Contribuição ao controle digital doparalelismo sem comunicação desistemas de energia ininterrupta

Abstract

Uninterruptible Power Supplies are equipment employed to deliver continuous high quality power to critical loads, raising supply availability and reliability to levels much higher than those originally found in the public mains. However, as all electronic equipment, the UPS itself is subject to failures. Higher reliability levels can be achieved by means of redundancy, which can be performed connecting the UPSs in parallel. This work concentrates in the study of the UPSs parallelism as a manner to improve the reliability or the power capacity of the energy supply without using communication between the autonomous units, what requires the use of local measurable information only. Each subsystem needed to carry out the parallelism without communication is investigated in details. The single phase active and reactive power calculation methods and synchronism techniques are modeled, analyzed and evaluated. The sources of the steady state active and reactive power sharing errors and their mitigation methods are also investigated. The output voltage control study is performed in discrete time taking into account the computational delay and the PWM strategy. The design of the discrete controller is proposed aiming to standards conformity and at the same time to the parallelism stability. From the analysis of a single UPS connected to the infinite bus, multivariable decoupling techniques are proposed in order to extend small-signal stability range regarding the magnitude and the nature of the line impedance between the UPSs. The proposed techniques are validated through experimental results.