Research On DC Microgrid Control Strategy For Pumping Unit

Pumping unit is the main machinery of oil field production.It is widely distributed in the field,wind energy resources are relatively rich,full and efficient use of wind energy resources to carry out oil production has important significance.The DC microgrid system composed of direct drive permanent magnet synchronous wind power generator and PWM rectifier and its control strategy are studied in this paper.Through effective control of pumping unit,the large inertia of pumping unit is used to store energy.In order to eliminate the "backward generation" and calm the system power fluctuations.In this paper,the control scheme of each unit in the system is studied,and the corresponding simulation is carried out.In order to control the instantaneous power and speed of the pumping unit effectively,the speed sensorless vector control technology of the induction motor used in the pumping unit is studied.The maximum power tracking method of direct-drive permanent magnet synchronous wind generator based on vector control is studied,and the voltage and current double closed loop control system of pwm rectifier based on grid voltage orientation is studied.Secondly,the realization scheme of load power change in matlab is put forward.Firstly,the moment of inertia of the whole pumping unit is equivalent to the moment of inertia at the rotor of the motor.The torque curve is obtained by fitting the load torque data of pumping unit,which is used as the input torque of motor module.Thirdly,in order to make DC bus voltage reflect the change of power in DC microgrid,the droop control is used for DC bus voltage,which is added to the conventional voltage and current double closed loop of grid-side inverter.The simulation model of grid and pumping unit is built to prove the accuracy of modeling and the effectiveness of droop control.Fourthly,in the DC microgrid with a single pumping unit,the output of rotating speed outer loop of vector control of asynchronous motor is limited.The load power of pumping unit is "peaking and filling valley" and "backward generation" is eliminated.When the bus voltage exceeds the reference value,the torque instruction is added at the output of the rotational speed outer ring.This control method is proved to be effective in energy saving and stable in the microgrid by simulation.Finally,in the DC microgrid with two pumping units,when the stroke of the two pumping units is the same,the load power of the two pumping units can be "complementary" by the delayed start of a pumping unit.When the stroke of the two pumping units is different,the RBF neural network method based on chaotic time series is used to predict the torque curve of the motor.Through the prediction curve,the proper time is found to change the speed of the motor in advance,and the peak value is staggered.At the same time,the DC bus voltage and motor speed of the system are monitored to meet the constraint conditions.If through coordinated control,constraints are not met,a torque value will be added at the torque instruction of the inner ring,and the control strategy of the motor is further adjusted to maintain the relative stability of the microgrid power change.The control method is verified by simulation.