In this paper, dynamic power management scheme is proposed for standalone hybrid AC/DC microgrid which constitutes photovoltaic (PV) based renewable energy source, proton exchange membrane (PEM) fuel cell (FC) as a secondary power source and battery-supercapacitor as hybrid energy storage. The power management algorithm accounts for seamless operation of microgrid under various modes and state of charge (SoC) limit conditions of hybrid energy storage, when all the sources, storages and loads are connected directly at the dc link. The power management scheme (PMS) generates current references for dc converter current controllers of fuel cell, battery and supercapacitor. The average and fluctuating power components are separated using moving average filter. The dc link voltage regulation under dynamic changes in load and source power variation is proposed. Also, PV power curtailment through control is formulated. The proposed power management is modified and extended to multiple photovoltaic generation system and batteries with all the sources and storages geographically distributed operating under multi-time scale adaptive droop based control with supervisory control for mode transition. The proposed power management scheme is validated using simulation results. Also, FPGA/Labview based laboratory scale experimental results are presented to validate the power management scheme under various critical conditions.
- PEM fuel cell
- Power management
- Voltage source converter
- Standalone AC/DC microgrid
- Moving average filter
- Multi-time scale
Fig. 1. Hybrid AC/DC Microgrid configuration 1
Fig. 2. Hybrid AC/DC Microgrid configuration 2
EXPECTED SIMULATION RESULTS:
Fig. 3. Variation of dc link voltage scenario I
Fig. 4. Variation of PV power and load power
Fig. 5. Variation of Battery, SC and FC powers scenario I
Fig. 6. Variation of PV boost converter duty ratio scenario I
Fig. 7. Variation of SC, FC and battery currents scenario I
Fig. 8. Variation of SC voltage and % SoC of Battery scenario I
Fig. 9. Load voltage (L-L) and load current scenario I
Fig. 10. DC link voltage variation scenario II
Fig. 11. DC link voltage variation
Fig. 12. PV1, PV2 and load powers.
Fig. 13. Variations in SC power.
Fig.14. Variations in BES powers.
The proposed PMS 1 for hybrid AC/DC MG1 successfully drives the MG1 from generation dominating mode to load dominating mode with efficient dc link voltage regulation. The presented PMS is robust to wide variation in operating point. The use of MAF efficiently separates the average current reference to be supplied by fuel cell and battery while transient and oscillatory component of power to be supplied by SC. The proposed MAF based multi-time scale adaptive droop PMS with supervisory control for MG2 offers reliable transition algorithm for operation of multiple PVs and BES in a geographically distributed location. It also considers the SoC charging and discharging rates for multiple BESs. Also, the PMS considers effective utilization of H2 in FC stack by using current slope limiter. The paper also proposes the control based PV power curtailment under critical conditions. The proposed PMS considers all the contingency conditions. The simulation and experimental results validates the proposed PMS under normal as well as critical conditions. Thus, PV-PEM fuel cell with HES and proposed PMS presents a promising scope for operation as a hybrid AC/DC microgrid.
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