Low Voltage Ride-Through Control Strategy For Matrix Converter-Permanent Magnet Synchronous Motor System

Matrix converter-permanent magnet synchronous motor system has the advantages of high power density,flexible power factor adjustment and sinusoidal input and output waveforms.It has broad application prospects in aerospace,shipboard and other fields.Matrix converter directly connects the output side with the input side through switching devices,and the fluctuation of the input side directly affects the output side.When voltage sags occur on the input side of the power grid,the system will be over-current,resulting in system shutdown,and even endanger the safety of production.In order to improve the low voltage ride-through ability of the system,the related research work has been carried out.In this paper,the superposition theorem and the Laplace transform are used to analyze the operation state of system under power grid voltage drop and the transient current expression is solved.This paper studies the judgment method of whether system needs to apply ride-through control when the power grid voltage sag.The method of dq transform and low-pass filter are used to detect the power grid voltage sag.Then the system needs to switch to ride-through control mode by comparing the operating range of torque-speed and the current value of motor.An auxiliary circuit for low voltage ride-through operation is designed.In order to realize the bidirectional flow of energy between motor and clamping capacitor,a switch device is inversely parallel at both ends of the diode in the original topology clamping circuit.A ride-through operation controller is designed.Based on load inertia principle,a unified mathematical model of matrix converter inverters and permanent magnet synchronous motors is established.A low voltage ride through control strategy based on clamping capacitor voltage control is proposed,and a voltage loop controller is designed by using active damping method.A low voltage ride-through experiment was carried out on a matrix converter-permanent magnet synchronous motor system.The proposed method was validated under different voltage drop depths and load conditions.The experimental results show that the proposed low voltage ride-through control strategy can suppress the over-current phenomenon when the voltage sags occur.During the ride-through period,the motor is in a controlled state and keeps running without shutting down.When the grid voltage is restored,the system can quickly resume operation and improve the low voltage ridethrough ability of the system.