【作者】 杨家强；

【导师】 黄进；

【作者基本信息】 浙江大学 ， 电气工程， 2005， 博士

【摘要】 测功机是电机性能测试台、机械传动测试台、以及发动机性能测试台等试验装置中的核心设备。常用的有电涡流测功机、磁滞测功机、机械测功机、水力测功机等,均是将测试中所产生的能量转化为热能而消耗掉,不仅造成能量浪费,而且还需配置散热设备。本论文在系统阐述各种类型测功机的基本原理和特点的基础上,基于PWM整流技术和异步电机直接转矩控制技术提出了一种新型交流变频动态电力测功机的构成方案,它不仅能将测试中所产生的能量回馈给电网,而且还可用作测功电动机,这是其它型测功机所不具备的。该测功机电机采用交流鼠笼三相异步电机,其结构简单,性能可靠,克服了直流电力测功机存在换向器所带来的低可靠性、噪声等问题。该测功机的变频控制主电路为“交—直—交”结构,为实现高功率因数、能量双向流动和高的动静态性能,采用三相PWM整流控制策略作为前级“交—直”转换控制;对后级的“直—交”采用具有高转矩动态响应性能的直接转矩控制策略来控制,把三相PWM整流技术和异步电机的直接转矩有机结合用于测功机具有较大的工程实用价值。 本文建立了电压型三相PWM整流器的数学模型,采用直流电流控制技术,设计了电压电流双闭环控制的控制器,在dq坐标系下引入了电流状态反馈,同时用电网电压对其进行前馈补偿,实现了对电流的解耦。解耦后电流变成了独立的dq直流分量,不仅在稳态时能够精确地跟踪电流指令,实现无静差,而且动态响应速度快。 采用空间电压矢量定向的PWM整流控制策略,提出了一种便于实现空间电压矢量定向的数字化算法,大大简化了计算。仿真和实验结果说明该控制策略下的三相PWM整流器,其电压和电流都具有良好的响应性能,电流畸变程度小,电压稳定,不仅能实现单位功率因数的PWM整流,而且可实现单位功率因数的能量反向流动。 从异步电机的数学模型出发,深入研究分析了直接转矩控制磁链控制和转矩控制原理,提出了一种较合理的直接转矩控制电压矢量开关状态表。对不同磁链模型下的直接转矩控制进行对比研究,提出了一种适合全速度范围的定子磁链观测u-i-n数字化模型,较好的改善了直接转矩控制系统的性能。 针对常规直接转矩控制系统在低速运行时转矩脉动比较大和电流畸变厉害的问题,在传统直接转矩控制的基础上,提出了一种转矩预测控制策略,预测下一个控制周期所需要的转矩,根据其转矩分配下一个控制周期的电压空间矢量作用时间。实验结果表明该控制策略没有增加系统的复杂程度,在低速时能够在很大程度上减小转矩的脉动,且没有改变传统直接转矩控制良好的动静态性能。 针对传统直接转矩控制Bang-Bang控制器的不足,本文把模糊算法用于直接转矩控制,提出一种全速度模糊模型直接转矩控制策略,用模糊控制器来优化开关表的选择,实验结果表明该方法动态性能好,能在全速度范围内有效地减小转矩脉动,在低速运行时效果更明显,为改善异步电机的直接转矩控制性能,提供个一种切实可行的智能控制方法。更多还原

【Abstract】 The dynamometer is core equipment of motor performance test station, mechanical drive test station and engine performance test station. The typical dynamometers including hysteretic dynamometer, eddy current dynamometer, mechanic dynamometer and waterpower dynamometer transfer generating energy into heat energy, so not only waste energy but also need some equipment to dispel heat energy. A type of novel AC VF dynamic power dynamometer project is presented based on PWM rectifier and direct torque control (DTC) of induction machine in this dissertation, on the basis of systemic expatiation the basic theory and characteristic of all kinds of dynamometers. The dynamometer not only can feed back generating energy to AC mains, but also can run in electro motion state, the others have no this function. A squirrel cage induction machine is used as its dynamo eclectic machine of testing power because of its simple construction and high reliability, which resolves lower reliability and noise of direct current power dynamometer on account of commutator. The variable-frequency main circuit of the dynamometer is AC-DC-AC configuration. In order to realize high power factor, bi-directional power flow and better dynamic and static performance, it adopts three-phase PWM technology for AC-DC conversion control and direct torque control of induction machine for DC-AC conversion control. This dynamometer that uses PWM rectifier and DTC possess biggish practicality value.The dissertation sets up the mathematical model of voltage source three-phase PWM rectifier, adopts direct current control technology, and designs the controller which consists of voltage and current double closed loop control. The controller inducts current state feedback and carries through forward compensation with AC main voltage to dismiss current coupling in dq coordinate. The dismissed-coupling current becomes separate dq current component, it can accurately track the current without static error in steady state, but also has quickly dynamic respond performance.Adopting voltage-oriented control (VOC) PWM commute control strategy, the dissertation puts forward an easy digital arithmetic to realize VOC, so calculation is reduced greatly. The simulated and experimental results show that the voltage and current of the three-phase PWM rectifier have better respond preference, the current aberrance is smaller and the voltage is steady under this control strategy. The PWM rectifier can implement PWM commute with unity power factor, but also feed back the energy to AC mains with unity power factor.Based the mathematics model of induction machine, the dissertation deeply analyzes flux linkage and torque control theory of DTC and presents a reasonable voltage- vector switch table. After studying on all kinds of flux observation model of DTC, the dissertation put forwards a type of full speed range stator flux observation u-i-n digital model, to improve the performance of DTC.The large torque ripple exists in induction machine based on conventional DTC, especially at a low speed. On the basis of traditional DTC, the dissertation presents a torque prediction strategy. Torque of the next control period is predicted by the proposed equation, and operational time of voltage space-vector in the correspondingperiod is determined based on the predicted torque as well. The experimental results show that the proposed strategy can quickly converge on the given torque and decrease the torque ripple effectively, and also keep a better dynamic performance as the conventional DTC.In order to overcome the weakness of Bang-Bang controller in conventional DTC, the fuzzy logic idea is adopted in the dissertation. The dissertation presents a full-speed fuzzy model DTC strategy, adopt fuzzy controller to optimize select of the voltage vector. The experimental results show that the torque response is improved, and torque ripple is effectively decreased in full-speed range, especially at a low speed, The system has a better dynamic and static performance. The dissertation provides a feasible intel更多还原