【作者】 石坚；

【导师】 李铁才；

【作者基本信息】 哈尔滨工业大学 ， 电机与电器， 2013， 博士

【摘要】 本文以无刷直流电动机驱动控制方法为研究对象，以改善工作性能和扩大应用范围为目的，以能够在产品中直接应用为目标，从高速实现、转矩脉动抑制、最佳换相控制和无位置传感器控制四个方向对无刷直流电动机驱动控制方法进行了研究。高速实现方面，通过定性分析和定量计算，研究了有限的工作频率对无刷直流电动机运行的影响。结论表明在传统三相PWM控制方法中采用的开关频率或在变母线电压六拍控制方法中采用的软件系统扫描频率，对电动机的运行会产生滞后换相的问题；并且随着电动机转速的提高，每一拍内所包含的工作周期个数越来越少，由滞后换相而产生的电流波动会使电动机的运行越来越差。为了给高速无刷直流电动机驱动器的设计提供参考，将滞后换相对绕组电流波动的影响制作到一个表中，开关频率或系统扫描频率的值可以根据性能指标通过查表比较选取。所提出结论的正确性在反作用飞轮调速系统和高速储能飞轮充放电系统中进行了验证。转矩脉动抑制方面，在详细分析换相转矩脉动产生原因的基础上，提出了一种理论上新型的“三区间调制法”。该方法通过三相绕组电压的配合调制，使换相过程中关断相电流的下降速度和导通相电流的上升速度在每个PWM周期内保持相等，从原理上消除了换相转矩脉动；该方法还可以通过采用不同的区间比例组合，使换相过程的持续时间根据实际应用要求进行调节。所提出方法简单并能够较大程度的改善电动机性能，非常适合在实际产品中广泛普及。针对如何具体实现三区间调制法的问题，提出了一种在全速段范围内以最短换相时间消减换相转矩脉动的方法和另外一种适用于低速应用的五段式实现三区间调制法的PWM调制方法。最终使用一台通用无刷直流电动机调速系统对所提出方法进行了实验验证，取得了良好的效果。最佳换相控制方面，在分析了最佳换相点选取原则的基础上，通过数学推导建立了超前换相角和PWM占空比、母线电压、负载电流的关系表达式；并提出一种在恒转矩负载下适用于变母线电压六拍控制结构的新型低转矩波动超前换相控制方法。该方法通过在每两拍之间插入一小段缓冲区来实现，该缓冲区使下一拍将要切入的电流提前切入，同时使当前拍将要切出的电流延迟切出。通过确定缓冲区的起始位置，即超前换相角的大小，保证每一拍所对应的相电流的中心和反电动势的中心重合，实现最佳换相；方法中转矩脉动的减小通过选取缓冲区内关断相PWM调制的占空比实现。所提出方法实现简单，只需根据额定负载大小将霍尔器件超前放置一个固定的角度即可在全速段实现最佳换相控制。最终通过风扇电机验证了超前换相的必要性；通过通用无刷直流电动机验证了所提出改进型变母线电压六拍控制方法的有效性。无位置传感器控制方面，为了解决传统Y型绕组连接无刷直流电动机的无位置传感器控制方法由于受到中性点电压的干扰，既不能在低转速段准确检测到反电动势过零点信息，又不容易在高转速段捕获反电动势真实值的问题，将三相H桥结构应用到高速无刷直流电动机的无位置传感器控制中，使三相绕组中参与导通的两相并联进行供电，同时使未导通相切出电路以进行反电动势过零点检测。由于是绕组并联，每一相利用全部母线电压产生电流；由于未导通相完全切出电路，位置信号检测精度提高。最终将所提出方法分别在小电感电动机和大电感电动机上进行了实现。理论分析和实验结果表明所采用方法不但可以在较高的转速段实现无位置传感器控制，而且可以较大程度的改善零速起动和低速控制精度的问题。所研制样机应用于新一代的高速风扇产品中。更多还原

【Abstract】 Technology of brushless DC motor(BLDCM) drives was studied in this dissertation in order to improve the performance of BLDCM and enlarge its scope of application. The aim is to develop new methods that can be used directly on products. High-speed control, torque ripple suppression, optimal commutation angle control and sensorless control are the four aspects being studied in detail.As to high-speed control, the influence of limited work frequency on operation of BLDCM had been studied. The conclusions show that a phenomenon of commutation delaying will always exist because of the limited switch frequency in three-phase pulse width modulation(PWM) control method or the limited software scanning frequency in the variable bus-voltage six-step control method. As the speed of the motor rises, the number of unit work cycles in one single step becomes smaller, and the motor operation performance becomes worse. The negative influences on phase current fluctuation respect to switch frequency or software scanning frequency were made into a quantitative table to direct the design of high-speed BLDCM drives. The feasibility and accuracy of the conclusions were confirmed both by reaction flywheel and high-speed energy storage flywheel.As to torque ripple suppression, a new ‘Three-segement modulation method’ was first presented in this dissertation to eliminate commutation torque ripple base on a thorough analysis of the fundamental cause of commutation torque ripple. During commutation, each PWM period is divided into three functional segments by three-phase cooperative modulation. Each of the three phases is assigned with different duty cycle by calculation, so that the average current slope of on-going phase can be kept equal with the average current slope of off-going phase in each PWM period. The commutation duration can also be adjusted as needed by adopting different duty cycle combinations, by which this method can have more flexibility. This simple and effective method is very suitable for product updating. In order to realize the presented method, a general full speed range implementation technique with minimum commutation time was given, and another five-interval implementation technique was given for low speed applications. The experimental results from a common BLDCM prototype confirm the feasibility and effectiveness of presented three-segment modulation method.As to optimal commutation angle control, the mathematical expression of advance commutation angle with PWM duty cycle, bus-voltage and load current was established, and a new variable bus-voltage six-step control method which solves the current lag problem and improves the current ripple problem was presented. The new method is implemented by adding a small buffer zone in the connecting place of two steps. This buffer zone allows the next step phase switching in before the present step is over, and lets the present step phase continue working for a short time after entering next step. The centerline of the phase current can coincide with the centerline of the back electromotive force(EMF) by determining the buffer zone’s start position which can also be seen as an advance commutation angle. The decrease of the current ripple can be achieved by choosing a proper duty cycle in the buffer zone. It only requires the value of load current to determine the advance commutation angle in this method, and applies to any speed operation once the angle is determined. The experimental results from a D200high-power fan and a common BLDCM show the necessity of advance angle control and feasibility of presented variable bus-voltage six-step control method respectively.As to sensorless control, the three-phase H-bridge structure was adopted to BLDCM, in order to solve traditional Y-connection windings BLDCM sensorless control drive’s problems of inaccuracy of zero-cross point detecting during start stage and difficulty of capturing real back-EMF during high-speed range because of distraction from its neutral point. The new structure makes two conducting phases work in parallel; meanwhile the non-conducting phase is cut off from the circuit for back EMF zero-cross detecting. Parallel connection makes each phase excited with full potential of bus voltage and non-conducting phase’s totally switching out from circuit makes the rotor position signal accurate. The theoretical derivation and analysis of presented method were given. The experimental results from a small inductance prototype and big inductance prototypes show that the presented sensorless control method can be used in higher speed applications and can greatly improve the performance at low-speed range operation. The prototypes were developed to be the next generation products.更多还原