Abstract
With the increasingly serious crisis of fossil energy and environmental pollution, clean renewable energy becomes the inevitable choice of energy structure adjustment. The instability of output power of distributed renewable energy system greatly affects the operation of DC microgrid. The hybrid energy storage system (HESS) composed of High-Energy Battery (HEB) and High-Power Battery (HPB) can solve the above problems. Thus, this paper proposes a dynamic and cooperative control strategy for multi-HESS based on state of charge (SOC). Based on the traditional LPF method and droop control, this paper proposes a control strategy that requires no communication among multiple hybrid energy storage (HES) modules. This method can realize the stable control of HEB current, reduce the change times of HEB charging-discharging mode, prevent HEB from overcharging and overdischarging, prolong the service life of HEB and balance different energy storage SOC, so as to improve the operation stability and economy of DC microgrid. In addition, the method has certain robustness against sudden failures. Simulation and experiment results show the effectiveness of the proposed method.
Highlights
The increasing penetration rate of renewable energy such as photovoltaic and wind power promotes the development of DC microgrid (Kathiresan et al, 2020; Zhou et al, 2020)
Because the control strategy proposed in this paper presents a coupling state inside a single hybrid energy storage (HES) module, it is difficult to adopt impedance analysis method
Aiming at the problem that the traditional distributed multiHESS cooperative control method of DC microgrid relies heavily on external communication, a communication free dynamic cooperative control strategy based on state of charge (SOC) is proposed
Summary
The increasing penetration rate of renewable energy such as photovoltaic and wind power promotes the development of DC microgrid (Kathiresan et al, 2020; Zhou et al, 2020). Iref_P refers to the initial reference current of the High-Power Battery, and Vdiff refers to the difference between the reference voltage and the actual voltage of the bus, which is used to characterize the charging and discharging state of energy storage unit at this time. The adaptive regulating frequency of power among HES modules is much lower than that in a single HES module, so the High-Energy where the X-axis is the SOC of energy storage unit and the Y-axis is the regulator of the reference voltage value of the DC/DC convert output. According to Eqs 12, 13 when the SOC of an energy storage unit is in the charging limit zone, the reference voltage value of the DC/DC convert output should be increased to reduce the charging current of the energy storage unit. IDCref is the total current reference value, Iref_e is the current reference value of HEB, Tf is the filtering time constant of the low-pass filter, kvp and kvi, kep and kei are the PI parameters of the voltage loop and the current loop in the control loop of HEB
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