【作者】 田斌；

【导师】 康勇； 张凯；

【作者基本信息】 华中科技大学 ， 电力电子与电力传动， 2004， 硕士

【摘要】 在电力电子装置中,以CVCF SPWM逆变器为核心的UPS系统得到了广泛的应用,其输出波形主要技术要求包括低的稳态总谐波畸变率(THD)和快速的动态响应。本文采用重复控制改善系统的稳态性能,采用带积分控制的极点配置改善系统的动态特性,主要的研究工作包括:阐述了SPWM半桥逆变器工作原理,把负载电流处理成扰动,在连续域和离散域建立了单相逆变器的通用数学模型,并通过坐标变换证明了三相逆变器可以转化为单相逆变器处理。从非线性负载、死区效应和直流分压电容电压不平衡三个方面分析了SPWM半桥逆变器输出波形畸变的原因。在MTALAB中建立了精确的仿真模型,其中考虑了具体的开关过程和死区效应。对重复控制系统进行了全面的理论分析,讨论了系统稳定性、误差收敛速度和稳态误差,针对具体控制对象完成了重复控制器的设计,其中利用陷波滤波器对消逆变器谐振峰,利用超前环节进行控制系统相位补偿。仿真结果表明重复控制能够很好的完成逆变器输出波形校正的任务。为了提高逆变器动态性能,采用状态反馈对逆变器进行极点配置。为了消除负载突变带来的稳态误差,在极点配置中引入了积分控制。以这种改造过的极点配置控制系统为内环,重复控制为外环,两种控制系统共同作用。仿真结果说明采用这种复合控制系统的逆变器可以得到理想的稳态和动态效果。在一台50Hz单相半桥逆变器上进行了实验,结果验证了前文的理论分析和仿真研究,在稳态时得到了低的稳态总谐波畸变率,动态时反应迅速,没有稳态误差。更多还原

【Abstract】 Among the power electronics facilities, the uninterruptible power supply (UPS) systems are widely used whose core is a CVCF SPWM inverter. The technical characters of the output voltage waveform consist of low total harmonic distortion (THD) at steady state and rapid transient response. In this paper a repetitive controller is adapted to improve the steady state performance and a pole-assignment controller with integral control is proposed to improve the dynamics of the PWM inverter. The followings are the main work: Illuminated the working characters of the SPWM half-bridge inverter. Treated the load current as a disturbance input, the continuous and discrete models of single-phase inverter are established. Using coordinate transformation, the model of three-phase PWM inverter is converted to two single-phase inverters. The causes of the output voltage waveform distortion are analyzed,which include the influence of nonlinear loads, dead-time and voltage imbalance of the split capacitor. A precise simulation model taking into account dead-time effect and switching process is established with MATLAB software. Comprehensive theoretic analyze is carried out on repetitive control system. System stability, error convergence and steady-state error are discussed. A repetitive controller is designed to control a special inverter, which used a notch filter to eliminate the high resonant peak of the SPWM inverter and a time advance function to achieve phase cancellation. Simulation results show that the repetitive controller is able to nearly cancel the output voltage waveform distortion. To improve the dynamics of the inverter, the state feedback pole assignment control is used . The integral control is added in the pole-assignment to eliminate the error caused by the sudden change of the load. This modified State feedback control used as an inner loop, the repetitive controller used as an out loop. Simulation results show that the combination of these two strategies gives excellent dynamic response as well as high quality voltage waveform. Experiments were finished with a 50Hz single-phase half-bridge inverter, the experimental results proved the theoretic analyze and the simulation results: the output voltage waveform THD is low at steady state, the transient response is rapid with no error.更多还原