This paper suggest a control method for an islanded microgrid to neatly coordinate hybrid power source (HPS) units and to strongly control individual integrate inverters under unbalanced and nonlinear load environment. Cascaded H-bridge (CHB) multilevel inverters are flexibly expand in order to improve the power quality and redundancy. The HPS employs fuel cell (FC) as the main and super capacitors (SC) as completing power sources.
Fast temporary response; high work; and high power density are the main quality of the planned HPS system. The given control method consists of a power management method for the HPS units and a voltage control method for the CHB multilevel inverter. A multi proportional resonant (multi-PR) controller is working to regulate the load voltage at unbalanced and nonlinear load environment.
The planned multi-PR controller contain a fundamental voltage controller with harmonic compensators. Digital time domain simulation learn in the PSCADIEMTDC environment are given to verify the overall planned system work.
- Hybrid power source
- Fuel cell
- CHB multilevel inverter
Fig. I. Proposed structure of the hybrid FC/SC power source.
Fig. 2. Proposed control strategy of hybrid FC/SC power source
EXPECTED SIMULATION RESULTS:
Fig. 3. Microgrid response to unbalanced and nonlinear load changes; (a) Instantaneous real and reactive power. (b) Positive-sequence, negativesequence, and harmonic components of load
Fig. 4. (a) Instantaneous current waveforms, (b) switching patterns of the output voltage, and (c) voltage waveforms of each phase of the DG unit’s CHB inverter due to the nonlinear load connection.
Fig. 5. (a) Instantaneous current waveforms, (b) switching patterns of the output voltage, and (c) voltage waveforms of each phase of the DG unit’s CHB inverter due to the single-phase load disconnection.
Fig. 6. (a) voltage THD, and (b) voltage unbalance factor at DG unit terminal.
Fig. 7. The dc-link voltage waveforms to the unbalanced and nonlinear load changes.
Fig. 8. Dynamic response of the DG unit to load changes: currents of FC stacks and SC units of each HPS, (a) phase a, (b) phase b, and (c) phase c.
This paper now an effective control method for an autonomous microgrid considering the HPS and CHB multilevel inverter under unbalanced and nonlinear load environment. The planned method contain power management of the hybrid FC/SC power source and the CHB multilevel inverter voltage control.
The main quality of the planned HPS are high work; high power density; fast temporary response. moreover, a multi-PR controller is given to organize the voltage of the CHB multilevel inverter in the existence of unbalanced and nonlinear loads. The work of the planned control method is checked using PSCADIEMTDC software. The results show that the planned method:
- strongly manage the voltage of the microgrid under unbalanced and nonlinear load environment;
- reduces THD and better power quality by using CHB multilevel inverters;
- improve the dynamic response of the microgrid;
- correctly balances the dc-link voltage of each H-bridge cell; and
- neatly manages the power among the power sources in the HPS system.
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