Examining solar system behavior and single-phase energy storage batteries in a small-scaled micro-grid to decrease reliance on AC network power
Working Group Number
CIRED 2018 Ljubljana Workshop
7 - 8 June 2018
behkesh noshahr, javad, Ardabil Province Electricity Distribution Company, Islamic Republic Of Iran
In the last decade, with an increase in growing demand of electric power consumers, the use of solar energy is significantly increased for power supply to the urban and rural residential buildings and houses. The solar systems are operated independent from network or connected to distribution network. The power generation of solar systems depends on atmospheric conditions (solar radiation and ambient temperature), therefore, in the network-independent solar systems, the energy storage batteries are used for reliable and stable power supply, but in the solar systems connected to the network, for lack of energy storage, the surplus energy generated by the system is directly transmitted to the distribution network. The power generation of singlephase household solar systems is between 1-5kW, while the peak of electrical consumption in a residential house is less than 2.5kW. Hence, by adopting an appropriate strategy such as storage batteries (capacity of 1000Ah), the power consumption of other residential homes that are located near the microarrays can be supplied with no reliance on power of network distribution. In this article, it has been attempted to model a micro-grid including a single-phase AC distribution system, solar system, storage batteries, and household load using Matlab/Simulink capabilities. The microarrays are connected to the distribution network through a singlephase distribution transformer of 20/0.24kV. The charging and discharging management of storage batteries are done through a control system. The control system strategy of the storage batteries is designed with minimum dependence on power generation of network, so that the solar system and storage batteries can supply total power at all periods under every conditions. The control system strategy of the storage batteries is planned in such a way that absorbed the surplus power generation of microarrays and can compensate for lack of power at peak consumption times. The current tracking by the storage battery control system made the transient active power to be approximately zero on secondary side of the transformer. However, at the times when control system is not in the circuit, the state of charge will be constant, and there will be no power storage or discharging, and surplus generation is transmitted to the network, and lack of power will also be obtained from the distribution network. The simulation has been done in two different scenarios, in the first scenario, the storage battery control system is in the circuit 24 hours a day, and in the second scenario, the storage battery control system is removed from the circuit at hours 12-18. The simulation results for a 24-hour period in the first scenario show that the micro-arrays can supply the total power without reliance on network power, and the exchange power from distribution network is almost zero, in the second scenario, merely 12.5% of power is supplied by the network, and the rest is supplied through micro-arrays.
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