Research on Development of Phtovoltaic Generating System without Using the Phase Information of Power Network

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Inverters which are connected to electrical power network operate according to informations of it like as voltages, phases and so on. Photovoltaic power system needs same informations when it is interconnecte d to electrical power network. If exact informations can not be received, large current may flow and transmission power loss may increase. But it is very difficult to detect exact informations because of inductances of electrical power network, distortion of voltage waveform and phase delay due to electrical machines connected to it. These unexpected informations sometimes make the total system unstable.Therefore, using inpedances of the photovoltaic system and the power electrical network, and output current from photovoltaic system, we estimated the power source by minimal order observer. Then we developed novel photovoltaic system. From simulation results of noval system, we recognized that phase of electrical power network could be estimated rapidly even if phases were differe … More nt from detected values and estimated one. Also if source phases change like step function, novel system can follow it. We concluded that novel system could operate stable in case where impedances of transmission line were long as photovoltaic system was apert from electrical power network and distortion of power waveform as large capacity converters exist near it.Until now maximum power following control of photovoltaic generator has been attended by purturbating small value of photovoltaic voltage, and comparating its value to before and after ones. Because system is operated by purturvation of voltage all times, generating power pulsates. Besides, this method has defect that response is slow when illuminance changes widely, though maximum power point can be found.In this paper we have developed novel method that maximum power can be gotten using three points of it ; actuating point, before ones and after. This metho d is one that power characteristic is approximated by second order function and maximum power point can be gotten by only one calculation. So pulsating number of terminal voltage can be decreased.From the results of simulatior which are composed of above mentioned method and source voltage phase estimation one by minimal order observer, it became evident that novel system can follow to maximum power point rapidly and has small pulsation in comparison with normal system. Less