Abstract

Background: Aiming at the power fluctuation of wind/ photovoltaic (PV)/ energy storage (ES) hybrid energy conversion system injected into the grid, this paper builds a mathematical model system of distributed microgrid with PV coupling to the DC side of the doubly fed induction generator (DFIG) and proposes hierarchical and phased power coordination strategy.

Methods: The hydrogen storage part and the Supercapacitor (SC) are used as backup power and power adjustment units to ensure power supply reliability and compensate for the shortcomings of wind and solar energy intermittent. The power coordination strategy assigns power reference control and the power controller follows the reference value (i.e., hierarchical control). The electrolysis cell (EL) and the Proton Exchange Membrane Fuel Cell (PEMFC) perform phased power control (i.e., minimum power, rated power, maximum power). The SC is divided into two operating modes, which are the same or opposite to the EL/PEMFC output power direction.

Results: To reduce the wait time of the SC, the SC is free to switch between the two modes by setting the recovery voltage. The SC is mainly aimed at wind speed and load abrupt changes, and the hydrogen storage part is designed to solve the short-term energy shortage and surplus.

Conclusion: In the 3-machine 9-bus system, the actual wind power, irradiance and temperature data of North China are used for verification. The method can effectively balance the wind wave fluctuation power, prolong the life of the EL, fully utilize the space of the SC, and reduce the cost.

Keywords: Doubly fed induction generator, supercapacitor, hydrogen storage, energy conversion system, hierarchical and phased control algorithm, mathematical model.

Graphical Abstract