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Research Of A Novel Adaptive Droop Control Strategy Based On Microgrid

Posted on:2019-11-12Degree:MasterType:Thesis
Country:ChinaCandidate:H L XuFull Text:PDF
GTID:2392330575459004Subject:Microgrid control and optimization
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With the increasing international concern about carbon energy environment pollution,distributed generation technology has become a popular research topic at home and abroad.Compared with the traditional power grid,distributed power generation technology shows potential advantages,such as high efficiency,energy diversity,low cost,and environmental protection.In spite of the advantages,there are still some problems to overcome.For example,due to the unsteadiness of wind and photovoltaic energy,the power of wind power generation and photovoltaic power generation system are so volatile that it is difficult to carry out frequency and voltage support alone and guarantee the quality of power supply.In order to solve these problems,micro-grid technology has been studied vigorously in recent years.This thesis mainly studies the novel adaptive droop control strategy of microgrid.Traditional droop control strategy includes current-type droop control strategy by calculating power signal through voltage and frequency,and voltage-type droop control strategy by calculating voltage and frequency system through output power.Considering that the traditional voltage-type droop control strategy adjusts the frequency and voltage with difference,we acquire voltage signal and current signal of distributed power generation unit converter at AC output,then calculating the unit output power value at this time.After the delay unit,we get the difference value of power value this moment and a sampling period before and the value is fed back in the droop coefficient of the system.Without communication device and through the adaptive adjustment of the droop coefficient,the second adjustment process of system voltage and frequency is achieved.This strategy improves the system voltage and frequency stability and reduces the difference of the traditional droop control.At the same time,this work studies the hierarchical control strategy of microgrid and energy storage allocation scheme of distributed generation.Three simulation models are established to validate the new adaptive droop control strategy.In addition to distributed generation units such as wind power,photovoltaic power generation unit in microgrid,energy storage devices should be installed in order to ensure the quality of power supply.In the hierarchical control strategy of microgrid,the bottom control strategy adopts the constant-power control strategy and the voltage source droop control strategy.The microgrid centralized and distributed energy storage allocation scheme involve parallel operation of energy storage units,wind power generation and photovoltaic generation.In the thesis,simulation model of basic direct-current energy storage and distributed generation units is established.In the model,the units work under the condition of the independent power supply and the loads are powered in the way of the novel adaptive droop control strategy.Next,analyzing the previous simulation model,the new adaptive droop control strategy is improved,and two models of parallel operation of the energy storage system are established to verify the effectiveness of the novel adaptive droop control strategy.It can maintain the microgrid frequency and voltage more stably.Finally,the thesis establishes the wind-store islanded power system model,in which wind power generation system and the energy storage system can carry out the coordinate control well.It maintains the stability of voltage and frequency individually and achieves more effective use of wind energy for load power supply through the droop curve adjustment.At the same time,an improved droop control wind-storage model is established and a comparative experiment is conducted to further verify the effectiveness of the novel adaptive droop control strategy.
Keywords/Search Tags:Microgrid, self-adaption, novel droop control strategy, hierarchical control strategy, energy storage unit, wind-storage island system
PDF Full Text Request
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