# Three-Phase Unbalance Analysis Method Based on Three-Phase Motor Current Instantaneous Information
## 3 Simulation Analysis and Experimental Verification
### Experimental Validation and Analysis
Considering the sampling frequency at the same time, the sliding window size is set to 0.2 s, 0.1 s, 0.05 s, and 0.02 s, respectively, and the results are shown in Figure 24:2 By analyzing Figures 29, 30 and 32a-c, it can be seen that the results of the 0.2 s sliding window are similar to those of the 1 s sliding window. As the sliding window size decreases, the instantaneous frequency coefficient of variation and instantaneous amplitude coefficient of variation can still reflect the three-phase unbalance change well when the sliding window size is 0.1 s, but the symmetrical components method has been unable to correctly reflect the  
Figure 24:3 Adjustment of three-phase unbalance at different rotational frequencies, with the results of this paper’s method and symmetrical components method (the C.V. of the instantaneous frequency, the C.V. of the instantaneous amplitude, and the symmetrical components method), while the sliding window size is 1 s: (**–c**) 5 Hz; (**–d**); 10 Hz; (**–i**) 20 Hz. Figure 24:4 The results of the symmetrical components method at a 15 Hz rotational frequency. three-phase unbalance change. When the sliding window is 0.05 s and 0.02 s, although the C.V. of the instantaneous frequency and the C.V. of the instantaneous amplitude fluctuate more, the trend of three-phase unbalances can still be seen. The accuracy of the fast Fourier (FFT) calculation results for single-phase currents in the symmetrical components method is affected when the sliding window size is too small. That is, the solved amplitude and phase have large errors, and the positive-sequence, negative-sequence, and zero-sequence are inaccurate, thus affecting the final results. From the above analysis, it can be seen that when the sliding window size is small, the proposed method in this paper can still reflect the change in the three-phase unbalances better than the symmetrical components method. However, when the sliding window size is too small, the deviation of the result of the C.V. of the instantaneous information value increases and affects the analysis. The mean value of the instantaneous frequency obtained using the proposed method in this paper can be used as a reference for selecting the appropriate sliding window. When the size of the sliding window is too small (less than the reciprocal of the mean value of the instantaneous frequency), the degree of fluctuation of the obtained coefficients increases. The single sliding window calculation times at different rotational frequencies are analyzed for sliding window sizes of 1 s and 0.2 s, respectively. The calculation is carried out using Matlab R2021b. The CPU used is an Intel Core i7 12700H (base speed 2.3 GHz), and the memory is DDR5 16 GB (4800 MHz). The test was repeated five times, and the mean  
Figure 24:5 Analysis of different sliding window sizes at a 15 Hz rotational frequency, the results of this paper’s method and symmetrical components method (the C.V. of the instantaneous frequency, the C.V. of the instantaneous amplitude, and the symmetrical components method): (**a–c**) 0.2 s sliding window; (**d–f**) 0.1 s sliding window; (**g–i**) 0.05 s sliding window; (**j–l**) 0.02 s sliding window. value of the test results was counted, as shown in Figure 24:6 For a 1 s sliding window, the calculation time of the proposed method in this paper is 0.022 \(\pm\) 0.004 times the symmetrical components method, and for a 0.1 s sliding window, the calculation time of the proposed method in this paper is 0.036 \(\pm\) 0.002 times the symmetrical components method. The computation time of the proposed method in this paper is less than that of the symmetrical components method, i.e., the computation is faster. In summary, it can be seen that the three-phase unbalance analysis method based on the instantaneous amplitude coefficient of variation and instantaneous frequency coefficient of variation of three-phase currents requires a smaller sliding window size and faster calculation speed compared to the symmetrical components method.