Parallel Inverter Module Switching for Current and Temperature Balance
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Solution Overview
Problem
Parallel connected inverter units experience current imbalance due to parameter differences and varying impedances, leading to uneven wear and potential overheating of switch components, despite efforts to balance currents through control pulse modifications.
Innovation Solution
A method and arrangement for balancing load between parallel inverter modules by determining a first time period for each phase based on current imbalance and temperature differences, modifying switching instructions to adjust turn-on or turn-off times, and prioritizing temperature control to prevent overheating, allowing currents to remain unequal if necessary to maintain safe temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control pulses are modified to balance currents between parallel inverter units, then current imbalance is reduced, but switch components may still be damaged due to excessive temperature from uneven cooling
Solution Approach 1:
The patent implements a feedback mechanism where temperature sensors continuously monitor the temperature of switch components in each parallel inverter unit. Based on this temperature feedback, the control system dynamically adjusts the switching instructions to prevent overheating. This resolves the contradiction by using real-time temperature information to modify current distribution, ensuring that units with higher temperatures receive reduced switching activity to allow cooling, while maintaining overall system reliability.
Solution Approach 2:
The patent changes the operational parameters of parallel inverter units dynamically based on temperature conditions. When temperature differences between units are detected, the control system modifies switching frequencies, pulse widths, or duty cycles for specific units to balance thermal loads. This parameter adjustment allows the system to prioritize thermal management over strict current equality, preventing component damage while maintaining acceptable current balance.
2Reliability
If turn-on or turn-off time instants are adjusted to equalize current stresses, then current imbalance is corrected, but components with uneven cooling may still overheat
Solution Approach 1:
The control system uses temperature feedback from sensors monitoring each inverter unit to adjust switching instructions. When temperature differences are detected despite current balancing, the system modifies turn-on or turn-off time instants for specific units to reduce their current stress and allow thermal recovery. This feedback loop ensures that thermal stress is managed dynamically, preventing component damage from overheating.
Solution Approach 2:
The patent implements dynamic adjustment of switching parameters based on real-time temperature conditions. Rather than fixed current balancing, the system continuously adapts turn-on and turn-off timing to account for varying thermal conditions of individual units. This dynamic approach allows the system to respond to changing thermal stresses, prioritizing component safety over strict current equality when necessary.
Data Source
AI summary
A method and an arrangement are disclosed for balancing load between parallel connected inverter modules, which inverter modules are arranged to supply a common load. The method can include providing similar switching instructions for parallel connected inverter modules, determining on the basis of phase currents of each parallel inverter module a first time period for each output phase of each inverter module for correcting current imbalance by advancing or delaying turn-on or turn-off time instants of switch components of the inverter modules, and advancing or delaying the turn-on or turn-off time instants of the switching instructions based on the first time period. The method also can include determining temperatures of each output phase of each inverter module, modifying the switching instructions for one or more of the parallel inverter modules for controlling the temperatures of the output phases, and controlling the inverter modules with a switching instruction in which the turn-on or turn-off times have been advanced or delayed in respect of one or more parallel modules and further modified in respect of one or more inverter modules.