To obtain low ac line current THD, the passive techniques described in the previous chapter
rely on low-frequency transformers and/or reactive elements. The large size and weight of these
elements are objectionable in many applications. This chapter covers active techniques that
employ converters having switching frequencies much greater than the ac line frequency. The
reactive elements and transformers of these converters are small, because their sizes depend on
the converter switching frequency rather than the ac line frequency.
获得足够低的网测THD,有无源途径和有源途径两种办法。前面的章节讲的是靠无源器件实现低频传递函数，这样做导致无源器件的体积特别大，实际应用中无法实现。本章会引进有源控制技术，及通过功率器件工作在高频开关状态实现THD控制。如此所用到的无源器件会减小很多，因为无源器件的体积和频率的平方负相关。
Instead of making do with conventional diode rectifier circuits, and dealing after-the-fact
with the resulting low-frequency harmonics, let us consider now how to build a rectifier that
behaves as ideally as possible, without generation of line current harmonics. In this chapter,
the properties of the ideal rectifier are explored, and a model is described. The ideal rectifier
presents an effective resistive load to the ac power line; hence, if the supplied ac voltage is
sinusoidal, then the current drawn by the rectifier is also sinusoidal and is in phase with the
voltage. Converters that approximate the properties of the ideal rectifier are sometimes called
power factor corrected, because their input power factor is essentially unity [244].
The boost converter, as well as a variety of other converters, can be controlled such that
a near-ideal rectifier system is obtained. This is accomplished by control of a high-frequency
switching converter, such that the ac line current waveform follows the applied ac line voltage.
Both single-phase and three-phase rectifiers can be constructed using PWM techniques. A typical dc power supply system that is powered by the single-phase ac utility contains three major
power-processing elements. First, a high-frequency converter with a wide-bandwidth input current controller functions as a near-ideal rectifier. Second, an energy storage capacitor smooths
the pulsating power at the rectifier output, and a low-bandwidth controller causes the average
input power to follow the power drawn by the load. Finally, a dc–dc converter provides a wellregulated dc voltage to the load. In this chapter, single-phase rectifier systems are discussed,
expressions for rms currents are derived, and various converter approaches are compared.
The techniques developed in earlier chapters for modeling and analysis of dc–dc converters
are extended in this chapter to treat the analysis, modeling, and control of low-harmonic rectifiers. The CCM models of Chap. 3 are used to compute the average losses and efficiency of
CCM PWM converters operating as rectifiers. The results yield insight that is useful in power
stage design. Several converter control schemes are known, including peak current programming, average current control, critical conduction mode control, and nonlinear carrier control.
Ac modeling of the rectifier control system is also covered
为了对低谐波整流器进行分析、建模和控制，本章扩展了前面章节中介绍的建模和分析技术。第三章的CCM 模式用于计算平均损耗和效率，这种方法表明其对功率级的设计很有用。有多种控制方法，比如峰值电流控制，平均电流控制，临界导通控制和非线性载波控制。最后还建立了变换器的交流模型。
