Supply Induced Interharmonic Effects in Wound Rotor and Doubly-Fed Induction Generators

Investigation of grid supply harmonic effects in wound rotor induction machines

“…This section presents generalized equations to calculate the numeric values of the possible stator current frequencies of a three-phase, p pole-pair WRIM operating with higher order harmonic content in the stator supply. The derivation of these equations has been presented in previous works [9], [15] and will therefore not be derived here again. fc is the stator current frequencies of interest, i is the stator supply induced harmonic order number (i = 1, 2, 3,...), s is the fractional slip, and k is the air-gap field pole-pair number (k = 0, 1, 2,...).…”

“…These grid supply harmonics produce stator current harmonics, which can cause torque pulsations and hence, mechanical vibration in the WRIM that may lead to mechanical faults and premature failure of WT components [9]. Furthermore, the grid supply harmonics can increase the core and copper losses and thus, reduce the efficiency of the WRIM [10].…”

Torque/current spectral analysis for healthy and eccentricity faulty synchronous reluctance machine using mathematical modeling method

“…Considering l ls as leakage inductance of each winding, modified WFT (MWFT) [1][2][3][4][5][6][7][8][9][10] has been used for the machine's inductances as written in (5) with the turn functions as shown in Figure 2. According to 6-8 in combination with Equation (4), self and mutual inductances can be computed between two arbitrary turn functions (n i and n j ) by the whole air gap function (f g ) that consists of three parts for rotor poles (f r ), slot opening (f s ), and conventional air gap (g) as written in (9).…”

“…In another work, eccentricity fault has been researched using current signature for silent pole synchronous and induction machines by Faiz, et al via the electromagnetic equations and finite element methods but did not proposed an exact model for air gap function and the machine's geometry [4][5][6][7]. The current/torque spectral analysis is the main approach for fault detection in electrical machines that were used for eccentricity and inter-turn short-circuit faults [4][5][6][7][8][9][10][11][12]. Wound rotor induction machine's faults were addressed in [8][9][10][11][12] by electromagnetic base modeling, but the air gap function were roughly modeled and basic equations were employed for the modeling.…”

“…The current/torque spectral analysis is the main approach for fault detection in electrical machines that were used for eccentricity and inter-turn short-circuit faults [4][5][6][7][8][9][10][11][12]. Wound rotor induction machine's faults were addressed in [8][9][10][11][12] by electromagnetic base modeling, but the air gap function were roughly modeled and basic equations were employed for the modeling. It is known that the winding function theory (WFT) and finite element method (FEM) are two powerful methods for numerical analysis of electrical machines.…”