## 4 Discussion  
The traction drive system represents a distinct class of automated electric drives. This distinction is determined by several factors:  
1. In contrast to most industrial electric drive systems, traction drives operate under conditions where the traction motor may function at frequencies exceeding its nominal value.
2. Traction drives are continuously subjected to non-steady-state operating modes caused by various operational factors.  
The aforementioned factors complicate the design and implementation of reactive power compensators in traction drive systems. Moreover, conducting experimental studies on real traction drives is highly energy intensive. Therefore, simulation-based modeling is considered a more practical and efficient approach for conducting such investigations.  
The analysis of the obtained results under steady-state conditions at the nominal supply frequency of the asynchronous motor (Tables 3-5), as well as at frequencies below and above nominal, has shown that using filters with an adaptive cut-off frequency in the compensator control scheme within an FOC system enhances both efficiency (\(\eta\)) and THD. Furthermore, implementing Butterworth filters, Chebyshev Type I and II filters, and elliptic filters in the compensator control structure contributes to a reduction in torque ripple and convergence time under both steady-state and transient operating modes of the traction drive.  
At nominal and sub-nominal supply frequencies, these improvements also apply to Bessel filters. However, at super-nominal frequencies, the traction drive operation with Bessel-filter-based compensator control becomes unstable, indicating a limitation of this filter type under such conditions.  
The comparison results of the performance indicators of the traction drive equipped with a reactive power compensator--based on the implementation of the higher-order harmonic damping algorithm of the supply voltage--with those of the traction drive using adaptive control algorithms [28] are presented in Table 6.  
The analysis of the results presented in Table 6 indicates that the best performance parameters among the adaptive filtering methods are achieved using the Wiener filter. In contrast, within the framework of the harmonic damping strategy, the most effective control performance is observed with the implementation of an elliptic filter. A comparison of these two control strategies shows that the Wiener adaptive filter provides superior outcomes in terms of THD and torque ripple coefficient. On the other hand, the harmonic damping algorithm employing an elliptic filter results in a shorter convergence time under steady-state operating conditions.  
The application of adaptive filtering for harmonic compensation under non-steady-state operating conditions becomes significantly more complex. This complexity arises from the fact that obtaining reference current signals, which is essential for adaptive filtering, is a non-trivial task requiring considerable computation time. Consequently, this increases the convergence time of the algorithms, which is a critical limitation in traction drive systems. This drawback is not present in the case of implementing a harmonic damping algorithm, as the reference voltage signals are synthesized by the FOC system.