A phasor calculation method for the start-up protection of the condenser suitable for the start-up of the static frequency converter

Abstract

The invention discloses a phase modifier startup protection phasor calculation method suitable for static frequency converter startup. Voltage between phases or neutral point current subjected to low-pass filtering is adopted to carry out zero crossing point interpolation frequency measurement on a phase modifier, and frequency measurement response speed is higher; if a three-phase short circuit happens to cause the voltage between phases to be lower than a frequency measurement amplitude threshold, the neutral point current is adopted to carry out frequency measurement, and therefore, a situation that the frequency measurement function is affected due to a short circuit fault situation is avoided; a fixed sampling rate is adopted to be suitable for upgrading a conventional protection device; a principle error brought by fixed sampling is corrected, and accuracy is higher; core calculation is optimized, a fit function is used for replacing sine and cosine functions which are widely used, algorithm execution efficiency is guaranteed, and the phase modifier startup protection phasor calculation method is suitable for protecting a phase modifier protection device which has more configurations and is sensitive to efficiency. The calculation method has the advantages of higher accuracy, higher response speed and higher calculation efficiency under frequency conversion environment, and integral harmonics can be filtered.

Description

technical field [0001] The invention belongs to the technical field of generator start-up protection, and in particular relates to a phasor calculation method for controller start-up protection suitable for starting a static frequency converter. Background technique [0002] There are many ways to start the condenser. The starting methods used in the prior art mainly include: asynchronous starting, low-frequency starting, and coaxial motor starting. The 300MVar condensers that have been put into operation are often started by Static Frequency Convertor (SFC) due to their large capacity. This method is precise in control, has little impact on grid connection, and can achieve soft start with synchronous devices. During the start-up process of the condenser, the frequency range of the secondary current and voltage analog input to the relay protection device is 0-52.5Hz. Since the output current harmonics are large when SFC is working, when the SFC adopts n-pulse inverter, the ...

AI Technical Summary

Problems solved by technology

Although the technical solution in this patent can solve the problem that the previous methods cannot measure or have large measurement errors under the condition of rapid frequency changes, it requires a large amount of interpolation on the sampled data, and there is a problem that the amount of calculation is too large

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