Control method for parallel power equalization of modular uninterruptible power supply

Abstract

The invention discloses a control method for parallel power equalization of a modular uninterruptible power supply. The control method comprises the following steps of constructing an equivalent control model of two single-phase uninterruptible power supply (UPS) inversion parts in parallel, wherein an inverter employs a half-bridge structure; and performing a virtual resistance feedback control strategy on current sharing and power sharing of two parallel UPSs, equivalently achieving suppression on a parallel ring current by connecting a virtual resistor in series, and improving the current sharing and power sharing capability of the system, wherein the step comprises of suppression on an active power ring current, reactive power ring current and a DC ring current. With regard to two single-phase UPS inversion part on-load power supply systems in parallel, and the control method of equivalently connecting the virtual resistor in series is employed; by additionally arranging a virtual resistor feedforward ring in a voltage-current annular control block diagram of the UPS inverter, ring current caused by difference between the parallel UPSs is greatly reduced, so that the suppression on the active power ring current and the reactive power ring current is achieved, and the output power of a parallel system is further equalized; and the suppression on the integral ring current is achieved, and the current sharing capability of the parallel system is improved.

Description

technical field [0001] The patent of the present invention relates to a control method for parallel power balance of modular uninterruptible power supply. Background technique [0002] With the continuous development of modern industry, electrical equipment has become more and more abundant, and a large number of precision instruments and equipment have appeared in modern industrial occasions, playing an irreplaceable role in the fields of transportation, information communication, and industrial automation production. Whether these equipment can operate safely, reliably and continuously is directly related to people's production and life. Whether the equipment can operate reliably and stably not only depends on the technology and quality level of the equipment itself, but also on whether it can provide stable safety Reliable power. [0003] With the continuous development of power electronic technology, power conversion technology makes AC-DC, DC-AC conversion possible. Un...

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Problems solved by technology

[0005] Although parallel UPS can improve the stability of the power supply system, due to the differences in the characteristics of each UPS device and the length of the connection line to the load, there are differences in the output internal impedance of different units in the parallel system, even if the amplitude, phase and frequency of the output voltage of each UPS Exactly the same, this difference will also cause uneven distribution of power and output current to the load, resulting in circulating current between parallel UPSs, affecting the output characteristics of UPS

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