Abstract
In this paper, a constant frequency control strategy of a microgrid by coordinating energy router (ER) and energy storage system is proposed to solve the frequency fluctuation problem of microgrid, in which ER is the core of the energy management system. The interface converter of ER connected to the microgrid adopts the virtual synchronous generator (VSG) control, which adjusts the mechanical reference power in real time according to the state of charge (SOC) of the energy storage. The energy storage system adopts constant voltage and constant frequency (V/F) control to maintain the frequency and voltage stability of microgrid. The energy storage system with fast charge and discharge responds to the power fluctuation of the microgrid. ER maintains the stability of the energy storage capacity through bidirectional power regulation. When the energy storage system fails, the frequency and voltage droop characteristics of ER controlled by VSG will play a role in maintaining the stable operation of the microgrid. By the coordinating control strategy, the maximum efficiency of intermittent distributed energy can be guaranteed, and the stability, reliability, and grid-connection friendliness of the microgrid operation can be improved. Simulation results prove the effectiveness of the proposed control strategy.
Highlights
In recent years, due to the rapid development of distributed power generation technology, a large number of distributed new energy grid-connection requirements have emerged
Based on the above analysis, this paper proposes a constant frequency control strategy of the microgrid by coordinating the energy router (ER) and the energy storage system
It can be seen that when the output power of wind energy and photovoltaic light fluctuates, battery energy storage system (BESS) can quickly respond to the unbalanced power of wind and light to ensure the balance of supply and demand in the microgrid, while ER reflects the virtual inertia to slowly adjust the output power according to state of charge (SOC), support BESS operation, and maintain its SOC stability
Summary
Due to the rapid development of distributed power generation technology, a large number of distributed new energy grid-connection requirements have emerged. Microgrids with ER as the core have been proposed successively [3,4,5] In this kind of microgrid, DER, local loads, and battery energy storage system (BESS) are usually connected to the main grid through the low-voltage AC interface provided by the ER. In the whole microgrid topology, the MPPT control is used to ensure the maximum power output of distributed generation When both ER and BESS are working properly, the BESS is used as the balance node to provide voltage and frequency support and respond to the unbalanced power of DER and load quickly. When DER output increases or load decreases, resulting in the power surplus of the microgrid, BESS quickly absorbs the surplus power, while ER slowly adjusts the SOC of the energy storage and transmits the surplus power to the main grid.
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