Induction Motor Drive For PV Water PumpingWith Reduced Sensors

ABSTRACT:

 This study presents the reduced sensors based standalone solar photovoltaic (PV) energised water pumping. The system is configured to reduce both cost and complexity with simultaneous assurance of optimum power utilisation of PV array. The proposed system consists of an induction motor-operated water pump, controlled by modified direct torque control. The PV array is connected to the DC link through a DC–DC boost converter to provide maximum power point tracking (MPPT) control and DC-link voltage is maintained by a three-phase voltage-source inverter. The estimation of motor speed eliminates the use of tacho generator/encoder and makes the system cheaper and robust. Moreover, an attempt is made to reduce the number of current sensors and voltage sensors in the system. The proposed system constitutes only one current sensor and only one voltage sensor used for MPPT as well as for the phase voltage estimation and for the phase currents’ reconstruction. Parameters adaptation makes the system stable and insensitive toward parameters variation. Both simulation and experimental results on the developed prototype in the laboratory validate the suitability of proposed system.

 SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

Fig. 1 circuit diagram (a) Proposed system,

EXPECTED SIMULATION RESULTS:

Fig. 2 Performance indices (a) PV array during starting to steady state at 1000 W/m2, (b) IMD indices at 1000 W/m2

 Fig. 3 Performance indices during insolation change 1000–500 W/m2

(a) PV array, (b) IMD indices 500–1000 W/m2, (c) PV array (d) IMD indices

Fig. 4 Adaptation mechanism

(a) Rs adaptation at rated speed and insolation, (b) τr Adaptation at rated speed and rated insolation

Fig. 5 Performance indices of the drive

(a) Starting at 1000 W/m2, (b) Starting at 500 W/m2, (c) Steady state at 1000 W/m2,

(d) Steady state at 500 W/m2

Fig. 6 Dynamic performance of the drive under variable insolation

(a) 1000–500 W/m2, (b) 500–1000 W/m2, (c) Intermediate speed signals at 1000–500

W/m2, (d) Intermediate speed signals at 500–1000 W/m2

Fig. 7 Intermediate signals in terms of

(a) Te* and Te at 1000–500 W/m2, (b) 500–1000 W/m2, (c) Reference stationary

components of flux and estimated flux at 1000–500 W/m2, (d) 500–1000 W/m2

Fig. 8 Reconstructed and measured current waveforms of phases a and b

at (a) Starting performance at 1000 W/m2, (b) 1000 W/m2, (c) 500 W/m2, (d) Boost

converter parameters at 1000 W/m2

CONCLUSION:

The modelling and simulation of the proposed system has been carried out in MATLAB/Simulink and its suitability is validated experimentally on a developed prototype in the laboratory. The system comprises of one voltage sensor and one current sensor, which are sufficient for the proper operation of the proposed system. The motor-drive system performs satisfactorily during starting at various insolations, steady-state, dynamic conditions represented by changing insolation. The speed estimation has been carried out by flux components in stationary frame of reference. The flux and torque are controlled separately. Therefore, successful observation of the proposed system with satisfactory performance has been achieved without the mechanical sensors. This topology improves the stability of the system. The stability of the system at rated condition toward stator resistance variation is shown by Nyquist stability curve and the stability toward the rotor-time constant perturbation is shown by Popov’s criteria. The DTC of an induction motor with fixed frequency switching technique reduces the torque ripple. The line voltages are estimated from this DC-link voltage. Moreover, the reconstruction of three-phase stator currents has been successfully carried out from DC-link current. Simulation results are well validated by test results. Owing to the virtues of simple structure, control, cost-effectiveness, fairly good efficiency and compactness, it is inferred that the suitability of the system can be judged by deploying it in the field.

REFERENCES:

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