Modular Direct AC-AC Multilevel Converters for Multiphase Systems with reduced number of arms - a systematic approach for a class of modular mutlilevel converters

用于减少臂数的多相系统的模块化直接交流-交流多电平转换器 - 用于一类模块化多电平转换器的系统方法

• 批准号: 254417319
• 负责人: Professor Dr.-Ing. Axel Mertens
• 金额: --
• 依托单位: Institut für Antriebssysteme und Leistungselektronik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/254417319?language=en
• 关键词: Modular; Direct; AC; Multilevel; Converters

Modular Multilevel Converters consist of a number of modules, each compring power semiconductors and a capacitor, but generally no power infeed. The outputs of several modules are connected in series to form a branch. This allows synthesis of branch voltage waveforms with rather fine resolution and low distortion. Thus, converters for transformerless connection to the medium voltage grid can be designed. The challenge is in the control of the module capacitor voltages; they must be kept within limits by appropriate operating strategies. While voltage sharing between the modules of one branch is easy to achieve, the control of the total energy content of a branch often requires additional circulating currents or common mode voltages. The control of the branch energies is the most important and challenging task.Within the project “Modular Direct AC-AC Multilevel Converters for Multiphase Systems with Reduced Number of Arms – a Systematic Approach for a Class of Modular Multilevel Converters”, a systematic and unified investigation of modular multilevel converter has been conducted. This investigation includes fully populated nxm-matrix topologies and their symmetrically reduced variants. These converters connect an n-terminal system with an m-terminal system. In the case of fully populated nxm-matrix topologies, each phase of one system is connected to each phase of the other system by a branch of the modular multilevel converter. For symmetrically reduced nxm-matrix topologies, some of these converter branches are removed, resulting in a symmetric configuration. The outcome of this project is a novel generalized control approach, which can be applied to all of the aforementioned modular multilevel topologies.This project application is about the corresponding follow-up project, which aims at extending the generalized control approach for special operating points, asymmetric systems and asymmetrically reduced topologies. The challenging special operating points include for example the connection of two systems of the same frequency. The adaption of the generalized control approach for unbalanced systems enables a stable branch energy balancing control during grid faults and imperfections. An extension to asymmetrically reduced topologies allows the operation of a fully populated topology as an asymmetrically reduced variant in case of failure of a converter branch.This follow-up project will complete the conducted investigations and the developed control approach. As a result, the generalized description and control will be valid for all topologies and relevant operating points.

模块化多电平转换器由多个模块组成，每个模块包含功率半导体和电容器，但通常没有电源馈入。多个模块的输出串联形成支路。这允许合成具有相当精细的分辨率和低失真的支路电压波形。因此，可以设计用于无变压器连接到中压电网的转换器。挑战在于模块电容器电压的控制；必须通过适当的运营策略将它们限制在一定范围内。虽然一个支路的模块之间的电压共享很容易实现，但对支路总能量的控制通常需要额外的循环电流或共模电压。分支能量的控制是最重要和最具挑战性的任务。在“用于减少臂数的多相系统的模块化直接AC-AC多电平变换器——一类模块化多电平变换器的系统方法”项目中，对模块化多电平变换器进行了系统和统一的研究。这项研究包括完全填充的 nxm 矩阵拓扑及其对称减少的变体。这些转换器将 n 端子系统与 m 端子系统连接起来。在完全填充的nxm矩阵拓扑的情况下，一个系统的每一相通过模块化多电平转换器的分支连接到另一系统的每一相。对于对称简化的 nxm 矩阵拓扑，移除了其中一些转换器分支，从而形成对称配置。该项目的成果是一种新颖的广义控制方法，可应用于所有上述模块化多级拓扑。该项目应用是相应的后续项目，旨在扩展特殊工作点、非对称系统和非对称简化拓扑的广义控制方法。具有挑战性的特殊操作点包括例如相同频率的两个系统的连接。对不平衡系统采用广义控制方法可以在电网故障和缺陷期间实现稳定的支路能量平衡控制。对不对称缩减拓扑的扩展允许在转换器分支发生故障时将完全填充的拓扑作为不对称缩减变体进行操作。该后续项目将完成所进行的调查和开发的控制方法。因此，通用描述和控制对于所有拓扑和相关操作点都有效。