Model Predictive control design for switched inductor quasi-Z-source inverter in comparison with the traditional two-stage inverter based on Photovoltaic.

• Applicant: Professor Dr.-Ing. Ralph Kennel
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives
• Term: from 2015 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 262773038

• Final Report Year: 2017

Final Report Abstract

This project has examined advanced direct MPC techniques for the quasi-Z-source inverters in order to improve the overall performance and efficiency of distributed generation applications. All the presented control algorithms have been experimentally validated by a low-cost and low-power FPGA. A thorough comparison between the quasi-Z-source inverters and the conventional twostage inverters is conducted in light of the voltage stress on the inverter switches, required active and passive components, steady-state and transient performances, and efficiency. It has been found that the qZSI features lower voltage stress on the switches than the traditional inverter when the voltage gain is in the range of (1-2). In addition, the experimental results demonstrate that the qZSI exhibits lower output voltage THD and higher efficiency than the traditional two-stage inverter. A long-horizon direct MPC—as a current controller—for the quasi-Z-source inverter connected with an RL load is designed and implemented. The proposed MPC strategy simultaneously controls both sides of the qZSI, namely ac output current on the ac side as well as the capacitor voltage and inductor current of the dc side. To improve the closed-loop performance of the converter, a long prediction horizon has been implemented. However, the underlying optimization problem may become computationally intractable because of the substantial increase in the computational power demands, which in turn would prevent the implementation of the control strategy in real time. To overcome this and to solve the problem in a computationally efficient manner, a branch-and-bound strategy has been used along with a move blocking scheme. These techniques have facilitated the implementation of a longhorizon MPC in an FPGA. The experimental results have verified the superior performance of long-prediction horizon MPC when compared to the existing one-step horizon MPC as well as to the established linear proportional-integral (PI)-based controller. More specifically, the proposed long-horizon direct MPC has exhibited better steady-state behavior with lower output current THD, while, at the same time, it has shown a much faster dynamic response on both sides of the quasi-Z-source inverter.

Publications

• “Direct model predictive control of quasi-Z-source inverter compared with the traditional PI-based PWM control,” Eur. Power Electron. Conf. (EPE), Geneva, Switzerland, Sep. 2015, pp. 1 − 10
  A. Ayad and R. Kennel
  
• “Direct model predictive current control of quasi-Z-source inverters,” IEEE Int. Symp. Pred. Control of Elect. Drives and Power Electron. (PRECEDE), Valparaiso, Chile, Oct. 2015, pp. 1 − 6
  A. Ayad, P. Karamanakos, and R. Kennel
  
• “Direct model predictive control with an extended prediction horizon for quasi-Z-source inverters,” IEEE Ind. Electron. Society (IECON), Florence, Italy, Oct. 2016, pp. 1 − 6
  A. Ayad, P. Karamanakos, and R. Kennel
  
• “Direct model predictive voltage control of quasi-Z-source inverters with LC filters,” Eur. Power Electron. Conf. (EPE), Karlsruhe, Germany, Sep. 2016, pp. 1 − 10
  A. Ayad, P. Karamanakos, and R. Kennel
  
• “A comparison of quasi-Z-source inverters and conventional two-stage inverters for PV applications,” EPE Journal, vol. 27, no. 2, pp. 43-59, May 2017
  A. Ayad and R. Kennel
  
• “A hybrid MPPT for quasi-Z-source inverter in PV applications under partial shading condition,” IEEE CPE-POWERENG, Cadiz, Spain, Apr. 2017, pp. 1 − 6
  A. Ayad,S. Hanafiah, A. Hehn, and R. Kennel
  
• “Direct model predictive control of bidirectional quasi-Z-source inverters fed permanent magnet synchronous machines,” IEEE CPE-POWERENG, Cadiz, Spain, Apr. 2017, pp. 1 − 6
  A. Ayad, P. Karamanakos, R. Kennel, and J. Rodriguez
  
• “Direct model predictive current control strategy of quasi-Z-source inverters,” IEEE Transaction on Power Electronics, vol. 32, no. 7, pp. 5786-5801, July 2017
  A. Ayad, P. Karamanakos, and R. Kennel
  
• “Variable switching point predictive current control of quasi-Z-source inverters,” IEEE Applied Power Electronics Conf. and Exp. (APEC), Tampa, FL, USA, Mar. 2017, pp. 1 − 8
  A. Ayad, P. Karamanakos, and R. Kennel