion, electric traction, more-electric aircraft, thermal and nuclear power plant, and battery and hybrid electric vehicles. Research in this field is tremendously going on, particularly from electric power generation point of view. Available literatures are showing a general feasibility of multiphase system [4, 5]. On generation side, the concept of multiphase (more than three-phase) machine was initially originated in late 1920s when larger power generation got hampered due to the limitations in circuit breaker interrupting capability. To overcome this situation, attention of scientists was diverted to the machine having double windings embedded in its stator [6]. It was after this time that research continued in the field of multiphase machine with steady, but in slower way. Utilization of multiphase synchronous generator was used in 1980 [7] for power generation in electric railway coaches. A few mathematical analysis of alternator with two three-phase winding was carried out by using orthogonal transformation for the elimination of time-dependent coefficient from system differential equations [8]. Six-phase synchronous generator in conjugation with three-to six-phase conversion transformer was analyzed for harmonic content [9]. In six-phase synchronous machine, mutual coupling effect between two sets of balanced three-phase stator winding is considered in [10], and under steady-state ac-dc stator connection [11] has been also presented and analyzed by using average-value modeling with line commutated converter [12]. A detailed mathematical modeling of six-phase synchronous generator using Park’s variable has been carried out in [13] under different working conditions at stand-alone mode, where an enhanced power handling capability by 173% СКАЧАТЬ