Control topology options for single-phase UPS inverters

Abstract

Abstract-Four control topologies for single-phase uninterruptible power system (UPS) inverters are presented and compared, with the common objective of providing a dynamically stiff, low total harmonic distortion (THD), sinusoidal output voltage. Full-state feedback, full-state command controllers are shown, utilizing both filter inductor current and filter capacitor current feedback to augment output voltage control. All controllers presented include output voltage decoupling in a manner analogous to "back-electromotive force (EMF)" decoupling in dc motor drives. Disturbance input decoupling of the load current and its derivative is presented. An observer-based controller is additionally considered and is shown to be a technically viable, economically attractive option. The accuracy transfer function of the observer estimate is used to evaluate its measurement performance. Comparative disturbance rejection is evaluated by overlaying the dynamic stiffness (inverse of output impedance) frequency response of each controller on a single plot. Experimental results for one controller are presented.

Estudo de estratégias de rastreamento da corrente e da tensão de saída CA de um conversor do tipo fonte de tensão.

“…Em geral na malha de corrente utilizam-se controladores do tipo Proporcional (P) (LOH et al, 2003), (ABDEL-RAHIM;QUAICOE, 1996), LAWSON, 1987), (RYAN; BRUMSICKLE; LORENZ, 1997), (SILVA, 1999). justificam o emprego deste tipo de controle num sistema com duas malhas em cascata para controle de uma UPS trifásica, relatando que erros de estado estacionário nesta malha não afetam o desempenho da malha mais externa.…”

Simulation of SPWM Control Method for UPS System

“…The simulation circuit is consists of three phase source, controlled rectifier, inverter, SPWM controller, filter, multilevel inner loop controller [9], [10], [11] and three phase nonlinear load. The simulation is done by Matlab /Simulink environment.…”

A simplified control strategy for single-phase UPS inverters

“…The dual-loop control for the single-phase UPS inverter includes an outer voltage loop which regulates the output voltage and ensures zero steady-state error and stability over a wide range of operating conditions and an inner current control loop which compensates the load disturbances and actively damps the possible resonances. It is shown that regardless of the controller type, in dual-loop techniques, the capacitor current feedback brings better disturbance rejection capability than the inductor current feedback [18,19]. This paper proposes a simple dual-loop controller for the single-phase UPS inverter with an LC filter.…”

“…The equivalent series resistance (ESR) of the filter capacitor is ignored, since it is usually such small that the break frequency becomes much higher than the range of concern. Assuming that the switching frequency is far above the fundamental frequency, Fig As aforementioned, in all dual-loop control schemes suggested for the single-phase UPS inverters, the inner and outer loops are used for current and voltage control, respectively [4,8,[16][17][18][19][20][21][22][23][24]. While these techniques exhibit an acceptable performance, the design of the feedback control loops is complicated.…”

“…Yet, it is possible to employ a single loop instantaneous voltage regulator along with a damping resistor in the filter circuit, it is more advantageous to use a dual-loop control to improve the system stability and dynamic performance and at the same time actively damp the resonance oscillations. Depending on the inner loop feedback variable and the type of controllers, several dual-loop control schemes have been proposed [4,8,[16][17][18][19][20][21][22][23][24]. The dual-loop control for the single-phase UPS inverter includes an outer voltage loop which regulates the output voltage and ensures zero steady-state error and stability over a wide range of operating conditions and an inner current control loop which compensates the load disturbances and actively damps the possible resonances.…”