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Simultaneous sampling for power parameter estimates of truncation error

Prime cause voltage waveform distortion. Therefore, error estimates of non-sinusoidal shape is more practical. However,[link widoczny dla zalogowanych], in theory,[link widoczny dla zalogowanych], be completely accurate as to the pure sine wave analysis is difficult because of distorted function is unknown, and generally can not be expressed by elementary functions. But for a real physical system in which two (only consider the steady-state, which contains only high harmonics of the situation, without considering the transient case.) Reason to believe that pure string system with the same: (1) still has a cyclical ; (2) is 39 with the total Volume 442 lO 2002 of Electrical Measurement & Instrumentation EleetricalMeasurement & InstrumentationV0l_39NO. 442Oet. 20o2 continued and fully smooth, you can expand it into a Fourier series to analyze. With high harmonic RMS voltage signal can be expressed as [21 C plant - a: \ / Σ (7) where,, ... ,(,._ I, 1,2, ..., n-order harmonic voltage RMS. According to equation (5), for r /, (n> 1) harmonics in the week period, the truncation error is E ≤ ( Cool

in accordance with the provisions of GB/T15945-93, China's current power quality and There are two common harmonic constraints, one harmonic content ratio, the upper limit of the odd harmonics as the fundamental of (1.6-4.0)%, the even (0.8 ~ 2. 0)% satirized (with rate refers to the harmonic content of periodic flow contains the first harmonic component of h the root mean square value of the fundamental component and its root mean square value expressed as a percentage ratio of the first sub-harmonic voltage h rate: (U) xlO0%, which for the first h harmonic voltage root mean square value for the fundamental voltage RMS value); the second is the total harmonic distortion, the upper limit value is fundamental in (2. 0-5.0)% (which is the harmonic content of periodic flow in the root mean square value of the fundamental component and its root mean square value of the ratio expressed as a percentage, that is, factory ----- A × 100%, where \ / Σ () for the harmonic voltage u1, h = 2 content). According to the above requirements, power grid can be estimated under normal circumstances the degree of distortion, taking the upper limit of the odd harmonic voltage is 4% of fundamental, the even 2%. then the first n harmonic truncation error according to equation ( Cool

, on the odd harmonics in a fundamental cycle with E ≤ n (0.04U) N on the even harmonics have E ≤ n (0.02U1) wide n = 3,5 ... ... (9) n = 2,4 ... ... (10) the total truncation error of the waveform distortion and the distortion of a relationship, it should first determine the upper limit of this value. try here, the upper limit of total harmonic distortion rate of 5% for the upper limit, different harmonics can get the same distortion, the actual situation, taking the first three, by two harmonics as a 【,[link widoczny dla zalogowanych], Volume 2. 0% for the third harmonic 【4.0%, fourth harmonic is 2.0%, 4.9% total harmonic distortion. truncation error estimate is given, all the harmonics are independent The measured parameters, the total uncertainty obtained by the following E. (Song) Song scratch 2) scraping 2 Song 2 + (Song) 2 (11) where OU / O is the total harmonic voltage and effective voltage RMS value of the partial derivatives, obtained by the following one OUU1Ul Lai Lai OU-4 according to equation (9),[link widoczny dla zalogowanych], (10) can be obtained by E, E:, E, E,[link widoczny dla zalogowanych], respectively, into (11), and rearranging E ≤ Wu U1 +2 (0.02) +3 (0.04) +4 (0.02) can be considered the relative error E ≤ N E ≤ (12) (13) and the ideal grid (when no distortion) of the formula ( 6) are equal, so the truncation error and the relationship between sampling points and the ideals of the same. Obtained by analyzing 5 Conclusion: In normal operation of power (in line with national standards allow distortion) case, truncation error and the relationship between sampling points and the ideals of the same. Should also note that the system voltage distortion and the distortion of the different system current and voltage distortion to a lesser extent, the current distortion and sometimes more serious. But for the current waveform distortion is also limited to the national standard corresponding regulations, and the cyclical and continuous, and therefore can be handled the same way. References: l】【Feng Kang et al. Numerical methods [M]. National Defence Industry Press, 1978. 【2】 Wu Jing Chang and so on. Power system harmonic EM]. China Water Power Press, 1988. 【3】 national standard, GB/TI4549-93ES]. [4】 Xiaoming Yao. Error Theory and Application of EM]. China Metrology Publishing House, 1985. First Author: Liang Qinghua (1955 -), male, associate professor, research direction for the testing technology and automation devices. Received :2002 --06-30 (Liu newly issued) a l5 a
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