Cascaded Current Transformer for Microinverter Measurement
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Solution Overview
Problem
Conventional energy management systems face a design trade-off between turns ratio and frequency bandwidth in current transformers, where achieving a high turns ratio results in lower frequency bandwidth, limiting the performance of microinverters.
Innovation Solution
The implementation of a cascaded current transformer configuration, where a first current transformer is coupled to the secondary winding of a power transformer, and its secondary winding is connected to the primary winding of a second current transformer, allowing for a high effective turns ratio while maintaining a low number of secondary turns, thereby enhancing frequency bandwidth performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high turns ratio current transformer is used, then the current measurement sensitivity is improved, but the frequency bandwidth decreases
Solution Approach 1:
The current transformer is divided into multiple cascaded stages, each with a moderate turns ratio. The first current transformer has a first turns ratio and the second current transformer has a second turns ratio, where the product of these ratios gives the overall high turns ratio. This segmentation allows each stage to operate within its optimal frequency bandwidth while achieving the required overall measurement sensitivity through the cascaded configuration.
2Measurement precision
If the number of secondary turns is increased to achieve high turns ratio, then current measurement precision is improved, but the frequency response deteriorates
Solution Approach 1:
Instead of using a single transformer with a high number of secondary turns, the solution segments the transformation into two cascaded stages. Each stage uses a moderate number of turns, which maintains good frequency response characteristics. The cumulative effect of both stages achieves the required measurement precision without sacrificing frequency response reliability.
Solution Approach 2:
The solution transitions from a single-dimension approach (one transformer with high turns ratio) to a multi-dimensional approach (cascaded transformers with moderate turns ratios). By adding the dimension of cascaded stages, the system achieves high measurement precision through the product of multiple moderate ratios rather than relying on a single high ratio, thereby maintaining frequency response across the bandwidth.
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 achieves a high frequency bandwidth while minimizing the number of secondary turns, resulting in improved performance for microinverters by maintaining a high effective turns ratio and increasing frequency bandwidth significantly.
Implementation Method 1
a first current transformer having a first primary winding configured to couple to a secondary winding of a power transformer of the microinverter
Implementation Method 2
a first secondary winding coupled to a second primary winding of a second current transformer having a second secondary winding coupled to a measurement device
Data Source
AI summary
An apparatus configured for use with a microinverter of an energy management system is provided. For example, apparatus can comprise a cascaded current transformer configuration comprising a first current transformer having a first primary winding configured to couple to a secondary winding of a power transformer of the microinverter and having a first secondary winding coupled to a second primary winding of a second current transformer having a second secondary winding coupled to a measurement device configured to measure a current of the microinverter.