Three-Phase PWM Control for Rapid Overcurrent Suppression
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Solution Overview
Problem
Conventional PWM control methods for power converters often lead to frequent switching between normal and abnormal logic in overcurrent phases, causing wave-by-wave current limiting and instability due to external disturbances like load fluctuations or power grid failures.
Innovation Solution
A method for controlling power converters with multi-level topologies that applies distinct PWM modifying strategies to each phase, where the overcurrent phase undergoes a larger voltage change and faster current decrease, while non-overcurrent phases maintain original control signals, ensuring rapid current reduction and stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PWM control is applied to power converters during abnormal conditions, then the power converter can maintain basic operation, but frequent switching between normal and abnormal logic occurs causing wave-by-wave current limiting and instability
Solution Approach 1:
The control method segments the three-phase power converter into overcurrent phases and non-overcurrent phases, applying different PWM modifying strategies to each phase independently. This segmentation allows targeted current suppression in overcurrent phases while maintaining normal operation in other phases, reducing unnecessary control logic switching and improving operational stability.
Solution Approach 2:
Different PWM modifying strategies are applied locally to different phases based on their current status. Overcurrent phases receive aggressive current suppression control while non-overcurrent phases maintain original PWM control. This local differentiation eliminates the need for system-wide logic switching and ensures stable operation.
2Object-generated harmful factors
If uniform PWM modifying strategy is applied to all phases during overcurrent, then current suppression can be achieved, but switching losses increase and control efficiency decreases
Solution Approach 1:
The control strategy applies PWM modification only to phases experiencing overcurrent conditions, while leaving non-overcurrent phases operating under normal PWM control. This localized approach suppresses harmful overcurrents without unnecessarily increasing switching losses in healthy phases, thereby improving overall control efficiency and reducing energy waste.
Solution Approach 2:
Instead of applying full PWM modification to all phases, the method applies partial modification only where needed (overcurrent phases). This partial action approach achieves sufficient current suppression while minimizing the side effects of excessive switching and control intervention.
3Reliability
If rapid current reduction is implemented in overcurrent phases, then overcurrent protection is improved, but voltage change range must be increased which may affect system stability
Solution Approach 1:
The method applies different voltage control strategies locally to different phases: overcurrent phases experience larger voltage changes for rapid current suppression, while non-overcurrent phases maintain smaller voltage changes. This localized differential control achieves effective overcurrent protection while preserving voltage stability in the overall system.
Solution Approach 2:
The control method continuously monitors phase currents and dynamically adjusts PWM strategies based on real-time current status. When overcurrent is detected in specific phases, the system feedback-triggeredly applies aggressive voltage modulation to those phases only, while maintaining normal voltage control in other phases, thus achieving rapid current reduction without compromising overall voltage stability.
Data Source
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AI summary
This application provides a power conversion system, a power converter and a method for controlling the power converter, which relates to the technical field of power electronics. The method includes detecting a current of the main circuit, and applying multiple PWM modifying strategies to power conversion topologies of three phases if overcurrent occurs in the main circuit. In addition, instead of uniformly modifying the power conversion topologies of the three phases in technical solutions according to the conventional technology, among the PWM modifying strategies in the present disclosure, a voltage at an AC side of a power conversion topology of an overcurrent phase has a largest change range and a current at the AC side has a fastest speed of decrease. Thereby, the current at the AC side of the power conversion topology of the overcurrent phase can rapidly decrease, avoiding switchover of PWM control logics frequently triggered due to the current at the AC side being in the vicinity of an overcurrent point. Finally, after the overcurrent is removed, the power conversion topologies of the three phases are restored to be in the original PWM control manner, thereby adapting to outside disturbance.