为什么慢性乙肝是流行的中压dri拓扑ves

Article By : David Levett, Tim Frank, Márcio Sari, Uwe Jansen, Klaus Vogel

There are multiple topologies for higher voltage (≥2400 VAC) motor drives for designers to select from to suit the different technical or commercial requirements of the application. Recently, one particular topology, the Cascade H Bridge (CHB), has come to the fore. The basic operating principles of CHB-based drives will be explained in this article, along with a brief review of some suitable new power modules.

Introduction

设计工程师拥​​有几种适合中型电压驱动器（MVD）的拓扑。These most common in use today include three level Neutral Point Clamp (NPC) type 1 using high voltage power modules, current source designs using reverse blocking semiconductors, five level T type and Modular Multi-Level (M2L), as well as others.

Although CHB was first developed in the early 1970s it was not until a decade later that Robicon USA commercialised the design. MVDs based upon the CHB topology are now quite common with multiple companies marketing drives based upon the technology. The Robicon brand survives in the product portfolio of Siemens Industry, which acquired Robicon in 2005.

图1中显示了一个五个阶段CHB转换器的一个相的框图。图2显示了单个单元的细节。

图1：Overall schematic of one phase of a 5 cell per phase CHB converter.

图2：Example of a typical CHB cell schematic.

Topology overview

级联拓扑的核心是多相隔离变压器，如图1所示。该示例具有中型电压原发，总计五个隔离的次级绕组，在此示例中为750VAC。每个变压器的辅助功率均可用一个单元格和所有五个单元格连接以创建一个完整的相位。完整的三相驱动需要另外两个阶段，总共有15个隔离的次级绕组，如图3所示。

Figure 3:Three phase system and showing unbalance with one phase being bypassed.

15个单元中的每一个都包括：

• A three phase input uncontrolled rectifier with a circuit to provide “soft” charging of the capacitor bank when the main power is applied. Note this soft charging can be performed with a separate winding on the main transformer, this allows the drive to be “control powered” without the grid three phase medium voltage being applied to the primary of the transformer.
• 使用4个IGBT和反行二极管的“ H桥”。这些可以按顺序切换，以将正，零或负电压应用于输出端子，总相电压是所有5个电池的电压之和。
• 电容器库平滑整流的波形并创建稳定的直流电源电源。
• 栅极驱动器所需的低压供应可以使用DC总线供电的SMP在本地生成。往返中央控制器的控制信号通过光纤电缆进行电压隔离。这使完整的电池电子组件可以在地球电位上“浮动”。
• 由于IGBT模块和其他组件没有所需的隔离额定值，因此无法将散热器连接到地球电位。通常，散热器连接到直流总线的人工中心点，或与DC负线连接，通常使用低欧姆电阻器来抑制任何潜在的高频振荡。对于液体冷却，需要使用去离子水来防止电流和电腐蚀和沉积效应。另一种方法是使用相变冷却。

图4a是18细胞转换器的照片。图4b是单个单元的照片。

图4a：MV3000 A 4160VAC从WEG驱动器1500hp驱动器。左侧的开关设备和变压器和中心的18个单元格。

图4b：Air cooled cell showing rectifier modules (black) in the centre and 62mm modules(white) on the right and left.

CHB优势

• The power cell design is very similar to a normal AC drive except that for CHB operation, only two half bridges are used. This approach permits the use of high volume components intended for lower voltage converters.
• 通过模块化方法添加更多的单元格和变压器绕组，可以增加输出电压。
• Redundancy is possible by bypassing cells, as shown in Figure 4. A bypass switch (either mechanical or solid state / thyristor) can short out any inoperable cells. The drive will function in an unbalanced condition as long as there is some voltage margin. If in a balanced condition is required, one cell on the other two phases can be shorted out.
• 输入谐波非常低，因为变压器辅助绕组可以相移。电机电流谐波非常低，并且将DV/DT应用于电动机绕组。H桥以低开关频率运行通常为500Hz-1kHz，因为电池的数量乘以电动机绕组看到的有效开关频率。
• 由于每个单元格是相同的，因此备件清单和成本降低。维护被简化，因为单个细胞可以“可插入”。

CHB缺点

• 如图4A所示，变压器相对较大且复杂。
• 细胞需要彼此和地面的电力隔离，从而增加了身体的复杂性和整体系统大小，以满足有关分离的相关安全标准。
• 细胞H桥的单相操作需要大量的平滑电容。
• 更复杂的液体冷却。

下一步：切换图案，级联H桥的谐波»