【作者】 陈伟；

【导师】 邹云屏；

【作者基本信息】 华中科技大学 ， 电气工程， 2009， 博士

【摘要】 三相PWM整流器是目前整流器领域研究的热点，由于其具有双向能量流动性，以及交流电流波形和功率因数任意可控性，应用场合越来越广泛。直接功率控制对变换器的瞬时功率直接进行闭环控制，本文主要内容即对三相电压型PWM整流器的直接功率控制技术进行全面深入的研究。根据瞬时功率理论，推导和建立了三相PWM变换器的功率数学模型。通过分析PWM整流器的有功功率和无功功率的功率流向，阐述了其工作原理。基于数学模型，分别研究每个开关矢量在矢量空间中对瞬时功率的不同影响，提出了一种非固定18扇区矢量空间划分方法，基于这种划分方法提出了新的开关矢量表。这种开关矢量表不仅可以克服传统开关表对无功功率控制上的缺陷，获得更好的稳态和动态控制效果，而且可以对其他开关表的不足进行一定的解释，具有很强的通用性。根据直接功率控制的特点，提出了PWM整流器交流侧电感值、直流侧电压值和直流侧电容值的设计计算方法。通过数学推导，得出了系统参数间相互关系，有利于指导系统设计。本文引入了数字控制器的实时性因子概念，来考察直接功率控制的数字化对控制效果的影响，同时给出了整个数字控制系统延迟时间的最大容忍值，并提出衡量数字控制系统效果的真实环宽的概念。死区效应也是影响波形质量的一大原因，本文通过分别分析死区时间对变换器交流侧电压和交流电流的影响，将死区时间对PWM整流器的影响归纳为死区的电压效应和电流效应，给出了这两种效应的表达式，并给出了一种优化的死区设置方法，该方法实现简单且不会增加控制器的负担。采用滞环比较器的直接功率控制系统的开关频率不固定，是实用化过程中需要解决的一个技术问题。将采用PI调节器的直接电流控制方法和采用滞环比较器的直接功率控制系统进行对比，指出滞环环宽与开关频率的矛盾关系，提出一种开关频率限制方法。该方法在新型18扇区划分方式的基础上，通过控制无功功率滞环比较器的环宽来达到提高波形质量、限制最大开关频率的目的。为了实现开关频率恒定的直接功率控制策略，本文将直接功率控制与空间矢量调制方法相结合，提出基于瞬时功率反馈解耦的DPC-SVM控制方法，通过实验分析了这种控制方法的性能。将交流电机中定子磁链的概念引入到三相PWM整流器中，定义为虚拟磁链VF，并利用虚拟磁链矢量进行定向控制和瞬时功率估算，获得了一种新的直接功率控制方法，称为VF-DPC控制方法。该方法不仅省去了电网电压传感器，提高了系统的可靠性；而且，由于虚拟磁链估算中积分环节的滤波器特性，可以在非理想电网条件下获得很好的控制效果。在实现过程中，利用一个二阶滤波器代替纯积分器成功解决了积分初值问题，而且获得了更好的滤波特性。本文还讨论了将VF-DPC控制系统与空间矢量调制方法相结合，获得一种恒频VF-DPC-SVM控制策略，它兼有三者的优点，是一种很有研究价值的控制方法。更多还原

【Abstract】 Three-phase PWM rectifiers, which have more and more widespread applications, is in a hot research area, because their ability of two-way energy flowing, as well as arbitrary AC current wave and power factor. Direct power control is a kind of method, which directly control converters’ instantaneous power with closed-loop. The main content of this paper is to conduct a comprehensive in-depth study about direct power control in PWM rectifiers.According to the instantaneous power theory, the three-phase PWM rectifier’s mathematical power model is established. By analyzing the energe flow of PWM rectifier’s active power and reactive power, its working principle is powered on. Based on the mathematical model to examine the different effects for instantaneous power of each switch vector in the vector space, a non-fixed 18 sectors dividing method with a novel switching vector table is proposed. They not only can overcome the defects of the traditional one in reactive power control, resulting better steady-state and dynamic effects, but also can give a certain explanation to the lack of other tables.Under the features of direct power control, main circut components design methods are proposed, including: value of the AC side inductor, DC capacitor and DC side voltage. The inter-relationship between the system parameters is researched to guid system design. A concept of real-time gene is introduced to digital direct power control system, to scale the influence of the digitalized system. At the same time, the greatest tolerance value of the entire digital control system delay is given. Another concept: real hysteresis-band is also introduced to measure effect of digital control system. Dead-time is one of the most impacts on the waves’ qualities. Through analysis of impact on the AC side voltage of the converter and grid current respectively, dead-time effect can be summed up as voltage-effect and current-effect to the PWM rectifier. The expressions of these two effects are dedused.The switch frequency of the direct power control system using hysteresis comparator is not fixed, which is a technical issue in practical needing be solved. By comparing to direct current control method using PI regulator, the contradictory relationship between the hysteresis-band and the switching frequency is analysed. Then a method of switching frequency limitation is proposed, which base on the novel 18 sectors space division method. By controlling the hysteresis-band of reactive power, the switching frequency can be regulated within a safty range, at the same time achiveing an improved wave quality. In order to achieve a direct power control strategy with constant switching frequency, a combining control method named DPC-SVM is proposed, which maintains the characters of simple control structure, no impact of coordinate transformation.In the paper, the stator flux concept is introducted from induction motor to three-phase PWM rectifier, which is defined as virtual flux: VF. And the instantaneous power can be estimated using of virtual flux. With virtual flux orientation, a new method of direct power control is gotten, called VF-DPC. This novle method has attractive merits, such as: saving voltage sensor and the low-pass filter behave of the integral. In the realization process, a second-order filter is used in place of pure integrator to solve the initial value problem. At the same time, a better filtering property is achieved. By combining space vector modulation method with VF-DPC, a constant frequency control strategy called VF-DPC-SVM is discussed in the paper, which is an ideal control method with great research value.更多还原