Finite Control Set Model Predictive Control for Grid Connected Packed U Cells Multilevel Inverter

ABSTRACT:

 This paper presents a Finite Control Set Model Predictive Control (FCS-MPC) for grid-tied Packed U Cells (PUC) Multilevel Inverter (MLI). The system under study consists of a single-phase 3-cells PUC inverter connected to the grid through filtering inductor. The proposed competitive topology allows the generation of 7-level output voltage with reduction of passive and active components compared to the conventional multilevel inverters.

The aim of the proposed FCS-MPC technique is to achieve, under various operating conditions, grid-tie current injection with unity power factor and low Total Harmonic Distortion (THD) while balancing the capacitor voltage. Parameters sensitivity analysis was also conducted. The study is conducted on a low power case study single-phase 3-cells PUC inverter and with possible extension to higher number of cells. Theoretical analysis, simulation, and experimental results are presented and compared.

KEYWORDS:

  1. Grid Connection
  2. Model Predictive Control
  3. Packed U Cells Inverter
  4. PUC

SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:

This paper presented the design, simulations, and experimental validation of a FCS-MPC technique that properly deals with the complex nature of the PUC. Digital simulation for a grid-connected 7-level single-phase PUC inverter was carried out. The simulation results showed that the proposed MPC is capable of simultaneously controlling multi variables of the PUC inverter.

The tuning of the weighting factor was conducted successfully based on minimizing the grid current THD as well as the capacitor voltage error. Using the properly selected weighting factor, the MPC has shown an efficient and stable tracking of the reference current at steady state and fast transient response. It is also capable of maintaining the capacitor voltage at its pre-selected and desired level.

Parameters sensitivity analysis was carried out and showed that the parameters variation does not have a significant effect on the controller performance. The obtained experimental results confirmed the simulation results and demonstrated that the proposed MPC is effective in controlling the grid current with high steady-state and dynamic tracking performances while keeping balanced capacitor voltage.

REFERENCES:                                                           

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[4] H. Abu-Rub, J. Holtz, J. Rodriguez and G. Baoming, “Medium-Voltage Multilevel Converters—State of the Art, Challenges, and Requirements in Industrial Applications,” IEEE Trans. Ind. Electron., vol.57, no.8, pp.2581-2596, 2010.

[5] J. Chavarria, D. Biel, F. Guinjoan, C. Meza and J. J. Negroni, “Energy-Balance Control of PV Cascaded Multilevel Grid-Connected Inverters Under Level-Shifted and Phase-Shifted PWMs,” IEEE Trans. Ind. Electron., vol.60, no.1, pp.98-111, Jan. 2013.

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