Power Converter Harmonic Signaling for Line-Free Common-Mode Control
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Solution Overview
Problem
In power conversion systems, transmitting common mode information without relying on communication lines is challenging, particularly in modular systems where conventional methods increase complexity and reduce reliability, and there is a lack of technology for distributed injection of zero-sequence voltage in three-phase Y-connected systems.
Innovation Solution
The method involves generating AC harmonics at power conversion cells with amplitudes representing information and using resonance control units for closed-loop suppression, allowing for the transmission of common mode information without additional communication lines, and applying this method to both single-phase and three-phase systems for efficient information sharing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional transmission methods relying on communication lines are used to transmit common mode information, then information transmission can be achieved, but additional communication load reduces system reliability and modularity, and increases installation and debugging complexity
Solution Approach 1:
The patent extracts the common mode information transmission function from the communication line infrastructure and relocates it to the power line itself. By using the existing power conversion system's electrical connections to carry both power and information, the solution eliminates the need for separate communication lines, thereby reducing system complexity while maintaining reliability.
Solution Approach 2:
The power line is made multi-functional by enabling it to carry both power transmission and information transmission functions simultaneously. The power conversion system's electrical connections serve dual purposes: delivering electrical energy and conveying common mode information, thus eliminating the need for dedicated communication infrastructure.
2Productivity
If the number of modules increases to expand system capacity, then system capacity improves, but communication speed decreases affecting dynamic performance
Solution Approach 1:
The patent removes the bottleneck of communication line bandwidth by extracting information transmission from the communication infrastructure and embedding it in the power transmission medium. This allows information to be transmitted alongside power without adding communication overhead, enabling system capacity to scale without compromising communication speed.
3Adaptability or versatility
If droop control is used for independent module control, then module independence is achieved, but static error occurs requiring additional communication for mean value transmission
Solution Approach 1:
The patent introduces an intermediary mechanism where AC harmonics serve as carriers for common mode information. Instead of directly communicating mean values through communication lines, the system uses harmonic signals injected into the power line as intermediaries to convey information about voltage, current, or power mean values, thereby eliminating static error without compromising module independence.
4Ease of operation
If centralized controller is used for zero-sequence voltage injection, then three-phase system control is achieved, but communication loops are required making debugging and maintenance more complicated
Solution Approach 1:
The patent segments the centralized zero-sequence voltage injection control into distributed control at each power conversion cell. Each cell independently generates and injects AC harmonics based on local measurements, eliminating the need for inter-cell communication loops while maintaining coordinated three-phase system control through the shared power line medium.
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 approach enables effective transmission of common mode information without harmonic pollution, improves voltage quality, and simplifies system control by using a narrower frequency band, reducing the need for communication lines and enhancing system reliability.
Implementation Method 1
each of the power conversion cells including a resonance control unit; generating, by each of the power conversion cells, an AC harmonic according to a first electrical signal at a first terminal of the corresponding power conversion cell; applying, by the resonance control unit in the corresponding power conversion cell, a closed-loop suppression to the AC harmonic
Data Source
AI summary
The present disclosure discloses a power conversion system and a communication method for transmitting common mode information in the power conversion system. The communication method comprises the following steps: (a) providing at least two power conversion cells; (b) generating, by each of the power conversion cells, an AC harmonic according to a first electrical signal at the first terminal of the power conversion cell, wherein an amplitude of each AC harmonic represents first information of the power conversion cell, and all the AC harmonics are at the same frequency; and (c) injecting the AC harmonic generated by the corresponding power conversion cells into the first terminal of the corresponding power conversion cell and applying a closed-loop suppression to the AC harmonic generated by the corresponding power conversion cell, and controlling the resonance control unit to output a second electrical signal related to the first information.