• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.2
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• pp.101-105
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• 2018

Shortage of electric power occurs frequently along with increased electric power demand. ESS is a precaution to solve this issue. Household ESS has a capacity of approximately 3 kW/7 kWh. Household ESS batteries are typically designed with nominal voltages between 40 and 50 V. To connect household ESS with a 220 V AC system, low battery voltages in power conditioning system (PCS) should be boosted. To boost low battery voltage and match it with AC grid voltage, the use of a transformer for a commercial frequency can be considered. To attenuate switching harmonics of the household single-phase ESS-PCS, LC filter can be installed in two positions: on the primary side or on the secondary side of a transformer. A method has been used generally in single-phase inverters for the ESS-PCS. In another method, however, the output efficiency of the ESS-PCS may be decreased. Parasitic components of the transformer can affect voltage losses, when the square wave with the switching frequency in the ESS-PCS is passed through the transformer windings. In this work, the characteristics of the transformer according to the position of an LC filter are investigated for household single-phase ESS-PCS.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.2
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• pp.94-100
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• 2018

Generally, in a single-phase energy storage system (ESS) for households, AC ripple component with twice the fundamental frequency exists inevitably in the DC link voltage of single-phase PCS. In the grid-connected mode of a single-phase inverter, the AC ripple component in the DC link voltage causes low-order harmonics on grid-side current that deteriorates power quality on an AC grid. In this work, a control system adopting a feedforward controller is established to eliminate the AC ripple interference on the DC link side. Optimal battery nominal voltage design method is also proposed by considering the voltage loss and AC ripple voltage on DC link side in a single-phase ESS. Finally, the control system and battery nominal voltage design method are verified through simulations and experiments.