| In the background of energy shortage and environment pollution,the demand for the development and utilization of renewable energy and the improvement of energy efficiency is increasingly urgent.The establishment of microgrids integrated with distributed generators,such as wind and solar energy,relevant loads and energy storage devices,can realize the centralized control of energy distribution,which can improve the quality and reliability of power supply.Switched reluctance generator has been applied in the field of wind power generation for the advantages of simple structure,high reliability and power generation efficiency.In order to build an efficient,reliable and low-cost communication system in microgrids,in this paper,we propose strategies of power/signal synchronous transmission using existing power lines and power electronic equipment for communication,in which there is no need to add extra signal modulation and transmission equipment.In this paper,we propose three modulation strategies based on switched reluctance generator applied in wind power generation.First of all,the structure and working principle of DC microgrids based on switched reluctance generator is introduced,the operation process and common topology of switched reluctance generator is analyzed,the mathematical model is established,and the whole range of flux characteristic curve is obtained by practical measurement and mathematical fitting.In the same time,the simulation model of switched reluctance generator is established in MATLAB,which provides the foundation for subsequent research and testing.Secondly,the soft-PWM control is proposed based on the angel position control,in which can realize power/signal synchronous transmission by the ripple at specific frequency injected into the output current and voltage of switched reluctance generator.Based on the soft-PWM control,the frequency-shift keying modulation is adopted,the signal data “1” and “0” are represented by different frequency respectively,and the ripple containing information is injected into the output voltage.At the receiving side,the sliding discrete Fourier transformation is employed to demodulate signal.The proposed modulation strategy is verified by experiment and tested under variable speed and loads.Then,the modulation strategy based on direct sequence spread spectrum is proposed to reduce harmonic components and improve the anti-interference performance.The baseband signal to be transmitted is spread by m sequence,PWM carrier is modulated by the spread spectrum signa using phase-shift keying modulation,and the ripple containing information is injected into the output voltage by employing soft-PWM control.At the receiving side,the discrete Fourier transformation is employed to demodulate signal,and the spread spectrum signal is despread according to the high autocorrelation of m sequence,by which the power/signal synchronous transmission is achieved.Finally,the modulation strategy based on the common-mode angle is proposed,in which the common-mode angle and differential-mode angle are introduced according the turn-on angle and turn-off angle.The differential-mode angle can be used to adjust the excitation intensity and change the output power.As for common-mode angle,the ripple containing information can be injected into the output voltage by imposing disturbance on the common-mode angel,and the amplitude of data carrier can be changed by adjusting the depth of disturbance.At the receiving side,the sliding discrete Fourier transformation is employed to demodulate signal.This thesis has 43 figures,3 tables and 70 references. |
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