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
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
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.
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.
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 Z-Source 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.
