In this paper, a novel algorithm, based on dc link voltage, is proposed for effective energy management of a standalone permanent magnet synchronous generator (PMSG)-based variable speed wind energy conversion system consisting of battery, fuel cell, and dump load (i.e., electrolyzer). Moreover, by maintaining the dc link voltage at its reference value, the output ac voltage of the inverter can be kept constant irrespective of variations in the wind speed and load. An effective control technique for the inverter, based on the pulse width modulation (PWM) scheme, has been developed to make the line voltages at the point of common coupling (PCC) balanced when the load is unbalanced. Similarly, a proper control of battery current through dc–dc converter has been carried out to reduce the electrical torque pulsation of the PMSG under an unbalanced load scenario. Based on extensive simulation results using MATLAB/SIMULINK, it has been established that the performance of the controllers both in transient as well as in steady state is quite satisfactory and I can also maintain maximum power point tracking.
- DC-side active filter
- Permanent magnet synchronous generator (PMSG)
- Unbalanced load compensation
- Variable speed wind turbine
- Voltage control
Fig. 1. PMSG-based standalone wind turbine with energy storage and dump load.
EXPECTED SIMULATION RESULTS
Fig. 2. Response of mechanical torque for change in wind velocity.
Fig. 3. (a) Load current; (b) wind speed.
Fig. 4. DC link voltage.
Fig. 5. RMS output voltage (PCC voltage).
Fig. 6. Instantaneous output voltage at s.
Fig. 7. Instantaneous output line current.
Fig. 8. Powers.
Fig. 10. DC link voltage.
Fig. 11. Powers.
Fig. 12. DC link voltage.
Fig. 13. Response of controllers.
Fig. 14. Three phase currents for unbalanced load.
Fig. 15. Electrical torque of PMSG with and without dc–dc converter controller.
Fig. 16. Instantaneous line voltages at PCC for unbalanced load.
Fig. 17. (a) RMS value of line voltages at PCC after compensation; (b) modulation indexes.
Fig. 18. Instantaneous line voltages at PCC after compensation.
Control strategies to regulate voltage of a standalone variable speed wind turbine with a PMSG, battery, fuel cell, and electrolyzer (acts as dump load) are presented in this paper. By maintaining dc link voltage at its reference value and controlling modulation indices of the PWM inverter, the voltage of inverter output is maintained constant at their rated values. From the simulation results, it is seen that the controller can maintain the load voltage quite well in spite of variations in wind speed and load.An algorithm is developed to achieve intelligent energy management among the wind generator, battery, fuel cell, and electrolyzer. The effect of unbalanced load on the generator is analyzed and the dc–dc converter control scheme is proposed to reduce its effect on the electrical torque of the generator. The dc–dc converter controller not only helps in maintaining the dc voltage constant but also acts as a dc-side active filter and reduces the oscillations in the generator torque which occur due to unbalanced load. PWM inverter control is incorporated to make the line voltage at PCC balanced under an unbalanced load scenario. Inverter control also helps in reducing PCC voltage excursion arising due to slow dynamics of aqua elctrolyzer when power goes to it. The total harmonic distortion (THD) in voltages at PCC is about 5% which depicts the good quality of voltage generated at the customer end. The simulation results demonstrate that the performance of the controllers is satisfactory under steady state as well as dynamic conditions and under balanced as well as unbalanced load conditions.
 S. Müller, M. Deicke, and W. De DonckerRik, “Doubly fed induction generator system for wind turbines,” IEEE Ind. Appl. Mag., vol. 8, no. 3, pp. 26–33, May/Jun. 2002.
 H. Polinder, F. F. A. van der Pijl, G. J. de Vilder, and P. J. Tavner, “Comparison of direct-drive and geared generator concepts for wind turbines,” IEEE Trans. Energy Convers., vol. 21, no. 3, pp. 725–733, Sep. 2006.
 T. F. Chan and L. L. Lai, “Permanent-magnet machines for distributed generation: A review,” in Proc. 2007 IEEE Power Engineering Annual Meeting, pp. 1–6.
 M. Fatu, L. Tutelea, I. Boldea, and R. Teodorescu, “Novel motion sensorless control of standalone permanent magnet synchronous generator (PMSG): Harmonics and negative sequence voltage compensation under nonlinear load,” in Proc. 2007 Eur. Conf. Power Electronics and Applications, Aalborg, Denmark, Sep. 2–5, 2007.
 M. E. Haque, K. M. Muttaqi, and M. Negnevitsky, “Control of a standalone variable speed wind turbine with a permanent magnet synchronous generator,” in Proc. IEEE Power and Energy Society General Meeting, Jul. 2008, pp. 20–24.