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A Reversible LCC-VSC Hybrid HVDC System

IP.com Disclosure Number: IPCOM000218069D
Publication Date: 2012-May-18
Document File: 5 page(s) / 34K

Publishing Venue

The IP.com Prior Art Database

Related People

ChengYan Yue: INVENTOR [+4]

Abstract

This is a novel reversible hybrid HVDC system which consists of LCC and full bridge type CTL (Cascaded Two-Level) converter. In the hybrid HVDC system, it can solve the power flow reverse for LCC-VSC HVDC system due to using the new VSC topology. Furthermore, it is easier to realize the reverse function in LCC-VSC MTDC (Multi-Terminal HVDC) with the new VSC topology

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Page 01 of 5

CNCRC Invention Disclosure

Invention Title: A Reversible LCC-VSC Hybrid HVDC System Principal Applications/Uses of the Invention

This is a novel reversible hybrid HVDC system which consists of LCC and full bridge type CTL (Cascaded Two-Level) converter. In the hybrid HVDC system, it can solve the power flow reverse for LCC-VSC HVDC system due to using the new VSC topology. Furthermore, it is easier to realize the reverse function in LCC-VSC MTDC (Multi- Terminal HVDC) with the new VSC topology.

Problem Overcome by the Invention

Existing Problems

Although the LCC-VSC hybrid HVDC transmission system has been studied since 1990s there is no related research realized the power flow reverse function in the hybrid system. The non reverse function is the greatest shortcoming for LCC-VSC HVDC system and also limits utility of the system. The main reason is the characteristics of the two converts, thyristor based rectifier and VSC. The thyristor based LCC converter cannot change the DC current direction only by changing the DC voltage direction, while it needs to be reverse its power. But the existing VSCs used in HVDC system are exactly the opposite in spite of two-level converter, NPC and CTL in ABB, MMC in Siemens, and Maxsine in Alstom. They usually change DC current direction for power reverse other than voltage reverse. Therefore the power flow reverse function cannot be realized with existing VSC topologies mentioned above, when LCC and VSC are mixed in a HVDC system.

Solution with the Invention

To overcome the problem mentioned above, in this invention, the author proposes to employ full bridge type CTL into LCC-VSC system. This new topology can realize polarity reverse of the hybrid HVDC system.

Detailed Description of the Invention

This invention is applied for a reversible LCC-VSC hybrid HVDC system. In this system, a basic hybrid HVDC system consists of thyristor based converter, a full bridge type CTL, transmission lines, smoothing reactors, converter transformers, AC sources and AC filters, which are connected in Figure 1.

Corporate Research

Doc. Name

A Reversible LCC-VSC Hybrid

HVDC System Chunming Yuan, Xiaobo Yang,

Dawei Yao, Chengyan Yue Mar. 14, 2012 2.0

Doc. Creator

Date Page

Revision

1/5


Page 02 of 5

CNCRC Invention Disclosure

Corporate Research

Doc. Name

Doc. Creator

Date

Revision

Page

A Reversible LCC-VSC Hybrid HVDC System

Chunming Yuan, Xiaobo Yang,

Dawei Yao, Chengyan Yue

Mar. 14, 2012 2.0 2/5

Figure 1 The basic LCC-VSC hybrid HVDC system

The key of the hybrid HVDC system is to use full bridge type CTL topology whose single line topology is shown in Figure 2. This is a multilevel converter cascaded with a number of full bridge type two-level converter cell (TLC). And reactors connect with TLC in series in each phase. The AC point sets in the middle of reactors.

DC bus

reactor

TLC

UVSC

AC

reactor

DC bus

Figure 2 Single line structure of the new VSC

The basic TLC shown in Figure 3, is a full H-bridge structure comp...