【作者】 马莉丽；

【导师】 程文明；

【作者基本信息】 西南交通大学 ， 机械电子工程， 2013， 博士

【摘要】 起重机大车、小车运行机构和起升机构的动力装置多采用三相交流异步电机,实现起重机低能耗、高效率经济运行的关键是对起重机电机拖动系统的有效控制。电机的能效问题包括电机运行时的能源消耗(简称能耗)和工作效率两个方面的问题。电机运行效率、功率因数对电机拖动系统能耗产生直接影响,而负载率是影响电机运行效率和功率因数的重要运行参数。一般,当负载率为30～40%时,能实现电机高效运行,当负载率超过60%时,电机的功率因数接近额定功率因数。相对于功率因数曲线,电机的效率曲线具有更宽的高效率区域。高效运行的电机,其功率因数不一定高,要使两者都接近较高值,应使电机的负载率不低于60%。通过分析电机效率数据得出电机效率与不同电机功率之间的数值拟合关系,电机效率与不同电机功率之间的关系符合指数变化规律。电机效率数值拟合曲线对于电机的生产和工程中电机选型具有理论指导意义。对电机运行的经济性进行有效判定,必须合理确定电机运行的效率、经济负载率。根据电机运行综合效率和额定综合效率的比较,将电机运行的经济性分为非经济运行、基本合理运行、经济运行等三种运行工况。电机综合节电率的计算方法主要有功率计算法、综合效率计算法和累积电能计算法三种。电机综合功率随电机所拖动负载转矩按二次抛物线规律变化,考虑了无功功率引起的线路损耗的情况时,电机的综合效率曲线低于效率曲线,从电机的综合效率曲线也可定义电机三种运行工况。由于考虑了无功引起线路损耗的情况,电机最高效率点向负载率增大的方向偏移,所以经济运行区域相对变小。电机拖动系统节能的重要要求之一就是电机高效运行,这就要求降低电机运行时的内部损耗,尤其是电机内部的电气损耗。为了实现具有恒转矩运行和变工况负载特性的起重机节能运行,基于电机Г型等效电路,将定子铜耗和铁耗看作不变损耗,将转子铜耗看作可变损耗,其中不变损耗仅与定子电压有关,可变损耗仅与起重机负载转矩有关。根据折算前后传动系统动能不变和功率平衡的原则,得到起重机吊重起升机构等效单轴电机拖动系统电机转子侧的等效转动惯量和等效负载转矩。为了方便计算,同时电机平稳运行时,转差率较小,通过求解转差率与负载转矩之间的近似关系,得到随负载转矩按指数规律变化的起重机节能的最优调节电压,以及使电气总损耗最小的目标函数。起重机以380V的恒定电压运行时,轻载工况总损耗最大,以220V恒定电压运行时,在重载工况总损耗最大,按照负载转矩变化适时调整的最优调节电压运行方式时的节能效果是显著的。对电机定子电压和频率同时进行控制,使电机根据负载变化,具有调速平稳、快速起、制动,并且快速跟踪负载转矩的动态性能,对起重机节能控制具有重要意义。为了达到这一目的,针对电机在同步旋转坐标系中的数学模型,基于电机定、转子转差频率设计的电机变频节能控制系统,通过实时测量电机运行转速,计算转速差,经过转速调节器计算定子电流转矩分量,从而计算转差频率,并得到同步旋转坐标系的同步旋转角速度,进而得到空间矢量变换角。定子电压转矩分量和励磁分量由矢量变换角经过两相旋转坐标系到三相静止坐标系变换成电压型逆变器的控制信号,由整流器和逆变器输出电机定子三相变压变频电压,实现电机以给定转速稳定运行,并快速跟踪变化的负载转矩。仿真研究表明：闭环系统的空载起动时间比开环系统快0.34s,并且电机平稳起动,起动阶段开环和闭环系统的峰值电磁转矩差值达148N·m；闭环系统电机消耗的电动率小于开环系统的电机消耗电功率,尤其是在起动阶段开环系统的峰值功率是闭环系统峰值功率的2.5倍,电机具有明显的节能效果。基于矢量变换的矢量变频控制对电机拖动系统的调速范围宽,并且属于转差功率不变型的无极调速方法,结合现代控制理论与方法,既能应用于对调速性能要求较高的场合,对电机拖动系统也具有明显的节能效果。针对基于内扰定义MT坐标系中的电机等效结构设计了起重机电机拖动系统自抗扰控制器,4个一阶自抗扰控制器分别控制磁链方程的磁链、转速方程的转速、励磁电流方程的定子电流励磁分量和转矩电流方程的定子电流转矩分量。闭环系统电机具有良好的起动动态性能。开环系统电机负载起动时的能耗随负载转矩的增大而增大,尤其是在重载和满载时,负载转矩对起动能耗影响较大；对于闭环系统电机负载起动的能耗几乎不随负载转矩的变换而变化；在重载和满载时,闭环系统电机起动时的节能效果是显著的。满载时,闭环系统的节电率可达88%,中等载荷时,节电率可达64%,轻载时,节电率可达55%。更多还原

【Abstract】 The power plant of mobile mechanism and load’s hoisting mechanism is often three-phase asynchronous motor for the bridge crane and gatry crane. If the crane could be economically running with low energy consumption and high efficiency, the key problem is that the crane’s motor driving system can be effectively controlled with low energy consumption and high efficiency. Motor’s energy efficiency problems are including two aspects of problems. The first is motor’s energy consumption and the second is motor’s working efficiency when the motor is running.Motor’s working efficiency and power factor can directly affect motor driving system’s energy consumption. And load rate is the important parameter that affects motor’s working efficiency and power factor. The relationship of numerical fitting between motor’s efficiency and different motor’s power was found by analyzing motor’s efficiency data. The relationship is accord with exponential change law. The numerical fitting carve has theoretical guiding significance for motor’s may be high efficiently running when the load rate is30-40%. Motor’s power factor may be close to rated power factor when the load rate is more than60%. The motor’s efficiency curve has more wide region of high efficiency comparing with motor’s power factor curve. High running motor’s power factor is not always high. When motor’s load rate is not less than60%, motor’s power factor and working efficiency is all high.In order to effectively judge motor operation’s economy, motor operation’s efficiency and economic load rate must be reasonably determined. There are three running conditions according to the combined efficiency and rated combined efficiency. The first is no-economic operation, the second is basic reasonable operation and the third is economic operation. The calculation methods of integrated power saving rate have mainly power calculation method, combined efficiency calculation method and cumulative energy calculation method. Motor’s combined efficiency will change according to parabola with load torque’s change. Motor’s combined efficiency curve is lower than efficiency curve when line loss caused by reactive power is considered. Motor’s peak efficiency point will deviate toward the direction of load rate’s increase. So the region of economic operation will decrease.One of important demand for motor driving system’s saving energy should be motor’s high effectively running. So motor running’s internal loss must be decreased, especially decrease motor’s internal electric loss. In order to realize container crane’s saving energy operation of optimal voltage regulation aiming at crane’s working characteristics of constant torque operation mode and variable working condition’s load, the direct relationship between electric total loss and stator voltage or load torque is obtained based on the asynchronous motor’s Γ-shape equivalent circuit because the stator’s copper loss and iron loss are regarded as invariable loss that only relates to stator voltage and the rotor’s copper loss is regarded as variable loss that is changed following load torque’s changing. The optimal regulation voltage is obtained through mathematical calculation on the condition that the asynchronous motor be stable running. The electric total loss will be minimum when the stator’s voltage is the optimal regulation voltage. The research and simulation results showed:the electric total loss was commonly influenced by the stator voltage and load torque; the optimal regulation voltage would be changing according to the exponential law with the load torque’s changing; the electric total loss’s error between the exact solution and the approximate solution obtained according to the approximate slip ratio while the asynchronous motor’s stable running was bigger when the stator voltage was less than220V, and the error was nearly zero when the stator voltage was more than220V.Motor’s stator’s voltage and frequency are samely controlled. Motor should have good dynamic performance, including smooth speed regulating, fast starting prompt braking and fast tracking load torque. These measures have important significance for crane’s energy saving. In order to achieve these goals, control crane’s motor driving system to real-time track the abrupt load torque and make the motor stably run with a given rotational speed, the equivalent moment of inertia and equivalent load torque on the rotor of the hoisting mechanism and the motor driving system’s dynamic equation are derived through equivalently calculating, and the synchronous rotating coordinate according to rotor flux linkage oriented is constructed, and the load torque tracking’s vector converter close-loop control system is designed with the slip angle frequency between the synchronous angular velocity and the rotor’s electric angular velocity. The research and engineering example calculation results showed:the close-loop control system’s starting time with no-load was faster0.34s than the open-loop system, and the motor could be stably starting, and the difference of electromagnetic torque’s peak value was148N-m for the open-loop system and the close-loop control system; the electric power that the close-loop control system’s motor consumed was less than the electric power that the open-loop system’s motor consumed, especially the open-loop system’s peak value of electric power was2.5times for the close-loop control system’s peak value on the motor’s starting stage, and the motor’s effect of energy saving was obvious.Vector inverter control’s motor driving system’s based on vector transfer has wide speed adjustable range. Vector inverter control is a stepless speed regulation method and motor’s slip power will be not changed. Vector inverter control that is combine with modern control theory and method can be applied into situation where the requirement of speed control performance should be high, and also has obvious energy-saving effect for crane’s motor driving system. Crane’s motor driving system’s active disturbance rejection controller is designed aiming at motor’s mathematical model’s equivalent structure in MT coordinate system. There are4first-order active disturbance rejection controller. The first can control magnetic flux linkage of flux-linkage equation. The second can control revolving speed of speed equation. The third can control stator current’s excitation component of field current equations. And the forth can control stator current’s torque component of field current equations. The closed-loop system’s motor has good starting dynamic performance. Energy consumption of starting will increase with load torque’s increase for the open-loop system’s motor, and especially when crane’s load torque is full and heavy, load torque’s influence on the energy consumption of starting is obvious. Energy consumption of starting for the closed-loop system’s motor is hardly not changed with load torque’s changing. Motor’s energy saving effect of the closed-loop system is prominent when motor is starting. For the closed-loop system, energy saving rate is88%when motor’s load torque is full, energy saving rate is64%when motor’s load torque is medium, and energy saving rate is55%when motor’s load torque is light.更多还原