Study On Low Voltage Ride Through Technology Of Power Plant Inverter

With the continuous expansion of the scale of the power grid,and the power grid accident will lead to the instantaneous low voltage drop in the power system of the power plant.On the other hand,the inverter is widely used in the power plant,and the low voltage drop may cause the transformer substation to trip,and then cause the whole plant to cut off the power.Therefore,it is of practical significance to study the low-voltage traversing technology of the high-voltage inverter of the power plant.the main contents are as follows:In this paper,the main circuit topology of the cascaded multilevel high voltage inverter is established,and the V/f low voltage ride through control strategy based on DC voltage loop is proposed.Through the comparison and analysis of the current mature wind power low voltage ride through technology,the control objectives and technical difficulties are clearly defined,and the task is refined as how to keep the constant DC link voltage in the low voltage transition period.Then the traditional V/f control is improved,low voltage control is added to form DC bus voltage closed-loop control,during the fault period of the power grid,the partial energy of the motor rotor is fed back to the frequency converter,the DC voltage is kept in a constant range,and the reliable operation of the frequency converter and the motor is ensured.Compared to the superior cost performance of V/f control,vector control has a better control performance.A vector control strategy based on improved voltage flux observer is proposed.Based on the speed sensorless technology,to improve the voltage type rotor flux observer as a reference,to solve the problem of distortion of signal of motor speed estimation,which laid the foundation for the application of vector control speed performance better;at the same time,the low voltage ride through control and conventional control are integrated into the vector control system,which can realize the stable operation under normal operation condition and the low voltage transition in the low voltage transition period.Finally,based on the MATLAB/ Simiulink simulation platform,the two k inds of low voltage ride through control strategy applied to high voltage inverter are simulated and verified,the simulation results show that the two control strategies can effectively realize the low voltage ride through.