CONTROL STRATEGY OF WIND TURBINE BASED ON PERMANENT MAGNET SYNCHRONOUS GENERATOR AND ENERGY STORAGE FOR STAND-ALONE SYSTEMS

CONTROL STRATEGY OF WIND TURBINE BASED ON PERMANENT MAGNET SYNCHRONOUS GENERATOR AND ENERGY STORAGE FOR STAND-ALONE SYSTEMS
Abstract:
This paper investigates a variable speed wind turbine based on permanent magnet synchronous generator and a full-scale power converter in a stand-alone system. An energy storage system(ESS) including battery and fuel cell-electrolyzer combination is connected to the DC link of the full-scale power converter through the power electronics interface. Wind is the primary power source of the system, the battery and FC-electrolyzer combination is used as a backup and a long-term storage system to provide or absorb power in the stand-alone system, respectively. In this paper, a control strategy is proposed for the operation of this variable speed wind turbine in a stand-alone system, where the generator-side converter and the ESS operate together to meet the demand of the loads. This control strategy is competent for supporting the variation of the loads or wind speed and limiting the DC-link voltage of the full-scale power converter in a small range. A simulation model of a variable speed wind turbine in a stand-alone system is developed using the simulation tool of PSCAD/EMTDC. The dynamic performance of the stand-alone wind turbine system and the proposed control strategy is assessed and emphasized with the simulation results.
EXISTING SYSTEM:
he weak-grid condition can be a result of intentional separation or islanding from the grid or grid faults. It applies as well to the stand-alone operating mode. For a stand-alone system, the output voltage of the load-side converter has to be controlled in terms of amplitude and frequency, while the DC-link voltage would be controlled from the generator-side converter. A hybrid adaptive control algorithm is proposed in that search for the optimal PMSG acceleration to achieve the maximum wind generator power change rate to match the load power variation. In , the DC-link voltage is indirectly regulated by controlling the PMSG speed variation to regulate the captured power by generator. Nevertheless, there are some drawbacks for this proposed algorithm. The effectiveness of the control, measured by how fast the captured wind power can be adjusted through the PMG speed control to match the load power variation, depends primarily on the characteristics of wind power versus turbine/generator speed, the system mechanical inertia, as well as the DC-link capacitor. As a result, in case of the large variation of the load power, there would be a large fluctuation for the DC-link voltage, which may affect the performance of the wind turbine and even damage the power electronics equipment. Reference presented a novel control strategy for a variable-speed wind turbine with a PMSG in a stand-alone system, where the load-side inverter is used to regulate the DC-link voltage, output voltage, and frequency. The generator- side converter is adopted to track the optimal energy from the wind. Here, the excess power during fault or over generation is dissipated by the dump-resistor and stored by the energy storage system. It means that the dump-resistor would continuously work in the stand- alone system if the load power is less than the optimal power and the energy storage system is full, which may be not practical.
Conclusion
A stand-alone variable speed wind turbine based on PMSG, full-scale power converter and ESS has been presented in this paper. A novel control strategy for this stand-alone wind turbine system is proposed. The load-side converter is controlled using vector- control scheme to maintain the amplitude and frequency of the converter output voltage. The ESS has the bidirectional power control ability, which is used to keep the DC-link voltage of the full-scale power converter constant. At the same time, the generator- side converter operates together with the ESS to support the loads. The variable speed wind turbine with the proposed control strategy is suitable for a small-scale stand-alone generation system installation for remote-area power supply. A 4MW generation system based on the presented variable speed wind turbine is developed using PSCAD/EMTDC. The simulation results show that its ability to meet the operational needs of a variable speed wind turbine in a stand-alone system. It is feasible to meet the demand of the loads and wind speed variation. As well, it is capably of limiting the DC-link voltage of the full-scale power converter in a small rang so as to ensure the normal operation of the power electronics. Finally, it is concluded that the presented variable speed wind turbine and the proposed control strategy can be an effective solution to achieve power supply in a small-scale stand-alone generation system.
PROPOSED SYSTEM:
Batteries are the most popular storage system. As far as their application range is concerned, battery energy storage systems (BESS) show almost no restrictions. While the BESS possesses higher energy capacity than several other energy storage media, and hence, is suitable for the long-term load-tracking operation , BESS is also shown to be cost-effective for use in power system [18-19] . Fuel cells (FCs) also show great potential to be green power sources of the future because of the many merits they have, such as high efficiency, zero or low emission of pollutant gases, and flexible modular structure. This paper incorporated ESS including BESS and FCs with a VSWT based on PMSG, full-scale power converter in a stand-alone system. The generator is indirectly connected to the load through the full-scale power converter, which is composed of a generator- side AC/DC converter, DC-link capacitor, and grid-side DC/AC inverter. The ESS is connected to the DC link of the power converter. In this paper, an efficient control strategy for a stand-alone VSWT conversion system is developed, where the wind turbine system is able to fast supply the load and wind speed variation, and keep the load-side voltage amplitude and frequency. The fluctuation of the voltage on the DC-link capacitor could be limited in a small range. This paper is organized as below. Section 2 investigates the basic design issues, such as system configuration, wind turbine size, ESS power and the storage capacity needed to support the intermittent power output and so on. Section 3 introduces the model of the VSWT system. In Section 4, a control strategy is proposed for this wind turbine in a stand-alone system, which is able to fast regulate the captured wind power to match the loads variation. The fluctuation of the DC-link voltage because of the wind speed change or load variation could be limited in a small range. Section 5 validates the proposed control with simulation. A model for variable speed direct- drive PMSG wind energy conversion and ESS in a stand-alone generation system is simulated and carried out with the PSCAD/EMTDC.
References
[1] Z. Chen, Y. Hu, and F. Blaabjerg, “Stability improvement of induction generator-based wind turbine systems,” IET Renewable Power Generation, vol. 1, pp. 81-93, March 2007.
[2] S. M. Muyeen, R. Takahashi, T. Murata, and J. Tamura “A variable speed wind turbine control strategy to meet wind farm grid code requirements,” IEEE Trans. Power System, vol. 25, no. 1, pp. 331-340, Jan. 2010.
[3] R. Zhu, Z. Chen, X. Wu, and F. Deng, “Virtual damping flux based LVRT control for DFIG-based wind turbine,” IEEE Trans. Energy Convers., vol.30, no.2, pp.714-725, Jun. 2015.
[4] S. Abulanwar, W. Hu, Z. Chen, and F. Iov, “Adaptive voltage control strategy for variable-speed wind turbine connected to a weak network,” IET Renewable Power Generation, vol. 10, no. 2, pp. 238-249, Feb. 2016.
[5] J. G. Slootweg, S. W. H. de Haan, H. Polinder, and W. L. Kling, “Aggregated modelling of wind parks with variable speed wind turbines in power system dynamics simulations,” in Proc. IEEE Power Tech. Conf., Bologna, 2003, pp. 1-6.
[6] F. Huerta, R. Tello, and M. Prodanovic, “Real-time power- hardware-in-the-loop implementation of variable-speed wind turbines,” IEEE Trans. on Ind. Electron., vol. 64, no. 3, pp. 1893-1904, Mar. 2017.
[7] M. E. Haque, M. Negnevitsky, and K. M. Muttaqi, “A novel control strategy for a variable-speed wind turbine with a permanent-magnet synchronous generator,” IEEE Trans. on Ind. Appl., vol. 46, no. 1, pp. 331-339, Jan./Feb. 2010.
[8] Y. Kim, M. Kang, E. Muljadi, J. Park, and Y. Kang, “Power smoothing of a variable-speed wind turbine generator in association with the rotor speed–dependent gain,” IEEE Trans. Sustainable Energy, vol. PP, no. 99, pp. 1-1, Dec. 2016.
[9] H. Li, and Z. Chen, “Overview of different wind generator systems and their comparisons,” IET Renewable Power Generation, vol. 2, no. 2, pp.123-138, Jun. 2008.
[10] Zhe Chen, J. M. Guerrero, and F. Blaabjerg, “A review of the state of the art of power electronics for wind turbines,” IEEE Trans. Power Electron., vol. 24, no. 8, pp. 1859-1875, Aug. 2009.