Parallel Power Converter Current Sensing for Circulating Current Detection
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Solution Overview
Problem
The multiple power conversion system disclosed in PTL 1 faces the issue of circulating current among the plurality of power converters, requiring a large number of current sensors for detection.
Innovation Solution
The system includes a plurality of unit power converters with DC positive and negative sides connected to each other, and current sensors are placed on the DC neutral points to detect currents, allowing for circulating current detection with a reduced number of sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current sensors are provided in each phase on the AC side to detect circulating current, then circulating current detection accuracy is improved, but the number of current sensors increases
Solution Approach 1:
The patent merges the function of circulating current detection with the DC-side current sensors that are already present for other control purposes. By calculating circulating current based on DC-side current measurements rather than directly measuring it on the AC side, the system combines multiple functions into existing sensor infrastructure, thereby reducing the total number of sensors needed while maintaining detection capability
Solution Approach 2:
The patent uses DC-side current sensors as an intermediary to indirectly detect circulating current. Instead of directly measuring circulating current on the AC side with dedicated sensors, the system uses DC-side current measurements as a mediator to calculate and infer the circulating current, achieving detection with fewer sensors
2Reliability
If a large number of current sensors are used to detect circulating current, then detection reliability is improved, but system complexity and cost increase
Solution Approach 1:
The patent makes the DC-side current sensors universal by using them for multiple purposes: both for their original control functions and for circulating current detection. This multi-functionality ensures reliable detection without adding dedicated sensors, thereby maintaining reliability while reducing system complexity
Solution Approach 2:
The system uses its own existing DC-side current sensors to serve the additional function of circulating current detection. The sensors essentially self-service by providing data for both their primary control role and the secondary circulating current detection role, eliminating the need for separate detection infrastructure
Data Source
AI summary
A multiple power conversion system includes a plurality of first to n-th unit power converters. DC positive sides of the plurality of unit power converters are connected to one another, DC negative sides of the plurality of unit power converters are connected to one another, and n is an integer of two or more. The multiple power conversion system further includes a detector to detect a current flowing through the DC positive side or the DC negative side of a corresponding one of (n−1) or more of the plurality of unit power converters. The multiple power conversion system that can detect a circulating current with a smaller number of current sensors.