Sliding mode control of quasi z source inverter with battery for renewable energy system (2)

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Sliding-Mode Control of Quasi-Z-Source Inverter with Battery for Renewable Energy System ABSTRACT: In order to meet the energy storage requirements, a battery unit is required for the voltage-fed quasi Z-source inverter (q ZSI) system in renewable energy applications. However, the order of the system will be increased accordingly, which make the control of the high order nonlinear systems more complicated. This paper presents a sliding mode current control based on fixed frequency operating with fast response and improved stability. Unlikely the conventional sliding mode control (SMC), the proposed controller engaged a fixed frequency SMC based on the equivalent control theory to cooperate the modulation index and shoot through duty ratio. By establishing the large-signal dynamic model, the system will obtain a wide operating range to adapt to the renewable energy system. Using linear approximation, the small-signal model near steady-state operating point will be obtained to analysis the stable working conditions of the control system. Compared to the conventional current mode controller, the proposed controller can achieve a faster response, lower current ripple and better stability for q ZSI when the supply and load variation is large. Experimental results are presented to validate the theoretical design and the effectiveness of the proposed controller.

SOFTWARE: MATLAB/SIMULINK

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0-9347143789/9949240245 BLOCK DIAGRAM:

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

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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.

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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.

CONCLUSION: A fast-response sliding mode controller operating at a fixed frequency has been proposed for the voltage-fed quasi Z-source inverter with battery energy storage unit. Various aspects of the controller are discussed in the paper, which includes the selection method of the sliding surface, the existence condition and stability properties analysis, and the control parameters design.

Since the SM controller is designed 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 satisfactorily under parameter or large load variation because they are designed based on the linearized small-signal models. It is experimentally demonstrated 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.

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0-9347143789/9949240245 Furthermore, the simulation and experimental results presented in the paper are in close agreement and have shown the achievement 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 validating the proposed design methodology. In this sense, the approach presented in this paper can be applied for a robust and accurate high order Quasi ZSource conversion involving other output voltage amplitudes and frequencies by applying the design procedure presented in the paper, and changing the converter sinusoidal voltage reference accordingly.

REFERENCES: [1] P. Fang Zheng, "Z-source inverter," Industry Applications, IEEE Transactions on, vol. 39, pp. 504-510, 2003.

[2] P. Fang Zheng, et al., "Maximum boost control of the Z-source inverter," Power Electronics, IEEE Transactions on, vol. 20, pp. 833- 838, 2005.

[3] J. Anderson and F. Z. Peng, "Four quasi-Z-Source inverters," in Power Electronics Specialists Conference, 2008. PESC 2008. IEEE, 2008, pp. 2743-2749.

[4] L. Yuan, et al., "Quasi-Z-Source Inverter for Photovoltaic Power Generation Systems," in Applied Power Electronics Conference and Exposition, 2009. APEC 2009. Twenty-Fourth Annual IEEE, 2009, pp. 918-924.

[5] Bagen and R. Billinton, "Evaluation of Different Operating Strategies in Small Stand-Alone Power Systems," Energy Conversion, IEEE Transactions on, vol. 20, pp. 654-660, 2005.

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