Title : Feasible Performance Evaluations of Digitally-Controlled Auxiliary Resonant Commutation Snubber-Assisted Three Phase Vo

Corresponding Author: a.hoseinpour@uoz.ac. ir Tel: +98-9153409088, , University of Zabol Faculty of Electrical and Computer Engineering, University of Zabol, Zabol, Iran International Journal of Industrial Electronics, Control and Optimization . © 2020 IECO. In addition, due to their nonlinear profile and switching action, PE converters are the main source of harmonics in the grid that reduce the power quality. In the past, a passive filter was used to reduce PE harmonics. In this kind of filter, the undesired harmonics are canceled out by adjusting passive element values, i.e., the values of inductors and capacitors. The main drawback of passive filters is that they create resonance frequencies that correspond with the system impedance at a frequency below the tuned frequency, which causes current magnification; therefore, it would be less efficient in the reduction of harmonics [4]. To solve this problem, the idea of using an active filter was proposed [5]. In this type of filter, system signals are measured and accordingly a shunt current or series voltage is injected into the line to reduce the system harmonics. An active filter consists of three parts: identification, modulation, and inverter. Among the issues contained in an active filter, the reference signal production methods play an important role in filter designing because of the effect on speed and precision of the filter response [6-8]. These methods can be divided into time and frequency domain methods [9-12]. The time-domain methods are quicker, but frequency-domain methods are more accurate. The time-domain methods, such as p-q transformer (active and reactive instantaneous power theory), do not exhibit good performance in the presence of harmonic sources. However, frequency-domain methods, which are mainly based on FFT, can overcome the above-mentioned problem. Sinusoidal pulse width modulation (SPWM) is the most commonly used method of modulation. In this paper, a modified modulation method with a variable index is used that is based on the integral of the output signal from the phase detection stage. Also to decrease the filter losses, an inverter with a reduced number of switches is employed in the filter circuit. In other words, the three-phase four-switch inverter is replaced with a conventional six-switch three-phase inverter. The proposed energy conversion system includes one inverter. The performance of the inverter is affected by three important parameters: the number of the switches, modulation method, and identification approach. The presented identification algorithm does not affect the harmonics of the source. A Unified Power Controller for Variable-Speed Fixed-Pitch Wind Energy Conversion System is designed [13] that is composed of a new MPPT controller in low wind speed and a proposed constant-speed and constant-power controller in high wind speed. Moreover, a linear quadratic regulator control active power conditioner is implemented for effective source utilization and voltage regulation in low-power WECS [14]. A boost converter is used in the proposed controller. As well, intelligent control of grid-connected AC–DC– AC converters for a WECS based on T–S fuzzy is performed [15]. Further, reducing harmonic instability and resonance problems in wind farms are solved [16-17]. The present paper uses both fourand six-switch inverters. Furthermore, either sine pulse width modulation (SPWM) or variable index pulse width modulation (VIPWM) is employed. Finally, in addition to the reduction of the current harmonics, the voltage harmonics are reduced. The second one is the lateral advantage. All subjects investigated in this paper are illustrated in Fig.1. Fig. 1. All subjects investigated in this paper The use of the VIPWM method in the modulation stage and four-switch inverter are our innovations to improve wind turbine power quality. Section 2 describes the proposed system. The SAF is explained in Section 3. Section 4 discusses new suggestions to improve system operation. The simulation results are presented in Section 5. Finally, Section 6 provides some conclusions for this research. II. SYSTEM UNDER STUDY The literature has talked about four configurations of wind energy conversion systems (WECS) based on the type of electrical generator and PE converter as follows:  Squirrel cage induction generator with a soft starter  Wound rotor induction generator with a rotor variable resistance and a soft starter  Doubly fed induction generator with a power electronic converter  Permanent magnet synchronous generator (PMSG) with a power electronic converter Looking from another perspective, wind turbine configurations can be divided into three configurations in terms of the application of PE converters in the WECS: directly connected to the grid without any PE converter, connected via a full-scale PE converter, and connected via a partially-rated PE converter. The generators and PE converter configurations most commonly used in wind turbine systems are discussed below. The PMSG rotor and stator are connected to the wind turbine and PE converter, respectively. Lateral advantage=reduction of voltage harmonic Main advantage=reduction of current harmonic Number of switch Modulatio n Identification method VIPWM SPW M Four six Number of switch