Abstract
In two-stage single-phase inverters, inherent double line frequency ripple is present at both the input and output of the front-end converter. Generally, large electrolytic capacitors are used to eliminate this double line frequency ripple. It is well known that low frequency ripple shortens the lifespan of capacitors. Hence, the system reliability can get worse. In order to eliminate the double line frequency ripple, additional hardware combined with an energy storage device is required in most of the methods developed so far. In this paper, a novel power-decoupling control method is proposed to eliminate the double line frequency ripple at the front-end converter of two-stage single phase DC/AC power conversion systems. The proposed control algorithm is composed of two loops, a ripple compensation loop and an average voltage control loop, and no extra hardware is required. Since the proposed method does not require information from the phase-locked-loop (PLL) of the inverter, it is independent of inverter control. In order to verify the validity and feasibility of the proposed algorithm a 5 kW Dual Active Bridge (DAB) DC/DC converter and a single-phase inverter are implemented. The effectiveness of the proposed method is verified through the simulation and experimental results.
Highlights
Two-stage DC/AC power conversion systems are widely used since they provide galvanic isolation between the input and output, and a flexible voltage gain for the rear-end inverter
It is well known that the instantaneous input power of the two-stage single-phase inverter pulsates at the double line frequency, which results in double line frequency ripples at both ends of the front-end dc-dc converter
It is desirable to limit the input ripple to be as small as possible to minimize the losses caused by the interactions among the renewable energy source, the double line frequency ripple and the power rating of the components used in the converter such as the transformer and the switches [24,25]
Summary
Two-stage DC/AC power conversion systems are widely used since they provide galvanic isolation between the input and output, and a flexible voltage gain for the rear-end inverter. By boosting the low voltage of the source to a suitable DC voltage level, front-end converters play an important role in providing a suitable input DC voltage for the rear-end Voltage Source Inverters (VSIs) to produce an AC voltage [1]. For two-stage single-phase DC/AC systems, the Dual Active Bridge (DAB) converter has attracted a lot of research interests as a front-end converter due to its high-power density, galvanic isolation, and bidirectional power flow. It is well known that the instantaneous input power of the two-stage single-phase inverter pulsates at the double line frequency, which results in double line frequency ripples at both ends of the front-end dc-dc converter
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