An Improved Torque and Current Pulsation Suppression Method for Railway Traction Drives Under Fluctuating DC-Link Voltage

ABSTRACT:  

For railway traction drives, the dynamic front end typically receives a separate stage rectifier. Be that as it may, the dc-combine voltage of this single-stage rectifier contains a second-arrange change part because of the variance of the immediate power at both the air conditioner and dc sides. Encouraged by the change dc-interface voltage, the footing engine experiences serious torque and current pulse. The equipment arrangement with an extra LC booming channel is basic, yet it will lessen the power thickness of the framework.

Railway Traction Drives

An optional arrangement is to wipe out the beat part in the stat-or voltage/current through adjust proportion or frequency payment. Notwithstanding, it is hard to accomplish superior for the customary feed forward technique. In this paper, an enhanced shut circle torque and current throb hiding technique is proposed, and which can wipe out the q-pivot current throb part in the field-arranged control framework through recurrence pay. The torque throb concealment is additionally accomplished consequently. Recreation and test results demonstrate that the proposed plan can successfully lessen the torque and current throb in different activity modes contrasted and the ordinary feed-forward strategy.

CIRCUIT DIAGRAM:

Fig. 1. Circuit schematic of the ac/dc/ac traction drive system.

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation results of two methods in the asynchronous modulation mode. (a) Line voltage of the motor. (b) and (c) Sta-tor current and torque with the conventional method. (d) and (e) Sta-tor current and torque with the proposed method. (f) DC-link voltage of the invert-er without and with the proposed method. (g) Transition wave forms of the stat-or current without and with the proposed method.

Fig. 3. Spectrum analysis of the simulation results of the two methods in the asynchronous modulation mode. (a)–(c) Sta-tor current without compensation, with the conventional method, and with the proposed method. (d)–(f) Torque without compensation, with the conventional method, and with the proposed method.

Fig. 4. Simulation results of the two methods in the synchronous modulation mode. (a) Line voltage of the motor. (b) and (c) Sta-tor current and torque with the conventional method. (d) (e) Sta-tor current and torque with the proposed method.

Fig. 5. Simulation results of the two methods in the square-wave modulation mode. (a) Line voltage of the motor. (b) and (c) Sta-tor current and torque with the conventional method. (d) and (e) Sta-tor current and torque with the proposed method.

CONCLUSION:

A closed-loop torque and current pulsation suppression method for railway traction drives under fluctuating dc-link voltage is proposed. This method aims to eliminate the q-axis current pulsation component in the F O C system through output frequency compensation. The torque pulsation suppression is achieved on the basis of q-axis current pulsation elimination automatically. A resonant controller is proposed for the closed loop control of q-axis current and dynamic compensation of the output frequency. Different from the conventional feed forward open-loop frequency compensation method, the torque pulsation with the proposed method is suppressed through the elimination of the q-axis current pulsation component rather than the beat component in the output voltage.

Proposed method

The effectiveness of the proposed method have been verified by simulation and experiments on traction drives with the invert er operated in asynchronous, synchronous, and square wave modulation modes, respectively. The results have been compared to those with the conventional feed forward frequency compensation method based on fluctuating dc-link voltage detection. Both simulation and experimental results show that the suppression of stator current and torque pulsation are obvious in different modulation modes with the proposed control method using the same dc-link capacitance. The proposed suppression method can reduce the sensitivity of the system to variations of the grid frequency. However, the fluctuating component in the dc-link voltage will be increased with the proposed method compared with the LC resonant filter solution.

REFERENCES:

[1] R. J. Hill, “Electric railway traction. II. Traction drives with three-phase induction motors,” Power Eng. J., vol. 8, no. 3, pp. 143–152, Jun. 1994.

[2] A. St e i m e l, “Electric railway traction in Europe,” IEEE Ind. App l. Mag., vol. 2, no. 6, pp. 6–17, Nov./Dec. 1996.

[3] H. O u yang, K. Zhang, P. Zhang, Y. K an g, and J. Xi o n g, “Repetitive compensation of fluctuating DC link voltage for railway traction drives,” IEEE Trans. Power Electron., vol. 26, no. 8, pp. 2160–2171, Aug. 2011.

[4] J. K l i ma, M. Ch o  mat, and L. Sch re i e  r, “Analytical closed-form investigation of P WM invert er induction motor drive performance under DC bus voltage pulsation,” I ET Elect r. Power App l., vol. 2, no. 6, pp. 341–352, Nov. 2008.

[5] A. Che o k, S. K a w a m o to, T. Mat sum o to, and H. Obi, “AC drive with particular reference to traction drives,” in Proc. 4th Int. Conf. Adv. Power S y st. Control, Op er. Manage., 1997, pp. 348–353.

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