Inverter Frequency Correction to Prevent Grid Overcurrent
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Solution Overview
Problem
When the frequency of AC power output from an inverter decreases due to a system accident, it can lead to an overcurrent state, causing instability in the power grid.
Innovation Solution
A power conditioner with a controller that calculates a frequency change amount based on differential power and sets a target frequency by adding a correction amount to the rated frequency to stabilize the frequency, preventing overcurrent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the frequency of AC power decreases due to system accident, then the AC power rises according to the frequency decrease, but the output current of the inverter falls into an overcurrent state
Solution Approach 1:
The controller calculates a frequency change amount based on differential power and applies a correction amount to prevent the frequency from dropping too low. This preliminary counteraction prevents the AC power from rising excessively and causing overcurrent in the inverter, thereby maintaining reliable operation during system accidents.
Solution Approach 2:
The controller dynamically adjusts the frequency parameter of the AC power by calculating a corrected target frequency. When system accidents cause frequency to drop, the controller modifies the frequency parameter through correction amounts derived from differential power, preventing the cascading effect that would lead to overcurrent and inverter failure.
2Stability of the object's composition
If the frequency of AC power is stabilized by conventional control methods, then the frequency fluctuation is reduced, but the output current still falls into overcurrent state due to low frequency
Solution Approach 1:
The controller goes beyond simple frequency stabilization by dynamically adjusting the frequency parameter based on differential power calculations. This ensures the frequency remains within a safe range that prevents overcurrent, while still allowing necessary frequency adjustments to maintain power balance during system accidents.
Solution Approach 2:
The controller continuously monitors the AC power and frequency, calculates differential power, and adjusts the frequency accordingly. This feedback mechanism ensures that frequency stabilization does not lead to overcurrent conditions, as the controller actively responds to power imbalances by applying correction amounts to maintain both stability and safe operating parameters.
Data Source
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AI summary
A power conditioner includes an inverter that converts DC power output from a battery into AC power and supplies the AC power to a power grid and a controller that controls the inverter. The controller calculates a frequency change amount of the AC power based on differential power that is a difference between the AC power and target power. The controller calculates a correction amount for correcting the frequency change amount to be smaller than a threshold. Further, the controller sets, as a target frequency, a frequency obtained by adding a rated frequency of the inverter to a difference between the frequency change amount and the correction amount. Furthermore, the controller instructs the inverter to bring a frequency of the AC power close to the target frequency.