A. Balogh, Z.T. Bilau, and I. Varjasi (Hungary)
High efficiency, 3 state control, photovoltaic converter, control strategy.
The efficiency of the converter is one of the most important parameters of a grid connected PV system, since the price of PV cells is still very high. One possible method of increasing the efficiency is constructing a power circuit without transformer. For avoiding EMC problems in this case we need not only differential u mode, u but u also u common u mode u filter u at u the DC-AC converter. Just connecting the middle point of the DC capacitive filter to the neutral line of the grid, the high frequency current between the PV array and the grid become acceptable, but the ripple current in the filtering AC inductance become somewhat higher. As the major part of core-loss caused by the ripple current, this will decrease the efficiency especially at low power (i.e. at low radiation). The proposed control method u will u decrease u the u ripple u current, u hence significantly u improve u the u efficiency u in u the u low u power operating u domain. u With u the u proposed u 3SC u (Three State u Control) u method u each u leg u of u the u inverter u have u 3 possible states (high on, low on, both off) unlike the 2 states at the traditional control method.
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