Interleaved Switching Choke Air Gap Inductance Control
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Solution Overview
Problem
In power generation systems using interleaved switching, high-frequency ripple and common mode current can lead to increased costs and complexity due to the need for filtering components, as existing techniques do not adequately mitigate these issues.
Innovation Solution
The implementation of a power generation system with a generator outputting a multi-phase power signal and a power converter system featuring parallel converter paths, where each phase is connected to a separate choke, allowing for manipulation of air gaps to provide different inductance for common mode current compared to grid current, thereby reducing common mode current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If interleaved PWM switching is used, then high-frequency ripple is reduced, but filtering components such as choke are still required
Solution Approach 1:
The patent divides the single choke into multiple parallel converter paths, each with its own choke. By segmenting the filtering function across multiple paths, the high-frequency ripple is reduced more effectively while allowing each individual choke to be smaller, thus addressing both the ripple reduction goal and the complexity/cost concern.
Solution Approach 2:
The patent employs interleaved switching where multiple converter paths operate with phase-shifted PWM signals. This dynamic coordination between paths causes their high-frequency ripple components to cancel each other out, reducing the overall ripple without requiring oversized filtering components.
2Productivity
If interleaved switching is used, then switching frequency can be higher, but common mode current is generated
Solution Approach 1:
The patent connects each parallel converter path to a dedicated choke rather than sharing a common choke. This local configuration ensures that common mode current generated by each path is contained and filtered locally, preventing it from propagating and accumulating in a shared path, thus allowing higher switching frequencies without excessive common mode current issues.
3Object-affected harmful factors
If traditional choke configuration is used, then filtering is provided, but size and complexity of filtering components increase
Solution Approach 1:
Instead of using one large choke to handle all filtering requirements, the patent segments the filtering function into multiple smaller chokes distributed across parallel converter paths. Each choke handles a portion of the total current and filtering requirement, resulting in smaller individual component sizes while maintaining effective overall filtering performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively mitigates common mode current flow between parallel converters, reducing the size and complexity of filtering components and lowering the overall cost of the power generation system.
Implementation Method 1
an electrical choke including a plurality of windings. A first winding of the plurality of windings is coupled to a first output of a first path of the plurality of converter paths and a second winding of the plurality of windings is coupled to a first output of a second path of the plurality of converter paths
Implementation Method 2
The choke also includes a first air gap in the second leg, wherein a width of the first air gap is larger than a width of a second air gap in the core
Data Source
AI summary
When performing interleaved switching, a power generation system may include chokes for filtering out a high-frequency ripple. However, because the chokes are interconnected, a common mode current can flow between the different parallel converters. Instead of connecting all the outputs of a parallel converter to the same choke, the same phase of each of the parallel converters is sent to one of the chokes. For example, the first phase signals are sent to a first choke, the second phase signals are sent to a second choke, and so forth. By doing so, air gaps in the chokes can be manipulated in order to provide a different inductance for the common mode current than a grid current. For example, the air gaps may be arranged such that the inductance corresponding to the common mode current is greater than the inductance corresponding to the grid current.