A novel instantaneous current sharing control for parallel connected UPS

Abstract

This paper proposes a novel instantaneous current sharing control scheme ensuring a fast dynamic response and an equal load sharing capability in parallel connected UPS(inverter). The proposed novel instantaneous current sharing control scheme is based on the instantaneous output voltage control with the current deviation control and the instantaneous current deviation cancellation control utilizing the current share bus circuit. The proposed novel instantaneous current sharing control circuitry employs the share bus signal line interconnecting all the paralleled inverter on a noise insensitive line. The voltage control circuitry forces all the paralleled inverter to share load current, almost equally, by adjustment of the instantaneous reference voltage signal obtained from the current share bus. With the current share bus and the current deviation controller, the paralleled inverter with the highest output current becomes the master inverter; then all the other inverters become slave inverters. The instantaneous output current of the master inverter is subtracted from the other inverters' output currents, and the current deviations in each inverter module are calculated. Hereafter, the instantaneous current sharing controller forces the output current deviations of each inverter to be zero in every switching period. Furthermore, the output reference of the voltage controller is instantaneously to eliminate the unbalanced power. This results in superior power balance performance for parallel operation.

Analysis and control of PV inverters operating in VAR mode at night

“…The current loop controller may be any of the conventional current loop controllers such as PI, PI with feed forward [9] [10], [11], as well as P+R [4].…”

Stability analysis and duty cycle limitation of grid‐connected current control strategy for multiple parallel three‐level T‐type grid‐connected inverters

“…Circulating current suppression is to reduce the harmonic pollution to the power grid and increase the sinusoidal degree of grid‐connected current. For the first aspect, current sharing control of the multi‐inverters is usually used in the microgrid or off‐grid situations with the loads [5–8], and the references on current control in the grid‐connected case are relatively more although some of them are not designed for the 3LT 2 Is [9–12]. A master–slave control by communication [5] or by the current sharing bus and synchronous bus [6] is a common method, the reference current is sent to each slave by the host.…”

“…For the first aspect, current sharing control of the multi‐inverters is usually used in the microgrid or off‐grid situations with the loads [5–8], and the references on current control in the grid‐connected case are relatively more although some of them are not designed for the 3LT 2 Is [9–12]. A master–slave control by communication [5] or by the current sharing bus and synchronous bus [6] is a common method, the reference current is sent to each slave by the host. A circular chain control strategy is proposed, and the adjacent module tracks the current of its previous one and the first module tracks the last one to form a circular chain connection so that an equal current distribution is achieved [7].…”

Effect of connection cable impedance on multi-inverter parallel system and an optimized controller with zero steady circulating current

“…Multi-inverter parallel system has the advantages of modularization, standardization, high reliability, good maintainability and power distribution [1][2][3][4][5][6][7]. Among the presented current-sharing schemes in previous papers, the instantaneous current-sharing control scheme is an attractive selection.…”