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The proportion of renewable energies in power generation has increased according to the political aims in recent years. In low-voltage grids, these are mostly decentralized renewable energy systems such as photovoltaic (PV) that are connected through the inverters to the grid. The temporary reversal of the power flow causes overvoltage problems. Consequently, regenerative sources need to be turned off temporarily or on the long term the grid infrastructure has to be extended by the utility company. The concept described in this paper uses reactive power which is generated by the solar power inverters to increase power capability and quality of the grid. Thus grid extension can be avoided in many cases or at least can be delayed. Voltage fluctuations due to varying power input, e.g. caused by passing clouds, can be reduced. Additionally, the inverters can be remotely controlled to compensate harmonic distortion and to improve phase voltage balance by feeding unsymmetrical currents into the three phases. Distributed data collection and central control is required for control of a distributed system of multiple solar inverters installed in a grid segment. The concept can be applied not only to PV systems; it is rather a basic technology which can be used in future grids with distributed generation and storage.
Date of Conference: 11-13 Oct. 2010