Inverter Current Command Compensation for Parallel Overcurrent
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Solution Overview
Problem
In parallel inverter systems, communication delays can lead to uneven current distribution among inverters, causing overcurrent in one inverter and reducing output voltage, resulting in potential damage and inefficient operation.
Innovation Solution
The inverter device includes a current command value compensating unit that adjusts current commands based on detected output voltage, ensuring even power distribution by adding compensation to current commands, and a voltage controller that reduces load voltage to prevent overcurrent, allowing immediate recovery of output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parallel inverter systems operate with communication delays, then system operation is maintained, but uneven current distribution occurs causing overcurrent in individual inverters
Solution Approach 1:
The inverter operates in voltage source mode initially to establish system voltage before current sharing is achieved. This preliminary voltage establishment prevents immediate overcurrent conditions when inverters are first connected or when communication delays occur, as the voltage source mode provides stable reference voltage that prevents uncontrolled current surge.
Solution Approach 2:
The inverter dynamically switches between voltage source mode and current source mode based on real-time operating conditions. When communication is normal, it operates as current source for optimal power sharing. When communication delays are detected, it switches to voltage source mode to prevent overcurrent, and switches back when communication is restored. This dynamic adaptation resolves the contradiction by adjusting operating mode to maintain both system continuity and prevent harmful overcurrent.
2Reliability
If parallel inverter systems operate with communication delays, then system operation is maintained, but output voltage is reduced
Solution Approach 1:
The inverter establishes voltage source operation as a preliminary state when communication delays are detected, ensuring system continuity is maintained first. This preliminary switch to voltage source mode prevents complete system collapse but accepts temporary voltage reduction as a trade-off to maintain operational continuity until communication is restored.
Solution Approach 2:
The inverter dynamically adjusts its operating mode between voltage source and current source based on communication status. When communication delays occur, it switches to voltage source mode which maintains system operation but with reduced voltage. When communication is restored, it switches back to current source mode to恢复正常 voltage and optimal power sharing. This dynamic switching resolves the contradiction by prioritizing system continuity while accepting temporary voltage reduction.
3Stability of the object's composition
If current command compensation is applied to maintain even power distribution, then power distribution uniformity is improved, but control complexity increases
Solution Approach 1:
The inverter changes its operating parameters by switching between two distinct modes: voltage source mode and current source mode. This parameter change approach simplifies control complexity compared to continuous adjustment methods. The compensation is achieved through discrete mode switching based on communication status, which maintains power distribution uniformity while avoiding complex continuous control algorithms.
Solution Approach 2:
The inverter uses dynamic mode switching between voltage source and current source operations to achieve power distribution uniformity. This dynamic approach simplifies control complexity by using predefined operational modes rather than complex real-time calculation and adjustment mechanisms. The controller simply monitors communication status and switches between two established modes, maintaining uniform power distribution without requiring sophisticated control algorithms.
Data Source
AI summary
According to one embodiment, an inverter including a detector which detects a value of an output voltage and a value of an output current; a command value input unit which is capable of receiving a current command value; a current command value compensating unit which, when the value of the output voltage detected by the detector is equal to or lower than a predetermined value, computes a compensation current value for compensating the current command value; an adder which adds the compensation current value to the current command value and outputs the compensated current command value; and a current controller which computes a voltage command value so that a difference between the compensated current command value and the output current detected by the detector becomes zero.