Research On DC Microgrid In Oil Region

At present,oilfield is mainly powered by three-phase AC power.Because of geographic location of oilfield,it causes a lot of problems which are long distance power supply,high cost,high loss of line and voltage sag etc.The pumping units and mine hoists which are used in the oilfield are energy feedback loads.In order to suppress the impact loads on the power grid,the traditional method is using the capacitance compensation,or the transformation of the mechanical hardware equipment,even using the brake unit consumption of excess energy which are high cost,large energy consumption and small gains.Distributed power supply can make full use of renewable energy,but it will inevitably produce a shock on power grid in the operation.The concept of micro grid is introduced to solve the problem of distributed power.This paper summarizes and analyzes the research methods and the power flow calculation of microgrid in detail.In view of the fact that the device of oilfield are energy feedback loades,the paper puts forward the control strategy of common DC bus,which can achieve energy feedback sharing and recycling,reduce the impact on the power grid and achieve the purpose of energy saving.In addition,in order to make full use of renewable energy,DC bus connectes the photovoltaic cells and wind power and other power supply.In order to stabilize the DC bus voltage,DC bus also connectes the battery,gas turbine,fuel cell and other power supply.The grid control strategy uses the four quadrant converter,in order to achieve the two-way flow of energy.In this paper,the modeles of every unit are builted based on the characteristics of photovoltaic cells,batteries,gas turbine and fuel cell.Based on the established model,for the control strategies of each micro source attached to the DC bus,this paper draws on DC micro grid droop control mode,using the droop control of photovoltaic cells,batteries and fuel cells,in order to better control of each output energy;the pumping units adopts the frequency droop method and the modulation ratio droop method to suppress and control the inverted power generation.According to the characteristics of each micro source,the paper selectes appropriate converter to enable it to play to the best state.For the full use of renewable energy,the output of photovoltaic cells is in priority,which is used Boost converter in the DC system,to ensure the PV in the state of maximum power output;battery uses Buck-Boost bi-directional converter to realize bidirectional flow of energy;fuel cell uses Boost converter for energy control.Based on MATLAB,the paper simulates the control strategy of individual micro source and pumping droop control methodes;and the grid connected system,the isolated network and running mode switching,the simulation results prove that the droop control strategies used in the each micro source and the control mathods of common DC bus are correct.