Three-phase large-power intermediate-frequency power supply parallel method and system based on drooping characteristic control

Abstract

The invention discloses a three-phase large-power intermediate-frequency power supply parallel method based on drooping characteristic control. When a power supply is in single operation, a digital controller module is used to perform instantaneous tracking to an output waveform so as to guarantee waveform output quality. When the parallel system is determined to be cut in, a digital phase-locked loop of the power supply firstly captures a common signal of an alternative current bus, then calculates phase difference between the alternative current bus signal and an output signal itself, controls the output itself so that the phase difference maintains in a setting scope, and simultaneously collects active and reactive values. When the phase difference satisfies a requirement, drooping control immediately cuts in so that the power supply is cut in the parallel system. The invention also discloses the system which can realize the method. The system comprises: the digital controller module, an inverter circuit, a LC filter module, a digital phase-locked loop module, an active and reactive acquisition module and a drooping control module. The method and the system are realized based on the drooping characteristic. A current equipartition effect is good. A structure is simple. Stability and reliability of the parallel system can be effective improved.

Description

technical field [0001] The invention belongs to the technical field of inverter parallel control, and in particular relates to a method and system for parallel connection of three-phase high-power intermediate frequency power supplies based on droop characteristic control. Background technique [0002] Compared with centralized power supply technology, parallel power supply has many advantages: (1) It is easy to form a power supply system with larger capacity; (2) It is easy to realize modular design. (3) It is easy to design redundancy and improve the reliability of the system; (4) It is easy to maintain. When one of them fails, it can be disconnected from the system immediately, and the rest of the power supply can still be used as usual. Based on these advantages, the parallel control technology of inverters has developed rapidly in recent years. Common parallel control technologies are divided into two categories: parallel technology with interconnection wires and pa...

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Problems solved by technology

[0003] In recent years, there have been a lot of domestic researches on the field of power frequency 50Hz, especially the parallel connection of UPS, but there are few researches on the parallel connection of three-phase high-power power supplies in the field of intermediate frequency (400Hz). The reason is that the design of 400Hz controller is relatively difficult. The reasons are as follows: ( 1) At the same switching frequency, the number of 400Hz voltage pulses is 1 / 8 of 50Hz, and limited by the switching speed of high-power power devices, the switching frequency cannot be designed too high, which will lead to harmonics of the 400Hz output voltage content increases, the stabilization speed slows down, and the difficulty of controller design increases; (2) For a 50Hz system, the third and fifth harmonics are all below 300Hz, and they are far away from the cutoff frequency of the LC filter, so the gain design of the controller can be Very high, the waveform quality is very ideal; and for the 400Hz system, the third harmonic is 1.2KHz, the fifth harmonic is 2KHz, which is very close to the LC cutoff frequency, so the controller design is relatively complicated. If you want to increase the controller gain, you need Design complex notch filters, FIR, etc., otherwise the system is easy to oscillate; and the sampling link is a pure lag link, which has a relatively greater impact on the 400Hz system; (3) In the case of parallel connection, the phase corresponding to the interval of the same switching frequency, The 400Hz system is 8 times that of the 50Hz system, and it is prone to short circuit, so parallel control is more difficult

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