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The extremely fast algorithm of phase sequence detection

Wang Shuhua 1, Yan Dongchao 2, Wang Yubo 2 (1. No. 1 Xiaolingwei, Nanjing, Jiangsu 210014;

2. Department of automatic control, School of engineering, Air Force University of engineering, Xi'an, Shaanxi 710038). 1 introduction phase sequence refers to the phase relationship of three-phase alternating current. Phase sequence detection is to detect the phase sequence of three-phase alternating current, and its essence is phase detection. Usually, phase detector is used to detect the phase of three-phase alternating current, and then compare them to determine their phase relationship. There are also special electronic circuits to realize phase sequence detection. There are many phase sequence detection circuits. At present, phase sequence detection mainly depends on hardware circuits, and its performance is poor. In particular, the hand wheel of the oil return valve with fast performance and slow rotation is poor and slow in response, and the general speed is between 1 ~ 2T. Today, with the rapid development of digital circuits, the speed of phase sequence detection is so slow that it is extremely disproportionate. The software method of phase sequence detection is still immature. For this reason, the author designed a new phase sequence detection software scheme: using the phase sequence detection extreme speed algorithm, the sampled three-phase AC signal, through a specific algorithm, can calculate whether the phase sequence to be measured is consistent with the reference phase sequence, so as to achieve fast, accurate, stable and reliable phase sequence detection and give the phase sequence determination signal. Its advantages are fast, accurate, flexible and convenient. 2 theoretical derivation of extreme speed algorithm 2.1 two phase sequence is consistent let the mathematical expression of three-phase alternating current be: (the amplitude is set as 1) reference phase sequence:

2.2 two phase sequence is inconsistent when the phase sequence is inconsistent, such as the exchange of a and C in the phase sequence to be measured, we can also construct w (T, φ) Function, and note that the function is: 2.3 necessary and sufficient condition discretization can be obtained: Δ W(t， φ)＝ 0, that is: w (turn off the power TK + 1, φ)＝ W(tk， φ) Therefore: if w (TK + 1, φ)＝ W(tk， φ)， Then the phase sequence of the two is consistent. If w (TK + 1, φ) ≠W(tk， φ)， Then: the two phase sequences are inconsistent, that is, the phase sequence to be measured is wrong. In general, it is impossible to have two points in a sampling period, making 2 ω t－4π／3－ φ＝ K π, that is, when the phase sequence is inconsistent, w (TK + 1, φ) ≠W(tk， φ) equation holds good under all circumstances Based on this, we can determine the correctness of the phase sequence and give the phase sequence determination signal for correcting the wrong phase sequence. 3 data analysis 3.1 reference phase sequence according to the expression of the reference phase sequence group, we can easily get the waveform shown in Figure 3-1. Assuming its frequency is F0, we first sample the three-phase AC signal of the reference phase sequence with a certain frequency f = 12f0. And store its value in the ROM of the computer. China is still in the deep development stage of industrialization, informatization, urbanization, marketization and internationalization. These values can also be obtained through theoretical calculation. However, the phase interval between values must be consistent with the actual sampling interval. (the sampling frequency f is taken as 12f0 for the convenience of analysis, and the actual situation is much higher than this.) suppose that the sampling starts from the zero point of phase A: the sampling value of the three-phase alternating current with reference to the phase sequence is shown in table 3-1. These friction testing machines mostly adopt static position selection to inspect the friction test pieces. It is shown that the above data can be obtained through theoretical calculation. It is directly input into ROM, which only takes up space, not time, and the data interval is π/6. According to the mathematical expression, the phase sequence to be measured can be obtained as shown in Figure 3-2

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