矿用高频隔离型变频调速无速度传感器矢量控制

High-frequency isolated variable frequency speed regulation sensorless vector control in mine

在煤矿中、高压及有限场合,变频器采用工频变压器接入电网且被控电动机大多采用开环控制,存在工作空间狭小、结构复杂和电动机控制鲁棒性差等问题。针对上述问题,提出了一种基于高频隔离型变频调速拓扑结构的无速度传感器矢量控制策略。对矿用高频隔离型变频调速主电路拓扑及功率传输进行了分析:通过不可控整流环节将输入的三相工频交流电源整流为直流电源,将脉动直流电源进行平滑滤波处理,得到稳定的直流电源,经高频隔离DC−DC级进行变压,然后经三相逆变级将直流电源逆变为电压和频率均可调的交流电源。为减少IGBT开关损耗、节约整体成本并减少其整体结构复杂性,三相整流级采用二极管不控整流策略;高频隔离DC−DC级采用等脉宽调制策略(EPWM);三相逆变级采用无速度传感器矢量控制策略,在该控制策略中采用模型自适应系统(MRAS)进行异步电动机速度估测。采用0.75 kW的三相异步电动机作为被测电动机,对矿用高频隔离型变频调速无速度传感器矢量控制策略进行实验验证,结果表明:①高频隔离DC−DC级两侧直流母线电压波动小于10 V且高频方波电压相等,原边单相逆变方波和高频变压器耦合方波电压波形平滑,整体稳态性能好。②三相逆变级电压、电流波形正弦度良好,波形对称且光滑度较好,三相逆变级稳定性能好,满足电动机运行要求。③随时间增加,励磁电流变化较稳定,转矩电流在启动时响应迅速,且启动阶段转矩电流较大,能产生较大的转矩。④电动机速度稳定阶段速度波动小,加、减速阶段波形趋于一次函数,电动机能够平稳启停。电动机在刚启动时最大转矩可达到稳定转矩的5倍以上,能够较快启动进行工作。

In the coal mine's medium and high voltage and limited occasions,the frequency converter is connected to the power grid by power frequency transformer.Most of the controlled motors are controlled by open-loop control,which has the problems of narrow working space,complex structure and poor robustness of motor control.In order to solve the above problems,a speed sensorless vector control strategy based on high frequency isolated variable frequency speed regulation topology is proposed.This paper analyzes the topology and power transmission of the main circuit of high-frequency isolated variable frequency speed regulation in mine.The input three-phase power frequency AC power supply is rectified into DC power supply through an uncontrollable rectification link.The pulsating DC power supply is smoothed and filtered to obtain a stable DC power supply.The DC power supply is transformed through high-frequency isolation(DC-DC level).Then,through the three-phase inverter stage,the DC power supply is converted into AC power supply with adjustable voltage and frequency.In order to reduce IGBT switching loss,save the overall cost and reduce the complexity of its overall structure,the three-phase rectifier stage adopts a diode uncontrolled rectification strategy.The equal pulse width modulation(EPWM)strategy is adopted for the high-frequency isolated DC-DC stage.The speed sensorless vector control strategy is adopted in the three-phase inverter stage.In this control strategy,the model reference adaptive system(MRAS)is used to estimate the speed of the asynchronous motor.A 0.75 kW threephase asynchronous motor is used as the tested motor to verify the speed sensorless vector control strategy of high-frequency isolated variable frequency speed regulation for mine.The results show the following points.①The voltage fluctuation of the DC bus on both sides of the high-frequency isolation DC-DC level is less than 10 V and the high-frequency square wave voltage is equal.The voltage waveforms of the primary single-phase inverter square wave and the high-frequency transformer coupled square wave are smooth and the overall steadystate performance is good.②The three-phase inverter voltage and current waveform sine degree are good.The waveform is symmetrical and smooth.The three-phase inverter level stability performance is good,which meets the requirements of motor operation.③With the increase of time,the excitation current change is stable.The torque current responds quickly at startup.The torque current is large at the start-up stage,which can generate large torque.④The speed fluctuation of the motor is small in the stable phase.The waveforms of acceleration and deceleration phases tend to be a linear function,and the motor can start and stop smoothly.When the motor is just started,the maximum torque can reach more than 5 times of the stable torque,and the motor can be started quickly to work.