| Development and utilization of renewable energy is one of the main ways to solve energy shortages and environmental degradation.However,due to the high randomness and intermittent nature,the large-scale utilization of renewable energy will cause many uncertain factors to the grid,which may affect the reliability of power supply.The promotion and application of microgrid is an effective measure to realize the large-scale integration of renewable energy power generation systems into the grid.With the increase of DC equipment such as solar photovoltaics,electric vehicles,LED lights and energy storage devices,DC microgrids have attracted more and more research attention.Wind power generation has been applied to DC micro-grids due to its advantages such as clean and pollution-free,good economic benefits and flexible installation.Switched reluctance generator(SRG)has the advantages of simple structure,good heat dissipation and strong fault tolerance,and has been applied to distributed power generation systems such as wind power generation.Stable and reliable communication is essential to improve the system performance of SRG status monitoring,fault warning,energy management,etc.Traditional wired communication(such as optical fiber communication)has strict requirements on modulation devices and transmission cables,and its installation and maintenance costs are actually high.Due to the use of open frequency bands,wireless communication is susceptible to external signal interference and obstacle shielding,and the signal attenuation in the air transmission limits the wireless data transmission distance.Therefore,designing a low-cost and reliable communication network for DC microgrid systems containing SRG has important research and application value.Based on this,the research content of this article is as follows:(1)A new power and signal composite modulation and signal demodulation strategy is researched to realize effective power line communication between SRG and other converters in an inverter interface distributed power grid.This modulation method modulates voltage ripples by controlling the turn on/off angle of SRG,and utilizes voltage ripples to transmit information to the receiving ends.By utilizing the maximum entropy spectrum estimation method,the demodulation of the signal is realized.Finally,experiments are conducted to verify the feasibility of the proposed modulation and demodulation method for data transmission between SRG and other power equipment.(2)Based on the method of current chopping control,two power and signal compound modulation methods are researched,and the power line communication of the distributed microgrid system with SRG is realized.The two signal modulation methods respectively modulate the reference value of the winding phase current and the chopping threshold value of the phase current to obtain voltage ripples of different frequencies to load the signal to achieve composite modulation of power and signal.At the receiving end,the fast Fourier transform method is used to process the sent data to realize signal demodulation.(3)The remote control of the DC microgrid system with SRG and the transmission of fault signals in the state of phase loss are researched.In DC microgrid,the control commands of each device are coded reasonably,and the signal modulation is simulated and verified by taking the switching of the regional load as an example.For the SRG system under phase failure,a modulation strategy to extend the unit signal length is studied,and the feasibility of synchronous transmission of power and signal under phase failure is verified by simulation.There are 58 figures,10 tables and 86 references in this thesis. |
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