Journal of Modern Power Systems and Clean Energy

ISSN 2196-5625 CN 32-1884/TK

Dynamic Modeling and Closed-loop Control of Hybrid Grid-connected Renewable Energy System with Multi-input Multi-output Controller
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Department of Electrical Engineering, Ardabil Branch, Islamic Azad University, Ardabil, Iran

Fund Project:

This work was supported by Islamic Azad University–Ardabil Branch.

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    Abstract:

    In this study, a novel approach for dynamic modeling and closed-loop control of hybrid grid-connected renewable energy system with multi-input multi-output (MIMO) controller is proposed. The studied converter includes two parallel DC-DC boost converters, which are connected into the power grid through a single-phase H-bridge inverter. The proposed MIMO controller is developed for maximum power point tracking of photovoltaic (PV)/fuel-cell (FC) input power sources and output power control of the grid-connected DC-AC inverter. Considering circuit topology of the system, a unique MIMO model is proposed for the analysis of the entire system. A unique model of the system includes all of the circuit state variables in DC-DC and DC-AC converters. In fact, from the viewpoint of closed-loop controller design, the hybrid grid-connected energy system is an MIMO system. The control inputs of the system are duty cycles of the DC-DC boost converters and the amplitude modulation index of DC-AC inverters. Furthermore, the control outputs are the output power of the PV/FC input power sources as well as AC power injected into the power grid. After the development of the unique model for the entire system, a decoupling network is introduced for system input-output linearization due to inherent connection of the control outputs with all of the system inputs. Considering the decoupled model and small signal linearization, the required linear controllers are designed to adjust the outputs. Finally, to evaluate the accuracy and effectiveness of the designed controllers, the PV/FC based grid-connected system is simulated using the MATLAB/Simulink toolbox.

    表 3 Table 3
    图1 Grid-connected PV/FC hybrid energy system.Fig.1
    图2 Equivalent circuit of grid-connected PV/FC hybrid energy system.Fig.2
    图4 Steady-state waveforms of DC-DC boost converters in grid-connected PV/FC hybrid energy system.Fig.4
    图5 Proposed control structure for grid-connected PV/FC hybrid energy system.Fig.5
    图6 Compensation network.Fig.6
    图8 Equivalent circuit of PV input source.Fig.8
    图9 Equivalent circuit of FC input source.Fig.9
    图10 Steady-state response of proposed MIMO controller for grid-connected PV/FC hybrid energy system. (a) Output current of PV source. (b) Output current of FC stack. (c) Voltage of DC-link capacitor. (d) Grid current versus its reference value. (e) Grid voltage. (f) Total harmonic distortion (THD) of grid current.Fig.10
    图11 Transient response of proposed MIMO controller during start-up process of grid-connected PV/FC hybrid energy system. (a) Transient response of PV panel. (b) Transient response of FC stack. (c) Transient response of DC-link capacitor voltage. (d) Grid current.Fig.11
    图12 Transient response of proposed MIMO controller during step changes of PV reference current. (a) Current of PV panel. (b) Current of FC stack. (c) DC-link capacitor voltage.Fig.12
    图13 Transient response of proposed MIMO controller during step changes of FC reference current. (a) Current of PV panel. (b) Current of FC stack. (c) DC-link voltage.Fig.13
    图14 Transient response of proposed MIMO controller during simultaneous step changes of PV and FC reference currents. (a) Current of PV panel. (b) Current of FC stack. (c) DC-link voltage. (d) Grid current. (e) Grid voltage.Fig.14
    图15 Transient response of proposed MIMO controller during step changes of DC-link reference voltage. (a) Voltage of DC-link capacitor. (b) Grid current.Fig.15
    表 1 Table 1
    表 2 Table 2
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History
  • Received:June 17,2018
  • Revised:
  • Adopted:
  • Online: January 22,2021
  • Published: