Parallel Converter Commutation Timing for Current Balance
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Solution Overview
Problem
In parallel-connected power converters, current imbalances between units can lead to uneven stress on components, premature wear, and increased temperature due to differing switch component parameters and impedances, which existing methods have not adequately addressed.
Innovation Solution
A power converter system with a control arrangement that adjusts switching instants for each converter leg based on sensed current values, shifting mode A commutation later and mode B commutation earlier by a variable timestep proportional to the current, to balance current sharing between parallel-connected inverter legs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If parallel-connected inverter units are used to increase output power capability, then the power output is improved, but current imbalance occurs between units due to parameter differences and impedance variations
Solution Approach 1:
The invention dynamically adjusts the switching instants of parallel-connected inverter units by modifying pulse width modulation (PWM) parameters. Specifically, it changes the turn-on and turn-off timing of switches based on detected current imbalances, thereby altering the conduction time of each unit to achieve balanced current distribution while maintaining increased power output capability
2Reliability
If switch control pulses are modified to balance currents by delaying turn-on or turn-off times, then current balance is improved, but component stress becomes uneven and switch components with higher current wear prematurely
Solution Approach 1:
The invention implements a feedback mechanism where current sensors continuously monitor the output current of each parallel-connected inverter unit. The control system processes these feedback signals to detect current imbalances and automatically adjusts the PWM switching instants of individual units, creating a closed-loop control system that maintains balanced current distribution and prevents premature component wear
3Power
If higher current flows through a switch component, then more power can be delivered, but dissipated power increases and component temperature rises
Solution Approach 1:
The invention dynamically adjusts the conduction time parameter of each switch component by modifying PWM switching instants. When current imbalance is detected, the control system reduces the conduction time of switches carrying excessive current, thereby limiting the power dissipation and temperature rise in those components while maintaining overall power delivery through other balanced units
Data Source
AI summary
Current sharing between the plurality of parallel-connected ARCP or hard-switching converter legs is balanced by a control arrangement. The control arrangement senses a leg output current in each of the parallel-connected converter legs and have an individual autonomous leg-specific switching instant adjustment for the main switches of each of the parallel-connected converter legs to shift the first mode A commutation of the respective converter leg later in time and to shift the second mode B commutation of the respective converter leg earlier in time by a variable timestep proportional to the value of the sensed leg current of the respective converter leg. In other words, if the value of the sensed leg output current in one converter leg is larger than in the other converter leg, then in mode A, the higher-current leg will commutate later than the leg with less current, and in mode B, the higher-current leg will commutate earlier than the leg with less current.