Objectives Aiming at the distributed hybrid energy storage system (HESS) in the shipboard integrated vessel power system, a multi-HESSs collaborative control method based on the state of charge (SOC) of the energy storage device (ESD) was proposed to achieve the relative consistency among multi-HESSs and the reasonable power distribution between the supercapacitor energy storage and battery energy storage within a single HESS.
Methods The droop control method will be adopted in the outer control loop of a single HESS to realize the initial power distribution, while the master-slave control mode will be adopted in the inner control loop to reduce the communication demand among multi-HESS's. Given the characteristics of a fast dynamic response but the small capacity of supercapacitor and large capacity of battery energy storage, the SOC value of the supercapacitor is calculated to obtain the output power of the battery within a single HESS. Between multi-HESSs, the total charge/discharge power of each HESS unit is calculated based on the SOC value of the internal battery.
Results Through the simulation of PSCAD/EMTDC, the discharge response characteristics of multi-HESSs under high energy load switching and random fluctuation conditions are verified. Under the charge-discharge mode transformation condition, the bus voltage fluctuation is within the allowable range of 2.5%. The SOC of a supercapacitor is controlled between the upper and lower limits, and the SOC consistency of two supercapacitor units is maintained. In both charging and discharging modes, lithium batteries operate only when the supercapacitor is limited.
Conclusions On the premise of not depending on the high-low pass filter unit, the multi-HESS's collaborative control method has better bus voltage stability and strong robustness.
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