ANPC Switch Sequencing for Parasitic Inductance Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power conversion systems in wind turbines face issues with parasitic inductance, leading to voltage overshoots and increased losses due to long commutation paths during diode recovery, which can damage devices and reduce converter rating.
Innovation Solution
An active neutral point clamped (ANPC) switching sequence is implemented, where current flows through at least two parallel recovery paths during operation, minimizing commutation paths and reducing parasitic inductance by strategically transitioning between operating states to manage energy discharge in switching devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional NPC topology with alternate recovery paths is used, then higher operating voltages can be achieved through series connection of switching devices, but large voltage overshoots occur at inner switching devices due to different parasitic inductance levels
Solution Approach 1:
The patent implements dynamic control of the switching sequence where the turn-off order of switching devices S2 and S3 is optimized based on current flow conditions. By dynamically adjusting which device turns off first, the patent minimizes voltage overshoot at inner switching devices while maintaining the ability to operate at higher voltages through series connection.
Solution Approach 2:
The patent changes the operational parameters by introducing an optimized switching sequence that alters the timing and order of device turn-off. This parameter change affects the current commutation paths and reduces the impact of parasitic inductance, thereby reducing voltage overshoot without changing the physical topology or hardware configuration.
2Device complexity
If conventional switching sequence is used, then simpler control is maintained, but increased parasitic inductance causes larger diode losses and reduced converter rating
Solution Approach 1:
The patent applies preliminary action by pre-planning and executing an optimized switching sequence before diode recovery occurs. The control system proactively manages the turn-off timing of switching devices S2 and S3 to ensure that current commutation follows paths with minimal parasitic inductance, thereby reducing diode losses before they can occur during natural diode recovery.
3Reliability
If soft switching and snubber circuits are added to reduce voltage overshoots, then device protection is improved, but switching speeds decrease and costs increase
Solution Approach 1:
The patent enables the power converter to protect itself from voltage overshoot through intelligent control of existing switching devices. By optimizing the turn-off sequence of S2 and S3, the system uses its own switching capability to minimize stress on devices without requiring external protection circuits like snubbers, thereby maintaining fast switching speeds and avoiding additional hardware costs.
Data Source
AI summary
A method for operating a multi-level bridge power converter of an electrical power system connected to a power grid includes providing a plurality of switching devices of the power converter in an active neutral point clamped topology. The method also includes operating the plurality of switching devices in a plurality of operating states such that current simultaneously flows through at least two parallel recovery paths of the plurality of switching devices during operation of the power converter to minimize a commutation path of the current when at least one diode of the plurality of switching devices recovers, thereby reducing parasitic inductance affecting the recovering antiparallel diode or the switch.