NPC Inverter Temperature Feedback for LVRT Reactive Power
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Solution Overview
Problem
Existing inverters face component damage due to overheating during low voltage ride through (LVRT) events, necessitating large component specifications or limited output capabilities, which increase costs and hinder reactive power support.
Innovation Solution
An inverter with a detection control unit that adjusts the on-duration of switching tubes based on neutral point clamping diode temperatures to manage current flow, preventing overheating and ensuring safe thermal stress levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the inverter increases output current to provide reactive power support during LVRT, then the reactive power support capability is improved, but the neutral point clamping diodes overheat and may be damaged
Solution Approach 1:
The patent dynamically adjusts the on-duration of switching tubes T1 and T4 based on real-time temperature feedback from neutral point clamping diodes. When diode temperature exceeds a threshold, the control system reduces the on-duration of switching tubes to decrease current through the diodes, preventing overheating while maintaining reactive power support capability within safe thermal limits.
Solution Approach 2:
The patent implements a temperature feedback control mechanism where temperature sensors monitor the neutral point clamping diode temperatures and feed this information back to the control unit. The control unit adjusts switching tube on-durations based on this feedback, creating a closed-loop control system that maintains diode temperatures within safe operating ranges during LVRT events.
2Reliability
If large specification components are selected to prevent overheating, then the thermal stress resistance is improved, but the cost increases
Solution Approach 1:
The patent changes the operational parameters (on-duration) of switching tubes based on temperature conditions rather than relying on larger, more expensive diode components. By dynamically adjusting the on-duration parameter, the system maintains thermal stress resistance using standard specification components, avoiding the need for costly large-capacity neutral point clamping diodes.
3Temperature
If the output capability is limited to prevent overheating, then the thermal stress on diodes is reduced, but the power generation capability is reduced
Solution Approach 1:
The patent dynamically adjusts the output capability during LVRT events by modulating switching tube on-durations based on real-time diode temperature. This allows the inverter to maintain maximum power generation capability when diode temperatures are within safe ranges, and only limits output when necessary to prevent overheating, optimizing the balance between thermal safety and productivity.
Data Source
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AI summary
Embodiments of this application disclose an inverter, a control method thereof, and a power supply system. The inverter includes a detection control unit, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, and two neutral point clamping diodes. When the first switching tube and the fourth switching tube are off, the two neutral point clamping diodes, the second switching tube, and the third switching tube form a current path. The detection control unit is configured to detect temperatures of the two neutral point clamping diodes, and adjust on-duration of the first switching tube and/or the fourth switching tube in one switching cycle based on the temperatures of the two neutral point clamping diodes to control a current flowing through the two neutral point clamping diodes. According to embodiments of this application, it can be ensured that thermal stress borne by the two neutral point clamping diodes is within a safe range. This avoids component damage caused by overheating of the two neutral point clamping diodes, and ensures normal operation of a circuit.