Parallel Inverter Current Sharing Control via Dynamic Switching
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Solution Overview
Problem
Current parallel inverter schemes for AC devices, such as Induction Machines or Interior Permanent Magnet motors, face inefficiencies due to imbalances in current sharing between inverters, leading to overcurrent and overheating issues, which are costly and complex to mitigate.
Innovation Solution
A controller is used to manage a parallel inverter scheme by configuring one inverter to operate in a specific state while the other is off, then transitioning both to ensure overlapping operations to balance current sharing, thereby reducing overheating and increasing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If two smaller inverters are combined in a parallel current sharing scheme to handle large current requirements, then the current handling capability is improved, but slight variations in the inverters cause current imbalance leading to overcurrent and overheating in one or more inverters
Solution Approach 1:
The patent applies dynamics by making the inverter operation flexible and adaptable through real-time control. Each inverter module can dynamically adjust its operating state (ON/OFF) based on control signals, allowing the system to optimize current distribution and respond to varying load conditions, thereby preventing current imbalance and overheating while maintaining high current handling capability
2Ease of operation
If switches in parallel inverters are commanded to turn ON simultaneously, then the switching operation is simplified, but one switch always comes on first causing it to carry double the current while the other carries zero current
Solution Approach 1:
The patent applies preliminary action by having one inverter module prepare and establish current conduction before the other module is activated. The first inverter module is commanded to turn ON and begins carrying current in advance, allowing the current to be gradually transferred or shared as the second module comes online. This prevents the harmful effect of one switch carrying double current while the other carries zero, thereby reducing conduction losses and improving efficiency
3Productivity
If the first inverter runs extra hot while the second runs extra cool due to unequal current sharing, then the system continues to operate, but overcurrent and overheating eventually lead to system shutdown
Solution Approach 1:
The patent applies feedback by implementing control mechanisms that monitor the operating conditions of each inverter module and adjust their operation accordingly. The controller receives information about the state of each module and uses this feedback to command appropriate ON/OFF sequences, ensuring balanced thermal conditions and preventing overcurrent situations that would lead to system shutdown, thereby enabling continuous operation
Data Source
AI summary
In one example embodiment, a controller is coupled to a first inverter and a second inverter forming a parallel inverter scheme. The first inverter and the second inverter are configured to provide power to a load. The controller is configured to control the first inverter to operate according to a first operating state, while the second inverter is off, and turn off the first inverter before transition from the first operating state to a second operating state. The controller is further configured to control the second inverter to at least partially operate during the transition.