Читать книгу Artificial Intelligence for Renewable Energy Systems - Группа авторов - Страница 13

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% was achieved when compared with its three-phase equivalent. A detailed experimental investigation of six-phase synchronous generator in stand-alone mode was carried out for renewable power generation in conjugation with hydropower plant [14]. Considering the suitability in generating mode, this chapter presents a mathematical modeling of grid connected six-phase synchronous generator applicable for wind power generating system, followed by the dynamic response under load variation.

Being an integral component in wind power generation, an operational stability of six-phase synchronous generator under steady state (i.e., small signal stability) is also of prime importance. Although, the small-signal stability analysis of three-phase synchronous machine is available in few available literature [15] using root locus [16] and Nyquist criteria [17]. But, for multiphase (i.e., six-phase) synchronous machine, a very limited literature is available for small-signal stability analysis. An introductory analysis of synchronous machine was reported in [18] followed by the determination of stability limits under parametric variation and different working conditions [19] when compared with its three-phase counterpart [20]. With the aim to access the suitability and applicability in wind power generating system, this chapter is dedicated to present a small-signal stability analysis of grid connected six-phase synchronous generator showing a comparison with its three-phase equivalent. For this purpose, a linearized version of six-phase synchronous generator model has been derived and used to evaluate the system eigenvalue. Eigenvalue criteria are used for small signal stability analysis under different machine parametric variation. A comparative analysis, from stability view point, is also presented using Park’s (dq0) variable for both grid connected three- and six-phase synchronous generator.