Examination of voltage control characteristics of solar photovoltaic inverters

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Supervisor:
Dr. Hartmann Bálint
Department of Electric Power Engineering

There is an increasing need and possibilities for using renewable energies in the world today which creates big improvements in the technology. The improvement and increased usage of solar cells are typical for the whole of Europe. There is a giant rise in the setups of solar cells in Hungary as well. This points to the fact that we have to check the effects of all these new solar cell systems when it joins the power network. The increasing usage of small solar cell systems under 50 kVA in households connect to the low voltage network, because of this we must check the negative effects on the low voltage network. Using technical literature research Ii will look up the voltage qualities and standards. During my thesis I will study the solar cell system’s influence on increasing voltage and different possibilities for reducing it. The tension straightaway affects the low voltage network indicators (SAIDI, SAIFI), network quality attributes. I will present different voltage regulation protocols and strategies for decreasing the voltage increasing effects, putting special focus on the method using PV(photovoltaic) inverters. If anyone want to join the Hungarian network, there are no regulations for solar cell systems for improving or fixing the voltage quality problems they create by joining the network. Suppliers They make an offer to the suppliers the small solar power plants for using cosφ=0,95 power factor throughput but it’s not law so usually the PV systems use cosφ=1 power-factor, that means they work with only real power. Following the joining of numerous households and the suppliers gauging there are low tension parts of the system where the increase in voltage create malfunctions in Hungary. Expecting a rise in the usage of similar solar cell systems together with the improved capacity of the already joined systems the pressure on the low voltage network is rising. Regarding this, new regulations and directions on the usage of said systems. The main point of my thesis is the said reactive power usage and regulations adaptable application. Therefore, I am using an approximate low voltage system grid which is close to on being used in Hungary, which is suitable to analyze and research the effects of solar cell systems negative effect on the network. In the investigational model I analyze , depending on the number of solar cells , 4 groups and different subgroups on arrangements. The PV system’s inverters in the household size powerplant category are analyzed on a real power scale. I analyze the inverters effect on increasing voltage as well as how and to what extent suggestible with waste reactive power compensation.

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