Inverter Voltage Drop Control for Ripple Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Overcurrent relays in power conversion apparatuses for AC power systems sometimes falsely operate due to increased ripple amplitudes in alternating current output, even when the instantaneous current of the fundamental component is within the safe range, leading to unnecessary protection actions during system voltage drops.
Innovation Solution
A power conversion apparatus with a control method that includes a voltage drop detection unit to adjust the limit value for the current command, reducing the output current and preventing the ripple from exceeding the overcurrent relay's setting value, thereby preventing false operations. This involves a power command calculation unit, current command calculation unit, limiter, current control unit, and PWM control unit working together to manage the inverter's output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the current limit is set high to allow normal operation during voltage drops, then system stability is maintained, but the ripple may exceed the overcurrent relay setting value causing false operation
Solution Approach 1:
The patent implements feedback control by continuously monitoring the fundamental wave current value and using this information to adjust the current limit value. This closed-loop control ensures that the system maintains stability during voltage drops while keeping the ripple amplitude within acceptable limits to prevent false relay operations
Solution Approach 2:
The patent applies preliminary action by proactively adjusting the current limit value based on detected fundamental wave current conditions before ripple issues arise. The control device anticipates potential false operation scenarios and preemptively modifies operational parameters to prevent them
Data Source
Figure 1
Figure 2
Figure 3
AI summary
There is provided an inverter (1) to be applied to a dispersed generation system (10) to interconnect with a system bus (7), which measures a system voltage (Vr) of the system bus (7), detects a voltage drop of the system bus (7), based on the measured system voltage (Vr), and decreases a limit value of a limiter (23) to limit a current command value (Iivr0), when the voltage drop is detected.