【作者】 王涛；

【导师】 张晓；

【作者基本信息】 中国矿业大学 ， 电气工程， 2017， 硕士

【摘要】 随着我国现代化进程地不断推进,各种工业设备和家用电器的精密程度也越来越高。为了提高生产效率、延长设备的使用寿命,人们对电能质量提出了更高的要求。然而,不论是在工业领域还是日常生活领域都存在大量的非线性负载,非线性负载产生大量的谐波,导致电网功率因数偏低,对电气设备带来了不利的影响。相比较于二极管等不可控整流器,PWM整流器作为一种“绿色”电能变换装置,不仅能够实现网侧电流正弦化,而且其直流侧电压稳定可控,可以从根源上消除谐波源,从而减少电网损耗,提高电气设备的运行效率。本文基于两电平三相电压源型PWM整流器结构,对PWM整流器的控制策略进行了研究。本文对三相电压源型PWM整流器数学模型进行了详细推导,对其控制策略进行了深入的研究。作为一种比较成熟的控制策略,基于电网电压定向的控制策略可以实现良好的稳态性能,但是其动态性能不够理想,PI参数的设计以及调节比较麻烦。为了提高整流器的动态性能,简化控制器参数设计,本文介绍了模型预测控制策略。单矢量FCS-MPC控制策略简单,动态性能良好,但是其开关频率不固定,等效开关频率低,稳态性能较差;双矢量FCS-MPC稳态性能较单矢量FCS-MPC有较大提高,但是其动态响应较差。FCS-MPC在选取最优矢量时将八个矢量都带入整流器数学模型进行计算,这极大地增加了处理器的负担,不利于系统性能的提升。针对这一问题,本文提出了一种简化算法,该算法不需要计算八个矢量的预测电流,从而减少了处理器的运算时间。不论是单矢量FCS-MPC还是双矢量FCS-MPC,功率管的开关频率均不是恒定的。为了实现功率管开关频率恒定,提高整流器的稳态性能,本文提出了一种定频模型预测控制算法,该算法通过计算得出在下一采样时刻作用的电压矢量,利用SVPWM调制算法将电压矢量转换成相应的开关信号,从而实现定频控制。针对模型预测控制算法易受模型参数失配以及外界干扰影响的缺点,本文将扩张状态观测器与模型预测控制相结合,将参数失配引起的模型误差和外界干扰通过观测器进行观测,将观测的结果进行前馈,实时修改系统的数学模型,从而消除参数失配以及外界干扰的影响,实现预测算法的鲁棒控制。本文对于扩张状态观测器的观测误差进行了分析,分析结果表明:扩张状态观测器观测出的扰动与实际值非常接近,由此可看出采用扩张状态观测器来观测扰动是合适的。为了验证算法的有效性,本文做了相关的仿真和实验,仿真和实验结果均验证了本文所提控制方法的有效性。更多还原

【Abstract】 With the continuous progress of China’s modernization process,the precision of various industrial equipment and household appliances is also getting higher and higher.In order to improve the production efficiency and prolong the service life of the equipment,people put forward higher requirements for power quality.However,both in the industrial and daily life field there are a lot of non-linear load,which produce a large number of harmonics,resulting in low power factor and bring adverse effect on electrical equipment.Compared with diode and other uncontrollable rectifier,as a "green" power conversion device,PWM rectifier not only can realize the sinusoidal current of the network side,but also can achieve DC side voltage stability and controllable,which could eliminate harmonic source from the root to reduce power losses and improve the operating efficiency of electrical equipment.Based on the structure of two-level three-phase voltage source PWM rectifier,in this paper,the control strategy of PWM rectifier is studied.In this paper,the mathematical model of three-phase voltage source PWM rectifier is deduced in detail,and its control strategy is studied deeply.As a relatively mature control strategy,the control strategy based on grid voltage orientation can achieve good steady-state performance,but its dynamic performance is not ideal and the design and adjustment of PI parameters are troublesome.In order to improve the dynamic performance of the rectifier and simplify the design of the controller parameters,this paper introduces the model predictive control strategy.Single-vector FCS-MPC control strategy is simple and its dynamic performance is good,but its switching frequency is not fixed,the equivalent switching frequency is low and steady-state performance is poor.The steady-state performance of the two-vector FCS-MPC is much better than that of the single-vector FCS-MPC,but its dynamic response is worse.FCS-MPC takes eight vectors into the rectifier mathematical model when calculating the optimal vector,which greatly increases the burden on the processor,and it’s not conducive to the improvement of system performance.Aiming at this problem,this paper presents a simplified algorithm,which does not need to calculate the predicted current of eight vectors,thus reducing the computing time of the processor.Whether the single-vector FCS-MPC or two-vector FCS-MPC,power transistor’s switching frequency is not constant.In order to achieve constant switching frequency,improve the steady-state performance of the rectifier,this paper proposes a constant-switching-frequency model predictive control strategy,which calculates the voltage vector acting at the next sampling time,and converts the voltage vector into the corresponding switching signal by SVPWM modulation algorithm to realize the fixed frequency control.Aiming at the shortcoming of the model predictive control algorithm which is susceptible to the mismatch of model parameters and the influence of external disturbance,this paper combines the extended state observer with the model predictive control.The model error caused by the parameter mismatch and the external disturbance are observesd through the observer,then the observed results are fed forward and the mathematical model of the system is modified in real time to eliminate the influences of parameter mismatch and the external disturbance and realize the robust control of the prediction algorithm.In this paper,the observation error of the extended state observer is analyzed.The results show that the disturbance observed by the extended state observer is very close to the actual value,and it can be seen that it is appropriate to observe the disturbance by using the extended state observer.In order to verify the effectiveness of the algorithm,this paper has done the relevant simulation and experiment,simulation and experimental results have verified the effectiveness of the proposed method.更多还原