Control Strategy Of Microgrid Hybrid Energy Storage System

With the continuous improvement of industrial civilization, the energy demandof modern society is exploding. The use of renewable energy is increasing due to thegradual depletion of conventional fossil fuels. Renewable energy power generationhas undulatory property, which severely affects the security and stability of thepower grid and limits the development of new energy technology. The appearance ofmicrogrid technology reconciles this contradiction effectively and microgrid needsenergy storage system. The share of renewable energy is rising in the microgrid,which demands for better performance of the energy storage system. The use ofhybrid energy storage system composed of battery and super-capacitor not onlygreatly improves the performance of an energy storage system but also is acost-effective solution. In addition, control strategy greatly affects the performanceof the energy storage system. Since the hybrid energy storage system has nonlinearcharacteristics of strong coupling and multiple variables, it is by nature moresuitable to adopt nonlinear control strategy to control the hybrid energy storagesystem.This paper studies on the hybrid energy storage system in the microgrid adoptsthe energy shaping control strategy which is a new kind of nonlinear robust controlstrategy. On the basis of subsystem decomposition modeling, the port-controlledHamiltonian model of the hybrid energy storage system is established by using thefeedback interconnection method. The port-controlled Hamiltonian model also is thebasis to study the energy shaping control strategy. Energy shaping control strategy isadopted to control the charge and discharge of energy storage devices. Battery bearsthe low frequency power component of the load by the means of direct powercontrol of battery while super capacitor is responsible for the low frequency powercomponent of the load by the means of keeping the DC bus voltage of the hybridenergy storage system stable. Energy shaping control strategy of hybrid energystorage system is designed both in the grid-connected mode and in islanded mode.The compensation and synchronization algorithm of hybrid energy storage system isdesigned for the microgrid mode transition to reduce the impact on the grid andelectrical equipment.This paper builds a simulation model of microgrid to test the performance ofthe energy shaping controller by comparing the control effect with the PI closedloop controller. Simulation results indicate the validity of the energy-shaping controlstrategy and it has better quickness and robustness than the typical linear PIclosed-loop control strategy. This paper focuses on the microgrid hybrid energy storage system which is a current research focus and proposed control strategy haspositively theoretical and practical significance.