Voltage Source Converter Common Waveshaper Block
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Solution Overview
Problem
Existing director valve based voltage source converters have limited cell usage, leading to high converter rating and cell count due to the traditional use of waveshaper phase arms in only one half-period of the waveshape, resulting in underutilization of energy storage elements and increased conduction losses, footprint, and cost.
Innovation Solution
The proposed voltage source converter design includes a common waveshaper block connected in series with upper and lower waveshaper sections, utilizing self-commutated or circuit-commutated components, and switches to enable cell usage in both half-periods, reducing conduction losses and overall converter rating by allowing the common waveshaper to contribute to both positive and negative half-cycles of the waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the traditional waveshaper phase arm configuration is used where cells are only active in one half-period, then the structure is simple, but the cell usage is limited leading to high converter rating and increased conduction losses
Solution Approach 1:
The common waveshaper block is designed to serve dual functionality by contributing to both positive and negative half-cycles of the AC waveform. During positive half-cycles, it operates with the upper waveshaper section, and during negative half-cycles, it operates with the lower waveshaper section. This multi-functionality allows the same hardware components to be utilized throughout the entire AC cycle, doubling the effective usage of the waveshaper cells and reducing the required converter rating by approximately half.
2Quantity of substance
If the traditional waveshaper phase arm configuration is used, then the design is straightforward, but the converter rating and cell count are high
Solution Approach 1:
The invention merges the common waveshaper block with both upper and lower waveshaper sections to form an integrated three-level waveshaper structure. This combined structure shares common components (capacitors, switches, and the common waveshaper block) between the positive and negative half-cycle paths, eliminating the need for separate waveshaper circuits for each half-period. The merging reduces the total cell count by approximately half while maintaining the required voltage synthesis capability through coordinated operation of the shared and dedicated sections.
3Area of stationary object
If the traditional waveshaper phase arm configuration is used, then the implementation is simple, but the footprint is large
Solution Approach 1:
The common waveshaper block is nested within the overall waveshaper structure, serving as a shared resource between the upper and lower waveshaper sections. The upper waveshaper section and lower waveshaper section are arranged to share the common block, creating a compact nested configuration where components are reused across different operational modes. This nesting approach significantly reduces the physical footprint by eliminating redundant components that would otherwise be required for separate positive and negative half-cycle waveshaping circuits.
Data Source
AI summary
A voltage source converter includes a number of converter modules, one for each of a number of phases, connected in-series between two DC terminals. Each converter module includes an upper director valve in series with a lower director valve, where a junction between the two provides a primary AC terminal, an upper wayshaper section, a common waveshaper block and a lower waveshaper section in parallel with the valves, where the upper and lower waveshaper sections include multilevel cells and the common waveshaper block include at least one common waveshaper connected between the upper and lower waveshaper sections, a first switching element connected between a secondary AC terminal and the upper waveshaper section and a second switching element connected between the secondary AC terminal and the lower waveshaper section.