【作者】 王斯然；

【导师】 吕征宇； 姚文熙； 汪槱生；

【作者基本信息】 浙江大学 ， 电气工程， 2011， 博士

【摘要】 异步电机变频调速系统具有重要的实用价值和广阔的市场空间,而研究和推广高性能的变频器是提高生产生活水平、促进节能减排、减少电网污染的有效途径,所以这也是人类社会实现科技进步和可持续发展的迫切需要。本文在调研异步电机相关控制技术和变频器硬件实现结构的基础上,主要对变频器传动单元中有利于降低系统成本、提高可靠性和适用性的无速度传感器矢量控制技术以及供电单元中有利于改善网侧电流质量、提高能源利用效率的有源前端实现结构进行了较深入的研究,并提出了一些新的解决方案。首先,本文在分析了几种适用于无速度传感器矢量控制的磁链观测结构的基础上,对转速自适应型全阶磁链观测器进行了较深入的研究。通过线性化小信号模型的方法说明了传统设计方案在低速再生制动工作状态下所存在的不稳定问题,进而提出了一种能够解决这一问题的全阶观测器反馈增益矩阵改进设计方法。然后,在设计并实现了异步电机无速度传感器矢量控制硬件系统的基础上对改进方案进行了实验,实验结果证明所提出的改进方案确实可以拓展无速度传感器控制在低速范围内的稳定工作范围。其次,本文从实际应用的角度出发分析了常见非理想因素对全阶磁链观测器的影响并研究了相应的解决方案。针对电机参数误差对于全阶观测器中磁链观测和转速估算准确性的影响,本文在综合考虑磁链和转速之间耦合关系的基础上进行了详细的理论分析,并且结合系统仿真结果总结了观测误差随不同参数变化的规律。然后分别对电机参数的全静止状态自整定方法和在线辨识方法进行了不同程度的分析和实验。针对传动单元中逆变器硬件系统实现过程中的非理想因素,则分别研究了数字化、采样、死区效应等三个方面。在数字化问题上分析了常用离散化方法应用于全阶磁链观测器时的优缺点,进而提出并实验验证了一种正向差分与双线性变换相结合的离散化方案。所提出的方案能够同时实现较高的精度和较少的运算量,一定程度上解决了高开关频率应用场合中离散化全阶观测器的实用问题。在采样问题上主要分析了定子电流采样不同频率范围误差对全阶观测器转速估算和磁链观测的影响,并说明了合理设计定子电流采样环节的重点问题。在死区效应的问题上详细分析了电压源逆变器死区效应的产生机理以及对观测器定子电压重构的影响,并在此基础上提出了一种考虑电流过零阶段的电流状态判断电路和方法,以及相应的死区补偿方案。理论分析和实验结果证明该方案可判断出逆变器输出电流的瞬时极性以及两种不同的过零状态,并可根据判断结果选择最适合的死区补偿量来提高死区补偿的准确性,从而有效地减小定子电压重构误差对磁链观测的影响。最后,本文对变频器中基于LCL型滤波器的有源前端供电单元的设计及其网侧电流优化控制技术的研究与实验。在分析了系统硬件参数和控制方案设计原则的基础上,实现了完整的以有源前端结构作为供电单元的变频器硬件样机,并对系统的驱动和回馈制动能力进行了实验。同时也分析了在电网电压畸变的条件下系统网侧电流谐波的抑制能力,并说明了LCL滤波器谐振问题给传统控制方案带来的局限性,进而对改进控制方案进行了研究和实验。一方面从稳定性条件、补偿函数设计、以及谐波抑制特性等方面对两种结构的复合重复控制方案进行了详细的分析,并结合实验总结了两种实现结构各自的优缺点和适用性；另一方面在反馈电容电压的有源衰减方案的基础上,提出了应用降阶观测器观测电容电压代替直接使用传感器对电容电压进行采样的方法来实现有源衰减的方案,而且也通过实验结果证明了该方案能够在不增加系统硬件成本和复杂度的同时实现有源衰减并提高控制性能。另外,也根据实验结果对比了重复控制和有源衰减应用于本系统时各自的优缺点。总之,本文以改善性能和提高实用价值为主要目标对异步电机变频器中的一些关键技术进行了研究。研究过程中提出了一些新的思路或改进方案,而且也通过大量的实验对所作分析和所提方案进行了验证。更多还原

【Abstract】 Nowadays, induction motor drives are quite essential for both the industrial applications and the social consumptions. The research and promotion of the variable frequency motor drives with high performance is an effective way to deal with the energy crisis and the environment problem, improve the quality of the industry and the living, and reduce the grid power pollution. So the improvement of the motor drives is important for not only the technology progress, but also the sustainable development of human society. Based on the investigation of the induction motor control and the motor drives’ hardware, this dissertation performs a detail research on the speed sensorless vector control technologies, which help to reduce the hardware cost and improve the system reliability, and the active front end related technologies, which help to improve the grid power quality and the efficiency. Some novel solutions are also proposed for performance improvement.First, several types of flux observer for speed sensorless control are analyzed and compared, and the speed adaptive full order flux observer is selected for further investigation. With the linearized small signal method, the instability problem of the conventional full order observer operating at the low speed and regenerative braking state is indicated. In order to deal with this problem, an improved strategy to design the feedback gain matrix of the full order observer. The indicated issue and the proposed solution are both verified by the theoretical analysis and the experimental results that are carried out on a prototype of induction motor drives with speed sensorless vector control. The results prove that the proposed solution is able to improve the stability of the sensorless control scheme at the low speed operating range.Secondly, this dissertation investigates the practical implementation issues for the full order observer in speed sensorless motor drives, and some novel solutions are proposed and verified experimentally. Taking the coupling effect between the flux and the rotor speed into consideration, the relationship between the error of motor parameters and the error of the flux estimation and the rotor speed estimation is analyzed in detail. Based on the analysis and the simulation results, the influence on estimation accuracy with respect to each motor parameter is concluded. Then, solutions for self-commissioning at standstill and on-line parameter identification are investigated and experimented respectively. Practical implementation issues of the inverter system in the motor drives are also investigated, including digital discretization process, sampling process, and dead time effect. The merits and demerits of the basic discretization methods are analyzed in the condition that they are implemented for the full order observer. Then a compound strategy using partial forward-difference method and partial bilinear transformation method is proposed. The proposed discretization strategy is able to realize better accuracy and lower computing burden simultaneously, which is quite essential for applications that require high switching frequency. In order to emphasize the key points for sampling process design, the influence of the stator current sampling noise and error on the accuracy of flux and speed estimation is also investigated. Furthermore, the dead time effect of voltage source inverter is analyzed in detail, especially its impact on the reconstruction of the stator voltage. Then, a novel method to determine the status of the inverter output current, together with a correspondent dead time compensation strategy are proposed. The proposed solution is verified by both the theoretical analysis and the experimental results, and it realizes better accuracy by selecting the different compensating terms based on the different current status, which effectively reduces the influence of stator voltage reconstruction error on the flux observer.Finally, this dissertation researches on the design and the control strategy of the active front end with LCL filter. The design criteria of the filter and the control scheme is investigated and concluded. According to the design criteria, a motor drives prototype is implemented with the LCL filter and the active front end as the grid interfacing stage, and both the motoring and the regenerating mode are tested on the prototype. Then, the harmonic suppression performance of the system in the condition of distorted grid voltage is analyzed in detail, and the limitation of conventional control scheme caused by the resonance problem of the LCL filter is also indicated, which leads to the research on the improved control scheme. Different structures of compound repetitive control scheme are discussed in detail, and are compared with each other in stability criteria, required compensation process, and harmonic suppression performance. Together based on the analysis and the experimental results, the merits and demerits of different compound repetitive control scheme are concluded. Furthermore, active damping is also analyzed in this dissertation. A novel active damping method that fed back the capacitor voltage estimated by a reduced-order observer to suppress the resonant peak of the LCL filter is proposed. The proposed method is able to implement active damping without increasing the hardware cost and complexity, and is verified by the experimental results. The performance of the proposed active damping method is also compared with the compound repetitive control scheme by the experimental results.In a word, this dissertation performs researches on several critical aspects of the induction motor drives, in order to achieve some improvement on the performance and the practical implementation. Some novel solutions are proposed in the dissertation, and a great quantity of experimental work is also carried out for verification.更多还原