Parallel redundant power system and the control method for the same

Abstract

A power redundant power system and a method for controlling the power system are presented, wherein the power system is composed of at least one inverter for supplying AC power to a load through a bus, a phase lock system to synchronize all output voltages of the inverters and a current sharing circuit to properly distribute the load current among all inverters. Each inverter is controlled by an unbalanced power to limit the increase of its cross current. Moreover, the information related to DC bus voltage is further applied to control the inverters, whereby the cross current is mitigated and entire power system is operated steadily.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention is related to a parallel redundant power system and the control method for the same, and more particularly to a power system that utilizes an unbalanced power calculation and a cross current limitation technique to control the response of the inverter. [0003] 2. Description of Related Arts [0004] With the almost total dependence of modern societies on electricity for employment, living, communication and entertainment, any disruption to an electricity supply brings about a temporary halt to civilization as we know it. Especially in the present age where a breathtaking variety of electronic products are widely used, serious economic loss may possibly occur if a company loses critical data when the electricity supply is suddenly interrupted. [0005] To solve the above problem, the uninterruptible power supply (UPS) has been developed for providing a stable power supply. The most important objectiv...

AI Technical Summary

Benefits of technology

[0008] The main objective of the present invention is to provide a parallel power system capable of controlling current sharing. When the power system experiences abnormal situations such as the current surge, a non-linear load or a short circuit, the gain value of the controller is instantly adjusted. Moreover, the cross current is controlled by utilizing a concept of power balance while the output impedance is simultaneously considered without separating the cross current into two vectors, so that the power system possesses superior reliability.

[0011] wherein the current sharing circuit controls the current rate that each UPS module should output, and furthermore by properly controlling the unbalanced power among the UPS modules, the cross current could be mitigated; and

[0022] multiplying the difference value with a gain value to obtain a compensation value to add to the inner current loop so as to improve the cross current transient of the load sharing.

Problems solved by technology

Especially in the present age where a breathtaking variety of electronic products are widely used, serious economic loss may possibly occur if a company loses critical data when the electricity supply is suddenly interrupted.

In the actual environment, the UPS may face many difficult problems, for example the fluctuation of the input voltage, thunderstorm interference, the sudden change of the load (the load may even short), and the continuous operation for twenty-four hours a day.

However, if the manufacturer intends to improve the reliability to be higher, not only will the circuit become more complex, but also the cost will also be greatly increased.

There is no doubt that the reliability of these inverters will be improved by implementation, however, most of the control means for the power supply system is accomplished by hardware, so the gain of the controllers is unable to be modified and thus the transient (dynamic) response of the power supply system is difficult to handle.

The method taught by the cited patent is so complex that a high reliability may not be obtained and the fabrication cost is increased to a non-commercially.

Furthermore, if the inverter is used as an adaptive inverter for the UPS, the cited patent does not take into account the input DC voltage of the inverter from the bus, and the influence generated while the inverter is coupled to any other module is also not considered either.

Once the synchronize signal experiences failure, the entire power system will breakdown.

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