【作者】 范必双；

【导师】 谭冠政；

【作者基本信息】 中南大学 ， 控制科学与工程， 2014， 博士

【摘要】 本文针对交流异步电机驱动,对背靠背三电平脉冲宽度调制(Pulse Width Modulation, PWM)变换器矢量控制系统进行研究。对三种常用的快速SVPWM算法进行分析与比较,在此基础上提出了一种计算量小、易于数字实现的任意多电平SVPWM通用算法。并将所提的通用SVPWM算法在现场可编程门阵列(Field Programmable Gate Array,FPGA)上设计实现。针对单侧二极管中点箝位型三电平PWM变换器,提出一种新的混合SVPWM的电容中点电位平衡控制算法。根据每个扇区不同的小矢量作用,并结合电容电压偏差量及三相电流的极性来设置不同的小矢量作用时间调节因子,然后根据三相电流的变化情况使调制在常规的SVPWM和基于虚拟矢量的SVPWM之间进行切换,以实现对中点电位进行分扇区的精细控制。针对背靠背的二极管中点箝位型三电平PWM变换器电容中点电压平衡控制问题,提出一种基于双侧信号的中点电位平衡综合预测控制算法。该算法对双侧的三相电流和直流侧电容电压进行采样和预测,进而给出一个能够表征电容中点电压预期控制指标的品质函数。通过递推运算使品质函数取最小值,从而获得下一个调制周期最佳中点电压控制的冗余矢量时间分配因子。在已有的三电平PWM整流器DPC的基础上,提出了在一个开关周期内具有双非零电压矢量输出的三电平PWM整流器DPC算法。该算法通过对下一时刻的有功和无功进行预测,每次选择对有功和无功调节作用相反的两个电压矢量进行输出,并通过一个分配因子对两个电压矢量的作用时间进行分配,从而实现了对功率的精细调整。基于递推最小二乘法,对三电平变频器的电机参数静态辨识进行建模和仿真,给出了中点电位不平衡与平衡的情况下,电机参数静态辨识的仿真结果。提出一种交流异步电机电机参数动态在线辨识方法,通过在负载恒定时控制电机速度使其保持恒定来消除转子磁链耦合项对参数动态在线辨识的影响,从而能够利用递推最小二乘法对电机参数进行在线计算,以达到电机参数动态在线辨识的实时性和高精确度要求。其中电机恒定速度的保持又是基于对转子磁链和转矩电流的恒定控制来实现。提出了一种能够使系统保持固定的开关频率和采样频率且随机效果不依赖于零矢量的三电平随机SVPWM方法。通过随机调整矢量在每个三角载波的上升段和下降段的时间分配来实现随机SVPWM,并设计一种三重随机化M序列来增强其随机效果。该方法可使输出的线电压和相电流频谱在较宽的频带范围内均匀分布,在整数倍开关频率处的谐波幅值也大大降低。更多还原

【Abstract】 The dissertation took the back-to-back three-level vector control converters as research models.Firstly, a comparison was made for three fast SVPWM algorithms.New general multilevel SVPWM methods were provided, which shows the absolute advantages of the established general multilevel SVPWM algorithms in briefness and FPGA resources use.A new hybrid SVPWM algorithm was proposed based on the single side diode neutral-point clamped (NPC)three-level converter. Different vector on-times factors were selected for different short vectors according to the diviation of capacitors voltages and the polar of three phase currents.Modulation was switched between the conventional SVPWM and the virtual vector based SVPWM according to the situation of three phase currents.Thus, a finer control to the neutral-point voltage balancing was obtained compared to the established hybrid SVPWM algorithm.Aiming at the neutral-point voltage balancing control issue of back-to-back diode NPC three-level PWM converters,a comprehensive predictive strategy for the grid side and motor side was proposed.The phase currents at both sides and the dc-link capacitor voltages were measured for the prediction of the neutral-point current.A quality function was found to balance the neutral-point, and a metabolic on-times distribution factor was used as a predicator to minimize the quality function at each switching state.Based on the conventional three-level rectifier direct power control (DPC),a new predictive three-level DPC algorithm was presented with an output of double non-zero vectors which distinguishes it from the conventional three-level DPC.The active power and reactive power were predicted to select the on-times distribution factor which enables the accurate control of the power.On the basis of analyzing the induction motor parameter identification of the two-level inverters,a mathematic model based on the recursive least square (RLS)algorithm for the static motor parameter identification of the three-level inverters was deduced.Simulation results were abtained under the unbalanced and balanced neutral-point voltage condition.A new model for the dynamic on-load parameter identification was built, for which a constant rotor flux was assumed.A control loop for the rotor flux was implanted into the model,which eliminates the influence of the flux coupling.A new random SVPWM method with fixed switching and sampling frequency was proposed.In this method, all vectors action time was randomly assigned between the ascent and descent stage of each triangle carrier on the basis of the unchanging voltage-second balance law, and the random effect dose not rely on the zero vectors.To insure better random effect of the SVPWM,a trebling randomized maximal-length shift register sequences (M-sequences) was designed.Simulation and experiment results show the proposed scheme leads to a well-distributed spectrum of the line-to-line voltage and phase current, and smaller harmonic amplitude at the integral multiple of the switching frequency compared with the conventional SVPWM.更多还原