Induction Motor Drive For PV Water PumpingWith Reduced Sensors


 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.



Fig. 1 circuit diagram (a) Proposed system,


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


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.


[1] Masters, G.M.: ‘Renewable and efficient electric power systems’ (IEEE Press,Wiley and Sons, Inc., Hoboken, New Jersey, 2013), pp. 445–452

[2] Foster, R., Ghassemi, M., Cota, M.: ‘Solar energy: renewable energy and the environment’ (CRC Press, Taylor and Francis Group, Inc., Boca Raton, Florida, 2010)

[3] Parvathy, S., Vivek, A.: ‘A photovoltaic water pumping system with high efficiency and high lifetime’. Int. Conf. Advancements in Power and Energy (TAP Energy), Kollam, India, 24–26 June 2015, pp. 489–493

[4] Shafiullah, G.M., Amanullah, M.T., Shawkat Ali, A.B.M., et al.: ‘Smart grids: opportunities, developments and trends’ (Springer, London, UK, 2013)

[5] Sontake, V.C., Kalamkar, V.R.: ‘Solar photovoltaic water pumping system – a comprehensive review’, Renew. Sustain. Energy Rev., 2016, 59, pp. 1038– 1067

Inner Control Method and Frequency Regulation of a DFIG Connected to a DC Link



In this paper, an inner loop for the control and frequency regulation of the doubly fed induction generator connected to a dc link through a diode bridge on the stator is presented. In this system, the stator is directly connected to the dc link using a diode bridge, and the rotor is fed by only a pulse width-modulated (PWM) converter. If compared to the DFIG connected to an ac grid, this system uses one PWM inverter less and a much less expensive diode bridge. Thus, the cost of power electronics is reduced. The application in mind is for dc networks such as dispersed generation grids and microgrids. These networks use several elements that should work together. Usually, these elements are connected with each other by power electronic devices in a common dc link. This paper presents a control system for the inner control loop in order to regulate the torque and the stator frequency. Simulation and experimental results show that the system works properly and is able to keep the stator frequency near the rated value of the machine.


  1. Control
  2. Dc link
  3. Dc microgrids
  4. Doubly fed induction generator



 Fig. 1. Structure of the DFIG-DC. Diode bridge on the stator, PWM converter on the rotor.


Fig. 2. Torque, stator flux, frequency error, and sinδ.

Fig. 3. Stator and rotor currents in closed loop.

Fig. 4. Torque, stator flux, frequency error, and sinδ.

 Fig. 5. Response to a voltage dip down to 0.5 p.u.

Fig. 6. Twelve-pulse rectification curves. Six-pulse stator currents, torque,

and equivalent three-phase current using 12 pulse and torque.


This paper presents a control method for the DFIG connected to a dc link through a diode rectifier on the stator windings. Simulation and experimental results show that it is possible to drive the stator flux at the rated frequency of the machine by using a simple controller that adjusts the rotor d-axis current reference in order to annihilate the orientation error. The method converges to the field orientation and the steady-state frequency error is zero.Agood dynamics is achieved in the electromagnetic torque. The waveforms of the stator current are not sinusoidal, due to the presence of the diode bridge, but have an acceptable harmonic content. The industrial application of this system could be implemented using a 12-pulse rectifier, which reduces not only the torque ripple but also the harmonic content in the rotor currents.


[1] S. Chowdhury, S. P. Chowdhury, and P. Crossley “Microgrids and active distribution networks,” in IET Renewable Energy (Series 6). London, U.K.: The Institution of Engineering and Technology, 2009.

[2] J. A. Pec¸as Lopes, C. L. Moreira, and A. G. Madureira, “Defining control strategies for microgrids islanded operation,” IEEE Trans. Power Syst., vol. 21, no. 2, pp. 916–924, May 2006.

[3] F.Blaabjerg, Z. Chen, and S. B. Kjaer, “Power electronics as efficient interface in dispersed power generation system,” IEEE Trans. Power Electron., vol. 19, no. 5, pp. 1184–1194, Sep. 2004.

[4] F. Blaabjerg, R. Teodorescu, M. Liserre, and A. V. Timbus, “Overview of control and grid synchronization for distributed power generation systems,” IEEE Trans. Ind. Electron., vol. 53, no. 5, pp. 1398–1409, Oct. 2006.

[5] D. Salomonsson and A. Sannino, “Low-voltage DC distribution system for commercial power systems with sensitive electronic load,” IEEE Trans. Power Del., vol. 22, no. 3, pp. 1620–1627, Jul. 2007.