Modular Converter PWM Control After Submodule Bypass Failure
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Solution Overview
Problem
In modular multilevel converters using pulse width modulation (PWM), the failure of a sub module can lead to unstable control due to unequalized carrier signals among normal sub modules, causing operational instability when a sub module is short-circuited.
Innovation Solution
A power conversion device with a control system that detects sub module failures, stops the switching operation of affected sub modules, bypasses them, and equalizes the intervals among carrier signals of normal sub modules to maintain stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sub module is bypassed when it fails, then the power conversion device can continue operating, but the carrier signals of normal sub modules become unequalized causing control instability
Solution Approach 1:
The patent changes the phase parameters of carrier signals dynamically. When a sub module fails and is bypassed, the control device adjusts the phase intervals of carrier signals for remaining normal sub modules to maintain equalized phases, preventing control instability while allowing continuous operation.
Solution Approach 2:
The patent implements dynamic adjustment of carrier signal phases based on the operational status of sub modules. The control device continuously monitors sub module health and dynamically recalibrates carrier signal parameters to maintain system stability despite component failures.
2Duration of action of moving object
If the power conversion device continues operating with a failed sub module short-circuited, then operational continuity is maintained, but the failed sub module does not respond to distributed carrier signals causing control instability
Solution Approach 1:
The control device modifies carrier signal phase parameters to account for the failed sub module. By adjusting the phase intervals of remaining operational sub modules, the system maintains reliable control responses while continuing operation with reduced capacity.
Solution Approach 2:
The system employs feedback mechanisms where the control device monitors the response of sub modules to carrier signals and adjusts phases accordingly. When a sub module fails to respond, the control device detects this through feedback and recalibrates the carrier signal distribution to maintain control reliability.
Data Source
AI summary
A power conversion device includes a power converter including a plurality of arms and a control device to control voltages of a plurality of sub modules by PWM control using a carrier signal for each sub module. The sub module includes a plurality of switching elements, a power storage element, a pair of output terminals, and a bypass switch. When the control device detects failure of a sub module in an arm, it performs stop processing for stopping a switching operation of the plurality of switching elements included in at least one sub module of the plurality of sub modules in the arm and has the sub module failure of which was detected bypassed. After the control device performs the stop processing, it equalizes intervals among phases of carrier signals of a plurality of normal sub modules in the arm caused by failure of the sub module.