Generalized active power decoupling method for H-bridge with minimum voltage and current stress

Abstract

Single-phase PWM rectifier, grid connected PV inverter system, static synchronous compensator (STATCOM) all can be implemented by an H-bridge inverter and a large electrolytic dc capacitor to absorb the ripple power pulsating at twice the line frequency (2ω ripple power). This paper proposed a generalized active power decoupling method for Hbridge with minimum voltage and current stress. By adding another phase leg to control an ac capacitor, the 2ω ripple power can be absorbed by the capacitor and theoretically 2ω ripples to the dc capacitor can be eliminated completely. The H-bridge and the addition phase leg can be analyzed together as an unbalanced three phase system. By adopting SVPWM control and choosing the optimum ac capacitance and the capacitor voltage reference, the voltage and current stress of the switches can be minimized to the same as the conventional H-bridge. The size of capacitor is reduced by 10 times compared to the conventional H-bridge system. Simulation and experimental results are shown to prove the effectiveness of the proposed active power decoupling method.

Modulation Schemes for Single-Phase B6 Converters With Two Asymmetrical Terminal Voltages

“…The B6 converter is thus more likely to be used for applications with a common terminal frequency and a phase shift that permits a much smaller dc-link voltage to be used. Some possibilities are UPS, power conditioner [14][15][16], and converter with power ripple decoupling [17][18][19][20][21][22], as also mentioned in Section I.…”

“…It should however be noted that B6 converter is not only used as a three-phase converter. It can also operate as a reduced-switch single-phase ac-dc-ac converter [14][15][16] or a single-phase converter with power ripple decoupling [17][18][19][20][21][22]. The reduced-switch ac-dc-ac B6 converter was, in fact, proposed in year 2000 for replacing two full-bridges with four phase-legs connected back-to-back.…”

“…Another usage of the B6 converter is as a single-phase converter with power ripple decoupling [17][18][19][20][21][22]. The three phase-legs in this case are divided such that one of them is connected to the intended single-phase ac system, and another is connected to a small film capacitor.…”

“…Placing the film capacitor in this manner has the advantage of requiring only ac fundamental voltage across the capacitor, which in general, demands a smaller capacitance and simpler control. Recent work in [22] has also shown that with proper modulation, the dc-link voltage required by the B6 converter for power ripple decoupling can be reduced, which although is important, is only one requirement out of a few that can be optimized. It is therefore clear that the B6 converter is not only a three-phase converter.…”

Modulation Schemes With Enhanced Switch Thermal Distribution for Single-Phase AC–DC–AC Reduced-Switch Converters

“…commonly sensed with single-phase systems [12][13][14][15][16]. In this case, one set of ac terminals must be tied to an ac film capacitor for storing the power ripples.…”