Parallel operation of three-phase UPS inverters by wireless load sharing control

Management of hybrid (AC-DC) micro-grids

“…However, they must be synchronized in frequency, phase and magnitude in order to avoid circulating current. Assume the circuit in Fig.1-3, if there is difference between the two sources, either in frequency or magnitude and phase, a circulating current i , defined in (1-1), flows from one source to the other causing an increasing output current [6]. …”

“…1-3 shows that every source works in parallel with its neighbor either in AC sub-grid or DC sub-grid. In a micro-grid systems are connected in parallel to increase the current that can be delivered to a load, as well as to add redundancy to the overall system [6].…”

“…The latter is very important to reduce the burden on the other sources, and to do so we need to develop a proper control technique [6][7]. Droop control is a popular technique, and further explanations about this process are provided in the next subsection.…”

“…The realization of (3-4) through (3-8) is shown in figure 3-6. Where the reference power (3)(4)(5)(6)(7)(8) has to be converted to current using division by AC micro-grid voltage, this is now the reference current that should be subtracted from the measured current to yield the error signal E that is being compensated to produce the signal U signal which in turn is converted to the duty cycle ratio by the PWM circuit. …”

Técnicas de control robusto basado en modelo de referencia aplicadas a sistemas modulares de alimentación.

“…Una aplicación interesante de este estudio sería la implementación de SAIs trifásicos modulares, escalables a altas potencias. [36][37] [38].…”