【作者】 李玉玲；

【导师】 张仲超；

【作者基本信息】 浙江大学 ， 电力电子与电力传动， 2006， 博士

【摘要】 PWM整流器根据直流储能元件不同可分为电压型PWM整流器和电流型PWM整流器。电流型PWM整流器具有控制电流更直接方便、动态响应更快以及内在的短路保护能力等优点,在中等功率应用场合将具有广泛的应用前景。超导技术的发展,解决了电流型PWM整流器的储能效率问题,为电流型PWM整流器在大功率场合的应用提供了优势。本文着重研究了电流型PWM整流器及其控制策略,主要包括以下几方面的内容。 建立了三相电流型PWM整流器在三相静止坐标系、两相静止坐标系和两相旋转坐标系的低频和高频时域数学模型,为电流型PWM整流器的控制系统分析和设计提供了理论基础。论文研究了三相电压型和电流型PWM整流器的频域数学模型,分析了两种整流器SPWM输出的频谱构成,并对两种整流器的直流输出进行了比较。在此基础上,对三相电压型和电流型PWM整流器用于有源滤波器(Active power filter,APF)的传输带宽进行了对比研究。 论文提出了三相电流型PWM整流器三逻辑SPWM的数字实现技术。该方法充分利用DSP的内部资源,根据开关次数最少的原则合理分配电流型整流器六个功率管的开关信号,有效的降低了开关损耗,节约了系统成本。研究表明,这种信号分配办法在本质上与电流型PWM整流器的常规空间矢量调制(Space vector modulation,SVM)技术是一致的,稍加改动便可应用于电流型整流器的SVM技术。论文对SPWM调制中,叠流时间对输出的影响进行了初步的探讨,对所提出的数字实现三逻辑SPWM方法进行了实验验证,为论文后续控制策略的研究奠定了实验基础。 直接电流控制是三相电流型PWM整流器控制方法的主流,论文在研究电流型PWM整流器的PI控制和极点配置状态反馈控制的基础上,提出了电流型PWM整流器的线性二次型(Linear quadratic,LQ)最优控制和改进的模型预测控制(model predictive control,MPC)。LQ控制按照系统稳态误差最小的原则寻找系统性能最优的极点,以此达到电流型PWM整流器稳态最优的控制目标。然而LQ控制是基于小信号模型的控制策略,有其固有的缺陷。因此,论文进一步提出了电流型PWM整流器的MPC控制。MPC具有预测和实时寻优的双重优点,但传统的MPC采用非脉冲响应作为预测控制模型,计算量大,很难直接应用到实时控制系统中。论文对这种传统MPC进行了改进,即从电流型PWM整流器被控制量与控制量之间的传递函数入手,得出整流器的一阶差分方程作为预测控制模型,同时保留传统MPC反馈校正、滚动优化等优点,使得MPC可以应用更多还原

【Abstract】 According to the dc-link energy storage elements, PWM rectifiers are classified into voltage-source PWM rectifiers and current-source PWM rectifiers. The current-source PWM rectifiers will be very attractive in medium power applications due to their advantages such as controlling the output current more directly and conveniently, faster dynamic response, and implicit short-circuit protection. The development of the super-conducting magnetic energy storage (SMES) technology, the efficiency problem of the current-source PWM rectifiers will be revolved, which supply advantages for the current-source PWM rectifiers in high power applications. This dissertation studied the current-source PWM rectifiers and their control strategies, mainly including following aspects.Low frequency and high frequency time space mathematical model of 3-phase current-source PWM rectifiers have been founded in abc stationary coordinate, αβ coordinate and dq coordinate. These Mathematical models of current-source PWM rectifiers establish theoretical foundation for the successive research on control system analysis and design in the dissertation. The models in frequency space of the three-phase voltage-source and current-source PWM rectifies have been studied, frequency spectra components of SPWM output in two rectifiers were analysis and dc-link outputs of the two rectifiers were compared. The transfers band of the two rectifiers applied to APF were studied and compared.The dissertation presents tri-logical SPWM digital implement technique of three-phase current-source PWM rectifiers. The proposed method fully uses the inner resources of DSP and distributes driver signals of six switches in principle of the switch time minimum. Consequently, the method reduces switch losses and system cost. Studies show the signal distribution method is in essential accordant with traditional SVM of the current-source PWM rectifiers. The proposed digital implement method changed little can be applied to SVM of the current-source PWM rectifiers. The dissertation primarily discussed the effect of overlap-current time on output in SPWM modulation. The proposed tri-logic SPWM digital implement method is confirmed by experiment, which lay experimental foundation for successive study of control strategies in the dissertation.Direct current control plays most important role in the control of the three-phase current-source PWM rectifiers. After PI control and pole-placement state-feedback control were studied, the dissertation presents linear quadratic (LQ) optimal control and improved model predictive control (MPC) for the current-source PWM rectifiers. LQ control method finds optimal poles of the system according to the minimum steady-state error, consequently, LQ control can reality steady-state characteristic optimal. Nevertheless, LQ control is based on small signal model, there are inherent drawbacks, so the dissertation proposed MPC for the current PWM rectifiers. MPC has merits of forecast and real-time optimization, however, in traditional MPC, non-parameter model based on pulse response is usually adopted as predictive control model, which results in complex computation, so this method is difficult to be applied to real-time control system directly. In this dissertation, the traditional MPC was improved, the first-order differential equations were derived from the transfer functions of controlling variables and controlled variables in the current-source PWM rectifiers, and the equations were used as predictive control model. Meanwhile, the merits of feedback correction and dynamic optimization in traditional MPC were reserved in the new MPC, which makes MPC applicable to fast-control system current-source PWM rectifiers. The simulation and experimental results verified the feasibility and correctness of the proposed method. Compare with traditional PI control and improved MPC when used in the unity power factor current-source PWM rectifiers system, the proposed MPC gets better robustness and faster dynamics characteristics than the traditional PI control.Direct current control is relatively complex compared with indirect current control, and when current-source PWM rectifiers feed a load demanding power factor regulation and energy regeneration, such as a dc motor drive, its realization is difficult. Indirect current control is deep researched in three-phase voltage-source PWM rectifiers. The dissertation studied indirect current control of current-source PWM rectifiers referring the idea that of voltage-source PWM rectifiers, unity power factor of current-source PWM rectifiers was obtained in abc stationary coordinate. This dissertation proposed an indirect current control technique based on dq coordinate. In the proposed technique, dc output of the converter is used as active current reference value of the network current, reactive current of the network is regulated by the produce of the active current reference value and tgcp, then the ac-link current steady-state equations of current-source PWM rectifiers are used to determine instant control variable that control network current of the rectifiers indirectly. Consequently, active power and reactive power of the rectifiers are controlled, and adjustable power factor and reversible energy are obtained. Experimental results of the proposedmethod were given, and the steady-state operation range of the rectifiers is analyzed in quantification.Under unbalanced source voltage supply, if control methods of balanced source voltage are employed directly in current-source PWM rectifiers, the input and output performance of the rectifiers will deteriorate, even work failure. The dissertation analyzes in detail the effect of unbalanced source voltage on ac-side and dc-side of current-source PWM rectifiers. Derived from complex power of system, a compensation control method eliminating the second harmonics of the dc output current is presented under unbalanced source voltage. In the proposed method, the second harmonics active power and average reactive power are set to zero. These conditions are used to calculate the reference values of the network currents, and then control variables are determined to real-time control rectifiers. Accordingly, the second harmonic component of the output dc current can be eliminated and low-order harmonics of the source current are reduced effectively. The validity of the proposed method is proved by simulation and experimental results. If the control condition of the method above depicted is altered, a compensation control method restraining negative sequence component of source current is achieved, simulation results confirmed the method.Finally, the dissertation makes a summary of full paper and an expectation of future study direction and application prospect about current-source PWM rectifiers.更多还原