Photovoltaic Microgrids Control by the Cooperative Control of Multi-Agent Systems

This paper presents a cooperative control which is applied to the secondary control of multi-agent controlled microgrid. Balancing power in a microgrid is essential that leads to voltage and frequency stabilities. The voltage and frequency regulations are limiting them within specified limits and approaching them to their nominal values. Limiting and approaching voltage and frequency to their nominal values is done by primary and secondary controls, respectively. Microgrid has both dispatchable and non-dispatchable sources. Dispatchable sources have been controlled by the conventional P-w and Q-E droop controls. A photovoltaic as a non-dispatchable source generates active power according to weather conditions, but the reactive power supply is done by using E-Q droop method. The E-Q droop uses the idle capacity of the inverters in the reactive power sharing. Distributed secondary control increases stability because of good, accurate and reliable controls. Frequency is constant in the whole of microgrid. Since line impedances are different, load terminal voltage control is needed. The load as another agent is considered, who can request desired voltage at its terminal bus.