Bipolar Bidirectional DC Converter with Segmented Valve Groups
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Solution Overview
Problem
Existing bidirectional DC converters face challenges in efficiently managing pseudo-bipolar and true-bipolar connections in DC power grids, particularly in high-voltage applications, where insulation stress and system cost are concerns, and existing solutions like AUTO-DC structures fail to maintain operation when one electrode fails.
Innovation Solution
A bipolar bidirectional DC converter design featuring two valve group series with Type-I and Type-II configurations, utilizing magnetic elements and isolating switches to maintain operation and reduce insulation stress, allowing pseudo-bipolar connection at the high-voltage side and true-bipolar connection at the low-voltage side, with a control method to adjust power transmission and handle failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If AUTO-DC structure is used to reduce converter capacity and cost, then system cost is reduced, but insulation stress to ground increases when pseudo-bipolar connection is adopted
Solution Approach 1:
The converter is divided into two independent valve group series (Type-I and Type-II), each capable of operating independently. This segmentation allows the system to maintain proper insulation characteristics while using the cost-effective AUTO-DC structure, as each series can be configured to handle pseudo-bipolar or true-bipolar connections appropriately.
Solution Approach 2:
Different valve group series are assigned different connection types (Type-I for pseudo-bipolar, Type-II for true-bipolar) based on local requirements. This allows the system to optimize each part's insulation characteristics according to its specific function while maintaining overall system cost efficiency.
2Ease of manufacture
If AUTO-DC structure is used to reduce converter capacity and cost, then system capacity is reduced, but the system cannot maintain operation when one electrode fails
Solution Approach 1:
The converter is divided into two independent valve group series (Type-I and Type-II), each capable of operating independently. This segmentation allows the system to maintain operation when one electrode fails, as the other series can continue to function and provide power conversion capability.
Solution Approach 2:
The system can dynamically change its operational parameters by switching between different valve group series based on system conditions. When one electrode fails, the control system can reconfigure to use only the healthy series, maintaining operation at reduced capacity rather than shutting down completely.
3Reliability
If MMC back-to-back structure is used to achieve isolation and handle different bus connection modes, then reliability is improved, but construction cost increases
Solution Approach 1:
The converter is divided into two independent valve group series (Type-I and Type-II), each capable of operating independently. This segmentation allows the system to maintain operation when one electrode fails, as the other series can continue to function and provide power conversion capability.
Solution Approach 2:
The system can dynamically change its operational parameters by switching between different valve group series based on system conditions. When one electrode fails, the control system can reconfigure to use only the healthy series, maintaining operation at reduced capacity rather than shutting down completely.
Data Source
AI summary
A bipolar bidirectional DC converter comprises at least two valve group series (101, 102) and at least six magnetic elements (103), and said valve group series are divided into a Type-I valve group series (102) and a Type-II valve group series (101) each valve group series (101, 102) comprises a high-voltage DC port, a low-voltage DC port and at least three AC ports, and each AC port is connected to a magnetic element (103); and the other ends of the magnetic elements (103), which are connected to all the AC ports in the same valve group series (101, 102), are connected.