In order to meet the energy storage want, a battery unit is needed for the voltage-fed quasi Z-source inverter (q ZSI) system in renewable energy use. However, the order of the system will be increased accordingly, which make the control of the high order nonlinear systems more complex. This paper presents a sliding mode current control based on fixed frequency operating with fast response and enhanced stability.
Unlikely the conventional sliding mode control (SMC), the planned controller engaged a fixed frequency SMC based on the similar control theory to help the modulation index and shoot through duty ratio. By beginning the large-signal dynamic model, the system will obtain a wide operating range to adapt to the renewable energy system. Using linear likeness, the small-signal model near steady-state operating point will be get to analysis the stable working conditions of the control system.
Compared to the conventional current mode controller, the planned controller can achieve a faster response, lower current ripple and better stregth for q ZSI when the supply and load variation is large. Experimental results are given to validate the theoretical design and the effectiveness of the planned controller.
Fig. 1: Proposed q ZSI with battery energy storage system configuration
EXPECTED SIMULATION RESULTS:
Figure 2: Waveform of the output voltage Vout and the battery charging current Ibat of the qZSI with the proposed SM controller operating at input voltage Vin=100 V. (a) Simulation results, (b) experiment results
Figure 3: Waveform of the battery charging current Ibat response to a step change in the load current Ic from 0 A to 5 A. (a) Simulation results, (b) experiment results
Figure 4: Experiment results of the output voltage Vout and battery charging current Ibat of the qZSI (a) with the SM controller operating at the input voltage Vin=200 V, (b) with the PI controller operating at the input voltage Vin=100 V.
Figure 5: Experiment results of the battery charging current Ibat response of the qZSI with the proposed SM controller to a slowly change in the input voltage Vin. (A) With the proposed SM controller from 100 V to 200 V. (b) With the PI controller from 200 V to 100 V.
A fast-response sliding mode controller operating at a fixed density has been density for the voltage-fed quasi Z-source inverter with battery energy storage unit. Various form of the controller are explain in the paper, which contain the selection method of the sliding surface, the existence condition and stability properties analysis, and the control parameters design.
Since the SM controller is plan from the large-signal converter model, it is stable and robust to large parameter, line and load variation. This is also a major advantage over conventional current mode and voltage mode controllers which often fail to perform sufficiently under parameter or large load variation because they are plan based on the linearized small-signal models.
It is experimentally display that, with the proposed SM controller, the battery charging current of the qZSI has a faster response with a lower ripple over a wide range of operating conditions than the traditional PI controller.Furthermore, the simulation and experimental results given in the paper are in close agreement and have shown the creation of a qZSI with a good charging current control accuracy
and fast response for battery energy storage unit, as well as robustness under input voltage and load perturbation, thus confirm the planned design methodology. In this sense, the approach presented in this paper can be applied for a robust and precise high order Quasi Z-Source conversion involving other output voltage amplitudes and density by applying the design process given in the paper, and changing the converter sinusoidal voltage reference properly
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