Optimal Energy Management Scheme of Battery Supercapacitor-Based Bidirectional Converter for DC Microgrid Applications

Abstract

Because of the splendid front of sustainable energy reassets in a DC Microgrid, it is profoundly willing to variances in energy age. A hybrid energy storage system (HESS) which includes a battery and a supercapacitor (SC) is used to decrease in-built fluctuations. The two different characteristics of the battery and supercapacitor make it a great match for HESS applications. The HESS is connected to the DC Microgrid through a bidirectional converter, which allows energy to be exchanged between the battery and supercapacitor. This paper discusses a converter presenting an approach for a double-input bidirectional converter. Related to this, a regulator was designed for use as a voltage regulation in a DC Microgrid. The designed controllers accelerated PV generation and load disturbance DC link voltage restoration, in addition to effective power balancing among the battery and the SC. The conventional PI, proposed PI, and predictive PI control techniques are effectively validated usingMATLAB Simulink. Experimental findings with low power have been used to validate the operation of the predictive PI control technique. The DC grid voltage profile showed substantial improvement while using the predictive PI control in comparison with the proposed and conventional PI control techniques in terms of setting time and maximum peak overshoot.

Keywords: battery; supercapacitor; bi-directional converter; HESS; PI controller

Block Diagram:

Figure 1. HESS-enhanced DC Microgrid with PV source.

Expected Simulation Results:

Figure 2. Bode plot of SC’s inner current controller of logic for control, both with and without controller.

Figure 3. Bode plot of SC’s outer voltage controller of logic for control, both with and without controller.

Figure 4. Bode plot of battery control logic’s current controller.

Figure 5. Simulation results for step change in PV generation for proposed PI control scheme.

Figure 6. Simulation results for step change in load demand for proposed PI control scheme.

Conclusions

The controller for the two-input bidirectional converter was designed and modeled for the HESS controller. The developed controller’s performance was assessed in a range of scenarios for voltage regulation in a DC Microgrid. The controller could really balance out the DC Microgrid against unsettling influences from the source PV age, as well as burden varieties. It could take advantage of the supercapacitor’s inherent rapid dynamics to absorb incoming microgrid transients. This unique controller played a substantial role in both the charging and discharging process in the HESS. The operation mode of the HESS converter was also demonstrated for maintaining the supercapacitor’s SoC within the optimal range. A performance evaluation of the predictive PI and proposed PI over the conventional PI control scheme with a step change in PV generation and load demand for peak overshoot and settling time to restore grid voltage was performed. The results showed that the performance of the predictive PI control method is better in terms of DC grid voltage regulation and SC utilization.

References

1. Xiao, J.; Wang, P.; Setyawan, L. Implementation of Multiple-Slack-Terminal DC Microgrids for Smooth Transitions Between Grid-Tied and Islanded States. IEEE Trans. Smart Grid 2016, 7, 273–281. [CrossRef]
2. Zadeh, M.K.; Gavagsaz-Ghoachani, R.; Pierfederici, S.; Nahid-Mobarakeh, B.; Molinas, M. Stability Analysis and Dynamic Performance Evaluation of a Power Electronics-Based DC Distribution System With Active Stabilizer. IEEE J. Emerg. Sel. Top. Power Electron. 2016, 4, 93–102. [CrossRef]
3. Graditi, G.; Ippolito, M.G.; Telaretti, E.; Zizzo, G. An Innovative Conversion Device to the Grid Interface of Combined RES-Based Generators and Electric Storage Systems. IEEE Trans. Ind. Electron. 2015, 62, 2540–2550. [CrossRef]
4. Choi, M.E.; Kim, S.W.; Seo, S.W. Energy Management Optimization in a Battery/Supercapacitor Hybrid Energy Storage System. IEEE Trans. Smart Grid 2012, 3, 463–472. [CrossRef]
5. Feng, X.; Gooi, H.B.; Chen, S.X. Hybrid Energy Storage with Multimode Fuzzy Power Allocator for PV Systems. IEEE Trans. Sustain. Energy 2014, 5, 389–397. [CrossRef]